Camera Movements

[Doremus Scudder]

But I only focus the bellows once. That's the whole point of asymmetrical tilting. There is no second focus point with the bellows. You tilt back the back standard to get the near point in focus after you focus the far point with the bellows. Are you saying I have to check other focus points with additional bellows adjustments beside the first and only one I do now?

Alan,

Yes and yes! You use two (or more) reference points for applying the tilt. You are, even with asymmetrical tilts, whether you realize or not and even though you're not using the bellows focus. You find and focus on the far point. Then you tilt to get a near point in focus. That's correct and it's exactly what one does with any axis tilt, whether the axis is centered or not. Base tilts are a different case, because tilting moves the whole standard and so you have to refocus.

Anyway, if you think about it, when you tilt, you're moving the film further from the lens, thus changing the focus.

And, the whole point of asymmetrical tilting is to speed up applying the tilt. It has nothing to do with focusing the camera for optimum depth of field. Please understand this!

So you find you're far point, tilt till the near is in focus and you've applied your tilt. You're still only half done! And, even if you don't use any tilt at all, you still need to focus the camera (applying tilt or swing is NOT focusing!).

Now you need focus with an eye to dealing with depth of field and choosing the f-stop. For that, you need two other focus points. You want to find the nearest and the farthest points from where the plane of sharp focus is that you want sharp in the final print. We've discussed at length how to do this, especially when tilt is applied ("above" and "below," remember?).

So, find your two focus point, note the positions on the camera bed/rail, place the bellows focus (using the focus knob) halfway between those two positions and, voilà, you have the right focus.

Now, since you know the focus spread, you can use that distance to choose the optimum f-stop. See the chart above and use it, or stop down till everything looks sharp on the ground glass and then close an extra stop like Vaughn does, but, somehow, you need to find the right f-stop. Larger focus spreads need smaller apertures.

And, please understand that when you tilt the back and move it away from plumb, you will have converging verticals in the scene. That may make no difference at the beach or whatever, but with architecture, if you want the vertical parallels to be rendered parallel on the film, you should NOT use back tilt once you have the camera set up with the back plumb and level. You should use front tilt.

Got it now?

Doremus

 

[Alan Edward Klein]

Alan,

Yes and yes! You use two (or more) reference points for applying the tilt. You are, even with asymmetrical tilts, whether you realize or not and even though you're not using the bellows focus. You find and focus on the far point. Then you tilt to get a near point in focus. That's correct and it's exactly what one does with any axis tilt, whether the axis is centered or not. Base tilts are a different case, because tilting moves the whole standard and so you have to refocus.

Anyway, if you think about it, when you tilt, you're moving the film further from the lens, thus changing the focus.

And, the whole point of asymmetrical tilting is to speed up applying the tilt. It has nothing to do with focusing the camera for optimum depth of field. Please understand this!

So you find you're far point, tilt till the near is in focus and you've applied your tilt. You're still only half done! And, even if you don't use any tilt at all, you still need to focus the camera (applying tilt or swing is NOT focusing!).

Now you need focus with an eye to dealing with depth of field and choosing the f-stop. For that, you need two other focus points. You want to find the nearest and the farthest points from where the plane of sharp focus is that you want sharp in the final print. We've discussed at length how to do this, especially when tilt is applied ("above" and "below," remember?).

So, find your two focus point, note the positions on the camera bed/rail, place the bellows focus (using the focus knob) halfway between those two positions and, voilà, you have the right focus.

Now, since you know the focus spread, you can use that distance to choose the optimum f-stop. See the chart above and use it, or stop down till everything looks sharp on the ground glass and then close an extra stop like Vaughn does, but, somehow, you need to find the right f-stop. Larger focus spreads need smaller apertures.

And, please understand that when you tilt the back and move it away from plumb, you will have converging verticals in the scene. That may make no difference at the beach or whatever, but with architecture, if you want the vertical parallels to be rendered parallel on the film, you should NOT use back tilt once you have the camera set up with the back plumb and level. You should use front tilt.

Got it now?

Doremus

Thanks for the clarification. Maybe I missed it, but I didn't see the second focusing process when asymmetrical focusing was explained elsewhere. Others stopped when the near tilt was done. Your method does seem like a lot of extra work. Isn't there a good chance I would just screw up the original focusing for the far and tilt for the near while trying to find those other points with the second bellows focusing? Wouldn't it just be easier and safer if I just picked f22 or something a little smaller based on the depth I can calculate based on far and near distances as one would do with regular 35mm or MF cameras without standards and bellows?

 

[Chuck_P]

Now, if I felt I needed tilt to help get more things closer to the plane of sharp focus, I would have simply chosen the obvious "near" points for my tilt reference points for both your images. These would be for you Chuck, the closest grass at the very bottom of your image and the very top branches of the tree.

Chuck, in your image, there's nothing below the lawn, so you'd look at the base of the building at it's greatest distance from you and the clouds at the right side of the image and see which one gave you the greatest focus spread (more later).

Ok, I think it just clicked so I'm hoping my comments here are indicative of that, lol. Given your two points above, the take home message I am getting is with tilt, finding and establishing "a" PoSF is step one with the near and far scenarios you have been mentioning. Step two is using the knob.......or in my case, I have to move the rear standard forward or backward for my focusing action with my curent lens (135mm) on my Canham..........at any rate, using the focusing action to then "place" that PoSF halfway between two locations on the GG that represent the greatest focus spread of the scene. Step three, select the optimum f/stop based on the chart you have shown. As I type this I am visualizing the angle of the tilted focus plane moving forward or backward.........it's the same visualization without tilt. With the focusing action, the PoSF moves forward or backward except it is parallel to the film plane and not tilted, duh!

As I'm thinking about the actual tilted PoSF.................I'd have to check the book, but I believe also that I've read in AA's "The Camera" that the tilted focus plane is tilted more than the actual tilt given to the standard itself.

 

[Doremus Scudder]

Thanks for the clarification. Maybe I missed it, but I didn't see the second focusing process when asymmetrical focusing was explained elsewhere. Others stopped when the near tilt was done. Your method does seem like a lot of extra work. Isn't there a good chance I would just screw up the original focusing for the far and tilt for the near while trying to find those other points with the second bellows focusing? Wouldn't it just be easier and safer if I just picked f22 or something a little smaller based on the depth I can calculate based on far and near distances as one would do with regular 35mm or MF cameras without standards and bellows?

The object of finding the focus spread between the objects you want in sharp focus on the final print is to first make sure the PoSF is centered between the near and far objects and, second, to be able to choose the optimum f-stop based on the focus spread. And, yes, the PoSF moves around when you do this; that's kind of the object. Usually, just leaving it where it was when you applied the tilt doesn't center it between the nearest and farthest objects you want in focus.

If you chose two reference points for applying the tilt that just happen to be in the right place, then your final position for focus won't be to far from that, but, as I described above, I often pick two close points, use those to apply the tilt, and then go about finding the final place for focus by looking for the far and then focusing halfway between my first position and it.

And, when you're not tilting or swinging at all, what do you do? Certainly you focus somehow. I think from your earlier posts that you guesstimate a place a third of the way into the scene and then try to focus there. That ends up being an approximation, at best, if your goal is to get everything in the image sharp in the final print. Using the near-far and then place the focus halfway between is more accurate. And, if you use the method I'm suggesting, you have the means to find the optimum f-stop as well. No guesswork there either.

As for "just picking f/22" or whatever, you can see from the above chart that in many situations, you are going to end up using smaller apertures than f/22. My most-used aperture is f/32. Sure, you can just guess at that, or use DoF tables, etc., but I don't think they are nearly as accurate or quick.

As for being a lot of extra work: It's no more work than you would do focusing the camera without the tilt; you just do it after applying tilt. And, if you can find two near reference points to use for applying the tilt, you can combine steps.

You don't have to use this method; many don't either. You keep asking me about it and I keep explaining Still, I get good results with it. I haven't had an unpleasant focus surprise for years and years. Only in the most extreme cases do I ever get an area of the print that ends up being a bit soft. But, if you can't get your head around this method, don't despair. Just do what you've been doing and refine it. Your images are well-seen.

Best,

Doremus

 

[Doremus Scudder]

Ok, I think it just clicked so I'm hoping my comments here are indicative of that, lol. Given your two points above, the take home message I am getting is with tilt, finding and establishing "a" PoSF is step one with the near and far scenarios you have been mentioning. Step two is using the knob.......or in my case, I have to move the rear standard forward or backward for my focusing action with my current lens (135mm) on my Canham..........at any rate, using the focusing action to then "place" that PoSF halfway between two locations on the GG that represent the greatest focus spread of the scene. Step three, select the optimum f/stop based on the chart you have shown. As I type this I am visualizing the angle of the tilted focus plane moving forward or backward.........it's the same visualization without tilt. With the focusing action, the PoSF moves forward or backward except it is parallel to the film plane and not tilted, duh!

As I'm thinking about the actual tilted PoSF.................I'd have to check the book, but I believe also that I've read in AA's "The Camera" that the tilted focus plane is tilted more than the actual tilt given to the standard itself.

Chuck,

Yes, I think you've got it for the most part. Keep in mind that there is always a plane of sharp focus when you have a lens mounted on the camera (unless you have the lens focused at greater than infinity). It's out there somewhere, you just have to put it in the optimum place.

Just to recap my suggestions above to maybe help clarify: If you wish to apply tilt, you need two reference points, one near the camera and one farther away. The object is to get both these points in focus by tilting (however you do that, since it varies depending on the type of tilts you have; axis, base, asymmetrical). Once you get the two points in focus, you then find two more points, that I'm calling focus points, that represent the limits of what you want sharp in the final image. One of these is on one side of the PoSF and the other on the opposite side. The object is to find the pair of points that give you the greatest focus spread (mm on the camera bed/rail). You then place focus on the rail or bed halfway between the two points and use the focus-spread distance to get the optimum f-stop from the table.

When you don't use tilts or swings, the second half of the above still applies: find the near and far, position focus halfway between them and use the focus spread to determine f-stop.

As I mentioned to Alan above, you're positioning the plane of sharp focus when you focus without any tilts or swings; it's just that it's parallel to the camera back and easy to visualize; you move the focus and the PoSF moves back and forth in the scene, remaining parallel to the camera back.

When you use tilts or swings, other things happen when you focus back and forth. Let's just look at tilts; swings are just tilts 90° transposed, so all this applies to them as well, just at right angles.

When you have applied tilt, the plane of the camera back - let's call it the film plane - the plane perpendicular to the lens axis that's exactly one focal length in front of the lens center and the plane of sharp focus end up intersecting at a line below the lens. When you focus with the camera back, the PoSF actually rotates around this line (Yes, it sounds complicated, but it's easy to understand if you watch the video here: http://www.trenholm.org/hmmerk/HMbook18.html ). It's about halfway down the page.

The point being, that when you reposition the PoSF after applying tilt, you end up tilting it a little one way or the other. In practice, this isn't much. The video I linked to shows the extremes. In any case, by doing this, you are still optimally positioning the PoSF in the scene.

If you really want to go down the rabbit hole of view camera focusing, read Merklinger's article entitles "Principles of View Camera Focus" that the article has a link to. It used to have nifty movies embedded in it, but they no longer seem to work. That article is seven pages long. For further reading, Google the 140-odd-page book by Merklinger entitled "Focusing the View Camera" and his 90-odd-page book "The Ins and Outs of Focus." They are both out there made available by Carnegie Melon University if I'm not mistaken.

They are fascinating, but you really don't need to have all that information in your head when working in the field.

Have fun,

Doremus

 

[Sharktooth]

There are really two issues to be concerned about, namely focus and perspective. The orientation of the film back controls the perspective. Best practise is to set up the position and orientation of the film back to get your desired shooting perspective. Once that is done, you can use the tilts or swings of the lens to adjust the plane of focus.

Changing the swing or tilt of the lens will change the focus plane, but it has virtually no effect on the shooting perspective. On the other hand, tilting or swinging the film back will change both the focus, as well as the shooting perspective. This is why you should leave the film back alone once you've got your desired shooting perspective. Think of shooting perspective the same way as you would with a 35mm camera. If you tilt your camera back to shoot a high building, the vertical lines will converge. Similarly, if you shoot a building from the side, your horizontal lines will converge. That's fine if that's the look you're after, but not so great if you're trying to avoid that. Objects can become distorted if you're not careful with the perspective. They could be elongated or shortened, and look funny.

Sinar introduced asymmetrical tilts and swings with the Sinar P. It made it easy find the tilt or swing angle by tilting or swinging the back. The key point here is that you used the back tilt or swing to find the appropriate tilt or swing angle, and then transfer that tilt or swing angle to the lens. After doing that, you'd set your film back to it's original orientation to maintain the perspective. It was never intended to be used only on the back, since this would cause perspective problems. The steps for tilt would be to focus a near or far point on the lower horizontal line on the ground glass, and then tilt the back until your other focus point was achieved. Next, you note the tilt angle of the film back from the marked scale. Use that noted tilt angle, and tilt the front standard to that same angle (but in the opposite direction). Go to the film back and straighten the tilt back to it's original position prior to tilting, and then refocus the scene. Now both points should be in focus on the ground glass, and your original perspective was maintained. This is still a relatively complex process, and may or may not be any significant advantage compared to just iteratively tilting and focusing the lens.

Field cameras with the asymmetrical rear tilt are really just a bastardized version of the original Sinar concept. Since these cameras don't have tilt or swing scale markings, there's no way to know precisely what angle they're set at, so there's no way to transfer that angle to the lens standard. You can do it all on the back, and that still might be useful if your perspective isn't important. For things like landscape work, the perspective might not be a big deal since the tilts or swings might be small, and nobody can really tell if a tree is distorted anyway. If you do it this way all the time, you're probably asking for problems. Just be aware of the perspective concerns.

 

[Alan Edward Klein]

The object of finding the focus spread between the objects you want in sharp focus on the final print is to first make sure the PoSF is centered between the near and far objects and, second, to be able to choose the optimum f-stop based on the focus spread. And, yes, the PoSF moves around when you do this; that's kind of the object. Usually, just leaving it where it was when you applied the tilt doesn't center it between the nearest and farthest objects you want in focus.

If you chose two reference points for applying the tilt that just happen to be in the right place, then your final position for focus won't be to far from that, but, as I described above, I often pick two close points, use those to apply the tilt, and then go about finding the final place for focus by looking for the far and then focusing halfway between my first position and it.

And, when you're not tilting or swinging at all, what do you do? Certainly you focus somehow. I think from your earlier posts that you guesstimate a place a third of the way into the scene and then try to focus there. That ends up being an approximation, at best, if your goal is to get everything in the image sharp in the final print. Using the near-far and then place the focus halfway between is more accurate. And, if you use the method I'm suggesting, you have the means to find the optimum f-stop as well. No guesswork there either.

As for "just picking f/22" or whatever, you can see from the above chart that in many situations, you are going to end up using smaller apertures than f/22. My most-used aperture is f/32. Sure, you can just guess at that, or use DoF tables, etc., but I don't think they are nearly as accurate or quick.

As for being a lot of extra work: It's no more work than you would do focusing the camera without the tilt; you just do it after applying tilt. And, if you can find two near reference points to use for applying the tilt, you can combine steps.

You don't have to use this method; many don't either. You keep asking me about it and I keep explaining Still, I get good results with it. I haven't had an unpleasant focus surprise for years and years. Only in the most extreme cases do I ever get an area of the print that ends up being a bit soft. But, if you can't get your head around this method, don't despair. Just do what you've been doing and refine it. Your images are well-seen.

Best,

Doremus

I really appreciate the advice and ideas. It think the problem I;m having is I don't really understand the places you pick for focus. This is when hands on with someone showing you what to do at an actual photoshoot would be very helpful. A face-to-face training class. As far as picking 1/3 down, that comes from shooting 35mm and MF which have no bellows focusing. Interestingly, my Mamiya RB67 has bellows. I wonder if I could try your aperture method with it?

 

[Alan Edward Klein]

There are really two issues to be concerned about, namely focus and perspective. The orientation of the film back controls the perspective. Best practise is to set up the position and orientation of the film back to get your desired shooting perspective. Once that is done, you can use the tilts or swings of the lens to adjust the plane of focus.

Changing the swing or tilt of the lens will change the focus plane, but it has virtually no effect on the shooting perspective. On the other hand, tilting or swinging the film back will change both the focus, as well as the shooting perspective. This is why you should leave the film back alone once you've got your desired shooting perspective. Think of shooting perspective the same way as you would with a 35mm camera. If you tilt your camera back to shoot a high building, the vertical lines will converge. Similarly, if you shoot a building from the side, your horizontal lines will converge. That's fine if that's the look you're after, but not so great if you're trying to avoid that. Objects can become distorted if you're not careful with the perspective. They could be elongated or shortened, and look funny.

Sinar introduced asymmetrical tilts and swings with the Sinar P. It made it easy find the tilt or swing angle by tilting or swinging the back. The key point here is that you used the back tilt or swing to find the appropriate tilt or swing angle, and then transfer that tilt or swing angle to the lens. After doing that, you'd set your film back to it's original orientation to maintain the perspective. It was never intended to be used only on the back, since this would cause perspective problems. The steps for tilt would be to focus a near or far point on the lower horizontal line on the ground glass, and then tilt the back until your other focus point was achieved. Next, you note the tilt angle of the film back from the marked scale. Use that noted tilt angle, and tilt the front standard to that same angle (but in the opposite direction). Go to the film back and straighten the tilt back to it's original position prior to tilting, and then refocus the scene. Now both points should be in focus on the ground glass, and your original perspective was maintained. This is still a relatively complex process, and may or may not be any significant advantage compared to just iteratively tilting and focusing the lens.

Field cameras with the asymmetrical rear tilt are really just a bastardized version of the original Sinar concept. Since these cameras don't have tilt or swing scale markings, there's no way to know precisely what angle they're set at, so there's no way to transfer that angle to the lens standard. You can do it all on the back, and that still might be useful if your perspective isn't important. For things like landscape work, the perspective might not be a big deal since the tilts or swings might be small, and nobody can really tell if a tree is distorted anyway. If you do it this way all the time, you're probably asking for problems. Just be aware of the perspective concerns.

The biggest issue I find with asymmetrical tilt with the back standard method is that often the far object you want to focus only in is not where the axis line on the ground glass is located. So then you have to raise or lower the front standard so it lines up. Then focus. Then you have to raise or lower the front standard to frame the picture the way it was originally making sure the front standard stays parallel to the film. Then go ahead and tilt the back standard to focus the near object.

It may be easier to forget rise and fall and just tilt the front standard with the number of iterations most people use without asymmetrical tilt.

 

[Vaughn]

Alan, what is nice about most 35mm and MF cameras/lenses it that they have a depth of field gauge built right in -- which are basically mechanical computers doing Doremus's work for everyone. (computations made easier by the lack of camera movements, though)

Like I have said, I am an all-on-the-GG worker, but only because I can also (through decades of mistakes) mentally relate the placement of the plane of focus in the landscape in front of me with what I am seeing on the GG.

 

[Chuck_P]

Just to recap my suggestions above to maybe help clarify: If you wish to apply tilt, you need two reference points, one near the camera and one farther away. The object is to get both these points in focus by tilting (however you do that, since it varies depending on the type of tilts you have; axis, base, asymmetrical). Once you get the two points in focus, you then find two more points, that I'm calling focus points, that represent the limits of what you want sharp in the final image. One of these is on one side of the PoSF and the other on the opposite side. The object is to find the pair of points that give you the greatest focus spread (mm on the camera bed/rail). You then place focus on the rail or bed halfway between the two points and use the focus-spread distance to get the optimum f-stop from the table.

Yes, I understand this better now.........I need to remember that when finding the greatest focus spread, I have to remember that one point on the GG is above and one point is below the PoSF. I failed to mention that in my previous comment.

When you have applied tilt, the plane of the camera back - let's call it the film plane - the plane perpendicular to the lens axis that's exactly one focal length in front of the lens center and the plane of sharp focus end up intersecting at a line below the lens. When you focus with the camera back, the PoSF actually rotates around this line

This was interesting to see in that short animation in the link you provided. I incorrectly stated in my previous post that I can only use the camera back to focus the 135mm lens. This discussion has shown me that I've been achieving focus the hard way with the Canham........it suffices to say that I do not need to use the camera back the way I have been.

So, after applying tilt, moving the rear standard toward or away from the lens rotates the tilted PoSF around the hinge line, I see that now, and it explains how I've thought that the focus plane just moved weird on the GG.

When moving just the lens forward or backward.........after applying tilt...........the tilted PoSF maintains its angle and is simply moved forward or backward, just like it would be if the standards were parallel to each other.

 

[Alan Edward Klein]

Yes, I understand this better now.........I need to remember that when finding the greatest focus spread, I have to remember that one point on the GG is above and one point is below the PoSF. I failed to mention that in my previous comment.



This was interesting to see in that short animation in the link you provided. I incorrectly stated in my previous post that I can only use the camera back to focus the 135mm lens. This discussion has shown me that I've been achieving focus the hard way with the Canham........it suffices to say that I do not need to use the camera back the way I have been.

So, after applying tilt, moving the rear standard toward or away from the lens rotates the tilted PoSF around the hinge line, I see that now, and it explains how I've thought that the focus plane just moved weird on the GG.

When moving just the lens forward or backward.........after applying tilt...........the tilted PoSF maintains its angle and is simply moved forward or backward, just like it would be if the standards were parallel to each other.

So if I used back tilt on the back standard for asymmetrical focusing, if I subsequently move the bellow's focus closer from the original far focus point, wouldn;t my original far focus point be further away from the new focus point? Wouldn't my near tilt focus point also now be closer than where it was with the tilt? The old close focus point is also further away?

 

[Alan Edward Klein]

Alan, what is nice about most 35mm and MF cameras/lenses it that they have a depth of field gauge built right in -- which are basically mechanical computers doing Doremus's work for everyone. (computations made easier by the lack of camera movements, though)

Like I have said, I am an all-on-the-GG worker, but only because I can also (through decades of mistakes) mentally relate the placement of the plane of focus in the landscape in front of me with what I am seeing on the GG.

I'm really having a lot of problems seeing that with LF. I get how the tilt allows the close point to be in focus with the bellows far point focus. But I having trouble seeing all the adjustments in between.

 

[Chuck_P]

So if I used back tilt on the back standard for asymmetrical focusing, if I subsequently move the bellow's focus closer from the original far focus point, wouldn;t my original far focus point be further away from the new focus point? Wouldn't my near tilt focus point also now be closer than where it was with the tilt? The old close focus point is also further away?

Sorry Alan......that's probably a question for Doremus.

 

[Axelwik]

There can only be one plane of focus. You can tilt or swing it, or use both swing and tilt to set it at an oblique angle. You'll have to decide where that plane of focus intersects the scene in front of you, then use depth of field if enough is available, to bring the rest of what you want into focus.

 

[Doremus Scudder]

...

When moving just the lens forward or backward.........after applying tilt...........the tilted PoSF maintains its angle and is simply moved forward or backward, just like it would be if the standards were parallel to each other.

So if I used back tilt on the back standard for asymmetrical focusing, if I subsequently move the bellow's focus closer from the original far focus point, wouldn't my original far focus point be further away from the new focus point? Wouldn't my near tilt focus point also now be closer than where it was with the tilt? The old close focus point is also further away?

Basically the same question you two. I'll deal with this before addressing Alan's previous question.

The little video on the page I linked to shows how the PoSF tilts with focusing. The example used back focus so the hinge point would stay in one place because the lens stayed stationary. The lens position determines the point of view for the photography. In effect, keeping the lens in the same place is keeping the camera in exactly the same place.

When we focus using the lens stage, we are, in essence, moving the camera because we're moving the point of view. This makes little to no difference when working at the usual distances we find in landscape and portraiture. However, with close-up work and focusing with the lens, it quickly becomes obvious that we're changing the point of view. Even a few millimeters make a difference at high magnification. That's why photographers who do a lot of tabletop work with view cameras always have cameras with both front and rear focus capability. That way you can focus with the back only, keeping the point of view, change the point of view with the front focus and then refocus or even move the whole mechanism back and forth using both focus knobs at once.

So, back to the tilt thing. What changes the angle of the PoSF in the scene is the combination of tilt and total bellows draw. With tilt and then moving the rear standard, we move the angle of the PoSF around keeping the point of view the same. When we tilt and then use the front standard to focus, we're still moving the angle of the PoSF around, but we're changing the point of view a bit too. No problem with anything but close-up work.

Hope that answers your questions.

Doremus

 

[Sharktooth]

It's a bit cheesy, but this is a nice video by Calumet about large format camera movements.



You can skip to the 15 minute point where it gets into the specifics about camera movements. The Scheimflug explanations starts at about 13 minutes.

 

[Sharktooth]

Here's another nice video from Mat Marrash with some rules of thumb for focus and movements.

 

[Doremus Scudder]

I really appreciate the advice and ideas. It think the problem I;m having is I don't really understand the places you pick for focus. This is when hands on with someone showing you what to do at an actual photoshoot would be very helpful. A face-to-face training class. As far as picking 1/3 down, that comes from shooting 35mm and MF which have no bellows focusing. Interestingly, my Mamiya RB67 has bellows. I wonder if I could try your aperture method with it?

Alan,

I'm back now. I was busy yesterday hanging photo exhibitions for the First Friday Art Walk openings here in town. To your question:

Let me give you a couple of examples, increasing in complexity, and see if we can clear things up.

First, let's look at a simple scene: A flat field with a barn (that's all, no trees no fences, no nothing). We set up the camera a hundred feet or so from the barn. We want everything in the image sharp. Here are the ways you can make the image using the near-far method I suggest.

Option 1 - No Tilt: Keep the camera in zero position. Find the nearest point (that would be the field in the foreground at the bottom of the image) and the farthest point, likely the horizon line behind the barn. Focus on these to points, noting their position on the camera bed. Now position the focus exactly halfway between the two points on the camera bed. This is always the best position for getting both near and far in the DoF, with or without movements. Now, if you're like me, you know the focus spread in mm between the near and far focus points, so you consult your table and choose the appropriate f-stop. Stop down and make the image. (Or, stop down while watching the ground glass till everything is sharp and then add a stop.) This is basically what you do with any camera without movements.

Option 2 - Using Back Tilt: Same scenario except we decide to use the back tilt to make the focus spread less than in the above example so we can use a larger aperture (which gets us a faster shutter speed and avoids diffraction degradation). We need two points in the scene, one near and one far, to use as reference points for applying the tilt (these are NOT points we use for finding focus spread!). Let's choose a very close foreground point and a point halfway up the wall of the barn to define our PoSF. We apply the tilt so that both these points are in sharp focus with the lens wide open (if you can use your asymmetrical tilt, fine, if not then use another method). Now, you can visualize that PoSF as starting on the ground not far from the camera position at the point you used for the near reference point and then extending to intersect the barn at the halfway point, and then on to the sky somewhere above the horizon. You can see that some things in the scene do not lie on the PoSF; some are above it (the top of the barn) and some are below it (the ground where it meets the base of the barn and even the horizon. Still, you want all those things in focus. By making the bellows longer, i.e., focusing closer, you can bring the top of the barn into focus. Great! There's nothing higher than that, so this becomes your "near" focus point for finding the focus spread (it's near because you focused nearer, even though the top of the barn lies above the PoSF - we're defining "near" and "far" by using the bellows extension; longer = nearer; shorter = farther). Note the position of the focus on the camera bed. Now we look for the "far." It will likely be the spot where the ground meets the base of the barn. Focus on that by shortening the bellows (shorter = farther) till it's sharp and note that position on your camera bed. At this point, I determine the focus spread, i.e., the change in distance between the near and far positions on the bellows. Note that distance and remember it. Now, position your focus exactly halfway between the "near" and "far" positions (this is always the best spot). Choose your optimum f-stop by consulting the table or do the stop down and watch routine and start to make the photo. ----- But wait! We just noticed that by tilting the back, we threw the perspective on the barn way out and now it looks like its falling over backward! We don't want that so...

Option 3 - Using Front Tilt: To keep the verticals on the barn parallel in the photograph, we need the back level and plumb, so we remove our back tilt and get the back set straight again. We still want the PoSF to be where it was in Option 2, so we apply front tilt to do the same thing. We use the same two reference points for applying the tilt. You simply have to deal with whatever kind of tilts are on the front standard (more later about tilts). Tilt till both of your reference points are in sharp focus. Now you have the tilt right, but you still need focus spread and focus placement, so, using the same two focus points as above, find the focus spread, note the distance, place focus halfway between, choose the f-stop from the table (or stop down while watching the ground glass...) and make the shot. Now you have nice straight verticals!

Now let's complicate things a bit. Same scene except now you have a picket fence that is about 15 feet from the camera position (i.e., in the middle foreground); otherwise, the scene is the same. You can use the same two reference points for applying the tilt, so do that and apply the tilt. The PoSF lies in the scene exactly as before, the only thing different is that the fence is there. The PoSF intersects the fence somewhere between the top and bottom of the fence pickets. Now you go about finding focus spread in a similar manner as before, but now you've got the fence to consider. So find that "near" point at the top of the barn, but check the top of the pickets in the foreground too (they're above the PoSF too and qualify as "nearer" the camera than the PoSF. You may well find that you need to focus even longer to get the tops of the pickets in sharp focus. If so, then that position becomes your "near" instead of the top of the barn. Now find the "far" The spot where the ground meets the base of the barn should work here too unless you used a different near reference point (the ground was all sharp in the first example). So far so good, it's just that you have a bit greater focus spread in order to get enough DoF to get the tops of the fence pickets sharp enough. So use that new focus spread, position the focus halfway between it and use the new distance to choose a smaller f-stop from the table (or just stop down watching the ground glass - you'll have to stop down more in this case than before).

When you have a lot of objects in the foreground that are tall, at some point tilting has no more value. If, from your viewpoint, the fence reaches almost to the top of the barn, then tilting won't help at all. Just make the photo without movements. But, if the fence only covers half of the barn in the image, then tilting will likely enable you to stop down less.

Can I complicate things more? Let's take the above scenario with picket fence and barn. When I set up for such a shot, I recognize that either the top of the barn or the tops of the pickets will be the "near" point for both applying tilt and finding focus spread. So, to speed things up, I'll start by using the top of the pickets and the top of the barn as reference points to apply my tilt. Once I have my tilt applied, the PoSF lies in the scene touching those points; there's nothing "nearer" because nothing else lies above the PoSF. So now I've applied tilt and found my "near" focus point in one, easy, operation. Now I just need to find the far (ground at the base of the barn), note the focus spread and proceed as above. This is a handy shortcut.

A few words about applying tilt. Even with asymmetrical tilts like you have on your back standard, it is not as easy as it could be if you don't have a reference point for applying the tilt that neatly aligns with the tilt axis line. You've found that using front rise/fall to position a reference point on the axis line works as long as you haven't tilted the front standard. But even that has its limitations. The other option is to "guesstimate" where the focus should be, i.e., focus the axis line on "thin air" about where you think the PoSF should be by first focusing on something not in the PoSF and then tweaking focus by about how much you think is necessary. Then you tilt and see if you can get your reference points both in focus. If one comes into focus before the other, then find the tilt positions for the two reference points and then set the tilt halfway between. Both points will be out of focus then, so refocus and see if they both are sharp. If not, repeat the above with smaller changes and see if it's better. A couple of iterations should do the trick. With practice, this gets really fast.

With center axis tilts (think of them as "symmetrical tilts"), the method is the same. If you have a reference point on the center axis line, great. Use that and tilt till your other reference point(s) are sharp (I like three reference points when working with axis tilts, one in the center and one on each side). The same iterative approach works here if you can't get a reference point on the axis line.

With base tilts, the act of tilting refocused the camera (it changes the bellows draw because the whole standard moves in the direction of the tilt). In 90% of cases, we tilt the back backward or the front forward, so when applying base tilt, the bellows lengthens and the camera focus is closer. So, we have to refocus to compensate. Because the top of the standard moves farther than the bottom when using base tilts, the following procedure works best:

Find a couple of reference points, one near, one far. Now focus on whichever point is closest to the bottom of the ground glass. In 90% of cases this will be the far. (Everyone always says, "focus on the far; tilt for the near," but this is not really true - it should be "focus at the bottom of the ground glass; tilt for the top.") At any rate, once you've focused on that first point at the bottom of the ground glass, tilt slowly, while watching both reference points. The point at the bottom of the ground glass will go out of focus while the out-of-focus point at the top of the ground glass will start to get sharper. Go slow. (I don't use a loupe doing this, but I do like my 3-diopter reading glasses.) Tilt till both points are equally unsharp. It's important that you don't overshoot; in other words don't go past the point where the reference point at the top of the ground glass comes into focus and starts getting blurry again. (And remember, top of the ground glass is the bottom of the scene, right?). When both points are equally out-of-focus, lock down the tilt, refocus on your initial point,and then check the other with the loupe. If your lucky (or practiced), both points will be in sharp focus. If not, you need to tilt a tiny (really tiny) bit more. If you didn't go past focus on the reference point at the top of the ground glass, tilt that tiny bit in the same direction. (If that ends up making things worse, you did overshoot the focus when you tilted - start over). Repeat till both points are sharp enough.

And remember, the point of applying tilt is to be able to use a larger aperture to get the desired DoF. It doesn't have to be perfect. If you can make the shot in the f/22 - f/32 range, then it's way good enough. Just remember to check all the possible candidates for focus points when determining the focus spread.

Better now?

Doremus

 

[Chuck_P]

I did this practice exposure on Saturday for a front tilt and focus spread exercise as I was trying to put into practice this focus spread idea utilizing a tilted focus plane. It's not the best example, it was a windy day and the 1/2 sec exposure does not help the example, anyway..............The yellow line (I had to free-hand it with the mouse) represents the tilted PoSF from the foreground stick to the top of the white pine tree behind the redbuds.....perhaps not the best plane because, it really left me without anything above the PoSF to use for a "far" focal point, if I understand Doremus correctly....that the focus spread needs to come from distances on the GG that are above and below the PoSF. The ladder, pre-exposure, was not in focus but I did have the top of the tree and the stick in sharp focus. The two red dots are the locations for the near and far focal points for determining the focus spread. I used the barn behind the white pines as the far point, even though it was below the PoSF. So I found the spread by using, I guess, two points below the PoSF. The spread was 3mm and I then moved the front standard to the halfway position of that spread. The aperture indicated was 32.2.....I had to use a 2x filter factor for the #21 orange filter, therefore, requiring the 1/2 exposure rather than a 1/4 sec.

I hope it is somewhat correct relative to Doremus' explanations.

 

[Doremus Scudder]

Chuck,

You're most of the way there. You need to realize that when you set tilt, as you did in your example, with nothing more "above" the PoSF, that you have already found the "near" point for determining focus spread. So, the top of the near stick and top of the distant tree become your "near" and your focus is already set there, since you've just finished using those points to apply the tilt. All you have to do then is find the "far" (which will be below the PoSF). This is a trick I use often to streamline the process a bit. By choosing two points below the PoSF, you're really not finding the "near."

Next time, set up and apply tilt just as you have here, but then realize you're already focused on the "near" and note that position for determining focus spread. Then find the far, realizing that it will be below the tilted PoSF and might be physically close to the camera position.

Hope this helps,

Doremus

 

[Alan Edward Klein]

Thanks Doremus. I have to admit it's difficult for me to see all these details. A couple of questions. Does the relocation of halfway to refocus actually move the focus 1/3 into the picture to get the DOF?

When you tilt you're bascially extending the bellows in only parts of the picture. So, there's more room for light to travel to parts of the film. Doesn't that cause falloff in the film in those areas?

 

[Doremus Scudder]

Thanks Doremus. I have to admit it's difficult for me to see all these details. A couple of questions. Does the relocation of halfway to refocus actually move the focus 1/3 into the picture to get the DOF?

When you tilt you're bascially extending the bellows in only parts of the picture. So, there's more room for light to travel to parts of the film. Doesn't that cause falloff in the film in those areas?

The placing of the focus on the camera bed/rail halfway between the extremes of the focus spread places the PoSF in the optimum position, so that the extremes are both within (although at the edge) of the DoF. (The 1/3-2/3 DoF thing is an inaccuracy; it really doesn't help to think of it that way - see my response to you in another thread).

The amount of falloff caused by tilt is usually insignificant, but with extreme movements can be noticeable. Err on the side of overexposure a bit and dodge those areas back (or burn the other side in) if this is an issue. Usually it only crops up in close-up work.

Doremus

 

[Chuck_P]

Hope this helps

It does, I can see it exactly now in my mind...............at the time I did not consider the "near" to be both the top of stick and the top of the tree, but it makes perfect sense that it has to be when there is nothing else to focus on that is above that plane......at the time I was thinking it was just the stick and that the stick itself was "below" the PoSF.

This sounds confusing but I have been going over in my mind my actions............After establishing the tilt, I noted the number on the bed, it was at 60mm, I wrote it down. Then I twittled with the focus knob ......while looking at the stick (because I was thinking I was focusing on the "near" for the first focal point to establish the spread)......looked at the mm scale again, it still said 60mm (I think this is where the bulb should've lit over my head but it didn't)......so that has to be the "near", I just did not see it that way at the time. I then focused on the base of the barn (which I knew was below the PoSF) behind the white pines, looked at the mm scale again, and it said 57mm, I wrote it down. I was thinking that I had two points below the PoSF, when in actuality, I had one point above, or perhaps more accurately, equal to the PoSF, that I did not realize at the time, was actually the "near" point. Then I moved the front standard to halfway between, what I thought at the time, was two focal points below the PoSF, when one was below and the other was actually above, or at the PoSF.

So it feels like I did it correctly without realizing that I did it correctly.

 

[Axelwik]

Thanks Doremus. I have to admit it's difficult for me to see all these details. A couple of questions. Does the relocation of halfway to refocus actually move the focus 1/3 into the picture to get the DOF?

When you tilt you're bascially extending the bellows in only parts of the picture. So, there's more room for light to travel to parts of the film. Doesn't that cause falloff in the film in those areas?

Think of it this way:

- You probably know that the lens projects a cone of light toward the film, and at some point within that cone of light there will be a flat plane of focus at infinity which is perpendicular to the lens axis and parallel to the film. This plane of infinity focus within the cone of light will be one lens focal length away from the optical center of the lens. So for example with a 90mm lens that plane of focus at infinity will be around 90mm away from the lens board.

- If that flat plane coincides with the entire sheet of film, the entire image is focused at infinity. Every camera with a focus control can do this.

- You probably (hopefully) know that to focus on nearer objects than infinity, the lens is moved further away from the film. Inversely, focusing on further objects moves the lens closer to the film, up to the point of being focused at infinity.

- If you tilt the lens downward, that flat plane of focus is also tilted. Now for example, if you re-focus so that the upper part of the image (bottom of the ground glass, say - mountains in the distance) is focused at infinity, then that infinity plane of focus on all other parts of the image except the mountains, is further away from the film. Because the other parts of the image are further away than the infinity plane of focus, they're focused closer than infinity. This is called tilting the plane of focus. You've created a plane of focus that is now tilted so that it's no longer parallel to the film. It's still a flat plane of focus, but now it's tilted so one end the image is focused at a further point and the other end is focused at a closer point.

- With some trial and error and practice, one can adjust the tilt and focus until the grass at one's feet, the mountains in the distance, and everything in between are in perfect focus without stopping down, assuming that the ground is relatively flat all the way to the mountains. Remember, this is NOT depth of field, it's the actual alteration of where you want the plane of focus to intersect the image.

- The same applies to swinging the lens and both swinging and tilting the lens at the same time to put that plane of focus at an oblique angle. This also applies to swinging and tilting the back.

- This works at infinity and also at any distance closer than infinity.

- To tilt the lens, the lens has to have an image circle (the cone of light) larger in diameter than the diagonal format of the film. If it doesn't, the only option would be to tilt the back, fall the lens, or raise the back until the image circle covers the film.

- There will always be light fall off toward the edges of the image circle, but it is more apparent with shorter lenses. This is why center filters are used with extremely short lenses.

 

[Kilgallb]

You can also tilt to put things out of focus. There is a famous photo of the Eiffel Tower with the tower in focus and the model much closer to the camera all in focus but everything else out of focus. Creativity!