Some help with the Scheimpflug Rule

[Chuck_P]

I have done some forum searches and did find a fairly good discussion about focusing the view camera. But, the "focusing" scenario I am having touble with is not answered.

Scenario:
I have my camera set up in the back yard and have set up a "receeding foreground" situation for which I have not been able to achieve focus. I have simply snaked the garden hose away from the camera in a receeding fashion along the ground. The most favorable composition is with the camera pointed downward (there are no verticle/horizontal planes for convergence to be a concern, these scenarios are the simplest, I have found).

Questions:
1. Is this subject situation referred to as being "planar"?

2. Clarify the Scheimpflug Rule please. I have tried to use it to achieve focus, but I must be doing something wrong. The rule seems simple to apply in this situation.

3. Am I supposed to be able to achieve focus in this scenario wide open or must I focus at shooting aperture? (some text examples I have say that this can be accomplished at wide apertures, but I feel it is mostly for wide angle lenses, perhaps not the moderate telephoto quality of the 210). Does anyone ever focus at shooting aperture?

- near point on the ground at the top of the ground glass is 9 ft. from the film plane

- far point on the ground at bottome of the ground glass is 34 ft. from the film plane.

I want sharpness from the top to bottom of the ground glass; shouldn't that be possible?. It seems fairly straight forward but I'm not achieving it. Perhaps I am achieving it and can't tell because, at the moment, I have no loup to rest on the ground glass, just a simple lens I am holding from my eye while trying to examine the ground glass. To add to the difficlulty, I am using a dark colored towel for a focusing hood because my "Black Jacket" 4x5 hood is not here yet.

4. Is this right? With all movements in the "zero" position", I brought the very bottom edge of the ground glass in focus and then tilted the camera back toward me to try and bring the top of the ground glass in focus. Since the camera is already tilted downward, effectively creating front lens tilt, I have tried to get focus by returing the camera back to verticle (and I also tried some additional front lens manipulation, but no good). It certainly will not come into focus at full aperture, but it does look better stopping down to f/32 but too dark to tell clearly.

Thanks for any help. I tried to think these questions out clearly, so I hope they make sense? I've really learned alot on my own in the short time that I have had the camera.

Chuck

 

[Lopaka]

Ok, it's been a while since I've done this stuff, but here goes.

What you are searching for may be called the plane of critical focus. When you have achieved it, everything on this plane will be sharp at the widest aperture. The Scheimpflug effect is that the plane of the film, the plane of the lens and the subject plane, if extended will all intersect at the same point. The thing to remember is this - the rear standard movements will affect both focus and perspective. The front standard movements will affect both focus and perspective. But the rear standard will have more effect on perspective than the front and the front will have more effect on focus than the rear. Setting the focus plane is then done primarily by tilting the lens. It should be noted also, that the depth of field from a receding focus plane of this type will be greater at the far end then at the near end.

It does take a little fussing to get the hang of it. Keep working at it, and good luck!

Bob

 

[Peter De Smidt]

To get the ground in focus, you have to either tilt the lens forward or tilt the rear back.

If you have center tilts, first focus on something in the middle of the picture. Now tilt until the foreground is sharp. Is the back also sharp? If not, you'll have to move focus a bit. Try to move it such that the foreground and back are equally sharp, and then adjust tilt again.

If you have base tilts, then when you tilt the lens forward or rear back, then you are increasing the the distance focused upon. As a result, you'll have to move the standards closer together. So focus on something in the middle of what you want the plane of sharp focus to be. Now slowly tilt the rear standard back and move focus in slightly at the same time, trying to keep the origianal point in focus the whole time. Eventually, the foreground will also be in focus. You will probably have to adjust focus and tilt a little.

If you want to keep the back plumb, I still start by moving the back because it's easier to reach. Find the angle of back tilt needed. Then plumb the back. Add the same degree of front forward tilt to the front standard. Adjust if necessary.

Hope that helps.

 

[Alex Hawley]

It does take a little fussing to get the hang of it. Keep working at it, and good luck!

That's about the sum of it. The only part of the Scheimpflug theory I keep in mind is that the two standards need some divergence from each other to move the focus plane to a point in line with or behind the ground glass. Other than that, what you see on the ground glass is what you get on film.

Most of the time, focus can be achieved with the lens wide open but sometimes it can't. So when I get tired of fiddling with the movements, I stop down until everything comes in, then go on down to at least f/22 or f/32 or more just for the DOF.

 

[MurrayMinchin]

Quick and dirty; focus on the far and tilt (the lens board) for the near.

Once you get things in focus step to the side of the camera. Imagine lines coming down to the ground along the same angles as the lensboard and ground glass...they should cross each other at the ground (if that's what you are focusing on). That there's yer shympfloog rule

Murray

 

[photographs42]

Chuck,
1. Yes, I would think that is correct in that the subject is a flat plane.
2. I think you understand the rule.
3. Yes, and it has nothing to do with focal length, and no, focus wide open. This is simple but you need to develop a feel for it. You should be able to achieve focus on the entire hose.
4. The type of camera has a little to do with how you achieve it but the result should be the same. Most people have a hard time figuring out that a little movement goes a long way. To get an idea of how much movement is required, focus on the nearest point with the film plane and lens plane parallel. Mark the location of the moving part (front or rear) and then focus on the farthest point. The distance between those two points is the amount that the film plane needs to be out of parallel with the lens plane. You will probably find it to be less than you expected.

Anything that makes the image on the GG stand out enough for you to see it is OK for a dark cloth but a loupe is a little different. If your GG has a grid on it, the grid should be in focus under the viewing glass or loupe if it is focusing on the proper point. If you are holding a viewing lens as you say, it could be focusing on anything and that could be your problem. If you don’t have a grid, it might help to put a couple of light pencil marks on the etched surface of the GG (they can be washed off or erased later) Don’t do this if you have some exotic type of GG. A good loupe is great but if you’re on a budget, a decent 4x model is relatively cheap.

You don’t have to do this in the back yard BTW. You can practice on the floor or a table. Put a ruler or a yardstick down and you should get a good idea working with that.
Good luck!
Jerome

 

[Steve Smith]

From what I can remember, the Scheimpflug rule has to be used in conjunction with the hinge rule in order to work out the plane of focus.

Sheimpflug gives one point and hinge gives another. A straight line through these two points gives the focus plane.

I found these links helpful:

http://www.trenholm.org/hmmerk/HMbooks4.html
http://www.trenholm.org/hmmerk/HMbooks3.html#SRpic
http://www.trenholm.org/hmmerk/index.html#SRpicR


Steve.

 

[Roger Hicks]

Think of it as points, not planes. The GG must be a certain distance from the lens in order to focus on a distant point. and further from it to focus on a closer point. As the image is upside-down, this means that in the example you give, the top is further from the lens-board than the bottom.

Everything on a line between the two points will be in focus. If no swings are employed, this means that in the example you gave, you have a plane of focus parallel with the ground.

Front tilts affect focus but not image shape; rear tilts affect focus and image shape.

Now consider a receding wall, and you can do the same in the vertical plane with swings.

Combine tilts and swings and your plane of focus can be quite hard to visualize: lower left-hand corner of the scene (close) to upper right-hand (distant), perhaps.

At first it's wasy to get everything backwards, but with practice, it become almost instinctive and you stop worrying about asymmetric tilts, on-axis movements, and everything else -- though some cameras remain easier to use than others.

Hope this helps,

Cheers,

Roger (www.rogerandfrances.com)

 

[eddym]

To all the above good advice I would only add: be careful that you do not run out of lens coverage.

 

[Chuck_P]

Thanks for the replies. I set up the situation again and actually did achieve crisp focus from top to bottom on the GG. The only thing I did different was give the camera a bit steeper tilt so that my receeding distance on the ground was not so long. I only had to use just a minimal of back tilt to get the focus.

Thanks again

 

[Len Middleton]

One other little addition is to watch for vertical objects in foreground or midground of the composition as parts of them may be out of focus. Assuming a front tilt, being vertical only part of the object will be in sharp focus.

That may require a little stopping down to compensate.

And of course I know that as I got caught on it a couple of times.

Len