Focussing close ups

[Pete H]

Yesterday was the first time I've tried close up (1:1) shooting with a 5x4. The subject: that old favourite, calla lilies. The image was extremely bright on the gg but I found it very difficult to judge focus because there are no hard edges on the flowers. I've shot plenty of 6x4.5 macro and found this problem at worst a moderate inconvenience. Does anyone have suggestions ?

 

[Dave Miller]

With still life studio close-ups it is usually possible to set up a test target (s) at the extreme focus points, focus, and then remove the target before the exposure is made. Somewhat harder on location, but still possible.

 

[Donald Miller]

As Dave mentioned, if you can focus on some facet of the flowers that give you a point of sharp focus. If that is not possible something like a ruler inserted into the scene to focus on will help.

However focusing is only part of the problem when doing photography at distances nearer then infinity.

In working on 1 to 1 photography, it might be wise to be aware of the effects of bellows extension and depth of field. Depth of field is a factor of the lens focal length and since most 4X5 camera lenses are longer then equivalent medium format focal length lenses the depth of field will be diminished for a given aperture. As magnification with a given lens focal length is increased depth of field will decrease. That leads to very small apertures and this coupled with bellows extension factor will probably lead to relatively long exposures. These long exposures, if they exceed one second with most films, will introduce reciprocity compensations which will extend the exposure time even further.

Small apertures will probably bring one into considerations of diffraction. This will become increasingly apparent as the degree of enlargement is increased.

 

[Dan Fromm]

<snip>

In working on 1 to 1 photography, it might be wise to be aware of the effects of bellows extension and depth of field. Depth of field is a factor of the lens focal length and since most 4X5 camera lenses are longer then equivalent medium format focal length lenses the depth of field will be diminished for a given aperture. <snip>

Donald, depth of field is controlled by magnification and relative aperture. Focal length doesn't enter.

I went up in format from 35 mm because I was frustrated with my flower shots. I couldn't capture fine detail in the main subject AND show its surroundings. With a larger piece of film I can accomplish both, but am often tempted to take the same old shot (frame filled with main subject) but bigger, i.e., at higher magnification. Then there's less DOF given aperture. Perhaps that's what you're thinking of.

 

[David A. Goldfarb]

Adjust the light so that you've got some texture to focus on with a loupe.

One thing that can make LF macros hard to focus is focusing with the front standard. Try focusing with the rear standard, use a macro focusing rail to move the whole camera (Linhof makes one for LF--usually around $100-150 used), or just move the thing you're photographing until it is in focus.

 

[Donald Miller]

Donald, depth of field is controlled by magnification and relative aperture. Focal length doesn't enter.

I went up in format from 35 mm because I was frustrated with my flower shots. I couldn't capture fine detail in the main subject AND show its surroundings. With a larger piece of film I can accomplish both, but am often tempted to take the same old shot (frame filled with main subject) but bigger, i.e., at higher magnification. Then there's less DOF given aperture. Perhaps that's what you're thinking of.

I will extend to you the respect to your viewpoint. However I tend to disagree. Taking the following example of a 300 mm lens and 16 mm lens in 35 mm the 300 mm lens will have markedly less depth of field at a given aperture then the 16 mm lens at the same aperture.

My 450 Nikkor M on 12X20 has less depth of field then my 90 mm Schneider Super Angulon on 4X5 at the same aperture. Recognizing that aperture is a function of aperture opening/focal length of the lens. The same 450 mm Nikkor M has aproximately the same aspect ration on 8X10 as my 210 mm Schneider Symmar on 4X5 yet the 450 mm Nikkor has less depth of field at any equivalent aperture then the shorter focal length lens.


Now you can say that this is because the longer focal length lens affords greater magnification but this is true of any longer focal length lens. (They include more of a given portion of the scene at the exclusion of other portions.) I tend to describe this characteristic as less depth of field for a longer focal length lens. Since it is normal for a larger format to use increasingly longer focal length lenses the effect becomes more pronounced with large format cameras then it does with 35 mm or medium format.

 

[David A. Goldfarb]

At greater distances DOF depends in part on focal length as Donald Miller suggests, but in the macro range for a given format, DOF can be calculated on the basis of magnification and nominal aperture alone regardless of focal length as Dan Fromm suggests, out to several significant figures. In other words, at magnifications of about 1:5 and higher, DOF is effectively the same for any lens at a given aperture and magnification for a given format.

 

[photobackpacker]

This is a very interesting thread to me. As I have gained experience and confidence with my 4X5, I have found myself brushing up against the DOF limits.

I have always used the Near-Far focus measure to gauge critical DOF aperture. It has yielded wonderful results and great predictability. Lately, however, I have found myself confronted with situations where I had no choice but to move back and crop the image on the enlarger. This was caused by situations where the plane of focus did not lend itself to swings and tilts.

As I tried repeatedly to get the shot without relying on cropping, I tried switching to wider-angle lenses, moving through a progression from the 210, 150, 90, and finally a 65. I found that when I recomposed the image on the GG, I was right back to where I had started with Near-Far differences exceeding 7mm. Empirically, it seamed that there was a slight improvement - I was closer to getting into the critical focus range but not close enough. Of course, I was already in the region where diffusion was going to be a factor.

The more I learn - the more I realize how much I have to learn.

 

[Dan Fromm]

I will extend to you the respect to your viewpoint. However I tend to disagree. Taking the following example of a 300 mm lens and 16 mm lens in 35 mm the 300 mm lens will have markedly less depth of field at a given aperture then the 16 mm lens at the same aperture.

My 450 Nikkor M on 12X20 has less depth of field then my 90 mm Schneider Super Angulon on 4X5 at the same aperture. Recognizing that aperture is a function of aperture opening/focal length of the lens. The same 450 mm Nikkor M has aproximately the same aspect ration on 8X10 as my 210 mm Schneider Symmar on 4X5 yet the 450 mm Nikkor has less depth of field at any equivalent aperture then the shorter focal length lens.


Now you can say that this is because the longer focal length lens affords greater magnification but this is true of any longer focal length lens. (They include more of a given portion of the scene at the exclusion of other portions.) I tend to describe this characteristic as less depth of field for a longer focal length lens. Since it is normal for a larger format to use increasingly longer focal length lenses the effect becomes more pronounced with large format cameras then it does with 35 mm or medium format.

Donald, reread what I wrote. AT THE SAME MAGNIFICATION AND RELATIVE APERTURE ALL LENSES PRODUCE THE SAME DEPTH OF FIELD.

You are comparing apples and pineapples. At the same subject to film distance, a shorter lens gives lower magnification than a longer lens, hence more DOF at the same relative aperture. That's what you assert. That is true, but has nothing to do with working at the same magnification or with photomacrography.

 

[David A. Goldfarb]

Dan, what you are saying is true in the macro range, but just for accuracy's sake, it's not true as the focal point approaches infinity. At a magnification of around 1:1 or even 1:5 and pretty much at 1:10 all lenses of all focal lengths have effectively (i.e., calculated out to four significant figures) the same DOF on the same format and at the same aperture. So why use a longer lens for macro if possible?--more working distance for lighting. Why use a shorter lens?--not enough bellows for a longer lens at the desired magnification.

However, if the magnification ratio is small, like 1:100 or 1:2000, it is true that a wider lens has more DOF than a longer lens at the same aperture and for the same magnification.

 

[Dan Fromm]

Dan, what you are saying is true in the macro range, but just for accuracy's sake, it's not true as the focal point approaches infinity. At a magnification of around 1:1 or even 1:5 and pretty much at 1:10 all lenses of all focal lengths have effectively (i.e., calculated out to four significant figures) the same DOF on the same format and at the same aperture. So why use a longer lens for macro if possible?--more working distance for lighting. Why use a shorter lens?--not enough bellows for a longer lens at the desired magnification.

However, if the magnification ratio is small, like 1:100 or 1:2000, it is true that a wider lens has more DOF than a longer lens at the same aperture and for the same magnification.

David, what you say is true and well known. That said, its practical significance is small.

For those of you who aren't clear on what we're discussing, the question is whether shooting a distant scene with a long lens and enlarging less or shooting the same distant scene with a short lens and enlarging more will give more DOF in the final print, with the final prints showing the same scene. As David wrote, using a short lens and enlarging more will indeed give more DOF in the final print, but there's a snag. The snag has to do with how much enlargement the negative will allow before acceptable image quality in the print is lost.

In practice, shooting with a short lens and enlarging a lot is not a kind of free lunch. If it were, we'd all shoot the shortest lens that covers with the movements we need and then enlarge as needed.

Choice of focal length for closeup work is driven, in my experience, by the need for working distance. There's a conflict between working distance and the extension needed to get it, and longer lenses tend to be larger and heavier too, so we rarely use really long lenses for closeup work. For magnifications above 1:1, it seems that lenses much longer than 100 mm are rarely used.

Also in my experience, different subjects can tolerate different working distances. For example, I sometimes shoot small parts of little fish. Dead fish, in alcohol to control specular reflections. My shortest lens, a 17/4 Tominon would be ideal for this, but I'm reluctant to risk wetting it, so I use a somewhat longer lens in that situation. For another example, those of us who shoot insects and such out-of-doors with SLRs try to use the longest lens we can manage. Skittish subjects that can get away don't like having a lens in the face. Same goes for fish in aquaria. Side point, an SLR is a much better tool for shooting mobile subjects closeup than is, say, a view camera.

Finally, the kinds of portable flash rigs I like to cobble up are problematic with my flashes (not powerful enough) and long lenses. Basically, when shooting closeup I compromise and generally can't quite win.

 

[Donald Miller]

quote: "For those of you who aren't clear on what we're discussing, the question is whether shooting a distant scene with a long lens and enlarging less or shooting the same distant scene with a short lens and enlarging more will give more DOF in the final print, with the final prints showing the same scene. As David wrote, using a short lens and enlarging more will indeed give more DOF in the final print, but there's a snag. The snag has to do with how much enlargement the negative will allow before acceptable image quality in the print is lost."

Perhaps I am not the only one who is confusing matters. (I believe that oranges and pineapples were mentioned.) I don't find any mention made of enlarging or printing as I read this post until you interjected these factors...no mention made of degree of enlargement, depth of field in a print or any of the other issues that you seem to be interjecting at this point. Since degree of magnification by definition would include any and all departures from the actual image size as it exists in reality and represented on film, the fact still remains that at infinity focus a shorter focal length lens will give more depth of field then a longer focal length lens. This increased depth of field exists on the negative and not solely on the print as I understand you to be inferring. I disagree with your position that this is an insignificant matter especially when I have worked to gain depth of field from 6 ft to infinity with a 450 mm lens on 8X10 (yes that is negative size). This awareness is especially true when I compare the depth of field constraints of this longer lens to a shorter 159 mm lens on 8X10 and contact printed (you will notice that i make not mention to enlarging here).

"In practice, shooting with a short lens and enlarging a lot is not a kind of free lunch. If it were, we'd all shoot the shortest lens that covers with the movements we need and then enlarge as needed."

Once again you seem to be thinking from within the box of thought relating to enlarging. For a number of us, we do contact print large negatives. We use lenses that will allow us to maximize depth of field consistant with a composition of our choosing. Most of us don't even think of cropping a portion of the negative because enlarging doesn't enter our frame of reference. We work to move the camera to the best possible position in consideration of the object or scene to be photographed, the presentation that we wish to make and yes the focal length of the lens.

"Choice of focal length for closeup work is driven, in my experience, by the need for working distance. There's a conflict between working distance and the extension needed to get it, and longer lenses tend to be larger and heavier too, so we rarely use really long lenses for closeup work. For magnifications above 1:1, it seems that lenses much longer than 100 mm are rarely used."

I am wondering what format you are describing when you make the statement above. Are you talking about 35 mm or medium format? I wonder about this since you have a penchant to approach this from the standpoint of enlarging. While I have no basis to argue with your personal experience, I would go on to say that working distance is not the only consideration....nor is it the primary consideration in many cases. In the area of product photography, for instance, a 90 mm lens on 4X5 will give a totally different product presentation then a 210 mm lens. Looming distortion and foreshortening will be totally different between these two lenses. Sometimes a 90 mm lens will not allow adequate lighting controls to be employed. In those cases there are certainly images photographed with lenses that exceed 100 mm...certainly true with 4X5 and larger.

In consideration of your statement about maximum focal length rarely exceeding 100 mm, I will say that on my 8X10 with 28 inches of bellows extension a 159 mm lens will allow me magnification exceeding 2.0 On my 4X5 with 20 inches of bellows extension a 150 mm lens will allow magnification in excess of 1.5.

I can certainly understand your strongly stated position if you are drawing from the limited perspective of smaller formats...however that is not true of all of photography.

 

[Bob F.]

Pete, you may want to download and print the Quickdisc from: http://www.salzgeber.at/disc/ (if you have not done so already). Not only will this give you the correct adjustment for bellows extension but you can use it as Dave suggests and focus on the text on it...

Cheers, Bob.

 

[Dan Fromm]

Donald, thanks very much for disagreeing so strongly with me. You forced me to reconsider what I thought I believed.

I've done the arithmetic, using magic formulas lifted from http://www.dofmaster.com/dofjs.html . First off, my Excel spreadsheet doesn't give exactly the same answers their java machine does. I've checked, can't find what I'm doing wrong. In any case, the answers I get are close to theirs, but not exactly the same. And they're very interesting.

It turns out that you're right when the shorter lens' focused distance is around half its hyperfocal distance (depends on focal length, relative aperture, desired circle of confusion) and the longer lens' focused distance is well inside its hyperfocal distance, both lenses set up to capture the same scene. In this case the the shorter lens will indeed give more DOF than the longer one.

It turns out that I'm right when both lenses are focused at much less than half their hyperfocal distances and capture the same scene; then they give very nearly the same DOF. Yes, the shorter lens gives more, but not a lot more. For example, at f/22, CoC = 0.03 mm, a 300 mm lens focused at 30m gives DOF of 13.7m and a 600 mm lens focused at 60m gives DOF of 13.2m. I'm not sure 50 cm is a big deal in that situation.

None of this has to do with format. Its all about focal length.

As for use of long lenses for closeup work there are process lenses made for use at 1:1 at least as long as 2.5m. They can be used as high as 3:1. My tiny little cameras can't handle one of those monsters, and neither can yours.

The longest macro lenses sold for general photographic use are arond 200 mm, and most, if not all, have maximum recommended magnification of 1:1. The major exceptions are ~ 100 mm Luminar, Photar, Neupolar, all of which will go to around 8:1 with good image quality. There's close, and then there's really close. My tiny little cameras won't reach 8:1 with my 100 Neupolar, and neither will yours. There are limits, alas.

Cheers,

Dan