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.