How to test macro lenses?

[hacked - darinwc]

Do any of you test your macro lenses?
What do you use as a target?
A coin? A fairy model?
A miniature brick wall?

I've heard it said that macro lenses are best at full aperture. What about normal lenses used for macro? What about reversed lenses?

 

[Dan Fromm]

darin, when I was testing macro lenses (mainly for work above 1:1) quite extensively I ran two sorts of tests.

First off, I did acceptance testing. I shot a 100 tick marks/mm Olympus stage micrometer at lens-appropriate magnifications -- typically lowest supposedly usable, mid-range, and highest -- at wide open and one stop down. I used flash illumination to reduce vibration's effects and an eyepiece magnifier to get better focusing. The point of this test was to see whether a lens could resolve features 10 microns apart -- that was my go/no go criterion -- and, by measuring the widths of the tick marks' images on the b/w negative, how well the lens did. I used a stereo microscope, looked at the negs at 40x, used an eyepiece reticle to measure the bars' widths. Narrower was better. The results were reproducible. Either the lens separated the marks or it didn't. Rough rankings were possible within the group that separated the marks.

Secondly, after my friend Charlie Barringer bought a USAF 1951 on glass target from Edmund, I used it. This time to estimate the closest features the lens could separate. I shot some film, then looked at images on the gg. Images on the gg were as informative as images on b/w negatives so I switched to just looking. Again, the results were reproducible.

If you want to know whether a lens is good enough for your purposes, simple acceptance testing with the subjects you want to shoot may be good enough. Sharper lenses will put more fine detail on the negative. This requires a subject with a range of spacings between features. I've seen people do this with coins, banknotes and printed circuit boards. This is fine for the narrow ranges of resolutions those targets give but won't in general tell you how fine a lens can cut.

The only way to find out which aperture gives best sharpness in the plane of best focus is to shoot a target with a range of scales at a range of magnifications. The answer is lens-specific. I know that my Luminars are best wide open because I've tested. Internet scuttlebut be damned, I put the question to my lenses. And that's why I know that a reversed 55/2.8 MicroNikkor AIS is better at f/4 than at f/2.8 or f/5.6 above 1:1. I asked the question. Similarly, I know that the Tominons I no longer have must be stopped down a little to get best image quality.

The best aperture can vary with magnification. My 55/2.8 MicroNikkor AIS gives better image quality -- front to back of DoF -- around f/8 at magnifications below 1:1. You can't assume anything, you have to test.

Test procedures are the same for all lenses regardless of orientation. I've tried out Charlie's 100/6.3 Luminars, which have mounting threads at both ends, in both orientations at a range of magnifications. My 100/6.3 Luminar, the $25 find of the week, was a dog. Charlies' were good, but no better than my 100/6.3 Neupolar or 90/6.3 Mikrotar.

 

[hacked - darinwc]

• Thanks Dan I had forgotten that you have done extensive testing.

I like to test my lenses in a controlled environment. (That same subject, a sign across the street) I am not a pixel peeper, but I like to know how my tools actually work.
I've found out some interesting things. For instance, my super angulon. I i had some ok results and some horrible result s with it. When I actually tested it, I discovered it really was bad, it wasn't me. Turns out, the lens was in a shutter with the wrong spacing. (A Seiko that was a bit thicker than a standard copal)

I like the idea of using a dollar bill as a target. I will try that first.

Do you use your graflex cameras for all your macros or do you also use a35mm with a bellows or tubes?

 

[Dan Fromm]

I've done nearly all of my closeup and macro work with 35 mm and digital SLRs.

The Graphics are too slow working for most flower photography and are impossible for insects and other mobile subjects. Wind is a huge problem with most, not all, flowers. By the time I've finished the "focus; compose; insert film holder; close and cock front shutter; stop lens down to shooting aperture; withdraw dark slide" process the bloom will have shifted enough to move the plane of best focus and change the composition. Some cacti are exceptions.

I've also backed away from my original plan to use the Graphics to photograph fine details of preserved specimens. In general I haven't needed the magnification that 2x3 allows. At 5:1, something couple or six mm long fits 24 x 36 very well.

Before you waste film shooting banknotes, look at them TTL. I'm not sure their fine detail is what you need.

 

[Dan Fromm]

Darin, forgive me for being slow. What are you trying to accomplish photographically? Which lenses are you considering using?

 

[mdarnton]

I do quite a bit of work--say 90% of my photography these days--with macro lenses in critical archiving of stuff that is basically flat, and have a couple of comments here regarding that very-revealing type of work:

If you are expecting to test to the corners, what you get will be more of a test of your ability to set up things parallel rather than the lens' ability. For critical focus, you can forget about depth of field covering your errors: parallelism needs to be spot on.

At normal, non-macro distances, most macro lenses have very short focus throw combined with negligible depth of REAL focus, which will limit your focus ability severely, which will consequently affect your perception of the lens' quality. Shooting at eight feet with my 105/4 Micro-Nikkor, I find it best to shoot a range of shots twitching the focus on each, picking the in-focus one from the resulting images, because I literally cannot focus the thing perfectly by eye, and my camera's auto-focus indicator doesn't do that great of a job, either. I'd estimate that at that distance with that lens at f/11, if focus is off by a half-inch, you can see it in seriously-degraded results.

That said, my most critical work is copying negatives digitally, around 1:2. Doing that, once parallelism is assured, the differences between stops in the lens' performance are real and quite large. For my 55-60mm Micro-Nikkors (I have three), f/7.1 gives the best results, and things get hopeless quite quickly when you stray too far from that. I also have a 63mm/3.5 Nikkor, which is a better lens at 1:2 and does best at f/11, so I don't use the Micro-Nikkors for this anymore, even though they did great. These differences pop up quite quickly if you do a series of very controlled tests.

If you're shooting something like flowers, that's a whole different situation compared with shooting flat things in the studio: flatness of field doesn't matter, focus moving a couple of mm doesn't matter, corners don't matter, and most of the subject will be out of the range of depth of focus, anyway. In that kind of situation, I don't think I'd worry about the quality of the lens at all, and I imagine that doing such work I would very quickly sacrifice ultimate sharpness in a very thin field in favor of more depth of field. Testing your real situation will be the ONLY way you will be able to decide for yourself what sacrifices are important or not to YOU.

 

[Jim Jones]

In the early 1970s I bought a microfiche Bible from Edmund Scientific similar to one now listed as unavailable on Amazon.com to use as a lens test target. As I recall, the entire Bible was reproduced on a chip about 2 inches square. Several years ago a similar product was again available online. In that application, the microfiche was placed in the normal focal plane of the lens and its image projected onto a fairly large screen for quick and crude analysis. Shortcomings in lenses were immediately apparent, but accurate comparison between lenses was difficult. If these items are now available, they would be useful for basic micro- and macro-lens testing A quick Google search revealed none for sale now, which may have been due to my inept Googling.

 

[Diapositivo]

A nice mail stamp (choose a special, commemorative one, not the plain ones) is usually a good subject for this kind of work. It contains fine detail all over, and allow you to test planarity of field as well.
A banknote would give you areas of high detail are often "monochromatic" and you have to choose a region of fine detail.

Usually the best corrected lens for flat subjects are those especially designed for bellows use, such as the Minolta Rokkor 100mm - f/4. For decent volumes of document reproduction I would consider the purchase of a bellows and such a lens. They are marked "bellows" as they have no elicoid and need a bellow for focusing. They are supposed to be superior to "normal" macro lens because they are conceived with a special attention to planarity of field and quality at the border of the image.

 

[hacked - darinwc]

All good information.
Dan: I dont know if I am going to go into full-on micrography. Most of the objects I will be photographing will be 2x2 inches up to 8x8 inches. They are 3d, not flat objects. So some depth of field is needed.
I have some macro lenses for 35mm -Nikkor 55mm f2.8, Zuiko 50mm f2, Tamron 90mm f2.5.

I can use 35mm film but I have been toying with the idea of using 4x5.
I dont have any macro lenses for 4x5.. but I am not sure if I need them if I shoot them at 1:1.
I have a Rodenstock Ysarex 127mm, Fujinon W 135mm, G-Claron 210mm. (I only have 300mm bellows draw, so the g-claron may be out.) I may have an old chrome barreled componon I could mount in a #0 shutter.

 

[Dan Fromm]

Darin, all of your macro lenses for 35 mm are, if in good condition, much much better than good enough for what you want to do. If you use 35 mm, you'll be shooting your subjects at magnifications ranging from 1:2 to 1:16. Use the lens that you're most comfortable with and examine the negs to see whether they contain the fine detail you need. That's really what matters.

If I were you I'd pick a macro lens for 35 mm and shoot test shots of smallest and largest subjects at a range of apertures from wide open to f/22 (set). Then I'd look at the negs to see whether they've captured as much of the fine detail as needed. Without knowing how deep your subjects are its hard to be sure, but I expect that what you want to do will turn out to be impossible. Compromises will be necessary.

I don't know how deep y'r subjects are, do know that you're probably not going to be able to get much DoF no matter what you do. At near distances DoF is symmetrical about the plane of best focus. Use it wisely. How far you can stop down depends on how large you want to print. In my experience, f/16 @ 1:2 (effective aperture f/32) is too small even though lighting considerations have often forced me to use it.

If you want to use 4x5, the G-Claron is your best bet. It will do just fine with your largest subject, will do no worse than 35 mm (if you use the same emulsion in 35 mm and 4x5) with your smallest.

If you want good image quality in depth and your subjects are static, digital image stacking is the way to go. Sorry, folks, but that's reality. Digital gear with image processing software does some things better than film.

 

[ic-racer]

You effective aperture will be a function of your magnification. Your level of diffraction will be a function of your effective aperture.

 

[hacked - darinwc]

Ah yes.. I was aware of the extension factor for effective aperture. I did not think of the difraction due to the reduced effective aperture. Is that why lenses used for macro are 'best' at full aperture?

 

[Dan Fromm]

Ah yes.. I was aware of the extension factor for effective aperture. I did not think of the difraction due to the reduced effective aperture. Is that why lenses used for macro are 'best' at full aperture?

Another Internet canard. It depends on the lens. Y'r macro lenses for 35 mm are all better stopped down somewhat than wide open. The "macro" lenses I've tried out that are best wide open are all for photomacrography, i.e., work at magnifications greater than 1:1.

About effective aperture and all that. It can be a killer. For a variety of reasons I've chosen to take many flower shots at f/16 set, f/32 effective. They're not very enlargeable. My bad.

Why don't you stop asking questions that no one can answer for you and start shooting?