How to evaluate lenses?

studiocarter · Apr 9, 2015

I like 6x9 folders, old ones, uncoated, shooting black & white slow film. I saw a great improvement from a Nettar 6.3 to a Voigtlander 3.5 when sharpness extended to the edges and corners were no longer dark.
Now I have different Kodak Viglant six-20 cameras, Solinar, Anastigmat, and today I bought a Special with a Supermatic shutter.
How does one evaluate different lenses?
Brick walls? I shoot long city scenes, thousands of houses.

Dan Fromm · Apr 9, 2015

From my lens diary (available on line at Dead Link Removed

I check my lenses out informally but not that subjectively. My test target is a patch of lawn about
thirty feet from the camera, sometimes my back fence. I shoot them at the apertures at which I
expect to use a lens, f/11, f16, and sometimes f/22. I rate lenses on how well they separate blades
of grass or show wood grain in the fence and, especially for long ones, how well they resolve the
blades’ structure.
19
I try long lenses out by photographing the stop sign at the end of my street, somewhat more
than 200 m from my shooting position. There is a “Children Playing” sign about 15 m from the
stop sign. I check the image of the stop sign to see how sharp its edges and lettering are and check
the “Children Playing” sign for legibility of text. My goal is to identify lenses that perform poorly
at distance. The long lenses I get for my Graphics all have much more coverage than my little
2x3 cameras can use, so I hang them in front of a Nikon for testing and shoot on EB or EPP. This
economizes on film and processing, still allows comparison of the lenses’ central resolution.
My test procedures are not substitutes for formal resolution testing but are informative. Their
results are repeatable and allow me to sort lenses into “good enough” and “not good enough.”
Their goal is not to determine which lens is in any sense best, but to help me decide which lenses
not to use.

One advantage of using grass or the grain in our back fence as targets is that they give a range of spacing between features, let me see what level of detail is finer than the lenses tested can separate.

RalphLambrecht · Apr 9, 2015

studiocarter said:
I like 6x9 folders, old ones, uncoated, shooting black & white slow film. I saw a great improvement from a Nettar 6.3 to a Voigtlander 3.5 when sharpness extended to the edges and corners were no longer dark.
Now I have different Kodak Viglant six-20 cameras, Solinar, Anastigmat, and today I bought a Special with a Supermatic shutter.
How does one evaluate different lenses?
Brick walls? I shoot long city scenes, thousands of houses.

by shooting a scene that is representative of what is important to you. The only objective way is to compare MTF charts and they are almost impossible to get for the cameras you've mentioned

film_man · Apr 9, 2015

How to evaluate lenses? Shoot a roll of stuff you normally shoot, if you like the results you like them, if you don't you don't.

snapguy · Apr 9, 2015

Agreed

I agree with film_man. Shoot what you want to shoot and decide if you like the results. All else is folly.

Meyer Trioplan · Apr 9, 2015

Agreed with much of what is posted here. I'll typically try a roll of varying situations to start in which I try to accomplish the following in some combination:

A shot taken at the widest aperture.
A shot taken in the sweet range (11-16) of the aperture scale.
A shot taken stopped down to about the smallest aperture.
A shot taken at the near range of the focusing scale.
A shot taken at around the infinity range of the focusing scale.

Since I shoot a lot of color, I'll often use a known film to see how the lens portrays colors:
In bright overhead sunshine on a colorful scene.
Under overcast conditions (some portray clearly while others get muddy)
and a night time bulb exposure.

Meyer Trioplan · Apr 9, 2015

For what it's worth, my own results on 6x9 folders of varying lenses. With items of this vintage, you mileage may vary:

Agfa Agnar 105 f/6.3: Decent, but very prone to flaring and sharpness issues in the corners, as well as some pin-cushioning. Best shot around f/11.
Agfa Solinar 105 f/4.5: My copy seems to focus too closely, but when stopped down, it delivers some outstanding sharpness, and a nice light depth of field at wider settings.
Steinheil Cassar 105 f/3.8: Not a fan. Really poor sharpness even when stopped down, very noticeable vignetting.
Meyer Gorlitz Trioplan 100 f/4.5: Adore this lens (as my handle may imply), surprisingly sharp wide open and outstanding color rendition. Slightly contrasty.
Zeiss Novar 105 f/3.5: Also an outstanding lens with some great sharpness and color fidelity for a triplet. A little less contrast than the Trioplan.
Zeiss Tessar Opton 105 f/3.5: Had lots of issues on this on my first outing, some of which was camera related, but on the second try, I'm very impressed by how it renders scenes at even wide apertures. Some of the best contrast I've seen.

Dali · Apr 9, 2015

studiocarter said:
I like 6x9 folders, old ones, uncoated, shooting black & white slow film. I saw a great improvement from a Nettar 6.3 to a Voigtlander 3.5 when sharpness extended to the edges and corners were no longer dark.
Now I have different Kodak Viglant six-20 cameras, Solinar, Anastigmat, and today I bought a Special with a Supermatic shutter.
How does one evaluate different lenses?
Brick walls? I shoot long city scenes, thousands of houses.

Evaluating lenses is not enough especially for 6x9 format. The way the camera back hold the film in place is more important than the instrinsic optical virtues of the lens. Too, 120 film is not the perfect medium for such test: thickness differences between brands and flatness issue play against you. And I doubt your camera can take 220 film...

Like others, get out and shoot whith your cameras, make some prints; this is the only way to figure out what works the best for you.

Jojje · Apr 9, 2015

Print a few USAF 1951 targets, photograph and compare results. Much better than brick walls, works for me. https://cmitja.files.wordpress.com/2011/02/f02.jpg

250swb · Apr 9, 2015

studiocarter said:
How does one evaluate different lenses?
Brick walls? I shoot long city scenes, thousands of houses.

Unless you have already done similar tests with your other cameras you wouldn't have anything to compare a brick wall test with anyway. So stop right now and don't get sucked into the nerdy end of photography. Go out and use the camera as you use your other cameras, if the results please you that's good, and after all pleasing results are so much more important than resolution.

Steve

BrianShaw · Apr 9, 2015

Agreed. But sometimes folly can be fun and if done right one might even learn something new.

snapguy said:
I agree with film_man. Shoot what you want to shoot and decide if you like the results. All else is folly.

DWThomas · Apr 9, 2015

Generally when I buy used fixed lens cameras, such as folders and most TLRs, I do some mechanical checks without film to make sure they are at least trying to work. I then load the camera up with film and go take some pictures. I have a favorite spot, a township park and historical site only a mile or so from the house. It has a stone barn with very prominent and contrasty mortar joints and lots of neat textures, a nifty beehive bake oven, and a kitchen garden surrounded by a picket fence. I usually shoot up along the fence at a shallow angle in such a way there is an identifiable target to see whether the focus scale is calibrated.

I will make two or three shots of some sharp subject at the widest range of equivalent exposures I can manage; that gets some idea if shutter speeds and lens apertures function. I'll take a distant shot at infinity focus, and try some stuff near the closest focus setting. Then if there is any film left on the roll, I'll just "take some pictures." I generally use a fairly hefty tripod for such tests so camera motion is not a factor.

So it is a functional test, but not optical lab stuff. If I buy just a lens for an interchangeable lens camera I might test a bit more exactingly, and yes, I have photographed a brick wall. The front wall of my house is such, so that's pretty convenient.

My view is that in the end, it depends on what you are going to do with it and what your expectations are. I can live with some occasional softness in the corners to have a camera that folds up and fits in my jacket pocket if it works reliably.

studiocarter · Apr 9, 2015

New to me is the idea of using a Graflex whatever with a 120 roll film adapter which then allows for interchangable lenses for 6 x9 format and reflex viewing. That's a 4x5 for 2x3 or 120 in 6x9. Whew.
I was hugely impressed with the content in the link above, the second post?

norm123 · Apr 10, 2015

Take pictures of newspapers with each lens. Enlarge them the more you can.
Just an idea.

studiocarter · Apr 10, 2015

Cool. Good idea. That is better than bricks.
I'll check the focus with ground glass held against the inside film area before loading it.

Dan Fromm · Apr 10, 2015

The problem with bricks and newspapers is that they don't have a range of spacings between features. They're fine for go-no go acceptance tests -- can the lens resolve that level of detail? -- but don't give much information about what more lenses that pass acceptance testing can do. They're also useful for checking how much worse the lens does in the format's corners than in the center if the target is fine enough. They're not particularly good for comparing lenses.

Incidentally, if you're interested in comparing lenses (not complete camera systems) then you have to work hard to eliminate most causes of variation in performance. When I shoot lenses against each other I try to use the same camera, the same roll holder, the same shutter, the same support, the same emulsion, the same film-to-target distance, ... When using adapters to mount lenses in front of shutters I try to eliminate glancing reflections inside the adapter. Flocked paper does the trick.

piu58 · Apr 11, 2015

I test all my lenses. I use therfore an USAF 1951 chart, which can be downloaded from many places. My own site has a evrsion of it:
http://kometen.fg-vds.de/piu/f/UsafChart.pdf
This chart gives a good idea about the virtues and problems of a lens. I check each lens wide open, moderately stopped and nearly full stopped down. I place such a chart in the center of the image an in one of the corners.

The chart gives linepairs per millimeter (of a contrast the target has). http://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart gives more information of the chart, especially the lines per millimeter of the original chart. They must be converted to the lines per millimertes in the focal plane by

lines in focal plane = lines original * distance to the chart / focal length of the lens

BrianShaw · Apr 11, 2015

Is that chart really accurate after being scanned, downloaded, and printed?

RalphLambrecht · Apr 11, 2015

BrianShaw said:
Is that chart really accurate after being scanned, downloaded, and printed?

the eps version of it is but the test result giving lp/mm is not a valuable indicator of lens quality. only an MTF chart will give you that

BrianShaw · Apr 11, 2015

Thanks Ralph

Dan Fromm · Apr 11, 2015

RalphLambrecht said:
the eps version of it is but the test result giving lp/mm is not a valuable indicator of lens quality. only an MTF chart will give you that

Gee, Ralphie, where can I find an affordable MTF machine?

The USAF 1951 chart is inexpensive. There's no need to download and print in sections, well-printed charts can be purchased from Edmund Optics. See http://www.edmundoptics.com/testing...tion-test-targets/resolving-power-chart/1665/ I have a couple of them, prefer my rough-and-ready tests. My rough-and-readies give the same rankings of lenses as the USAF 1951 does. Where the USAF 1951 shines for me is in making distortion clearly visible.

Edmund also has a smaller more expensive version of the USAF 1951 that can be used to measure contrast and resolution. Dead Link Removed Sounds like MTF to me.

Alan Johnson · Apr 11, 2015

I always thought they designed the USAF chart so that only really clever people could join the photo division.
Here's some others borrowed from the digital world:
Dead Link Removed
I use Norman Koren's charts occasionally but only for comparison, don't do the math.

benjiboy · Apr 12, 2015

I test lenses by shooting pictures with them, I've had the majority of my lenses for more than thirty years they are still better optics than I'm a photographer, I have no inclination to start shooting test targets with them and making a stick to beat myself with.

benjiboy · Apr 12, 2015

I test lenses by shooting pictures with them, I've had the majority of my lenses for more than thirty years and they are still better optics than I'm a photographer, I have no inclination to start shooting test targets with them and to make a stick to beat myself with.

Dan Fromm · Apr 12, 2015

Ben, I'm not sure you know why it makes sense to test lenses at least semi-formally. The main point of doing it is to find out whether a newly-arrived lens is good enough to use. A secondary but still important point is to decide whether the newly-arrived lens is better than the equivalent lens in hand. Which to use, which to move out.

How to evaluate lenses?

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