Testing lenses at home?

[tjwspm]

Who has ever tested lenses at home? What experiences have you had with this?
In order to test the resolution of cameras for which there were no evaluations yet, I was forced to carry out tests myself. But I had never done this seriously before, so I had to find out more first. There are many tips online, but they were either too technically complex or they were just the author's emotional assessments.

I was tired of hearing 'creamy bokeh' and 'sharp corners' in lens review videos. With a little effort, I could carry out meaningful lens tests at home. The results may not be as good as professional laboratory tests, but in most cases they were sufficient to get to know my own lenses better.

Do you have any ideas or comments on how to improve my process?
I've written down what I did here:

Testing lenses

This guide covers methods like using Siemens star and USAF 1951 test charts, measuring line pairs per millimeter, and practical field tests.

moments-of-now.com

 

[BrianShaw]

I don’t test lenses for resolution or seriously pay much attention to lens reviews for exactly the two issues you mention. I test empirically using the “does the lens reasonably give me the opportunity to capture a decent image” criteria.

Your dissertation is very interesting and appears quite well organized and readable. I skimmed it and will read in detail soon. One concept I did not see, though, was the impact of print viewing distance. That seems important to me from a practical standpoint.

Thank you for documenting and sharing your wisdom. It is very appreciated.

 

[Andreas Thaler]

I don’t test lenses for resolution or seriously pay much attention to lens reviews for exactly the two issues you mention. I test empirically using the “does the lens reasonably give me the opportunity to capture a decent image” criteria.

+ 1

Your dissertation is very interesting and appears quite well organized and readable.

+ 1

Thank you for documenting and sharing your wisdom. It is very appreciated.

+ 1

 

[tjwspm]

One concept I did not see, though, was the impact of print viewing distance. That seems important to me from a practical standpoint.

That's an interesting point!
I only implicitly included the viewing distance in the chapter “What does the resolution tell us?”. If I assume there that I cannot resolve more than 5 LP/mm with my eyes, then this means my reading distance (perhaps 400 mm).
I will think about how I can include the aspect of greater viewing distances there.

 

[BrianShaw]

Not just “greater” viewing distance, but appropriate viewing distance.

It drives me absolutely bonkers when folks stick their noses to a large print and then complain about being able to see grain. I suppose they’ve never been close to a billboard.

 

[tjwspm]

Not just “greater” viewing distance, but appropriate viewing distance.

It drives me absolutely bonkers when folks stick their noses to a large print and then complain about being able to see grain. I suppose they’ve never been close to a billboard.

That is simple. I've just tried it out. Using the USAF chart, I can just make out element 6 of group -1 at a distance of 2 m if I wear glasses. My resolution would then be 0.9 LP/mm. The image could then be about five times larger than at my reading distance: 800 x 1100 mm instead of 160 x 220 mm.

Just as you say, you then shouldn't get any closer. I then put up a barrier 2 m in front of the picture like in front of the Mona Lisa in the Louvre . Agreed, they do it for other reasons...

 

[Paul Howell]

I tested a brace of 50mm lens, maybe 20 years ago with the last of my microfiche film. Otherwise Tmax 100 with resolves at 200 LPM. I think modern lens will all resolve 200 LPM, older zooms do not. I have an early 3rd party zoom in Minolta MD mount, it came with a data sheet, it could resolve 87 LMP so I only shoot Tmax 400 or Foma 400. Other option for film is ortho film, advantage is that is now available from 35mm to 4X5. Microfiche resolve around 800 LPM, not sure what ortho film resolves at. You need to measure resolution at all apertures. If you scan you can scan the negative and count revolution at a given. You can measure distortion using a test chart an Air Force or other that has a grid. Some people use a brick wall. To measure contrast you need a denistomer, bokha is subjective. Then it comes down to what is your standard. In the 70s and 80 the Japanese Government used the Konica 50mm 1.7 as it standard.

 

[tjwspm]

I tested a brace of 50mm lens, maybe 20 years ago with the last of my microfiche film. Otherwise Tmax 100 with resolves at 200 LPM. I think modern lens will all resolve 200 LPM, older zooms do not. I have an early 3rd party zoom in Minolta MD mount, it came with a data sheet, it could resolve 87 LMP so I only shoot Tmax 400 or Foma 400. Other option for film is ortho film, advantage is that is now available from 35mm to 4X5. Microfiche resolve around 800 LPM, not sure what ortho film resolves at. You need to measure resolution at all apertures. If you scan you can scan the negative and count revolution at a given. You can measure distortion using a test chart an Air Force or other that has a grid. Some people use a brick wall. To measure contrast you need a denistomer, bokha is subjective. Then it comes down to what is your standard. In the 70s and 80 the Japanese Government used the Konica 50mm 1.7 as it standard.

To test my 8x11 Minox lenses, I use the ADOX CMS 20, which I expose to 12 ASA.

 

[xkaes]

If someone wants to test a lens, they don't need to get fancy at all -- and it's a good idea, just to make sure you didn't get a lemon.

Just take a newspaper and place it at a distance of 50 times the focal length -- or whatever. So for a 50mm lens, the newspaper is about eight feet away. No need to be exact.

Make sure there is a piece of paper in the center and in one corner of the viewfinder.

Using a tripod or solid surface, carefully focus, and make one exposure with the lens wide open, and another stopped down two f-stops.

See if you like the results. It helps if you have another lens to compare it to.

 

[Sirius Glass]

As an alternative to home testing for each lens, ask yourself if you are happy with the results you get for all your prints and-or slides? Are the corners sharp enough? Are you happy with the areas that are out of focus? Are you happy with the areas in focus? Such evaluations may well save you from extensive testing of every lens.

 

[Andreas Thaler]

As an alternative to home testing for each lens, ask yourself if you are happy with the results you get for all your prints and-or slides? Are the corners sharp enough? Are you happy with the areas that are out of focus? Are you happy with the areas in focus? Such evaluations may well save you from extensive testing of every lens.

This can certainly save you some disappointment and I do it that way too.

But if you want to know what your lenses can really do, you can't avoid a test setup like the one Thomas describes.

I fully understand Thomas’ motivation for this:

I was tired of hearing ‘creamy bokeh’ and ‘sharp corners’ in lens review videos. With a little effort, I could carry out meaningful lens tests at home.

Testing lenses at home ( October 27, 2024)

In order to test the resolution of cameras for which there were no evaluations yet, I was forced to carry out tests myself. But I had never done this

moments-of-now.com

@tjwspm Thomas, your website is great.

Thanks also for this article, one can only learn from your expertise.

 

[Angarian]

Who has ever tested lenses at home?

I am doing it for decades.

What experiences have you had with this?

Only the best. It is real worth it. But you have to do it right. A lot can be done wrong.

I've read your article.
First my most important question. I quote you:
"With analogue cameras, I digitize the negative before evaluation."

So you are exclusively evaluating the scans? Nothing else?

 

[MTGseattle]

To me, the most effective "real-world" evaluations of Bokeh I've seen are where there is foliage in the background of a portrait. Even that can get quite skewed depending upon how far into the background the foliage is.

 

[tjwspm]

I am doing it for decades.



Only the best. It is real worth it. But you have to do it right. A lot can be done wrong.

I've read your article.
First my most important question. I quote you:
"With analogue cameras, I digitize the negative before evaluation."

So you are exclusively evaluating the scans? Nothing else?

Yes, indeed. I digitize the Minox 8x11 mm negatives with a Sony A7R (61 MPixel). I hope not to lose any details in the negative. In the image processing program it is then easy to measure and evaluate the sizes within the test images.

How do you do it?

 

[Paul Howell]

When thinking about how sharp a lens is, the first question is what is the resolving power of the film? ADOX CMS 20 datasheet reports 800LPM, with your 16mm camera and lens I doubt that it will resolve 800LPM, I assume that a 61MP sensor can resolve more than the lens so you should be able to count LPM of the lens. With a AF test chart you sould be able to determine distortion. With a 16mm negative, the format is so small it will have great depth of field, would be interesting to see the bokha

 

[benveniste]

There is certainly a legitimate sector of the hobby which is concerned about maximizing sharpness. I'm not in that sector, but the only thing I see wrong with your approach is that it looks like you are testing at a fairly short distance. That's good for portrait lenses and for subjects such as flat art, but not so much for landscapes or sports.

A few years ago I had a smith make me a knife using a Pentax 110 lens as the pommel. So that's my "sharpest" lens setup .

 

[ic-racer]

The main thing for which I test lenses is collimation, or infinity focus.

I have occasionally compared my already collimated lenses for sharpness with an outdoor infinity scene. For example I once compared all my 28mm lenses.
Was I surprised that at f8 they were all the same? Not really; mostly reassured.

 

[koraks]

Do you have any ideas or comments on how to improve my process?

No, I'd just like to thank you for sharing this. I don't test lenses as such and rely on a more 'impressionist' approach - snap some photos and see if I like what I get. However, if/when I run into the desire/need to do some proper testing, I'll be sure to remember your writeup!

I was tired of hearing 'creamy bokeh'

I understand, and such subjective, difficult-to-interpret comments bug me too, much of the time. At the same time, when it comes to rendering of out of focus objects/areas, more objective testing tends to not really tell the full story, and certainly not the story a typical photographer will find particularly useful. For such aspects, we fortunately can always fall back on example images.

 

[Andreas Thaler]

Even if the implementation requires some effort, it is interesting to see how lenses can be tested objectively, beyond poorly or undefined attributions such as "sharp", "beautiful", "professional" etc.

I think contributions like those from Thomas raise the technical level in the forum and hope that there will be more of them

It is well known that dealing with formal subjects such as physics and the associated mathematics does not make everyone's heart beat faster.

But if you get involved, connections and insights will become clear.

This is written by someone who always had the worst grades in these subjects at school

 

[MattKing]

To make use of this detailed excellent work, it really helps if you have some sort of intended use in mind.
For most pictorial work, the differences between the wide selection of available "good quality" lenses aren't particularly important - issues of condition aside.
If you need highly accurate copies of original documents, issues like distortion are very important, as are high line pair resolution numbers.
If you regularly make very large enlargements, high MTF numbers are important.
If your needs include exceptional low light capabilities, great results with the lens wide open are important.
A "needed results" oriented approach can make good use of objective tests.

 

[Alan Johnson]

If you read it carefully and leave out the references to MTF, Norman Koren's downloadable and printable 2003 charts can give a good measure of lppm resolution BUT they will only go up to about 125 lppm lens resolution with T-max 100 and most good lenses will easily exceed this in aerial resolution. I know this because the guy who used to test lenses for Amateur Photographer used T-max 100 and the best always maxed out at 125 lppm unless he used microfilm.

Lens testing

 

[Paul Howell]

In the 50 to the 70s Leica tested their lens with Microfiche film so they could market how sharp their lens were. When I was in college in the 60s this topic came up. My college offered a minor in Photojournalism so the instructors were all former newspaper photographers. I don't recall the name but the instructor who said "so what. If Trix resolves around 95LPM and Plus X at 125LMP what is the point of having a lens that resolve 320LPM." As news photographers you are going to be shooting TriX, GAF 500, HP4 and Plus X on occasion.

 

[blee1996]

Thank you @tjwspm for sharing not only your experience, but also your custom made test chart and excel worksheet. This kind of "open source" testing is very valuable to a lot of us, who tend to be a bit of gear head once in a while.

Lens testing is really a complex system effort, especially taking into account of subject distance. I saw you mentioned 2m, while @xkaes mentioned 2.5m for 50mm lens. Is that a common practice vetted in mathematics, or industry tradition?

With mirrorless digital camera, it is much easier to nail focus and eliminate the film variable. But it does introduce another variable, in terms of lens adapter quality and alignment. Therefore film testing still has its merits, even though it is a bit more cumbersome.

 

[loccdor]

I do somewhat formal lens tests in situations where absolute resolution is critical:

1) On lenses I plan to use with teleconverters
2) On lenses I plan to sometimes heavily crop from
3) On lenses used for enlarging, copying, or digitizing film

Otherwise I skip the test charts, might instead view other people's review of the lens before going out and trying it myself on normal subjects.

 

[tjwspm]

If you read it carefully and leave out the references to MTF, Norman Koren's downloadable and printable 2003 charts can give a good measure of lppm resolution BUT they will only go up to about 125 lppm lens resolution with T-max 100 and most good lenses will easily exceed this in aerial resolution. I know this because the guy who used to test lenses for Amateur Photographer used T-max 100 and the best always maxed out at 125 lppm unless he used microfilm.

Lens testing

Many thanks for the link. An excellent technical mathematical presentation of the topic. However, anyone who does not know what a Fourier transform is, for example, will have difficulty understanding everything. But it's still an exceptionally good presentation of the MTF concept.

As far as the test chart is concerned, Norman Koren's chart has the great advantage that it can be analyzed with the software he offers. This is not possible with the USAF chat. So the evaluations of the USAF charts can be somewhat subjective. However, the deviations caused by different people when evaluating USAF charts are not very large in my opinion and they are easy to use.

In any case, a great website!