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DIY home lens testing

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skm.sa100 View Drop Down
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Post Options Post Options   Quote skm.sa100 Quote  Post ReplyReply Direct Link To This Post Topic: DIY home lens testing
    Posted: 13 March 2018 at 13:40
So far I've been using my lenses without being too critical or pixel peeping except for the occasional check, mostly for lens DB reviews.

I'd like to do a bit more thorough testing of all my lenses.
I'm curious to see what setup other members have at home for DIY lens testing.
My thought is to print the standard USAF chart and fill the frame and check.

If you have better suggestions I'll be happy to have them.

Thanks
Sashi
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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2018 at 14:10
I did my own years ago. Problem is getting the target big enough.. you don't want to be shooting from too close as a lens is less likely to be optimised for that sort of distance.

One way around it is to use two (or more) sheets arranged diagonally to each other... This way you can get the central resolution and the corners with a smaller sheet.

A standard chart is going to be fine, but mine tended to be arranged with lots of different sized fonts and I assessed sharpness by serving the smallest don't that was legible.

To be honest I gave up after a while as I found that it wasn't necessarily the sharpest lens that produced the best results for me.
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QuietOC View Drop Down
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2018 at 14:25
I use a big print of the ISO 12233 Test Chart, but almost anything flat with fine detail will work. My chart isn't even very flat since it is just paper taped up on a poured concrete wall.

I was testing in my bedroom last night just using a shelf full of magazines. My Tamron 70-300 USD is nowhere near as sharp as my Sony DT 55-300 at least when both are on the same 2X teleconverter, but Steady Shot actually works on the Tamron which was immediately visible when I enabled Steady Shot with Shutter.
A68 30M 35 50 60M 16-50 16-80 18-55 18-70 18-135 55-200 55-300
A6000 LA-EA1 6.5 16 20 30 50 60 16-50 18-55 55-210
600si: 20 24 28 50 100M 135 24-85 24-105 28-105 35-70 35-105 70-210 75-300 100-200
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amrep View Drop Down
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Post Options Post Options   Quote amrep Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2018 at 15:29
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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2018 at 17:18
It kinda depends on the focal lengths and other factors. For example, at one point I put together a small 3D test scene specifically for testing a group of 500mm lenses, and it indicated their performance differences very well ... but I wouldn't use that for testing wideangles.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2018 at 19:43
Target size certainly helps. I started by printing the ISO 12233 chart on 11" x 17" and then 13" x 19" paper. There really wasn't enough resolution in those prints, and the camera needed to be way too close with wide angle lenses. That size chart is handy with 300+ mm lenses.

A68 30M 35 50 60M 16-50 16-80 18-55 18-70 18-135 55-200 55-300
A6000 LA-EA1 6.5 16 20 30 50 60 16-50 18-55 55-210
600si: 20 24 28 50 100M 135 24-85 24-105 28-105 35-70 35-105 70-210 75-300 100-200
 



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Miranda F View Drop Down
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2018 at 14:37
With all due deference to those who, like QuietOC, use wall charts a lot and in many cases report their results here, I really do not either favour or trust wall chart tests. They bear very little relation to actual lens use and mostly serve to make you dissatisfied with lenses that work acceptably well in normal use. The real world is not flat.

The specific problem with wall charts is that the results are strongly dependant on accurate focussing and the lens's flatness of field. The reality is that most affordable lenses do not have a flat field at the usual focus distance used for wall charts, and as a consequence corners will look much worse than they do in normal pictures. In many cases the curvature flattens out near infinity. And although for many of the cheaper zooms (especially at the wide end) they still retain significant curvature of field, there are other issues too that charts don't help with.

Wall charts really only work well for a quite limited range of focal lengths and a few lenses which suit that kind of use. They're pretty much useless for wide angle lenses and long telephotos IMHO.

What do I recommend? I regularly test a lot of lenses (I keep buying cheap ones on ebay, I'm afraid ) and I use several different test methods according to what I'm after.

1) For close-focus behaviour (from 0.5m to around 3m, depending on focal length), I shoot a computer monitor set to white screen. I use MF with focus-peaking which shows immediately through the EVF where the lens is particularly soft. For the most detailed examination, take several images and examine 100% crops in centre and around the edges to look at the individual pixels. Much easier to interpret than a test chart. AT normal view, you can usually arrange to see moire patterns between the monitor and the image which can be a useful guide.

2). Sharpness at infinity. For wide angle lenses there really is no substitute for a wide and distant city landscape with buildings across the field of view. Stay in one place, take at least three pictures at every aperture, and then review. Discard any not sharp in the centre, then look at the edges/corners, both in normal view and magnified. Then decide for yourself how sharp you need the corners to be for your display medium.

3). For wide-to-medium lenses, especially zooms, I generally take an image of a particular large modern ware-house building across the water at Bristol docks, which has light yellow brickwork across the field of view to check softness in the corners, stainless-steel handrails to check PF and CA, and some more SS stanchions that show up flare very well. I try to take the pcitures at the same time of day each time, and I can compare most of my lenses at any focla length and aperture to see how well each does.

4). CA. The only successful method I have found to determine what kind of aberations a lens has and distinguish them properly is to take pictures of bare winter tree branches covering the top half of the frame (I don't generally care what happesn in the bottom corners). The point is that because there are branches at different distances from the camera in every part of the image, you can see whether the lens is soft or just out of focus. You can tell lateral from axial CA and from PF, you can spot curvature of field and decentreing.

5). Telephotos. Distant buildings are a good choice here, for general performance including softness, flare, veiling, and lack of contrast. The other issue here is often how much you can crop them and still ahve a picture worth looking at. A graded line chart like the Koren 2003 is useful here. You can put it on a sheet of card and stick it in the garden somewhere. It takes some work (and some thinking) to get absolute resolution measurements, but for comparison purposes its quite easy.

6) Bokeh. Very variable depending on the use, and the kind of background, and difficult to compare wiht other people, because lenses (in any given FL/distance/etc) tend to be more sensitive to some sizes of background object than others. twigs are usually a worst case, but not always. But you can do some checks in your garden and see what you think.



Edited by Miranda F - 14 March 2018 at 14:49
Miranda F & Sensorex, Sony A58, 5d, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
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Miranda F View Drop Down
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2018 at 15:00
Just to clarify the different kinds of CA: Choose black back-lit branches against a bright/white sky.

Lateral CA will give red/purple fringes on one side of the branch and green on the other, always worst in the corners and least in the centre, and generally at all apertures. Some older lenses were corrected for green and show red fringes not purple.

Axial CA gives the same colour fringes all around an object, but these may be green or purple accordoing to whethere the lens is focussed in front of or behind the object. This can occur anywhere in the field of view, but usually only near full aperture.

PF seems to mean different things to different people. I've seen it on old telephoto lenses, possibly as a mix of lateral and axial CA. Syber has seen it on highlights (see the article on his site), and I see it like that too. I think that may have something to do with sensor saturation, and not the lens.

Again, almost every lens will have some of these issues, (unless it is a dt lens with in-camera corrections switched on!), but it doesn't mean the lens is bad unless he results are too bad for your use.

Edited by Miranda F - 14 March 2018 at 15:03
Miranda F & Sensorex, Sony A58, 5d, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
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skm.sa100 View Drop Down
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Post Options Post Options   Quote skm.sa100 Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 01:43
All, thanks for taking your time to share your thoughts.

Bob, that's why I'm not a pixel peeper. I'm just trying to figure out how to test some lenses I have, that's all. Especially since I find myself with a Sigma 100-300/f4 and a Tokina 100-300/f4 and the 70-300G. Need to unload a couple of them.

QuietOC, I was hoping you'd reply as I know you test your lenses and post your findings. Thanks for that too, btwo.
I'll see if I can buy some printed papers. There are cheap papers available on eBay for a few bucks. Might not be totally industrial strength but should still help.

amrep, will go thru those links hopefully tonight.

syber, I'm aware of the challenge of testing UWA along with a 300mm. Especially if I'm going to fill the frame at 10mm with a printed sheet it's going to be a challenge.

Miranda, thanks for the very detailed reply. Will certainly put that knowledget to good use.

Regards
Sashi
More Dyxumer, less photographer.
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Jonas A-R View Drop Down
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 06:05
I would recommend Jim Kassonís protocols:


Lens Screening Testing
a9 a6300 35/2.8 55/1.8 85/1.8 90/2.8 70-200/4 LA-EA3 LA-EA4 16/2.8 fish 20/2.8 24/2 35/1.4 70-400/4-5.6Gii
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Post Options Post Options   Quote craig66 Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 07:33
By far the best and most robust way to test lenses "at home" (which basically means you do not have an optical bench) is suitable test chart and "slanted edge method" software such as Imatest or the free and excellent MTF Mapper which in some ways exceeds the capabilities of Imatest.

I said best and most robust, but I didn't say easiest. To get "professional quality" test results requires a good setup and considerable effect to get to the point having of a good setup. Focusing rails are mandatory for focus bracketing as reliably and repeatedly achieving critical focus even manually with all focus aids is beyond the capability of most people and certainly beyond mine. You probably want to have automated motor driven rails to cut the tedium and the errors and mistakes that rear their ugly head when tedium sets in. And you probably need to write the software to automate, supervise and collate present the results into useful and understandable form.

My setup consists of an (inadequate) DIY chart stand, A0 size test charts, DIY focusing rails moved by leadscrew driven by stepper motor controlled by an Arduino microcontroller. Test operation is controlled from a Java program on a notebook computer that commands the rails and controls camera shutter and aperture. Focus bracketing for each of a range apertures is achieved by press of a button. Then hands off. Afterwards the (possibly hundreds) of test images are transferred to a desktop computer, processed with MTF Mapper and the results analysed and presented in a useable form. If you want to test many lenses, you really need this kind of setup.

I'd rate this as the beginnings of professional grade setup. Alignment is a perpetual problem. There are quite a few degrees of freedom to manage. Chart flatness is also an issue. At the moment it's on the back burner because I don't have the time and I'm not buying any new gear.

Most people obviously don't want to commit to this sort of thing. But it's still worth downloading a copy of MTF Mapper, getting a chart printed, taping it to a wall, and doing your best to get alignment and focus right. It's very educational, demystifies MTF tests you see on the web and can still yield very worthwhile results.

Otherwise do as other suggest and look at Jim Kasson's methods or Lensrentals. Jim Kasson's blog is a mine of great information. He seems tireless in turning out excellent work.
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Jonas A-R View Drop Down
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 08:17
If you have followed Jim Kassonís work on the slanted edge method you know how labor intensive and difficult it is to get it right. I really do encourage anybody interested in lens testing to follow the link above
a9 a6300 35/2.8 55/1.8 85/1.8 90/2.8 70-200/4 LA-EA3 LA-EA4 16/2.8 fish 20/2.8 24/2 35/1.4 70-400/4-5.6Gii
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Miranda F View Drop Down
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 13:49
I really doubt the value of that kind of testing to an ordinary photographer when shooting well-selected real-life subjects is quick, easy, and shows up more defects than the supposedly-professional methods.
Miranda F & Sensorex, Sony A58, 5d, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
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QuietOC View Drop Down
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 15 March 2018 at 14:37
Useful lens testing is not as hard as Jim Kasson and Craig make it out to be. I can pretty much tell everything I want to know with just focus magnification hand held. Shooting the test chart is mainly just for the convenience of comparing stuff later. I am aware of how misalignment to the chart and the unevenness of the chart effects the results. I have no need for generating MTF plots or P-MP numbers. I find using the big chart is consistent with field testing but the controlled lighting and focusing are better.

Unfortunately, I find myself without a tripod right now. I did some field testing this weekend at a park and my tripod head fell off while I was carrying the tripod with the A68 and a Minolta AF 70-210 F4 attached. Luckily I caught the camera before it hit the ground. The threads on the tripod head are stripped. The tripod is an old aluminum Vivitar I purchased at a garage sale 15+ year ago. I don't love it, but it was perfectly adequate.

And I really want to do some testing. I got a Sigma 600mm F8 yesterday. It is definitely not as sharp as the 55-300 on a 2X teleconverter, but it is pretty sharp (maybe sharper than my Tamron 70-300 USD on a 2X) and more importantly Steady Shot works (maybe not as well as the Tamron 70-300 USD on a 2X, as it is not a D lens, but much better than the 55-300 on a 2X since that lens doesn't get its focal length corrected by teleconverters.) All of that I can tell hand-held using focus magnification and Steady Shot with shutter enabled on the A68.

Edited by QuietOC - 15 March 2018 at 14:49
A68 30M 35 50 60M 16-50 16-80 18-55 18-70 18-135 55-200 55-300
A6000 LA-EA1 6.5 16 20 30 50 60 16-50 18-55 55-210
600si: 20 24 28 50 100M 135 24-85 24-105 28-105 35-70 35-105 70-210 75-300 100-200
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