Help judging performance of my FE55z, FE35f2.8z horizon/infinity

Started Jul 5, 2016 | Questions thread
(unknown member) Contributing Member • Posts: 854
Re: Help judging performance of my FE55z, FE35f2.8z horizon/infinity
1

slstr wrote:

holin wrote:

I'm interested in cheap testing methods, too, so, I looked. Based on 1600 pix wide jpegs it's difficult to say anything. They look fine and if this is the format you'd always publish your stuff then there is little to complain. I'd use RAWs, unsharpened (not unsharp mask'ed ) exported to JPEGs if necessary. However, I would also like to ask, why do you want to test your lenses. Do you see something in your photos that prompts you to suspect there's something wrong?

As for the testing method, I'd test with a brick wall, carefully aligned, or try to find slightly flatter infinity subject - so that almost everything is far away in the photo. Now you only have very thin corner to corner line of detail (buildings) from which to judge sharpness. Trees won't do, especially when it's windy.

Sorry I was in a hurry when replying to you before and forgot to answer your question regarding why I want to test my lenses and whether I suspect something is wrong.
TL;DR I don't suspect anything wrong, testing is fun and funds are limited !
the corner to corner line of building-detail + antennas and also the lines holding up the TV-radio tower far away was specificly what i was going for in this test.
Brick wall tested earlier showed good detail in bottom-middle and top-middle, but brick wall did not tell me much about contrast and fringing in sides+corners etc.. not that I could see anyway.
My budget is limited and I don't want to keep a lens if it is not performing as expected i.e. normal or better ..

But here you have the problem. How would you ever know what's normal or better? Manufacturers afaik never publish their tolerances for lenses. Best you could do is have your lens tested by someone with huge resources like lensrentals and ask their opinion on what they'd consider a subpar copy of a given lens.

I recently got the "world's best, etc, etc..." Sigma 35mm f/1.4. To me it looked like the worst 35mm so far. Soft  right side and when focused over hyperfocal, very sharp right lower corner when there was something there that's a few feet away. Bit similar to what is seen in osv's sample photo. I had the lens checked by Sigma's service which concluded it performs similar to other copies of the same lens (surprisingly they didn't have a proper optical bench). Then I checked some other 35mm's with the same body and saw similar worse right side and sent the camera to service, who told it might have something wrong, but to make sure it will be fixed it would cost more than a brand new camera (a7). However, tele lenses work fine, and I'm still not sure whether the softness was normal for modern 35mm f/1,4 lenses on FF or if there was something wrong with some / one of the components. As a point of comparison, my Sigma 19mm does way better at f/2.8 on an APS-C body than the FF + Sigma 35mm did at f/4, and I expected better from the FF. Now I could, and might, go really overboard with this and build a proper resolution testing environment to take at least some of the human factor out of the equation, but since it's not professional, why spend so much effort on something I still couldn't do as well as those who do it professionally (and still have unconclusive results b/c of no points of comparison, no knowledge of tolerance limits...)

Returning "bad" lenses is also something I'm somewhat against. Where would you think the bad lens goes to? I'm pretty sure the seller sells it openbox at slight discount and surely does not mark it as a "bad copy", or it goes to the mfg or country representative / importer and gets its packaging checked and then sent back to circulation. In our chosen economic system, that doesn't help. The mfg should get no money from the bad lenses and / or should always get alerted about them (instead of the bad lens ending up to some poor soul who doesn't know how to test it in the return period) so that anything would change. Also better would be to send the "bad" lens to the service and if they claim it's inside mfg tolerances then just take it as it is, or if it is actually bad, they can service it.

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