How to find a Lens' flaw?

So I picked up a dirt cheap Tamron 200-400mm LD - with fungus. Price was right, so why not.

I really haven't used it much yet. Did the UV exposure to (hopefully) kill the fungus, and I've partially disassembled the lens to clean what I can. Looks like the coating is etched. The test photos I have done have shown really no imperfections that I can see. So that brings me to my question -

What is a good subject and settings to find a lens' flaws? I did some shots of a focus chart, and they looked good, and the few shots that I've done also show no flaws. I'm trying to figure out if there is a certain subject and/or settings that are most likely to bring out any imperfections in the lens, and that way I can avoid those circumstances. Of course sun flare may be a problem, but I don't foresee myself really using this lens in a way that I would run into that issue.

Any suggestions?

F22 pure white monitor.

KirkS518 wrote in post #16413689
So I picked up a dirt cheap Tamron 200-400mm LD - with fungus. Price was right, so why not.

I really haven't used it much yet. Did the UV exposure to (hopefully) kill the fungus, and I've partially disassembled the lens to clean what I can. Looks like the coating is etched. The test photos I have done have shown really no imperfections that I can see. So that brings me to my question -

What is a good subject and settings to find a lens' flaws? I did some shots of a focus chart, and they looked good, and the few shots that I've done also show no flaws. I'm trying to figure out if there is a certain subject and/or settings that are most likely to bring out any imperfections in the lens, and that way I can avoid those circumstances. Of course sun flare may be a problem, but I don't foresee myself really using this lens in a way that I would run into that issue.

Any suggestions?

Use the lens daily for about four months. With regular use, any shortcomings will be revealed. However, don't be surprised if you never find a "perfect" lens.

i assume there's a need for the lens that made you buy it...so why not use it for that, if anything pops out you'll notice it

DreDaze wrote in post #16414476
i assume there's a need for the lens that made you buy it...so why not use it for that, if anything pops out you'll notice it

Actually, it was more of a deal I couldn't pass up, and it does have a better reputation then mirror lenses, which were my only long reach lenses, so I figured I'd give it a shot. I gotta say, while it isn't an L lens, I'm sure liking it.

I tell ya, I've shot a number of 'test shots' with it, and I see no issues. Here's one that I took a little while ago, and I can't see anything.

Full Image (390mm, f/8, 1/13th, ISO 100, on tripod)

HTTP response: 404 | MIME changed to 'image/gif' | Byte size: ZERO | PHOTOBUCKET ERROR IMAGE

HTTP response: 404 | MIME changed to 'image/gif' | Byte size: ZERO | PHOTOBUCKET ERROR IMAGE