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

Started Jul 5, 2016 | Questions thread
l_d_allan
l_d_allan Veteran Member • Posts: 5,087
Re: Help judging performance of my FE55z, FE35f2.8z horizon/infinity

Nephi wrote:

I printed 3 large ISF charts and posted them on foam core. Despite all the effort a miniscule bend in a corner can give blurry false results. Half the time you won't know if its the chart, your camera, or your lens.

If feasible, I like to be 100x Focal Length or so from the target. That can present a problem with some/many focal lengths.

I wish I could fine the link for a lens test I found earlier online. Basically it is a $500 light box on a stand that has a test chart, perfectly flat, and perfectly lit. While knowing if you are perfectly parallel could be a challenge at least you could rule out the target!

I'd also be concerned about being able to get far enough away with many focal lengths.

Hmmmmm .... wonder if address'ing this niche issue could be a valid crowd-funding'ish project? IIRC, I had such related correspondence to Jim K's razor blade based protocol plus slanted wall or door.

I'm still looking for a DYI centering test that is reliable and accurate enough to detect decentering. I tried the flashlight test taking a shot of a test chart in each corner however I found the results be less than consistent and somewhat hard to interpret.

Drat. I've had my fingers crossed that such an approach could weed out the vast majority of "bad copies". However, that always seemed like wishful thinking on my part to make tedious, error-prone brick wall testing be obsolete.

I haven't tried either the OOF LED approach, or the more involved test from LensRentals several years ago.
https://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover/

I've heard taking a shot at infinity and then flipping it upside down works however I'm not quite sure what you need to flip a camera and how in the world you would line it up upside down.

I wondered the same thing ... and "not quite sure" ... but baffled. Seems like you'd need a rather advanced / specialized tripod head or a "rigid 3 sided L bracket".

I suppose a lens with a tripod collar would work, but those lenses are few and far between. My pano-head might work, especially if I could come to terms with using near-infinity horizons as a target.

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