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

Started Jul 5, 2016 | Questions thread
JimKasson Forum Pro • Posts: 26,618
Re: Full sized images

l_d_allan wrote:

JimKasson wrote:

These are full frame. Sorry for the earlier error. Comments?

Non-IQ comments (as I have negligible experience with using "tilted near-infinity horizons" (TNIH) for "good copy vs bad copy testing" (GCVBCT):

  • Odd that when you click on the image itself, you get use of the Loupe, and can view much closer than when you click on "Original Size". Has DPR always been that way? "Original Size" is not nearly 1:1 pixel peeking, and neither does the Loupe. Any idea what the viewing ratio is with the Loupe with a7Rii captures of 7952 horizontal pixels?

I have no idea on any of that.

  • Since you don't care whether the sky blows out or not, seems like you could use a longer exposure ... the EXIF shows EC of -1.3 EV. Do recall if you used "A" mode with EC, or "M" exposure with EC ignored?

A mode with EC set to -1.3. Noise is not a problem in this scene, and I didn't want to blow the highlights on the leaves, which don't show up in blinkies or the histogram.

  • However, "Sunny 16" with ISO 100 would be 1/3200s at f/2.8, so you clearly didn't use "Sunny 16" (if I did the reciprocity correctly). 1/2000s is actually about +0.7 EV, so perhaps the EXIF value of -1.3 EV reflects where the EC dial was?

That's what goes in the EXIF. The EXIF has no idea what the "correct" exposure is.

  • Do you recall if you used UniWB with Zebras to decide on exposure? If so, what Zebra setting ... I use 100+? Was the sky blinking or not? Or did you back off a click or so from the tree leaves blinking?

No blinking, even at EC = 0.

  • ...
  • I don' t have that lens, so have no basis of comparison on what the center, near edges at the APS-C off-axis, and extreme corners should look like.
  • I also don't enough experience with TNIH to comment on perceived IQ.
  • We apparently differ on whether validly done TNIH captures tends to be better, worse, or about the same as a validly done brick wall IQ test for GCVBCT.

Ideally, we could test with a very large brick wall 500m away.:-)

  • How far away would you estimate the tree line is at the horizon? Half mile? Full mile? Less? More? Ever actually stepped it off, if that would be feasible?

Answered earlier.

  • What magnification of focal length would your estimate work out to be? 1000X or greater? Much greater?

I don't understand the question. Are you talking about the object field to image plane ratio?

  • It wouldn't surprise me if you have a laser range estimator with at least a high degree of accuracy.

I don't. If I worked often with technical cameras, I would, but I don't, unless you count a Linhof Technika as a technical camera.

  • If so, have you checked out how far trees at the "left horizon" are vs the "middle horizon" vs "right horizon"? My experience is there is a definite "learning curve" to estimating distances, but with practice you can get pretty good at it ... such as golfers and hunters.

Everything is well over the critical 200m.

  • Are those distances within +/- [fill-in-the-blank]?

Everything is well over the critical 200m.

  • ....
  • OT?
    I've been pondering how much "field curvature" and "focus shift when stopping down" (which this example doesn't do) really matter with the relatively large DOF of a f/2.8 lens and relatively wide 35mm FL. Even with a very small CoC, I doubt even a large print or the DPR Loupe would have these issues be noticeable ... if you print full frame.

Hard to measure. I could try focusing on the corners and see if that makes a difference, but this test is unrelentingly qualitative, and there's no way to measure focus shift with it. How about a huge ISO 12233 chart 500m away?

  • However, those issues seems maybe relevant for non-IQ test images if you need to crop the image for a print or upload ... then the effective CoC can be truly minuscule.


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