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

Started Jul 5, 2016 | Questions thread
JimKasson
JimKasson Forum Pro • Posts: 26,613
Re: Help judging performance of my FE55z, FE35f2.8z horizon/infinity
1

l_d_allan wrote:

JimKasson wrote:

The format in which I find it easiest to do these tests is to export the images as full-sized TIFFs from your raw developers to Photoshop as separate layers. Then label the layers with the settings, write the file out as a PSD, host it on Dropbox or something similar, and post a link here.

I'm curious what kind of info you would include in the "separate layers".

Lens, aperture.

My observation is that the EXIF has most of the relevant info (EFCS?, temp?, IBIS?).

You lose that when you stack all the captures into a single image.

Would the layer have details about non-EXIF such as tripod usage? How much care taken for issues such as atmospherics?

I really try to stay away from TIFF's unless there are compelling reasons .. and I have TB's of inexpensive storage. I get impatient with the sluggishness of huge .tif files.

Try striping (RAID 0) with a fast disk controller.

My experience is that a .tif is about 5x larger than a cRAW, at least for my a7Rii. I almost always use uRAW and then DngConverter to get .dng's with "pragmatic lossless compression" ... so a uRAW goes from 85 MB to 45 MB. But then it would bloat to about 230 MB for the .tif.

Don't forget, you're going to throw away the TIFFs as soon as you create the stackled layer image, and you're going to throw that away as soon as you reach conclusions about the test you're performing.

Then anybody doing the reviewing can just click on the layer visibility icons to directly compare any images in the stack.

The downside of this is that it means that everybody involved has to have Ps, though.

Unless I'm unaware of lots of info that should be in the "separate layers", I'd speculate that a simple uRAW or cRAW or .dng ... WITH more or less detailed annotations about exceptions for standard practice... might suffice, and also avoid the need for PS.

Then it's harder to click back and forth. Also, with layers, you can align images that weren't perfectly captured.

I looked at your raws. They look fine to me.

I would very much appreciate learning how you went about evaluating the OP's raws.

Perhaps you could "think out loud with your keyboard" to explain what you look for, what you observed with the OP's raws, and what it meant.

I imported all the images into Lr. I exported them to PS as layers (down at the every bottom of the "open in" menu) thus avoiding the TIFFs. I zoomed to 2:1, and looked at and compared corner sharpness, comparing the tilts in one direction as a group and the tilts in the other direction as a group. If I really wanted  to get fancy, I would have flipped all the images that were tilted in one direction, so I could easily compare them all.

Have you done something like that as a TLW blog article?

Nope. At this point, I'm not sure I want to encourage people to do this kind of testing, after all the examples of how to do it wrong I see on the web (hot the images in this thread, however.).

Since being in the market for pricey Sony lenses with their earned rep for so-so QC,

I'm not sure that the rep is well earned. Decentering happens will all vendors. It's never happened to me with Leica, by Lloyd Chambers has reproted on several decentered Leica lenses. I do respect what Roger C has done on the subject, and his results don't put Sony miles away from other vendors, at least the way I read them.

I've done perhaps more than my share of brick wall testing. However, I have my doubts I really know how to evaluate the results of this tedious and error-prone "good copy vs bad copy" testing.

I never got close to getting valid, objective MtfMapper numbers, so it all seems rather subjective "by eyeball".

Most people's difficulty in getting good MTF Mapper numbers is, I believe, the result of several issues:

  • Alignment
  • Getting a high-resolution target
  • Alignment
  • Getting the target big enough.
  • Alignment
  • Getting the target far enough away
  • Alignment
  • Lighting the target properly
  • Alignment
  • Vibration
  • Alignment
  • Field curvature

Oh, and alignment is important, too.

Jim

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