GFX 100 vs a7RIV landscape IQ Locked

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Erik Kaffehr
Erik Kaffehr Veteran Member • Posts: 3,622
Re: Further thoughts on the GigaPixel AI results

JimKasson wrote:

I've thought some more about the GigaPixel AI results. The raw images received the same amount of sharpening on a per-pixel level in Lightroom: amount 20, radius 1, detail 0. If we're trying to compensate for the light-sensitive area of the pixels, that's appropriate. The pixel pitch of the two cameras is the same, the pixel design appears to be very similar, and so do the microlenses. But if we're compensating for depth of field and for diffraction, the radius for the larger sensor should be about 1.4 times that of the smaller one. As it is, viewed in relation to the picture height, the Sony image is getting about 1.4 times the sharpening that we're giving the Fuji one.

I see your point, I think. It may make some sense to look at slanted edges and check the effect of sharpening, radius vs. amount, etc.

As I said in the blog post, GigaPixel AI seems to sharpen more the more it upsamples. That also would benefit the Sony image, since the two images were somewhat undersharpened. This is probably worth more experimentation using upsampling algorithms that are less of a black box than the Topaz software. Because the software is essentially inventing information, its efficacy will depend on the content of the image. As an example of that, as we saw with the Siemens Star target tests that I showed in an earlier post, at some point, GigaPixel AI -- quite properly, in my opinion -- gives up and stops trying to make up detail. So before drawing any general conclusions, we should look at disparate example crops.

Finally (at least finally for now), I earlier observed that I thought the biggest advantage of the GFX 100 over the GFX 50x was not increased sharpness, but decreased aliasing. There is no aliasing in the crops above that is immediately obvious to me, but I'm sure that there is aliasing there, and one of the functions of aliasing is to turn high spatial frequency hard-to-see small details into lower frequency easier-to-see -- but wrong -- details. That may be a partial reason for the Sony images surprising sharpness.

Jim

That aliasing stuff may be interesting. It is entirely possible that GigaPixel AI picks up aliases and turns them into fake detail. I would presume that the A7rIV may have more aliasing as it is used closer to it's optimal aperture.

Comparing images at same aperture, aotbe, my be a good test?

Best regards

Erik

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Erik Kaffehr
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