Am 05.08.2017 um 04:12 schrieb Kenneth:
> I just noticed something strange about the PNG images I posted: When I look at
> the small *preview* images here in my post (using the latest version of
> Firefox), they look correct: identical to how they appear on my own machine,
> when viewed in either Photoshop or the Windows Photo Viewer. (BTW, I
> post-processed the images in PS, but only to combine two renders into one post.)
> 
> But when I click on the image previews here-- and the higher-resolution versions
> appear-- the gamma of the images isn't correct! They look darker, with more
> contrast.
> 
> Does anyone else notice this? Right now, I have no idea what's going on, or why
> they appear differently on the same website.
> 
> Honestly, I simply don't trust PNG images to show up consistently or correctly,
> anywhere! :-(  I should have posted them as jpegs.

Actually, it's the PNG images that should generally be considered more
trustworthy, as it is virtually the only image file format that includes
gamma handling right in its specification.

My bet is that you instead have a wonky post-processing workflow, as
your PNG file is seriously odd: The `gAMA` chunk in your PNG file claims
that the file was encoded with a gamma of 0.22727 = 1/4.4 (or
"pre-corrected for a display gamma of 4.4", as it would be called in
other file formats), rather than the typical 0.45455 = 1/2.2; I suspect
that `gAMA` chunk is outright wrong.


For the JPEG file format, as far as gamma goes there's only a W3C
recommendation for use on the internet. The file format itself is
blissfully unaware of gamma. So you just have to pray that the target
system /happens/ to interpret them in the way you intended them to be
interpreted.

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