Am 8/5/2017 um 23:27 schrieb Kenneth:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>> Another test-image post-- hopefully my final gamma test... ;-)
>>
>> This PNG render is post-processed in Photoshop, but I CHANGED my usual 2.2 gamma
>> there (in PS) to 1.0. *IF* this image shows up correctly here-- in both small
>> and large previews-- then I will at least have solved the major part of my *own*
>> problem...
>>

actually this PNG image has a embedded gamma of 2.0 and the image you 
did post earlier (the dark one) has a gamma chunk of 4.4 - and this 
doesn't make any sense at all.
>
> Success!! Both preview sizes here look identical, and correct--well, with maybe
> a *very slight* washed-out appearance in both-- but that could be from a number
> of reasons on my end, and is unimportant in the bigger scheme of things ;-)
>
> SO... it seems that my use of Photoshop-- at its *typical* gamma setting of
> 2.2-- was introducing a gamma change into the POV-Ray PNG image. I have aways
> assumed 2.2 to be the correct gamma in PS, for any/all PNG images that I've
> downloaded from the 'net, and even for Photoshop-created PNG images. But it's
> NOT correct for post-processing a POV-Ray PNG render: a PS gamma of 1.0 is
> necessary (at least for both of the newsgroup's two preview sizes to show up
> correctly!) So, *something* is amiss somewhere-- either a flaw in my version of
> Photoshop, OR in how the newsgroups treat preview images.
>

Which PS version do you use? Adobe changed the handling of various image 
file format between different versions a lot and especially Photoshop's 
handling of PNG in anything older than CS6 is known to be flawed.

I usually do recommend to open images in PS that do not include an ICC 
profile in a way that that PS does NOT assign a "working colorspace"
and also does NOT assign a color profile.

-Ive

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