Am 06.03.2018 um 00:02 schrieb Kenneth:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>> (There's also a HF difference
>> between images SAVED at different gamma values, for the same reason-- 1.0 being
>> a linear slope, 2.2 being more of a curve.)
> 
> Uh, I'm not so sure about that now. I made a test scene a couple of weeks ago
> that showed this. (Or so I thought.) Now, a newer test scene shows no
> difference-- producing the same 'linear' height_field slopes no matter what
> gamma the images are saved at (with either JPEG *or* PNG image files.) But then
> again, I'm using my older wonky Photoshop 5 to make and save the original
> images, which can't be completely trusted as far as gamma goes.  Hmm, a mystery.

By default, when using images in a height_field, POV-Ray presumes that
the image data is to be taken linearly no matter what gamma the file
claims to match, e.g. in an 8-bit image a data value of 240 will always
be interpreted as a height of 240/255, even if the file claims to be
saved for a display gamma of 2.2.

So if you just create an image in Photoshop and /assign/ a particular
gamma to it later, there will be no difference as the image data will
not change. You'd need to /convert/ the image from one gamma to another
to see an effect.

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