[libregraphics-resources] Guidelines for submitting and reviewing test images

[Elle Stone <ellestone@xxxxxxxxxxxxxxxxxxxx>]

Proposed submissions to the website should probably include a suitably 
sized jpg along with a description of what the full-size file is good 
for, and an indication of copyright information. I think the best way to 
come up with a good procedure is to work through some actual 
submissions. So here is a proposed submission in the category of raw 
files for testing raw processors:

http://ninedegreesbelow.com/files/test-images/very-yellow-flower.jpg
http://ninedegreesbelow.com/files/test-images/very-yellow-flower.cr2

It might be a good idea if people who want to submit an image first send 
just a jpeg, of perhaps maximum width/length of around 900px, in order 
to not be in the position of having to download a 36MB raw file or a 
200MB tiff just to see what the image looks like.

The jpg should be accompanied by an indication of what kind of testing 
the image would be good for, along with usage notes and the desired 
licencing information:

What the very-yellow-flower.cr2 raw file is good for:
*  This raw file is good for testing a raw processor's ability to not 
clip RGB data upon outputting an image with colors that exceed whatever 
interim color space the raw processor might push the data through. For 
example, RawTherapee pushes all images through ProPhotoRGB during its 
default rendering, and consequently severely clips the blue channel of 
the very yellow flower image to solid black, even though th blue channel 
is actually fully detailed. This is true even if the user requests a 
suitably large output color space. See 
http://ninedegreesbelow.com/photography/linux-raw-processor-review.html#radiometric, 
section F5, Figure 4 for details.
*  This raw file is also good for testing how the raw processor handles 
highlight detail that exceeds 1.0 after the white balance multipliers 
have been applied. UFRaw clips the highlight detail in the very yellow 
flower's red channel, even if the user tries to use negative exposure 
compensation and even though there are no clipped pixels in the raw file 
red channel. See 
http://ninedegreesbelow.com/bug-reports/ufraw-highlights.html for details.

My apologies for starting with such a complicated-to-describe test file. 
But it is an excellent raw file that reveals serious raw processor 
limitations, and especially so for people who primarily work with black 
and white renditions and really want to preserve channel detail.

Usage notes:
The "camera" white balance in very-yellow-flower.cr2 is "UniWB", but the 
actual white balance that should be used during raw rendering is 
"Daylight" (the image was shot in full afternoon sun).

Licencing:
I set the copyright as CC BY 
(http://creativecommons.org/licenses/by/4.0/legalcode), but I'm willing 
to make it public domain/CC0. Use "exiftool -a -G very-yellow-flower.jpg 
(or cr2)" to see the embedded copyright information in the 
very-yellow-flower images.

We might want to write up a page that informs people of useable 
copyrights, how to choose a licence, and how to embed the copyright 
information. I don't know how to embed the Creative Commons xmp file 
generated by the licence chooser at http://creativecommons.org/choose/.

Acceptable copyrights:
We probably should come up with a short list of acceptable copyrights, 
with public domain/CC0 perhaps being the preferred status, followed by 
CC BY. Images should probably have the relevant copyright information 
right inside the image metadata, as well as stated in words on the 
website, and the two sets of copyright information should match.

Elle
--
http://ninedegreesbelow.com
Color management and free/libre photography

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