Doug Kerr
Well-known member
Some recent lovely work by Chris Calohan included "very dark shadows" on a background that was "very dark gray".
As the image was rendered on my system, I could not distinguish on-screen the "very dark shadows" (about RGB 3,4,5) from the "very dark gray" background (about RGB 15,15,16). Apparently others here had the same experience.
This may lead to a discussion of the rendering of the bottom end of the gray scale by way of browsers onto typical display chains.
To help give a quick idea of what we each get in this regard, I have just "spruced up" a grayscale test image I have used in the past. Here it is presented through the forum in the usual way, from a JPEG file:
Then color space here is sRGB. Each "block" (I have not put visible boundaries between the blocks) has a color of R=G=B= the number mentioned. Those values range from 0 to (full black) through 64*, in steps of 4 units of RGB.
Across the top is a bar of RGB=0,0,0 (full black). This allows us to distinguish how well (if at all) can one of the gray colors be distinguished from black in our display chain and viewing environment in an "adjacent" juxtaposition.
The image file itself can be downloaded here:
As a JPEG file:
http://dougkerr.net/images/test/sRGB_step_wedge_22.jpg
As a TIFF file:
http://dougkerr.net/images/test/sRGB_step_wedge_22.tif
I can readily make other test images in this same vein if there is anything one of you would like to have.
As a matter of interest, on my current system, in its current state, in my current viewing environment, in my current state, with the file displayed from its presentation on the forum, in this very idealized juxtaposition, I can just barely distinguish the RGB 24 block from the RGB 0 block.
I would say, rather arbitrarily (this is of course so very subjective), that in this situation, the smallest distinction against black that could be exploited in an image (assuming a uniform "shadow" with a distinct outline, against a uniform RGB 0 background) would be with about RGB 32.
Best regards,
Doug
As the image was rendered on my system, I could not distinguish on-screen the "very dark shadows" (about RGB 3,4,5) from the "very dark gray" background (about RGB 15,15,16). Apparently others here had the same experience.
This may lead to a discussion of the rendering of the bottom end of the gray scale by way of browsers onto typical display chains.
To help give a quick idea of what we each get in this regard, I have just "spruced up" a grayscale test image I have used in the past. Here it is presented through the forum in the usual way, from a JPEG file:
Then color space here is sRGB. Each "block" (I have not put visible boundaries between the blocks) has a color of R=G=B= the number mentioned. Those values range from 0 to (full black) through 64*, in steps of 4 units of RGB.
*Ideally relative luminance 0.0513, "94.9% gray", 4.29 stops down from maximum luminance.
Across the top is a bar of RGB=0,0,0 (full black). This allows us to distinguish how well (if at all) can one of the gray colors be distinguished from black in our display chain and viewing environment in an "adjacent" juxtaposition.
The image file itself can be downloaded here:
As a JPEG file:
http://dougkerr.net/images/test/sRGB_step_wedge_22.jpg
As a TIFF file:
http://dougkerr.net/images/test/sRGB_step_wedge_22.tif
I can readily make other test images in this same vein if there is anything one of you would like to have.
As a matter of interest, on my current system, in its current state, in my current viewing environment, in my current state, with the file displayed from its presentation on the forum, in this very idealized juxtaposition, I can just barely distinguish the RGB 24 block from the RGB 0 block.
I would say, rather arbitrarily (this is of course so very subjective), that in this situation, the smallest distinction against black that could be exploited in an image (assuming a uniform "shadow" with a distinct outline, against a uniform RGB 0 background) would be with about RGB 32.
Best regards,
Doug