I've stumbled across an issue i've never had before. It is about a Black&White image. For some reason, it was originally written as a "pure" Black&White image, i.e. the color components value is 1. This image was accepted by Adobe Stock. But it is rendered too bright on the Adobe Stock website, much different from the original image file:
On the other hand, if i upload the original image to this forum post, its brightness is correct:
So, this seems to be a special issue of the Adobe Stock website.
Then, i re-saved the image to reset the color compoents value to 3. I didn't change anything about the images content! However, some minor differences may result from jpg recompression. As the corrected image is about the size of the original image, jpg loss (set to high quality) should not be an issue. This image was then rejected due to artifacts.
Note: The original 1 color component image renders correctly on any other medium (local image viewer, editing software, other stock sites). It is only rendered too bright on Adobe Stock. Of course i cannot know if this issue is only on the website. Maybe the software used by the reviewers renders the image in its correct brightness so they didn't notice.
I would appreciate help in this issue. Thanks.
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Thank you for giving us the opportunity to assist in this matter. I am not sure I am understanding all the details. This is what I am not sure of. Is the image a JPG photo converted to black and white, or was it created in illustrator?
If it was created in illustrator, then to prevent shade difference, you need to upload it with a JPG copy in a folder. In this way you will not see a shade difference. Otherwise please let us know.
Thanks for the response.
Technically, it is a normal photo which came out of a normal camera. As the image was taken in a Contre-jour light situation (shooting against the sun), i decided to convert to B&W because of color saturation issues. It seems that for some reason, the photo processing software set the "Color Components" flag to 1 in the jpg file when it realized that there wasn't any color data. Normally the flag is 3 for colored RGB data, obviously.
After doing some research about jpg data formats and metadata flags and doing some experiments, i'm quite sure that the image data (i.e. the actual pixel values) are fine. I think it is only the "Color Components" metadata flag which irritates the photo processing software of the Adobe Stock website while any other software seems to properly handle the "Color Components" flag. Or most of them just ignore it?
Some further explanation, as far i can understand this issue:
1. Data content of the image. If an image is converted to Black&White (or the image directly comes this way out of the camera if set to create B&W images), the RGB components are the same for all color channels. i.e. conly values between (0,0,0) and (255,255,255) will exist in the image. But for the software, it should be a normal image. Black and white and greyscale pixels also exist in normal, colored images, after all. So the only special thing about a B&W image is that only color tones between Black and White will occur. So, technically, a &W picture should be displayed just like a normal picture, as the only difference is that a B&W image lacks pixels where the RGB color components are not equal.
2. Data encoding. It seems that my processing software tried to be super smart to mark the image as a B&W image when it realized the RGB values were identical for all pixels. This is done with the "Color Components" metadata flag. It is 3 for a colored image, it may be 1 for a B&W image.
So, the content of the image should be just fine. It is the only "Color Components" flag which seems to irritate the image processing functions of the Adobe Stock website. Note that i was able to change the "Color Components" flag from 1 to 3 (by loading and re-saving with an application which handles the flag correctly). However, Adobe Stock may possibly reject the image - although it is the same image! - when i re-upload it because you can never know for sure if an image be accepted or rejected, so i'm hesitant to try this (again).
Thank you and best regards
Its me, again 🙂
I have been some further research and experiments, maybe there is something you may find useful for resolving this isssue.
1. Upload the original image file to Adobe Forum.
-> Image brightness is correct:
1. Upload orignal image file to Adobe Stock.
2. Download preview image as it is displayed in Adobe Stock, using the browser's "save image as" option.
3. Upload the downloaded preview image to Adobe forum.
-> Image is too bright:
As both strategies, using the same original file, lead to different results, it is clear that there is something happening in the way Adobe Stock processes the uploaded image.
I also checked the brightness value of some pixels in the images, comparing beween the original darker image and the Adobe Stock image which is too bright. There was no directly comprehensible numerical correlation between the brightness values. As the correlation seems to be nonlinear, my guess this is a gamma value issue.
Looking forward to your reply.Thanks.
What I do know from experience is that all applications display, or reproduces colors differently. For this reason when I upload I do not place great emphasis on the brightness of colors as displayed. An image upload to different websites will display differently. The same image will also display differently in different photo viewers or editors. I will however see if I can get the input of others just in case there is really an issue.
My suggestion is let it remain as is. The moderator knows the file has a high probability to sell as is. That is why it was accepted. Once it is accepted by the moderators, you can safely accept that it is fine.
Otherwise the only way is to delete the uploaded file and re-upload. However as you by now realize, that is a big risk of your file not accepted at all. So let it remain and move on.
You're probably right. Besides, i've come to the conclusion that the effect may be limited to when the image is rescaled to a smaller size. Then, this effect would only affect the previews. When a customer buys and downloads the original image, the brightness will be correct, then the customer will be surprised by a different look of the image - for better or for worse 🙂
I'm going to assume that the moderators also see the full sized, original image as this is required for judging the quality of the image. So they are probably also unaware of this issue.
So, everything is fine unless customers are discouraged to buy the image if the bright preview gives them a wrong impression of the available image.
So, i'll consider this as a marginal issue and, as you suggested, leave it as it is.
I'll mark your answer as the correct answer as this is the final result.
Of course, thanks to D_Fosse for the technical background which was very insightful.
As a final remark for anyone stumbling upon this thread, be careful about ImageMagick's auto-grayscale function.
So thanks again to both of you.
You are welcome
The question is - has the file been converted to grayscale in Photoshop, as opposed to RGB? In other words, does it have one or three channels?
If it has, don't do that. Proper grayscale support is virtually non-existent outside Photoshop. The image will display, but with unpredictable tonal values. Grayscale requires a very disciplined workflow, and is really only appropriate in a very few special scenarios (such as K-only offset print).
Hi JG, Hi D_Fosse
Thanks for your input. After some research, experiments and thinking, here are some results:
* I agree that images may be displayed diffferently, depending on hardware (LCDs, OLEDs, Prints) and software (color profiles). But in this issue, it is not only about how a image is displayed. It is that the image is modified. You can see this in the following example. Here, i used ImageMagick to generate a gradient (greyscale from black to white). Then, i uploaded this image to Adobe Stock, downloaded the resulting thumbnail and appended the thumbnail to the original image:
You can see that the thumbnail image created by Adobe Stock (bottom) is brighter than the original image (top): The black end has become smaller, the white end has become bigger. The mid tones have become brighter. This can also be seen in the histograms:
Histogram of original image:
You can see that the tones are distributed equally. The spikes may be caused by quantization (rounding issues) and are thus irrelevant.
Histogram of the thumbnail generated by Adobe Stock:
You can see that the histogram is shifted to the right. The nonlinearity of the ramp-like shape may indicate a gamma value issue.
* I can confirm that this is a file format issue. This only happens for a 1 color components file. For a 3 color component RGB image (regardless if it has greyscale content i.e. all pixels have R=G=B values) there is no change of brightness.
* I used ImageMagick for a batch automated final postprocessing step. Unfortunately, i was unaware of the fact that ImageMagick will write a 1 color component file if it detcts that only grayscale tones are present in the image. This can be averted with the -type truecolor command line switch which will generate a 3 color components RGB file. Of course, this won't affect the content the of image. If it is grayscale it will remain grayscale, just in an other file format.
* As i see it, the tonal change in Adobe Stock has a signifcant impact. While the original file has a pencil drawing appearance, the modification by Adobe Stock makes the look faded or bleached out.
* I have already created a corrected version of the image. Using a copy of the image before the last postprocessing step and repeating the final postprocessing step with applying the -type truecolor command line switch, a file was created with the correct 3 color components RGB image file format - with the same content (i.e. it is still greyscale as intended). As there were no additional postprocessing steps, jpg compression noise should be identical to the original file.
So regarding its contents, the corrected file should be a 1:1 identical replacement for the original file, just in another, more compatible file format. But, Adobe Stock won't accept it due to "technical issues".
So, this image was accepted:
And this image was rejected:
Regarding their content, they are exactly the same. The only difference is the file format.They were generated n the same (slightly modified by the -type truecolor 3 color channel file fomat switch) finalizing step. So, what makes AdobeStock accept the first one but reject the second one? Or do they prefer the artificially brighter version of the image?
Looking forward to your replies. Thank you.
So it is grayscale. That explains it. And most importantly, this is fully expected and normal behavior, given that you haven't taken any precautions. Here's what and why:
What you need to understand is that in Photoshop, grayscale is subject to normal color management, just like an RGB file. There is still a color profile at document level, which gets converted into the monitor profile for display.
The problem is that all this color management stops outside Photoshop. Almost no other applications support it.
The document profile, in this case a grayscale profile, determines the actual numbers in the file. Convert to a different grayscale profile, and the numbers change. Again, this is the way color management works. You must have a profile for the numbers to have a precise meaning. Without a profile, it's just naked undefined numbers, and they will display randomly according to the destination's characteristics, whether a monitor or a printing press.
If you haven't picked a certain grayscale profile from the start, it will be whatever you have set as working gray in Photoshop. And the default is the pretty useless Dot Gain profiles (originally intended as generic offset print profiles). A dot gain profile has no relation whatsoever to a normal monitor.
That's fine as long as you view the file in Photoshop. It color manages correctly, and the file displays correctly. The dot gain profile is remapped into your monitor profile.
Outside Photoshop it all falls apart. There is no longer any color management to remap the dot gain profile. So it displays very very wrong.
Bottom line is still don't use grayscale. But if you absolutely must, pick a profile that is fairly close to your monitor's characteristics. Gamma 2.2 is close, but even better is the one called sGray. That's the gray component in sRGB, the same tone curve. If you use that profile, it should display roughly right.
But still - my sincere advice is to not use grayscale unless you are absolutely sure of what you're doing and why. Post a monochrome RGB instead.
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In addition to the explanation given by D_fosse, you may find some useful info at https://www.linkedin.com/learning/photoshop-2020-essential-training-the-basics/color-modes-and-bit-d... tutorial.Hopefully they are applicable to your situation and you find them helpful.
Hi D_Fosse, Hi JG
Thanks for your help. Color management is an important tip, although colorspace may be more important than color profile, which is as i understand primarily a part of an output medium's calibration.
My conclusion: Originally, the image came as a colored sRGB out of the camera. While being converted to monochrome content(!) in postproduction, it remained in sRGB colorspace during postprocessing. When using ImageMagick for a batched final postprocessing step, it automatically converted the monochrome image from sRGB colorspace to gray colorspace. ImageMagick does this automatic conversion when it detects that the content(!) is monochrome. Then, Adobe Stock converted back to sRGB colorspace when creating the thumbnail. It would seem that this conversion and back conversion is the root of the problem.
Note that ImageMagick offers parameters to deactivate the automatic grayscale conversion or to force the colorspace of the output file. Unfortunately, i was unaware of this issue when submitting the image.
Anyhow, i think we can settle this issue. I totally agree, don't use greyscale, use monochrome RGB instead. Be careful about the auto-grayscale option or the colorspace or type setting when using monochrome images in ImageMagick.
Once again, the conversion to greyscale colorspace was unintentional. ImageMagick did this behind my back. The only problem is that Adobe Stock won't accept the corrected image (in sRGB colorspace) while they accepted the image with the wrong grayscale colorspace. Is there any way to inform the reviewers about this issue so they will allow me to replace the image?
Thanks and regards
"although colorspace may be more important than color profile, which is as i understand primarily a part of an output medium's calibration."
Nothing so esoteric. It's very simple:
A color profile is a description (a map) of a color space. They refer to the same thing - but one is a map (profile), and the other is the landscape itself (color space).