Altering images based on a sample.

[Paul Sinyard]

Hello,

Is it possible to alter images based on a sample from a black area in another reference image?

Does anybody know if it is possible to alter an image based on a sample taken from a black area of another image? I have lots of images of stamps taken on a black background. Some batches have had different lighting and color adjustments. I would like to change all the images based on a reference image that I believe gives the truest representation of color. Would it be possible to sample some of the black area on the reference image and then have Photoshop make an adjustment to another image that gives the same color/lighting to the black area and also applies the same transformation to the rest of the image? I hope it is possible and that I will then be able to do batch processing to ensure all my images provide the truest representation of the stamp color.

Many thanks for any help you can provide on this tricky issue,
Paul

 

[IamSam]

Would it be at all possible if you provided some reference screen shots so we can better understand what it is you are trying to accomplish?

From what I'm understanding, you are just wanting to adjust all other stamp photos based on the color and lighting of one stamp photo? This may depend on the consistency of the existing color and lighting of the photos of the stamps, and their black backgrounds, to be altered. Are they all the same?

Again, not seeing but assuming, unless the black areas are all the same, we may have to mask out the stamp in the photo so that adjustments can be made independently. One adjustment for the background and one for the stamp. If the photos are not consistent, this would likely have to be done for each stamp photo. But if they are consistent, an automated process may be possible.

Would have to see the photos...............sorry.

 

[Paul Sinyard]

Thanks IamSam,

The differences are not huge. I have attached two images for comparison. C37 has the correct and more subdued lighting/color adjustments. C10 has incorrect lighting/color adjustments that make it a bit too vibrant. Just to be clear, I am not looking for the red to be the same on C10 as it is on C37, this is a different stamp with a different color. I am just wondering if it is possible to make adjustments to the entire image that will result in the same appearance as the black background on C37 and thereby give the correct adjustment to the C10 stamp to tone down the vibrancy.

Kind regards,
Paul

 

[Rich54]

If I take color samples from various points of the black background of your C37 image, I get slightly varying results, meaning that it is not uniformly lit (or perhaps that the actual black paper itself is not uniform). The differences are fairly small and if I take an average of all the various measurements, we can say that your "correct" black background should have an RGB value of 50,50,50.

If I do a similar analysis of the C10 image that needs to be adjusted, its rough average RGB value for the black background is 45,45,45. To make it the same as C37, the black background of C10 needs to be brightened using either a Levels or Curves adjustment.

However, if I sample the tan color in the bottom-left corner of each stamp (i.e., the tan areas surrounding the letters F and Q, like below), then I find the opposite result: image C10 is already brighter than image C37. Therefore, if we go ahead and increase the brightness of the black border of C10 (as we must do from the above discussion), then we make the disparity of the tan colors even worse, and that will also make the reds even brighter. You want the reds to go the other direction.

In other words, I don't think that equalizing the black backgrounds—by itself—will accomplish what you desire.




In the image below, the left side is your original C10 as you posted it. The right side contains my adjustments where I first brightened the black border to 50,50,50 and masked the adjustment so as not to affect the stamp itself. Then I used a separate Curves adjustment to bring the tan color in line with C37, which also affected the red areas of the stamp. I masked this second adjustment so as not to affect the black border.

Hope some of this is helpful.

 

[Paul Sinyard]

Thanks, everybody for the help and suggestions.

It seems that what I had in mind is not possible. I have however come up with a workaround. I signed up for a 7-day trial of Phototshop and created an image export action of hue +5, saturation -10. This seems to give good results. I have purchased an annual subscription to Photoshop in order to do batch processing as a result.

Not quite as comprehensive as what I was hoping for, but certainly a lot better than before.

Best wishes,
Paul