Photoshop: Pixel Separation in Photoshop CS5 - Not Correctable Using Lens Correction Sliders

  • 1
  • Problem
  • Updated 7 years ago
  • Not a Problem
  • (Edited)
Russell Brown asked me to e-mail a sample of my issue to you and describe the problem. That file is attached. I have called the problem "pixel separation" rather than fringing because the manifestation of this problem is not a color fringe; instead it is a pure white border of pixel separation between elements of diffent colors, such as between foreground objects and backgrounds such as mountains or skys. The color fringing tools in Lens Correction (Photoshop CS-5) do not remedy this problem, which is quite evident in large size printes and shows as a pure white border between elements, as can be seen in the attached photo file.
Photo of Paul Stynchcomb

Paul Stynchcomb

  • 4 Posts
  • 0 Reply Likes

Posted 7 years ago

  • 1
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 769 Reply Likes
It's not fringing - it looks like a bad case of over sharpening. That won't be easily correctable outside of the camera or software that applied that sharpening.
Photo of Paul Stynchcomb

Paul Stynchcomb

  • 4 Posts
  • 0 Reply Likes
Thank you for your prompt reply. I am aware that this issue may, in fact, be an artifact of "oversharpening". This image was originally sharpened in CS-2. "Oversharpening" is a relative term. "Overshaprening" may be necssary for some digital files in order to make larger prints - details are held in the elements of the photo but the side effect is pixel separation. I can repair this problem using a localized Replace Color command, but it is very time consuming. It seems to me that Photoshop CS-5 should have a feature that detects this white border pixel separation (regardless what what caused it) and apply the color that was present in the regions which were originally occupied by the colored pixels. This pixel separation problem also occurs in CS-5 when converting a color file to B&W, using the color sliders to produce an infra-red effect - it's very noticable and, in my opinion, should be addressed by a software fix. The attached JPG files shows a Canon 5D Mk II file processed in CS-5 - zoom in on the tree to the left of the building and notice the distinct pixel separation. That is difficult to repair using the Color Replacement tool. Thank you
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 769 Reply Likes
No, in this case it is severely over sharpened - more than necessary for print, screen or any reasonable usage of the image. It blew out detail and created significant halos (which you see now). It would likely be faster to fly to the location and reshoot the photo than to repair this particular image.

There is no good way to repair damage like that -- because much of the detail has already been destroyed. The only good way to "repair" it is to go back to the original image before it was over sharpened.
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 769 Reply Likes
Also, this is not a lens or camera issue - and should not be part of Lens Correction or even ACR.
Photo of Paul Stynchcomb

Paul Stynchcomb

  • 4 Posts
  • 0 Reply Likes
Chris, I respectfully disagree with your opinion. I oversharpened the sample image to make this problem more discernable, however this pixel separation problem crops up in may CS-5 processed RAW images and since CS-5 can "see" pixel separation, I do not believe that it is unreasonable to ask why the program can't fill in the white space created by the user - for whatever purpose - oversharpening, infra-red result, or for whatever look your customer is trying to achieve. As to flying back to Pompeii to reshoot the image, you are welcome to forward round trip business class airline tickets to my attenion - I will pay for ground transportation, food and lodging.
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 769 Reply Likes
This would only happen if the image is severely over sharpened. This is not a normal problem, nor a camera problem. And it is unlikely to be corrected automatically - again, because a lot of detail was lost in the over sharpening.

Photoshop cannot reasonably fill in the white space because it cannot tell what is detail and what is over sharpening. (any more than a typewriter can automatically fill in missing parts of a story)

You threw away image detail when you chose to over sharpen the image. Again, the way to solve that is to go back to the original image before the sharpening damage was applied. If you don't have that original image: then you can live with the damaged image you have, manually replace the damaged areas (paint in false detail), or reshoot.
Photo of Paul Stynchcomb

Paul Stynchcomb

  • 4 Posts
  • 0 Reply Likes
I maintain a safe repository of evey original image I have ever shot in it's native format. As I noted to you, I purposely over-sharpened the sample image to demonstrate the problem, which occurs at lower levels of sharpening but can become very noticable when enlarging. While I respectfully disagree with your conclusions - your typewriter metaphor is really a non sequitur as to my issue of pixel separation - you work for Adobe and I don't, so I cannot direct its policies. It seems to me that the Photoshop software "knows" the colored pixels in an area that Photoshop basically pulls apart to reveal a white band around objects, and can replace the white band with the color of the displaced pixels. What is more basic; perhaps you should ask the question why Photoshop pulls apart the pixels in the first place. To me, if you wanted to fix the problem and it's clear that you don't, that is where Adobe should start. However, I assume this matter is closed.
Photo of Chris Cox

Chris Cox

  • 20280 Posts
  • 769 Reply Likes
No, the typewriter example is very similar to this situation. You want to fill in details that are entirely missing after the over sharpening damage occurs. That is not really possible without using the original image, or some sort of artificial intelligence. Yes, Photoshop knew more about the colors BEFORE you over sharpened the image. Afterward, the detail is gone - it's just blank space. And Photoshop can't tell that blank space from real detail that may have been in the original image.

Photoshop is sharpening, using the parameters you gave it. Part of the sharpening will produce a halo, and over sharpening will produce halos like you show in your examples. Normal sharpening parameters would produce fewer to no noticeable halos.

But we cannot fix this problem, because it is not directly solvable.
And we should not fix this problem because it is only your problem, not something that other customers need to solve.

The bottom line is that you are over sharpening your images -- you are applying too much sharpening for any known output. You probably want to read the book "Real World Image Sharpening" for guidelines on how to sharpen correctly for various outputs.
Photo of Jeffrey Tranberry

Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

  • 13977 Posts
  • 1671 Reply Likes
Hi Paul, I agree with Chris, more or less. It looks like you're oversharpening your images and introducing artifacts.

The book that Chris suggested on sharpening is quite excellent:

http://www.amazon.com/World-Sharpenin...