Jump to content
You must now use your email address to sign in [click for more info] ×

Identifying/masking burned pixels


Recommended Posts

A way to identify pixels which are burned out (white), which can be handy for example in creating mask to clean them up:

 

  • Duplicate layer (Ctrl-J)
  • Invert (Ctrl-I)
  • Blend Mode: Colour Burn

Any burned pixels will appear white. Everything else will be black.

 

This works because (across RGB channels):

  • The blend calculation formula is: Result = 1 - (1 - Base)/Blend
  • For white in bottom layer, Base = 1. For black (inverted white) in top layer, Blend = 0.
  • In this case, Result = 1 - (1 - 1)/0 = 1 (white)
  • For all other colours, say 0.4, Result = 1 - (1 - 0.4)/0.6 = 1 - 1 = 0 (black)

To see what is in the image below, get a white brush and hover over any area - it acts like a torch.

Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

Link to comment
Share on other sites

Having said all this, in another test I got some coloured pixels - red, yellow, magenta, green, blue.

 

So I did a further test - Duplicate layer. Blend Ranges (gear icon) Pull left node on left graph to bottom right corner. Add empty layer below, filled with black. This also selects white. Comparing the two methods, the coloured pixels are black on the second method.

 

Then a lightbulb went on somewhere. The pixels which appear non-white are saturated in at least one RGB channel but not all of them. So partial burn. I guess that's useful to know too, but as masks are not per channel (without fudging) not so helpful in this.

Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Terms of Use | Privacy Policy | Guidelines | We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.