Select and Mask decontaminate colors issues.

[Petr Holusa]

Hello,

After latest updates to 2017.1.1 I have problems to decontaminate colors when I'm masking image and getting really strange results.

Simply I select image white background by magic wand tool, Select and Mask tool with refined edges. I used to use selection Decontaminate colors.

During work when I switch off the mask I will get this result like never before. I don't know why.

Anyone had this experience?

Thank you.

[melissapiccone]

Why are you using decontaminate with a white background??? It's meant for green screens - the green gets everywhere. This image looks nice and neutral - no color spill anywhere.

[jeffs235]

I tried this on a similar image of raspberrries downloaded from Google images. When the mask is disabled, there is a bit more pixelization around the selection edge with this method, though not quite as severe as you have experienced here.(see attached images) I would suggest that is a result of the refining of the edge with the Refine edge brush and using the Decontaminate Colors option, which is going to have a tolerance setting that affects how the edge is rendered. Once the layer mask is created, it appears to recalculate the transition edge, resulting in a smoother, less pixelated selection. I don't see this as a cause for concern.

What is the resolution of your image? This may be a significant factor in the edge pixelization.

[jeffs235]

One more thing-Your image has already been isolated on a transparent background, and your layer mask is further isolating the edges in your layer. Did you make an initial selection, delete the pixels around the raspberries, and then revisit the selection using the select and mask option to refine it further? Deleting pixels with a low res image selected could also result in a ragged edge, especially if the tolerance of the tool was low.

[davescm]

Simple answer is do not use decontaminate colors in Select and Mask - it does not work.

If you need to decontaminate - create a new empty layer above the masked layer and clip it to the masked layer. Set the blending mode of this new layer to color.

Now with a soft brush at 25-30% opacity use colour picked up from the image (Alt-Click) and brush around the edges.This will colour using the image colour and cover any contamination from the old background.

In this case though it does not look like you have much , if any, contamination to deal with

Dave

[Terri Stevens]

Dave is right. Decontaminate color works by detecting colors on the image edge which have been wrongly extracted from the background. It then changes those colors on the cutout edge to more accurately match adjacent pixels on the cutout edge. It does this separately of the mask ie it's a destructive modification of the image, which is why turning the mask off makes it look worse

[Petr Holusa]

But I don't understand why. Couple of versions back it was totally fine without any destruction of image layer. Logically It should be non destructive way. I liked decontaminating colours because it kept all shadows, so it saved a lot of time.

[trevorr65060795]

I agree, I've used this plenty of times when cutting out portraits when they are standing in front of a tree and it really helps with the green haze which comes through. Worked fine a few updates ago.

[Chuck Uebele]

I've seen this happen when the feature was just released, so it's been there a long time. If you have to use it, use it on a duplicate layer.

[lailah021288]

What decontaminate colors does is getting information from inside the subject and fills the edges. I solved my problem following this tutorial, really helpful: How to fix Decontaminate Color issues in Photoshop from Complex Selections in Photoshop Class | Crea...

In short:

- use the refine edge and decontaminate colors and choose new layer with mask

- you'll have your cut out

- then have a duplicate of the original image up your cut out

- create a clipping mask with it (so it will only show what's masked on the cut out layer)

- create a mask in that duplicate of the original layer

- now you can choose what you don't want to be affected by the decontaminate colors

Much better to follow the instructions in the tutorial if you're not familiar with clipping masks, but there you go.