Strange marks on background of image post editing

[lilyc66963996]

Hi,

I am trying to edit out a plain background that had lots of marks/shadows to a clean, plain background.

I use this method:

Edit lighting, contrast etc

Touch up photo with clone/patch tool

Duplicate layer

Surface blur > create layer mask > invert

Fill in the background with the surface blur

Go back to the layer (not the layer mask with blur)

Select the exact colour I want, use a soft brush tool with opacity of around 50%

Go over image with brush tool.

The image looks exactly how I want it to.

I then flatten (have also tried not flattening) and export as jpg.

However, then once the image is saved and I view out of photoshop, the background has these strange marks all over it. They can look slightly like oil spill marks , or just lighter blobs.

It does appear to be where I have edited the background, but I don't understand why when I am in photoshop the image looks perfect but then out of it looks awful!

Please help

[Chuck Uebele]

Can you post screen shots of before and after?

[lilyc66963996]

Have no before photos - it was just on a scratched up grey/white board. Can you see the strange marks I am talking about? They are green/white/grey. Even if I brush too 100% opacity over them, they remain when exported. It isn't only on this image too, it is other images that are similar

Thanks

[Chuck Uebele]

I pumped up the contrast to see better. Are these green areas what you're talking about? And they don't appear until after you export? what bit depth are you using to edit 8 or 16? what color spaces are you using?

[lilyc66963996]

Yes!

And I believe I used 16 bit.

What is colour spacing? I am self taught and haven't heard this term before.

Thanks

[Chuck Uebele]

Reducing down to 8 bit when you export could cause the posterization of subtle colors that you're seeing. Different spaces can further accentuate this issue by reducing the gamut of your colors: say going from a wider gamut color space of Adobe RGB to sRGB.

[Theresa J]

As Chuck explains, these marks are probably in your image before you export, but they aren’t noticeable because the 16bit size creates a much smoother transition between the subtle color changes. You could proof your image before exporting it using the technique Chuck used to check your exported image. Add a levels adjustment layer on top of the layer stack, and crank up the contrast. I’m guessing that you will see the marks. Let us know what you find. Maybe post another screen capture with the results.