Unwanted colours pulled in by Gaussian blur filter

[IanWorthington]

I've been trying one of the suggestions from Katrin Eismann's book to deal with a distracting background: I run a Gaussian blur filter on a copy of the photo and then mask it in where I need it.

That seems to work well enough apart from close to areas where the colour changes between the main image and the background: the filter pulls in colours from the main image that don't belong in the background and I end up with a light flesh-coloured strip alongside skin areas.

Any suggestions on how I can avoid this?

[Doug Nelson]

For higher blur settings (it sounds like you either have it set pretty high, or the original is low resolution) you can use quickmask to select the background first, then blur. The selection will protect anything in your foreground from blurring at all. If you copy the selected area to a new layer before blurring (leaving it selected) your original will remain intact. You can then finetune the blur with a layer mask and opacity.

You might also want to check out Lens Blur if you have PScs. It gives a bit more control, including variable blur vis masking.

[IanWorthington]

Thanks Doug, but its not that the foreground is blurring -- that's coming in from another layer. Its that the background is being blurred with colours from the foreground that don't exist in the background.

But I'll check out lens blur and see it that does any better.

Thanks!

ian
...

[Leah]

Another thing you can do is put another (unblurred) copy of your background layer on top of the blurred copy and set the blend mode to Color. Then add a Hide All layer mask to the unblurred copy and paint in white on the layer mask over the areas where the foreground subject colour is bleeding into the blurred background.

[Flora]

Hi Ian,

Welcome to RP!

You could try this.... Nothing more than what Doug and Leah suggested but done in a slightly different way...

• Duplicated the Background Layer twice (3 Layers, Top layer made invisible for now )
• Selected the Flower and saved the selection.
• Decreased Saturation and strongly blurred the middle Layer.
• Activated the top Layer, loaded the selection and applied a Layer Mask.

At this point you see the original, sharp subject over the blurred/partially desaturated background.
Around the subject there is a big halo of colour from the blurred Background. (middle image in attachment)

To eliminate this, I created a new blank Layer between Blurred Background and masked subject, set its blending to color and with a soft brush (Opacity 40-60%), sampling colour from surrounding areas, I painted over the 'bleeding'.

By placing the color correction layer under your masked subject you don't have the risk of messing up the edges of your selection....

This corrected the colour of the halo, but not the brightness ... so, to correct that, I duplicated the 'Color' Layer set its blending to Multiply and blurred it until I was satisfied with the result. (If necessary, duplicate the multiply Layer and adjust its blending).

[IanWorthington]

Many thanks for all your replies -- I'll have a go in the next few days, though I'm not sure I fully understand how to perform some of those steps!

ian
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[Flora]

Hi Ian,

Thank you for your feedback!

Originally Posted by IanWorthington

....I'm not sure I fully understand how to perform some of those steps!

You know where to find us if you need more detailed help!!