Photoshop: Modify selection between two points

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  • Updated 6 months ago
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Having made a selection in Photoshop, it would be great if you could isolate and modify a section of the selection boundary.

I use the pen tool for tracing the edges of objects then convert to a selection.

For example, today I had an active selection of a complex object with dozens of corners but with a single gently curved edge at the base. This curve was uneven. It would have been very useful to be able to select two points on the crawling ants (perhaps just circle the area with the lasso tool, or place a dot at either end) and instruct Photoshop to smooth this 'super-active' section out.

You could take it further by allowing other modifications to a 'super-active' selection such as feathering, straightening, converting to path, saving etc.

As with most features in Photoshop, I'm guessing there must already be a way of achieving this, but I'm not aware of a simple way to isolate and modify an active selection boundary.

Thank you for looking.
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R Cassidy

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Posted 6 months ago

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christoph pfaffenbichler, Champion

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Why are you even creating Selections and not working with Vector Masks? 

Anyway, you can switch to Quick Mask Mode (Q), make a Selection, apply a Filter (like Median to smooth out the Channel at the selected areas) and exit Quick Mask Mode (Q). 
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R Cassidy

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Thank you for your reply.

"Why are you even creating Selections and not working with Vector Masks?".

Good question. Probably because there are at least three ways of doing everything in Photoshop and I have no idea what a vector mask is :)

I do my own website product photography, so I photograph something on a white background, but to get near to pure white, I trace around the object with the pen tool, make a selection, then make an inverted layer mask from the selection. I'm then able to manipulate the background.

I save the selections. It would be useful to revisit a saved selection, modify it, and make a new layer mask.

EDIT:

I just discovered vector masks!

Thank you so much!
(Edited)
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christoph pfaffenbichler, Champion

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If the objects combine parts that are in focus and parts that are very much not then Vector Masks are not very useful, but otherwise they can be. 
By setting a Feather in the Properties Panel one can even »blur« them, albeit only in their entirety and not locally. 
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R Cassidy

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I watched a PTC tutorial on making selections with vector masks today. I can make it work for me.

Select subject
Make path and refine it
Make vector mask
Duplicate layer and switch off for backup
Rasterise vector mask
Make my curves adjustment on my white background :)

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christoph pfaffenbichler, Champion

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I wonder if it might not be easier to move the Layer with the Vector Mask to the top of the Layers and add the additional Layers beneath that. 
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R Cassidy

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Thank you. Yes, that makes sense.

I have got used to doing things in a particular order - I also have conventional layer masks firmly embedded in my brain - the first thing my brain wanted to do with a vector mask is rasterise it!

It will be a hard habit to break.

Thank you for your help.
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James Gray

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I think you can do most of what you have in mind using quick mask mode and then modifying the  quick mask.  You can make a selection of the quick mask and work on that part of the quick mask.  You can do almost any manipulation of the quick mask as it works just like a channel.
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R Cassidy

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Thank you for this.

I have a pen/tablet, but I don't seem to have a particularly steady hand and so I have ignored quick mask mode until now - probably because most of my Photoshop projects are pretty simple and involve geometric shapes rather than hair/clothing etc.

I can do dot-to-dot though - so the pen tools are good for me. Christoph hit the nail on the head - I can achieve what I want to do by making editable vector masks.

Wish I'd found this forum a year ago.