How to create a 20% / 80% channel in Photoshop?

[swag72]

I'm not totally sure how to do this, so thought I'd ask here.

If I want to create a red channel for example with 80% Ha and 20% OIII data - How do I do that in Photoshop?

Is it as simple as opening both sets of data, having the OIII as a layer on the Ha and setting opacity at 80% for example? That just seems too easy!!

[Gina]

Yes, simple as that   It's what I do.  Actually the other way round - I use the major component as the background and the minor one as a layer on top.  Just open the minor component, Select > All, Edit > Copy then open the major component channel and Edit > Paste.  That will add a layer to the channel.  Set this layer to Lighten mode and select the Opacity slider and slide it to the required amount.  Do any layer adjustments you want then Layer > Flatten Image.

HTH

[swag72]

Thanks Gina

[Dave Smith]

Thanks Sara for asking the question - you always seem to ask the right questions   and thanks Gina for the reply.

Dave

[martin_h]

In CS3 there is a command.........."Image - Apply Image" where you can set a source and target image, blending mode and opacity.

[swag72]

Thanks Martin - So assuming I use this way ..... bear with me.

I want an 80% Ha and 20% OIII split. So I'd set the source as the OIII and the target as the Ha and use blend mode lighten and 20%? Is that the right way round? And do you normally use blend mode lighten for this?

[fwm891]

Sara - go with Martin on this but you must be working with layers. Watch your blend mode because some blend modes will only work with values above or below a certain point - lighten/darken modes are like that

[steppenwolf]

Sara, I find that blending Ha and Red channels using 'Lighten' mode can work very well to keep the high contrast of the Ha whilst maintaining good star colours. You can then do a further Ha/Red blend using 'Normal' mode and a reduced Ha opacity percentage to use as a new Luminance channel as this gives a good contrast match.

Sent from my iPhone from somewhere dark .....

[martin_h]

Thanks Martin - So assuming I use this way ..... bear with me.

I want an 80% Ha and 20% OIII split. So I'd set the source as the OIII and the target as the Ha and use blend mode lighten and 20%? Is that the right way round? And do you normally use blend mode lighten for this?

Yes but use ADD as the blend mode (add and subtract are not found in the normal layers menu) Or Screen mode....try both and see which gives the best results.

[sloz1664]

In CS3 there is a command.........."Image - Apply Image" where you can set a source and target image, blending mode and opacity.

This option is also in CS2

cheers

Steve

[swag72]

Thanks Martin, this is just what I was after