Blending Options – Blend if: Blue reveals Red

PG
Posted By
Pat_Gilmour
Nov 12, 2006
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252
Replies
4
Status
Closed
Hi,
I have a two layer image. On layer 1 is a portrait with bright red hair. On layer 2 (above) is an image of a garden with various colours in it.
What I want to do is use the Blend If: options in Layer Styles>Blending Options to bring the red hair up through the garden image as a blend. So I select layer 2, open the Layer Styles>Blending Options dialog, select Blend If: Red and use the Underlying Layer sliders to try and bring the red hair through the upper layer 2. It works to a certain degree, especially if I split the sliders (using Option). But what I don’t understand – and would be very appreciative if someone could shed some light on – is the fact that if I use Blend If: Blue and split and slide the shadows on the Underlying Layer I get much much better results and the red hair blends through the upper layer really well. Can anyone explain why Blend If: Blue works better than Blend If: Red?
Thanks,
Pat
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RC
Ric_Cohn
Nov 12, 2006
Unless you have an excellent sense of what the individual channels in an image will look like, you should look at the individual channels before deciding on which will work best for a blend. Many times it works better to select something for "what it’s not". The red hair would be mostly yellow with some magenta. In other words mostly "not blue". In this case, if there are a number of areas with magenta in them but not as many with yellow, then blue will work better.
PG
Pat_Gilmour
Nov 12, 2006
Ric, thanks for the reply. I’ve been finding this really tough to understand. You’re 100% right: the red hair has mainly yellow and magenta in it in CMYK. In RGB, an average reading is R-175/G-38/B-0. So in either case mostly "not blue", as you say.

So, by blending the Blue channel up, I’m actually revealing the places where the blue channel is mainly black (i.e empty) and creating space in the upper layer where the red is clearly visible. And that makes sense! Because I was blending the Blue Channel using the shadows sliders which correspond to the black areas in that channel, right?

I checked, and that’s exactly what’s happening. The shadows in the Blue channel are equivalent to the place where Blue is not present (i.e black on the channel) and so they best reveal the other colours present – red in this case.

Thanks a million Ric. Really helped.

Pat
RC
Ric_Cohn
Nov 13, 2006
Glad it helped. I find Channel Blending with "Blend If" to be one of the most powerful image editing techniques, but also one of the most difficult to get my own head around.
PG
Pat_Gilmour
Nov 13, 2006
Yeah, that and the Channel Mixer which seems to require knowldge through revelation 😉 Thanks again, Pat

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