Topic: Blend If option

[ganna]

Since Chris started with the subject of Blending under the "Sharpening" subject, I was doing research and a lot of playing. This example is a way to replace ie a burned out sky. Please tear this story appart if there are better or easier ways. (I use PS CS4) This is not a perfect sky colour, I just want to share the workflow.
1. In PS duplicate the original layer (Crl + J) and rename CM.
2. Open in CM and under RGB (screenshot 1) I moved the red and green sliders down on the right hand side to change the colour of the sky to blue. Everything else also change to blue, but ignore for now. Go out of CM (save)
3.Double click on right hand side of the layer (CM) to open "Layer Style" window (screenshot 2). Move Dark slider of "This layer" under Blend If to the right (here 150) This will now prevent the CM adjustment from affecting any tonal value of 150 and lower.
Look at the horizon left of Zebra's nose.. a harsh transition. To soften this transition, hold the alt key while double clicking on this slider and move the right hand half to the right (here 185) We have created a feathering effect. No value below 150 is affected and from 151 is affected gradually more until the full strenght is active from 185 to 255 (screenshot 3)
4. Fine tuning can be done with a layers mask. Paint with a black brush on the layers mask to prevent the undesireable blue effect on the white of the zebra.
5. Can also paint with a large soft edged brush on the horizon for furher fine tuning and lastly we can lower the opacity of the CM layer to say 85%.

[themightyzog]

Hi Ganna,

I'm glad you are getting into BlendIFs, I think it would be great if CM had that facility - I'm surprised that Greg has not jumped in to show you how this can be done entirely within CM.  This screen shot shows you how with the mask facility (I used the L channel) it is easy to do.

Playing with the CM mask feature can be a bit tricky at first, but then with a little practice it is quite easy - the trouble is trying to remember that the feature is there!

Happy Easter
Chris

[derekfountain]

This screen shot shows you how with the mask facility (I used the L channel) it is easy to do.

What's going on with that fringe around the mane? Ganna's image didn't have that!

[themightyzog]

Not being able to set the mask well enough!!  I'm sure Greg will show you the correct curve for it.

I should add that personally I think that the BlendIF feature gives one much more control when making colour changes to objects - especially in Lab as you can adjust each channel independently and decide how much of the original and adjustment layer you want to show through.

[Greg Groess]

Zog,

I am going to take a hack at the zebra but I wanted your take on this as well you have hit upon one of the problems with masking.  The fringe on the mane is troublesome and may require a bit more work.

As I continue to explore masking in CM, it is starting to be apparent that it can be a blending option.  When we think of mask we typically think of hard black and hard white.  I have been exploring areas where the tonal areas can help.  The image of the child on the beach for instance.  The green is not consistent across the entire image and blending may be a better option.

For the Pony in this image...OK Zebra...The fringe should be able to be reduced you might try setting the hardness of the mask. 

I'll have more on this hopefully later today.
I will say that because of you..yes you Chris...I am trying to learn much more about Blend If.

Greg

[themightyzog]

Ganna & Greg, here is the same adjustment but using Lab

1st image is adding the blue tint on it's own layer

2nd is making the blue stay in the sky and returning the yellow of the strips back to exactly what they were - I have left the clouds a bit posterized to show how controllable this is.

3rd is making the far background back to roughly what it was - look at the bit next to his nose.  This is the tough call

The last image is a difference between the 3rd and the original with an added level adjustment (taking 255 down to 91) to really show what has changed.

I think if you try this in lab you will get a much better result than using BlendIFs in rgb.

[ganna]

Chris, did you use Lab in CM or is it purely Lab mode in Photoshop or both? If in CM, I'm not sure how to get the L, a, and b  channels as layers in PS.
Greg and Chris, I purchased Mark Johnson's "Photographer's Photoshop CS4 Companion" ebook (www.msjphotography.com) and in it he describes under "Sophisticated selections using an existing channel" a process of selecting a cat and keeping the fine fur visible, very similar to how the masking selections in CM works. I think CM is much easier. He finally refines the edges (fur) by using the Dodge tool exposure 70% and on highlights with a soft brush on the white side- and then the Burn tool, exposure 70% and shadows on the black side of the mask. It would be nice if one could use the "PS Tools" inside of CM to refine a mask even furher. It should work if one could move CM from  "Filters" to  "Adjustments" in the layers palette in CS4. Shall we turn Mikes' arm?

[themightyzog]

Ganna, both - I used CM (on a duplicate layer) to set the blue sky, then on exit converted the image to Lab (no flatten) in order to use the blendIF feature on the individual channels

[ganna]

Few years ago I read an article "Curves on steroids" in Earth Bound Light which lead me here to  CM2 at the time and this community. Here I read about Dan Margulis and decided to buy his book "Professional PS" It was like a school child reading a book written for post graduates. When complaining to my son, he said "read the title dad, its for professionals, not beginners like you."  Amongst this, over my head content, I saw he mentioned a very important part of PS, called 'Blend If'. I always want to know how things work and not only use it as recipe and hope for the best. Looking on the internet and in books on PS and even in the help files of PS, very little is available about Blend If.  To quote Mark Johnson: "Buried at the base of the Layer Style dialog, the Blend If sliders are among PS's most mysterious and least understood compositing features. Given their extraordinary power, it's a shame that more people don't use them."  For myself, we have a saying in my mother tongue " I start hearing the sound, but I do not know where the bell is hanging" (free translation). 
I'm writing this, because there may be more dummies like me out there.
Chris, I'm patiently waiting for you to explain this in your website (your promise of June or July)

[themightyzog]

Sorry to have failed you Ganna - I thought that this
http://www.broadhurst-family.co.uk/lefteye/MainPages/Tutorial_BlendIF.htm
was enough to get people interested and wanting to explore it more - is that enough?

My web site is rather like my mind - totally disorganised!

[ganna]

I've previously missed this one. Thanks a lot 

[Greg Groess]

Zog,

This is why I am trying to learn from you as well...I am afraid of times like this where as a carpenter, holding my hammer, everything begins to look like a nail.

I would have to say that while I can correct this in CM I cannot approach the fine details of the blend if.  The mask is still far to coarse for this kind of correction...Perhaps in a future release you might see something that allows you to approach that level of blending..

Greg

[curvemeister]

The broader point is well taken - if Curvemeister were an improvement on the hammer or saw, that should not deter anyone from using pliers or sandpaper.  The blend-if sliders are an incredibly valuable tool, though they do require a mode conversion in order to use a channel from that mode as a mask. 

Curvemeister already supports a single channel blend-if, in the form of straight lined curves on a mask channel.  IOW, for each *single channel* blend-if has an equivalent mask/curve combination in Curvemeister.  Once you go to multiple channels, blend-if has the edge, though this could be addressed also by having multiple masks in Curvemeister.

The splittable sliders in blend-if are more convenient than curves, which is the same as saying there are situations where a levels-style slider control is more convenient than curves.  Who'da thunk it?