Before Roger's excellent Tutorial on 'Blend If', I had used The 'Blend If' Option in Photoshop only a couple of times following precise instructions from some tutorial, but never really understanding what I was doing, or, better said, what IT was doing, how, and how powerful it can be!
Roger's Tutorial "opened my eyes" at least in theory, but when I tried to put what I'd learnt from it into practice, I got frustrated and, after a while, I gave up.... But the thought of it kept nagging me .... I was thinking of it as 'an open highway' ... only I wasn't able to see where it could lead....
It was a great tip from Mitch (gmitchel) posted on my Neat Image Tutorial Thread, which finally made the penny drop!! (thanks again Mitch!!!!)
"If you want to limit the effect and not frog around with all those sliders on three channels, you could run NeatImage on a layer and use the BlendIf sliders for the layer in order to target where the effect is applied."
Well....I tried it and I got great results in much less time than with my Neat Image with Selections!!!Wow, I actually had more control on how much noise I wanted to remove/leave on higlight and on shadows separately in one single go!!!! No masks, (even though you can always add a Layer Mask for minor corrections...) no running Neat Image twice with different settings for the selections ... Just the Blend If Option!!!
I 'experimented' a little more with Blend If, using it to selectively show/hide corrections (or for controlling how strongly these corrections should appear) for Tone, Contrast, Exposure, Sharpness ... you just name it but, for me, its most spectacular effect is if used when replacing backgrounds and blown out or plain dull skies.
Since 'Blend If' influences the pixels from black to white in the channels individually (Blend If Red, Green or Blue etc. Options), or together (Blend If 'Gray' Option), it works best in pictures with stronger contrast (light-shadows) or with clearer boundaries between colours. (colours fading smoothly into one other, make any selection difficult anyway...).
For me, experimenting with Blend If came simply down to:
- Understand what the sliders do.
...Having finally got that (better late than never!!!) ... I tried it for something practical I need to do quite often when restoring/retouching pictures ... replacing backgrounds and blown out or plain dull skies.
- Open the picture you want to work on, duplicate the Background Layer and place your New Background between Background and Duplicate.
- Working on the top Layer (your duplicated Background) double click on it to open the Layer Style dialog box.
Since the background to be replaced in my picture is a light blue sky, I went for the Blend If Blue Option and started moving the slider on the right (for the lightest pixels)....
...and this is what I saw happening....
- After moving the sliders to get the best result ...
- I changed the blending Mode to Multiply and lowered its Opacity to 88%... I did this to add strenght to the image and darkening the light 'leftover' on the palm's contour which I didn't want to eliminate completely as not to lose too many details.
- After that, I duplicated the working Layer (top one) (click on it and, keeping the left mouse button pressed, drag the Layer to be duplicated on the 'Create a New Layer' button at the bottom of your Layers Palette) changed its Blend mode to Normal and its Opacity back to 100%. (I was amazed by the result achieved in only 5 minutes!!).
- I had replaced the Background, but, all around my palm there still was a bluish edge from the 'old' sky... To correct that, I created a Hue&Saturation Adjustment Layer and, working on the 'Blues' and 'Cyans' I tweaked hue, saturation and luminosity until I was satisfied with the result.
- Finally, I merged visible, (here is a tip on how to do it) added a Layer Mask (white) to the merged Layer, hid from view all the Layers but Merged and Background and, using a soft black Brush (adjust Opacity) I corrected a few spots where the new purple background had 'come through' on a couple of coconuts and on a branch.
15 minutes work and here is the final result.
...and here is an example on how I used this technique to replace the sky, on an image posted in the Restoration, Retouching, and Manipulation forum.
Even though it will never be a substitute for Masks, the Blend If 'technique' can be applied to layers and Adjustment Layers for adapting the strenght of corrections on lights and shadows individually but at the same time!
Just a Tip .... before starting to 'play' with Blend If ... read Roger's Tutorial as to really understand how it works ....
Thank you so much Roger, for taking the time to do the research and sharing your results .....
....and thank you so much Mitch for pointing me in the right direction!!!
Ciao, ciao...Flora. :o)