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Blend-if In Photoshop

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Old 03-12-2004, 05:01 PM
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Ed_L Ed_L is offline
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That looks easy enough. Thanks for the link.

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Old 05-29-2004, 04:40 PM
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byRo byRo is offline
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Thumbs down Blend-if, some answers..........

(Seems like I only do posts with numbers...)

First thanks to Ed_L for proposing the question....

As dpnew pointed out the ´magic´ number is 97. The blend-if takes effect when the slider passes the number. So for the white slider it´s between 97 and 96, and for the black between 97 and 98.

At first I thought this would be the average of the three numbers, but the average would be 95.3.
The problem is that the choice of numbers 35 / 123 / 128 gives a ´magic´ number very close to the average. If you turn them around, 128 / 123 / 35, you´ll get a number of 115. In fact, if you try pure red, green and blue you get 76 / 150 / 28 - which, sort of, explains it.
The ´magic´number is the ´perceived´ gray and not the average gray. It´s all because of the way the eye works - we see more green things brighter than blue things.

If you really want to calculate the number try:
Red * 76 / 255 + Green * 150 / 255 + Blue * 28 / 255 - it works.

And what´s the purpose of blend-if ?
I understand it as yet another way to make a layer mask. This time using precise pixel values. I´ve used it sometimes to mask of areas where a channel has clipped to be able to mix in a patch made of the other two.

Just thought of another use... going to try it out....
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Old 06-28-2007, 11:21 AM
ralphjramirez ralphjramirez is offline
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Re: Blend-if In Photoshop

Originally Posted by roger_ele View Post
This tutorial focuses just on the blend-if sliders in Photoshop. I put this in the "The Basic" category because my goal was to write this tutorial clearly enough for all experience levels (and there is not an advanced category). [details]
How do I go about downloading the test image for working with the sliders? I couldn't find a link. Thanks.....Ralph
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Old 06-29-2007, 09:36 PM
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Graphics23 Graphics23 is offline
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Re: Blend-if In Photoshop

I'm quite late to this discussion, but since it got bumped I thought I'd offer some examples:

The first attachment is a shot for a realtor's website. But they don't like the lawn.

We need to fix the lawn and the dirt and we need to do it fast.

Everything in nature that's green actually has a lot of yellow in it. Referring to my "Power of Ten" tutorial, we know that the opponent of yellow is blue.

Using the info palette, we can see that all the green areas and dirt patches, being more yellow, have less blue than everything else in the picture. The sky of course is quite blue, the house and street are neutral.

With this in mind, I used the Eyedropper to sample a nice shade of green from the trees on the right. Then I created a solid color fill layer and set it's blend mode to Hue. Then I opened up the Blending Options window and used Blend If to allow everything from the bottom layer that's more blue (less yellow) than the top layer to show through.

I've included a screen grab of the Blend If as well as my finished version.

No cloning, no masking. Job done and the Realtor is happy!

Less than a minute's work. It took longer to explain than to do.


Attached Images
File Type: jpg 9207_lr3.jpg (52.7 KB, 14 views)
File Type: jpg BlendOptions.jpg (95.3 KB, 14 views)
File Type: jpg 9207_lr3-EDIT.jpg (93.6 KB, 15 views)

Last edited by Graphics23; 07-30-2007 at 12:18 PM.
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Old 06-29-2007, 09:56 PM
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Graphics23 Graphics23 is offline
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Re: Blend-if In Photoshop

Here's another example

We want to change the car from yellow to blue without affecting the flames.

Switch to LAB color mode.
Create a curves adjustment layer.
In the curves dialog, go to the B channel.
Drag the endpoints to the opposite corners; left one to the top, right one to the bottom. Hit "OK".
Now double-click to the left of the adjustment layer's name to open the Blending Options dialog.
At the bottom of the window is a pop-up menu called Blend If, select the A channel.
Drag the bottom right-hand sliders to the left until you get to the middle. The number above it should now read 127.
Now Alt drag that same slider to the right. This will split the slider creating a transition zone. Move it to the right until the new number reads 194. Hit "OK".

Instant paint job! Again, no masking. But notice how nicely the blue blends into the flames. No hint of yellow remains.

This would be very difficult to reproduce by masking the flames.


Attached Images
File Type: jpg Original.jpg (97.8 KB, 14 views)
File Type: jpg screenshot.jpg (95.3 KB, 11 views)
File Type: jpg BlueCar.jpg (98.6 KB, 15 views)
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Old 06-29-2007, 10:05 PM
des151 des151 is offline
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Re: Blend-if In Photoshop

Thanks Michael. That was very informative.
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