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Blend-if In Photoshop

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  #11  
Old 03-09-2004, 04:31 PM
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bhall07 bhall07 is offline
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Quote:
Originally Posted by roger_ele
Jeffrey,

That is a wonderful example. Understanding blend-if is new enough to me that the examples are not tripping off of my tongue, Thanks.

Roger
I used the blend if with A & B to get C.
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File Type: jpg b.jpg (78.0 KB, 67 views)
File Type: jpg c.jpg (77.7 KB, 98 views)
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  #12  
Old 03-10-2004, 12:04 AM
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roger_ele roger_ele is offline
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I wasn't clear, it is not that I can't find images that will show that bend-if works - the test shows that, and the images would also show it. It is that I don't have images that come to mind that show it as a perfect way to mask without needing to do additional stuff to them.

There is another factor to this that has been rumbling around in the back of my mind - The goal is to be able to think in 'blend-if', zen ''blend-if' if you will:

If I found perfect images then it would prove the power, but not how to think about images to know what to do. Yes, I know that if I have a great difference in colors or tones I can use blend-if to mask, but that doesn't teach me to use it except in real obvious ways. So,I have found two images that are close together in tones that I will add to the tutorial - not because they blend well, but because I think they might show what is happening - what to look for.

After adding this, when I next get a chance I will add an example with an image more suited to blend-if.

Roger
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  #13  
Old 03-10-2004, 12:33 AM
sdubose99 sdubose99 is offline
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Hi Roger -- thanks for the expanded tutorial on blend-if. FYI, Adobe has an exellent description of how to use blend-if on this page that helped me out quite a bit. It's a 2.8MB Quicktime movie so you might need a fast connection to view it... http://www.adobe.com/web/tips/totalphs3/main.html#

Scott
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  #14  
Old 03-10-2004, 01:25 AM
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roger_ele roger_ele is offline
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Thanks for the link Scott.

Everyone, I have added the example images, let me know if you think I should use a different image or if this one works - and if there is anything else I should cover..

Thanks,
Roger
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  #15  
Old 03-10-2004, 09:58 AM
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Iíve worked with the images that I downloaded, but I had a little trouble understanding what was happening. This is not a shortcoming of the tutorial, but a lack of understanding on my part. So I made some test layers myself, to try to get a better grip on this. Hereís what I did, and what I learned (and didnít learn).

Top layer is a gradient, black to white. Bottom layer is R35, B123, G128. Top layer is targeted. Working with the top layer, adjustment of any channel gives results according to the same numbers on the slider because the layer is neutral. Working with the bottom layer (gray channel), no results are seen until I drag the white slider to 99. I am having trouble understanding this. At first I thought this would be the average of the three numbers, but the average would be 95.3. Dragging the black slider requires the number to be 101 before any change is detected. This was expected because the white slider reading was 99. Using the red channel, I had to drag the white slider to 34 before a change was made. This was expected since the red component was R35. Blue channel results were that I needed B122 to see change. Also expected. Green channel came out at G127. Also easy enough to understand. Hereís what I learned: To force any color through the top layer, while using the bottom sliders, any reading of the RBG components can be used to force that (mixed) color through. I realize Iím just touching the basics, and I expect to have many more questions before Iím able to really make good use of blend-if. Iíll post my questions here, and possibly learn more about what seems to be a very flexible tool. Can anyone explain why I needed to drag the top slider to 99 before seeing results?

Roger, I think the new images you posted are great examples to work with. Iíve also worked some with the moon in back of the rock. I was able to duplicate the results, but not without questions, which Iíll try to figure out myself. If I canít do that, Iíll be asking for help. Thanks again for a great tutorial. Iím not going to quit until I ďget itĒ, or everyone gives up on me.


Ed
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  #16  
Old 03-11-2004, 04:22 AM
dpnew dpnew is offline
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Hi Ed_L,

On my pc, 96 seemed to be the point where the right underlying layer slider caused the underlying color to force through. At 97, I could still see the gradient, but at 96 the image turned blue. So, if you round 95.3 up, that seems to be close.

Interestingly enough, it is not consistent with the left slider. When I moved the left slider to level 97, the color did not force through. It wasn't until I moved the left slider to 98 that the blue showed through.

To see why the number 96 or whatever you get is the number, create a Threshold adjustment layer for your blue color layer. You should see one vertical line--mine was between 97 and 98. Why the Threshold number, the right slider number, and the left slider number, and the average of 35, 125, and 128 aren't all exactly the same, I can't explain.

If you are interested in some applications for Blend If, you can use it to target ranges of tones in your image for any type of adjustment, e.g. Levels, Curves, Hue/Sat, etc., you can use it to blend different exposures for the same image, and you can use it to get rid of sharpening halos, as well as all kinds of special effects.

Last edited by dpnew; 03-11-2004 at 04:33 AM.
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  #17  
Old 03-11-2004, 06:44 AM
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Quote:
Originally Posted by dpnew
Hi Ed_L,

On my pc, 96 seemed to be the point where the right underlying layer slider caused the underlying color to force through. At 97, I could still see the gradient, but at 96 the image turned blue. So, if you round 95.3 up, that seems to be close.

I have no idea what I did, but I checked again, and I came up with the same numbers as you.


[/QUOTE]
Interestingly enough, it is not consistent with the left slider. When I moved the left slider to level 97, the color did not force through. It wasn't until I moved the left slider to 98 that the blue showed through..[/QUOTE]


In everything I've done so far, I've always seen a difference of two between the left and right sliders. This leads me to believe the actual number is 97, and it must be surpassed in order to see results. Could be wrong, though.

[/QUOTE]
If you are interested in some applications for Blend If, you can use it to target ranges of tones in your image for any type of adjustment, e.g. Levels, Curves, Hue/Sat, etc., you can use it to blend different exposures for the same image, and you can use it to get rid of sharpening halos, as well as all kinds of special effects.[/QUOTE]

Yes, I'm interested in that, but I fear it's a long way away. Thanks for the post. If I'm having trouble understanding this, there must be others too.

Ed
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  #18  
Old 03-11-2004, 07:29 AM
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Quote:
Originally Posted by dpnew
you can use it to blend different exposures for the same image, and you can use it to get rid of sharpening halos, as well as all kinds of special effects.
Goodness me... was that the sound of dpnew volunteering a tutorial on "using blend-if to get rid of sharpening halos"? Or one of the others ... we're not fussy!

Seriously, if you could at any point spare the time to do a more specialist tut on one of these applications of blend-if I think it would be a great help to members.

(that's the closest I could get to a grovelly pleading sort of smiley)
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  #19  
Old 03-11-2004, 12:34 PM
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Absolutely! But if someone makes up a tutorial, could you please explain what's going on in your head as you make adjustments? For example: "I want to bring the dark blue chair from the underlying layer through the roof of the house. Since the chair is dark blue, I'll ........................" . OK, that doesn't pertain to the halos, but you get what I mean. The reason and the thought for making adjustments should go a long way toward helping someone (like me ) to better understand.

For those of you who are used to using blend-if, do you use the eyedropper to find the numbers, or do you just eyeball the image? I'm not very good with color, so is it a waste of time to monitor the numbers?

Ed
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  #20  
Old 03-12-2004, 03:51 PM
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sPECtre sPECtre is offline
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The tutorial to get rid of shapening halos using the blend if sliders can be seen at : http://www.adobeforums.com/cgi-bin/w...a4.2@.2ccf89ab (free registration required -no spam -official Adobe Website)
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