RP Tutorials - - Blend-if In Photoshop

roger_ele · #1 03-08-2004, 12:59 AM

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]

Leah · #2 03-08-2004, 01:14 AM

Wow -- there's a lot of content in a small space there!

It's good to get some more background detail on aspects of blend-if. I've used it and knew roughly how it worked, but there's a whole range of aspects I hadn't thought about.

Note to others - this is one of those tutorials that isn't likely to sink in just by reading it -- you'll need to dive in and have a play with the sample images yourself.

Flora · #3 03-08-2004, 09:56 AM

Thank you Roger!!!

I had already 'played' with the 'Blend if' option sometimes ... but never knowing what I was really doing ....

It's something new to try .... and it looks very powerful!!!!

I agree with Leah:

Quote:

this is one of those tutorials that isn't likely to sink in just by reading it -- you'll need to dive in and have a play with the sample images yourself.

Ed_L · #4 03-08-2004, 04:11 PM

Hi Roger,

I had only a short time on the computer this morning, but I wanted you to know that I saw the tutorial, so I replied. Since I now have a little more time, I've deleted the first post, and replaced it with this one.

First of all, thank you very much for the kind words, but I am not deserving of all that. I never thought I did any *work* at RP. I just enjoy the site like many others. Now on to the tutorial.

Thank you very much for an inside look at how blend-if works. I printed the tutorial, and began to work with it in Photoshop. I only spent a few minutes with it so far, and it's still a little fuzzy to me (I'm a slow learner

). But I think you did a fantastic job with it, and I think it's the best I've seen to get someone started. By this time tomorrow, I'm pretty sure I'll understand it better. If I have a problem with it, I'll put you in the hot seat, and ask for assistance.

I really appreciate your time to write up the tutorial. It's one I've been wanting for some time. Thanks again.

Ed

Ed_L · #5 03-08-2004, 08:54 PM

I think I'm *beginning* to get it, but still having a problem visualizing masking an image with blend-if. Would it be too much to add an image, and show how it's masked? Please don't feel any pressure to do this, but if you want to kill a little time some day, that would be great. My brain is smoking. Think I'll turn in early.

Ed

roger_ele · #6 03-08-2004, 11:15 PM

Hi Ed, Flora & Leah,

Thanks for your kind words. Ed, if it is or isn't 'work', your effort is appreciated.

I added some more info to the tutorial, hopefully it will make it a little easier to understand.

It really is necessary to download the test images, make a two layered image and play with the blend-if sliders to really get it - The fact that the test images have pure colors makes it a lot easier to understand. I thought I had 'got it' until I made the test image (I tried a couple of different variations on what you see) - only after playing with the test image did I figure the rest of it out.

Quote:

Ed wrote: Would it be too much to add an image, and show how it's masked?

I don't mind - but I am not sure what would be learned that the test images don't show more clearly. Throw in a couple of images with what you want to do and then we can discus what we can (and more importantly can't) do with them with 'blend-if'. I think that might help 'reveal' any missconceptions that might be getting in the way of an understanding.

Thanks,
Roger

Leah · #7 03-09-2004, 01:54 AM

I think part of the trouble with blend-if is that initially it's hard to think of a practical example of what you could do with it - which is where a "real" image would come in.

Scott Caplin has some good real-world examples in his book How to Cheat in Photoshop, if anyone has access to that. That's what made the little lightbulb come on inside my head...

jrolinc · #8 03-09-2004, 06:44 AM

Hi

I was reading along with this and thought of a book I have, Photoshop6 WOW Book. I remembered a small example of the Blend If that I just couldn't believe, that is until I got the pic off the accompanying CD and try it myself.

It is pretty amazing...I've kind of copied it in the pics below, but please note that all rights, etc are to the great folks who put out the WOW series books.

At least this may help those out there to see the powerful potential of this tool.

Oh yeah...the info about what's happening might help...this was done in Photoshop 7 also.

In the 2nd step...Blend If, Gray, This Layer (1st Blend If screen shot), you can "split" the little triangles by holding the Alt key (PC).
In the 3rd step...Blend If, Blue, Underlying layer (2nd Blend If screen shot)
The last step is changing the Layer Blend mode to Screen and dropping the opacity.

Hope that helps as a "real" world example.

Ed_L · #9 03-09-2004, 08:45 AM

[quote=Leah]I think part of the trouble with blend-if is that initially it's hard to think of a practical example of what you could do with it - which is where a "real" image would come in. QUOTE]

I think that's right. I'll take another look at the tutorial, and play around with the information jrolinc provided. Thanks everyone, for trying to help me understand.

Ed

roger_ele · #10 03-09-2004, 11:47 AM

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

bhall07 · #11 03-09-2004, 04:31 PM

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.

roger_ele · #12 03-10-2004, 12:04 AM

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

sdubose99 · #13 03-10-2004, 12:33 AM

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

roger_ele · #14 03-10-2004, 01:25 AM

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

Ed_L · #15 03-10-2004, 09:58 AM

I’ve 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. Here’s what I did, and what I learned (and didn’t 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. Here’s 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 I’m just touching the basics, and I expect to have many more questions before I’m able to really make good use of blend-if. I’ll 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. I’ve also worked some with the moon in back of the rock. I was able to duplicate the results, but not without questions, which I’ll try to figure out myself. If I can’t do that, I’ll be asking for help. Thanks again for a great tutorial. I’m not going to quit until I “get it”, or everyone gives up on me.

Ed