I do not think you are going the get that type of technical information from any Adobe publication, help or support. I have seen some web site with the math behind Photoshop's blending modes. I'm sure there is information on the web as to how image editing programs like Photoshop, Gimp and others do some of the adjustments the do. Try some web searches. http://www.amazon.com/Algorithms-Image-Processing-Computer-Vision/dp/0471140562
Yeah, I realize that I'm asking for a bit much ... but I recall some FM'ers (Peter comes to mind) having a technical dialogue @ how levels works mathematically. I realize that someone could do a "reverse engineer" study of each of the functions. I'm not looking for "everything" ... but the more I understand how / what something is going to do, the better I can incorporate it into the process.
As is, I do far too much iterative work, yet the straightforward methods don't yield the results I desire. For instance, I'm hoping to find a few clues so that I better know how to decide @ using levels vs. curves vs. exposure vs. contrast vs. USM vs. etc. They can all change the numbers, but they go about it from a different approach. While I have a visceral understanding of which to use when (developed through T&E) ... I'd like to change that from visceral to cerebral in some regard.
Just wondering if there is something out there that objectively/scientifically/mathematically explains the processes a bit more directly @ their underpinnings.
RustyBug wrote:
Just wondering if there is something out there that objectively/scientifically/mathematically explains the processes a bit more directly @ their underpinnings.
+1, I'd buy that book too.
Per discussion in another thread, I ordered a copy of Photoshop Channel Chops but it hasn't arrived yet. It's pretty old, but it was touted as explaining the architecture around the datasets (channels) in the image very well.
Layer bending math operations have been examined in Photoshop Channel Chops briefly but more importantly the book goes a long mile to discuss the Calculations command for manipulating alpha channels. Deke also has a title devoting entirely to blend modes. Dan Margulis has done an excellent video for Kelby titled There Are No Bad Originals, in which you will learn tons of insights: http://kelbytraining.com/course/margulis_no_bad_originals1/ . The take away from that title is you really need to do nothing is ACR and work with channels in Photoshop (by default Photoshop gives you ten channels for each image you open in Photoshop), if you desire to obtain the best possible images. By using either Calculations or Apply Image command, you can come up with unlimited number of alpha channels on the fly using those ten native channels.
I set everything in ACR to "0" and mostly work from PS only (LR for some production oriented projects). The main thing I miss @ ACR in PS is color temp (i.e. 5500, etc.) numeric slider and more than 4 info point. But, I probably haven't strove to harness ACR to its max either.
+1 @ Dan Margulis & 10 channels. I'm comfortable with all, more @ RGB & LAB, not using CMYK nearly as often (since CMY is the inverse of RGB, K notwithstanding) using any of them via layers, but it's time to "raise the bar" @ refinement and go beyond my current comprehension / application.
Gee ... and it was only a couple years ago that I thought the saturation slider fixed everything.
At this rate, it'll be 2020 before I get "good". But, even though technology changes very rapidly and there are always new iterations around every corner ... color theory and value control is really the same as it has been for the last 10, 100, or 1,000 years, i.e. light & color don't change, only our tools for capturing & presenting them do. So, if it takes me another 10 years to get "command & control" of the tools ... I'll still have plenty of time to put them to good use.
K in CMYK can be used to do some amazing stuff in a RGB image. For example, K can be used to bring back lost shadow details or can be used to desaturate shadows on the fly.
Desat using whatever the tool you feel like in RGB and add an inverted K as the mask. Blur the mask using the mask properties to get that seamless effects. That's it.
mshi wrote:
K in CMYK can be used to do some amazing stuff in a RGB image. For example, K can be used to bring back lost shadow details or can be used to desaturate shadows on the fly.
Can you give us an example? How do you segregate K to work with it?
Wayne Willison wrote:
Can you give us an example? How do you segregate K to work with it?
Wayne
There are many different ways to achieve that. One simple way to do is to create different COLOR modes. You can use Duplicate command under Image menu to make a copy of your image opened in RGB,
Now you have two identical image open in Photoshop, one in RGB Color, the other in CMYK Color.
Back in the RGB image, put a desaturation adjustment layer using whatever tool you like, such as using Vibrance Adjustment Layer. Desat the image by playing with two sliders, then click on the white mask.
You just added an inverted K channel as the mask for Vibrance Adjustment Layer in RGB. Now double click on the mask to open up its Properties tag, and drag the Feather slider to the right, somewhere around 100 px, to soften the effects.
Mshi, thanks for the well done walkthrough. I followed each step as you laid out, but I can't see the advantage of doing this when I can easily open the shadows in ACR.
Am I missing something?
Wayne Willison wrote:
Mshi, thanks for the well done walkthrough. I followed each step as you laid out, but I can't see the advantage of doing this when I can easily open the shadows in ACR.
Am I missing something?
Wayne
Yes, you can use ACR to bring up shadow details too. There are differences in results.
Per discussion in another thread, I ordered a copy of Photoshop Channel Chops but it hasn't arrived yet. It's pretty old, but it was touted as explaining the architecture around the datasets (channels) in the image very well.
@ Pg 150 of PCC
e.g. Multiply =
Pixel A * Pixel B / 256
128 * 128 / 256 = 64
.5 * .5 = .25
Includes a few others as well.
Shame it doesn't have more, but it is good to see the few that it does have.
The early versions of Real World Photoshop also had basic descriptions of the math behind many of the blending modes. Of course, I haven't looked at those in many years.
