CMYK for the web

[Doug Nelson]

I've noticed several of the Challenge entries mention working in CMYK mode. This intrigues me, since the originals and destination are both RGB.

Is it simply a case of working in the mode you're most comfortable with, or are their more pragmatic reasons for converting?

[Tim_S]

Well, if you read the books by Dan Margulis you'd think CMYK was the only model worth working in.

Margulis does in fact make some valid points, but the one that has me converting to CMYK most often is simply to find a channel with the best contrast, or detail. As we often see, the blue channel can be badly damaged by noise due to scanner physics. Similarly the red or green will have the best faces or other feature.

Often by converting to CMYK one or more of those channels will have better detail, or contrast than the equivelent RGB channels. I have at times replaced the blue channel in an RGB with the K channel from CMYK. It all depends on the colors in the original picture.

Also, after reading Margulis's book I find that certain kinds of color corrections are easier in CMYK. Mostly because I have a better picture of what will happen. I guess I'm just not that good with color models, and once I have one that sorta works I want to stick with it.

Still, I do most of my work in RGB.
--tks

[john_opitz]

You can work in cmyk for the web. CMYK and RGB are "almost" alike. Execpt working the highlights are better in RGB. Working the shadows are better in CMYK(because of the black channel). RGB has a longer range in most of the channels(in curves) than CMYK. CMYK has a shorter range. Meaning you can work better with the shorter ranges for color and contrast moves without affecting other parts of the image. Photographers like........, I should say most photographers, like to work in RGB. Because "most" printers,scanners, output/input in RGB. Me. I work in either RGB,CMYK,LAB. You just have to know the colorspaces.
RGB is good for channel blending into RGB or CMYK, or if the image is way off color of what it should be. Lab can be better for that too,also. LAB is good for color casts. For intensifing colors, in the 'a' and "b" channels. When I convert from RGB to CMYK. I'll go through LAB first then to CMYK. The conversion does it anyway(go through LAB) so I'll make a pit stop in LAB and blur the "a" and "b" channels of noise, in those channels without losing anything. then go to CMYK. Sometimes when I start out with an image in RGB. I'll do a channel blend. As I said, go to LAB. Blur the a,b channels and go to CMYK and finish it off. I use my own seps. for CMYK(not the defaults). But that depends on that image I have on what space I work in.
So my thing is. Knowing ALL the spaces are better than, knowing just one. It's good also for making masks for objects instead of selections(a lot of the times). You have ten channels to choose from instead of 3 or 4 channels.

[Sharon Brunson]

That's the most concise, easily understood explanation I've ever read of the different color modes. Thanks John.

Sharon

[john_opitz]

Hello Ms. Brunson, If you don't mind me asking. Where in Texas(Gods' Country) are you from?

[Sharon Brunson]

Hi John,

I'm from the big city of Burleson. About 10 miles south of Fort Worth. How about you?

Sharon

[john_opitz]

Got up real early this morning. Just got your response from the e-mail. OOO! Man! Burleson ! I live in Watauga. I worked for a studio in.............forgot what city it was in. That did the schools out there(High School Seniors).That was a few years back. The studio I'm in now...........is in Irving. Not to far from where 'Americas'" football team plays. The reason, I list Dallas/Ft.Worth is for reference. A lot of people would not know where Watauga is. Even the people in Texas. I say its in the Mid-Cities area. Around Haltom/Richland Hills. I'm before Keller. I was born and raised in the N.Y./N.J. area. So some look strange at me.......with my New York accent. When I say quater and water and car. Something between a Rocky and a DeNero accent.

[Sharon Brunson]

Hey John,

Of course, I know Watauga. I've been off-line a couple of days. Charter Internet decided to have a major crash. I know what you mean about people in our area not recognizing your town. Happens to me all the time.

Sharon