Color in the Computer....or how to get better and consistent color and avoid oopses

Transcription

1 Color in the Computer...or how to get better and consistent color and avoid oopses

2 First, odds and ends... Some Common Camera Color Problems white balance - can use RAW format to avoid problem fringing - usually blue or purple around hard edges. Can correct somewhat in newer Photoshop versions banding - not enough color to go around, either from bad camera or extreme adjustments in Photoshop cross-over - darker areas have one color cast, lighter areas have the opposite (or other) color cast white balance wrong fringing banding cross-over (exaggerated)

3 RGB or CMYK? The native mode of any device where the addition of color leads to black is CMYK. (all print processes) The native mode of any device where the subtraction of color leads to black is RGB. (just about all non-print processes) Photoshop / Image So, one would think converting a Photoshop image to CMYK would make a better print... It would not because all ink-jet printers expect RGB and do the conversion themselves. Commercial print-shops may want you to convert your images to CMYK so that they don t have to, since printing press plate-makers usually do require CMYK images. But, you may want them to do the conversions themselves... The moral of this slide is to always use RGB as your color mode.

4 RGB Everything in this lecture from now on refers to the RGB model...on a Macintosh (though all concepts are the same for Windows) RGB RED GREEN BLUE

5 Wow, look at that 21r 220g 150b! Computers have a hard time with this as well - what number will represent what color? This first problem is defining what color the numbers refer to...

6 Working Color Space How many Microsoft technicians does it take to change a light bulb? None, they just declare darkness the new standard. Ever since computers displayed color, technicians have aligned the numbers with colors they should represent. This is called the color space of the image. How it has turned out is that there are two commonly used color space definitions - Adobe 1998, and srgb. In the world of photography, Adobe 1998 is used by professionals who print (since it has more colors), and srgb is used by others. Many of your cameras will only take photos as srgb. This is probably the best to use anyway, since it is the more common standard. If you use Adobe 1998, then you should know a bit more than what is in this lecture.

7 Not to get too complicated... This is a 3D representation of the srgb color space (solid color) and the Adobe 1998 color space (translucent). Just so you can see that there are more colors available in the Adobe 1998 color space. Who wouldn t use it for printing if they could?

8 A Problem ColorSync Utility Your camera sees colors differently than your monitor. Different cameras see colors differently, and different monitors see colors differently. There has to be a language and a translator to get them all talking the same. The language is called a device profile (also called a color profile, ColorSync profile or ICC profile) In Macintosh computers, the translator is called ColorSync. These languages and translations are somewhat invisible and automatic.

9 Color Workflow ColorSync ColorSync Camera File Computer Monitor Printer embedded profile embedded profile embedded profile language language language translator translator profile = color description of device color profile, ICC profile, device profile, ColorSync profile can all be the same

10 Camera Profile Image Capture / Options Photoshop / Edit Since most cameras save their images with an srgb color space, the computer will assume that to be the case. But if you want you can also embed a profile during image import using image capture to do it automatically or Photoshop to do it manually.

11 Monitor Profile Monitors are all different (both models and individual monitors), therefore it is important to: 1. Adjust your monitor to a standard setting (as close as possible) 2. Create a device profile for your monitor so that ColorSync knows what language it is speaking. The controls in System Preferences / Displays do both of these things....but, even the standard device profile that your computer comes set with is probably pretty good nowadays.

12 Monitor Profile (cont) Since the adjusting the color and creating a profile in the last method relies on subjective viewer judgement, an even better way of doing it is with products that read the precise color characteristics of your monitor. By the way - the color characteristics of your monitor change radically according to the environment you view your monitor in.

13 Now we have the possibility of good and consistent color from camera to monitor. Printing is the final step.

14 Simple Printer Color Management 1) Tell Photoshop you want the printer (software) to manage the colors. It reminds you what the color space (profile) of the image is. Photoshop / Print with Preview 2) Now you are telling the printer software the information it needs to translate your color space into the printer s color space. The color translation is almost totally hidden in the printer software. Photoshop / Print It does need to know the color space your image is in - in this example even though Photoshop knows the image is an Adobe 1998, the printer software thinks it is srgb.

15 Better (?) Printer Color Management 1) Tell Photoshop you want it to convert the colors for the printer. Note that you have to tell it not only what printer you are using, but also what paper (in this case Epson Premium Glossy Photo Paper). Ever notice that different papers have different color capabilities? Photoshop / Print with Preview Photoshop / Print 2) Now the important thing is to tell the printer to lay its hands off the color (you don t want to translate the colors twice!). You still have to tell it what paper you are using, but in this case it will only determine the optimal ink dispensing for that paper, and not adjust the color.

16 Photoshop / View Using the printer color profiles you can even preview in Photoshop an approximation of what your colors will look like when they are printed. This works better in theory than in practice (monitors have much greater range of lightness to darkness than prints for one thing), but can give you a good approximation if you are used to doing it.

17 You can determine how Photoshop uses color management in Edit / Color Settings

18 We have talked about one color workflow - here are some others

19 Intermission You may turn off your brain now - the rest of this lecture will not be quizzed.

20 Color on the Web Pretty much the same things apply - but you cannot see nor control the color profiles of the output devices....but they may use profiles embedded in images.

21 Mac - Safari Mac - Preview Windows - Explorer Windows - Fax & Picture Viewer Mac - Firefox (not color managed) Windows - Firefox One image from Yahoo with Adobe 1998 profile embedded

22 Web Page (NY Times) in Safari (Mac) and Explorer (Windows) No embedded profile (computer assumes srgb) Windows does not look for profile, but assumes srgb Mac looks for profile, seeing none, assumes srbg, then converts to display profile. This example assumes the same monitor

23 Mac - Safari Windows - Explorer Mac - Preview Windows - Fax & Picture Viewer Mac - Firefox Windows - Firefox No embedded profile, but image converted to srgb (supposedly)

24 Color for Press Pretty much the same things apply - but you are not the one controlling press device color....color management becomes very important.

25 RGB image with profile Lose color, have to know settings for press CMYK image with profile Lose color, have to know specific press settings CMYK image with press profile (proof) Someone else Separations (proof) Someone else Press Run (proof) You Reprint

26 Oh, and by the way The short version: In Illustrator and InDesign use CMYK for print, RGB for web (screen) The long version: Another lecture