Using PhotoShop CS2: should i adjust my display colours?

Question

I've never had to consider this before, but seeing my images on a pc made me wonder:
I have a lot of slides that I used to teach a course in photography, about 15 years ago. They are photos of images in books, mostly taken on tungsten slide film because of the lighting I used. The colour of the slides themselves is still very good.
I scanned the slides with my Epson (Perfection 3490 photo scanner). The scans of slides of black and white images are fine (probably because I set the scanner to grayscale), but most of the colour images have a reddish cast to them.
I opened them in PS CS2 and did some colour correction (levels, curves, replace colour, whatever worked)... did some at home on my iMac, and others at school on the pc (don't know what kind, but a flat screen monitor). I noticed that some of the ones i had opened at home, but hadn't corrected, looked much better on the pc, and didn't need as much correction as I thought.
Then tonight, i opened up (on the iMac) the ones i corrected at school and they look washed out and wimpy. Yet, the contact sheet that i printed (Epson stylus colour 880, on glossy paper) shows almost the correct colour, but not at all like the wimpy image on screen.
Should I be making some changes in my display, in System Preferences? I have it at the imac default, with 1.8 gamma and D65. Or should I make some changes to PS's colour settings?
(FYI, when i upload pictures off my camera, what i see on screen is pretty much what i get on the paper, but I don't print very often)
(and: when i open these scanned images I get the 'no colour profile ' message and i tell the app not to colour manage)
More FYI: i need these images for a new photo course I'm teaching, adding them to powerpoint instead of projecting slides, and would really like the images I show to be the correct colour, but if what I see at home isn't what i show at the school, I'll have problems. (The school i'm presenting this at is not the one I'm teaching at currently so I can't check it out ahead of time)
Any help would be appreciated.
Thank you
Eliz
iMac 17", Intel Core Duo , 512 Ram, 160 GB   Mac OS X (10.4.8)  

Answer 1

I have it at the imac default, with 1.8 gamma and D65.
That's the main issue with the images looking washed out on the Mac. In Windows, the default gamma is a much darker 2.2. Change your Mac's display profile to match that gamma setting and the images should look much closer to how you see them in Windows.
The scans of slides of black and white images are fine (probably because I set the scanner to grayscale), but most of the colour images have a reddish cast to them.
Your scanner needs to be profiled to get the correct color for items you scan. Check to see if your scanner came with any. Although I don't know if the Epson software supports ColorSync. If it does, using the correct input scanner profile will give you much better color. Assuming you have accurate profiles.
when i open these scanned images I get the 'no colour profile ' message and i tell the app not to colour manage)
That's an issue. Profiles are very important in RGB. They let color management software (Kodak in Windows, ColorSync in the Mac OS) know what to do with the image when you open it. That is, when the source and destination profiles don't match (both the monitor and image profiles), the software knows how to alter the image values so the picture looks close to the same on one computer as another. With no profiles embedded, ColorSync can't determine the original color spaces used when you created them in Windows.
If you can, you could set up an action in Photoshop on the Windows side to open each file and save them with an embedded profile. Which would be whatever your current working color space in Photoshop is. When you then open them on the Mac, Photoshop will know what to do with them to make the color appear the same. A second benefit is that some (not all) web browsers are aware of profiles. Safari is one. So even if your files have a gamma of 2.2, and a person visiting your web site has their monitor set to a 1.8 gamma, Safari can adjust the color of the images on the fly to have them view correctly by knowing the difference between the embedded image profiles and the user's monitor settings. It's not perfect, but works pretty well.