Every time I have to deal with preparations for print and conversion from RGB to CMYK I ask myself the same question. What is your advise? Best practice?
It depends entirely on your setup and goals. Here's my (mostly) tl;dr take on it.
••• Prepress/CMYK ••• Calibrate everything. Use profiles everywhere, all the time. Listen to advice from your printer. Try to set up a workflow so you limit profile conversions (each one causes rounding errors and loss in quality).
••• Photography, being uploaded to the net ••• Calibrate everything. Use profiles everywhere, all the time. Probably convert to sRGB and use a JPEG with an ICC profile as your web delivery format. Different browsers will do different and whacky things with your images, but... YOLO?
••• Web design ••• You're probably going to want to ditch colour management entirely, because results across your page — colours in HTML/CSS matching images — is more important than trying to get consistency across different computers, which is near-impossible, given the current mish mash of colour profile support on the web. I'd also recommend leaving your display calibration as is. If you're using a Mac, then the best setup to see what others see is to LEAVE YOUR DISPLAY ALONE.
••• App design ••• As above, but make sure you preview on device. Yep, this is one of the main reasons we built Skala Preview.
Here's how I set up Photoshop and Illustrator for web and app design: http://bjango.com/articles/photoshop/
Here's a giant thread where I discuss the matter with an Adobe engineer. We don't see eye to eye on it. FWIW, he's wrong. Lots of nitty gritty details are discussed though, so it might be worth a read: http://feedback.photoshop.com/photoshop_family/topics/convert_to_srgb_should_be_off_by_default_or_removed_altogether
Thank you for the detailed answer. It is in fact a real issue and completely messy. I had to calibrate the white/black and color balance on some images and used a 27 LED Thunderbolt display for it. Everything looked perfect. Before sending the files I re-checked on an iMac 24 and the colors where yellowish. Photoshop gave me warnings about different color profiles as well, there is Apple RGB, sRGB etc. How can I be sure that when sending my things to the printer some hundred miles away the result will look exactly as on my display? I might just lack the knowledge and the understanding of how these profiles work and what they actually do. Will need to read some more.
BTW, this is a great post: http://bjango.com/articles/photoshop/
How can I be sure that when sending my things to the printer some hundred miles away the result will look exactly as on my display?
The simple answer is that you can't. For starters, your display deals with additive light (RGB) and printing is subtractive. The best way to get a good preview of how something will look when it's printed is to get a printed proof from the printer. Expensive, but it should be the closest you'll get to the actual offset printed result.
I might just lack the knowledge and the understanding of how these profiles work and what they actually do.
They're quite complex initially.
Colour profiles give colours relevance: If you have a web colour that's #FF0000, it's full strength red, or 100% red, 0% green, 0% blue. A colour profile plots that colour within a colourspace, changing it from being a relative colour (how bright is 100% red?) to absolute.
I manage it like this: http://cl.ly/QVD4
LOL, so good :D