If you don’t care too much about colour management, feel free to ignore this.
The current RB T-shirt printing uses 4 inks, and relies on the underlying white cloth to provide a white. The range (gamut) of colours that can be reproduced on a T-shirt with this printer is much smaller than that reproduced on the other RB printed products.
How much smaller you ask? If you have a calibrated monitor and use software such as Photoshop which uses ICC colour profiles, here is the answer!
I’ll demonstrate with a few images from my RB portfolio. For each image I’ll show 3 versions: the original (well, in sRGB), as the T-shirt printing would produce it without correction, and lastly as the T-shirt printing will produce it with the corrections I describe further below.
You’ll see that by default purples don’t come out very well!
The 3rd of each of those images is the “corrected” one: the colours are a little faded compared to the original, but not badly.
To achieve the corrections, I have generated an ICC colour profile for the current RB printing process. You can download it in a zip file then extract the file RB_whiteT_070615.icc and install it onto your system. Simply copy it into the appropriate directory:
OS X: ~/Library/ColorSync/Profiles/ or /Library/ColorSync/Profiles/
Photoshop and other profile-aware software on your system will then be able to access the new profile “RB_whiteT_June07” (you may need to restart the software to pick up the new profile).
How you use it is up to you, but my suggestion is to continue to work on your graphics in your favourite profile (e.g. sRGB, Adobe RGB) but before saving the PNG file to upload to RedBubble, make sure you use Convert to Profile… to convert the image into this RB_whiteT_June07 profile. I recommend you use the Perceptual rendering intent.
Photoshop won’t attach the RB_whiteT_June07 profile to the PNG file which you upload to RedBubble, but the Convert to Profile step will have changed the pixel values to get the colour approximately correct.
NOTE: this profile was measured from a white T-shirt freshly printed by RedBubble in mid-June 2007. It provides us with a starting point for understanding the colour behaviour of the current T-shirt printing service. If/when RedBubble change their T-shirt printing this profile will no longer be valid.
Of course the T-shirt printing will fade over time. I may generate additional profiles as this happens, but we’ll see how useful that ends up being.
Also note that the T-shirt previews shown on RB will be a bit weird although the T-shirt colour will come out correctly. Using the above 3 examples, the previews on RB would look like:
Hopefully when RB introduces the new T-shirt printing service (which will apparently have its own white ink for consistent colour across all cloths) they will do something to handle these colour conversions automatically behind the scenes as they do for normal prints.
Given the above variables, no guarantees are provided that this profile is 100% accurate. But if you’re willing to give this a try with one of your own T-shirt designs, please let me know how you go!