Datacolor User to User Support Group.

You may recall that I was having intermittent trouble printing through the Canon print plug-in to my iPF5100... a sad state of affairs, since this software is otherwise much better than the regular printer driver. Certain images printed fine through the plug-in, but others printed with terrible color (exactly as if they had no output profile applied). I could find no pattern to it, though I knew certain files were reliably "good" and others always "bad". Eventually I copied a bit of a "bad" image and pasted it into a "good" document... and it printed fine. My jaw dropped.

Studying the "bad" and "good" versions of the file, I found only a single difference -- the original "bad" file contained 2 alpha channels, which were left behind when I pasted to the "good" file. (I do a lot of local image corrections and often save my selections. Saved selections appear as alpha channels.) Alpha channels, I remembered, are tweaky... I cannot use the Google Picasa program with its nice browser, for instance, because any file with an alpha channel is invisible to that program.

It turns out the Canon print plug-in has a similar quirk. Specifically, files with 0, 1, or 3 alpha channels all print OK. Files with exactly 2 alpha channels print, but do not have any output profile applied, giving bizarre colors. It sounds crazy, but I've just spent an hour creating and deleting alpha channels (by saving and deleting random selections), and it works every time -- images with 0, 1, or 3 alpha channels print with correct color, while images with 2 alpha channels gets messed up. I am making no other changes to the image or the plug-in settings between tests. It seems completely repeatable... 2 alpha channels = bad news... every time, every image.

I have forwarded my results to the Canon dealer from whom I bought the 5100 and asked them to check it on their systems. If anyone on this list is having this sort of trouble with a 5100 and the plug-in, I would suggest checking the offending file for alpha channels. I don't know whether the quirk is universal, or is specific to my system. All of my files are PSD's, my color space is Adobe RGB 1998, my operating system is Windows XP Pro (Service Pack 3), the Canon Plug-In is version 3.13, and my Photoshop version is CS2.

I hope this helps save someone a bit of grief!

John