C. David Tobie: Mac Finder Color Issues
Sep 2013 19

Mac users have been noticing that thumbnails of their images, in the Mac Finder, are not always showing correct color. Most commonly, this occurs when using a wide gamut working space, and results in very flat, and sometimes off-hue image color in the Finder preview of the image. I have received a number of questions about this, and while there I can’t offer a simple answer, I can provide some interesting information on the topic.

First, it’s important to remember about that unique Mac feature: Mac files have both a resource fork, and a data fork. Some functions of the resource fork are duplicated elsewhere (typically the file name, or the data fork), to make files cross-platform, as PCs don’t use a resource fork at all. Recently, Apple has eliminated most of the operating system calls that allow third party applications to write to the resource fork. This makes sense, given security concerns, but it also complicates this issue somewhat.

Older versions of imaging applications used to write image preview thumbnails to the resource fork themselves. Updated versions, such as Photoshop CC, no longer do that. Older apps may still try, but there are no guarantees, given the changes in Apple’s access to such functions. So your results may vary, not just with which version of Mac OS X you use, but with which version of your imaging application you are using as well. With older versions of Photoshop, turning off the option to create thumbnail previews when saving image files can solve some thumbnail color problems, by letting the OS do this instead of the application.

Yet another variable is where in the Finder you are looking at the image thumbnails. Previews that do not show correct color on the desktop may be correctly color managed when viewed in OS X’s “Get Info” window; or not, depending on assorted factors. This last clue would lean towards an OS X inconsistency, and Apple needing to extend it’s own color management to the desktop. But keep in mind: Apple is working towards an sRGB standard for their own displays and most files, and anything that does not cause problems in sRGB-based systems does not get the same level of priority as bugs and issues which affect standard Apple uses.

Lets look at a screenshot of two color image’s thumbnails on a Mac screen. On the left, each image is in ProPhotoRGB. As you can see, the color saturation is reduced, and in both cases the color hues are incorrect as well. The versions of each image on the right have had only one change made to them: they have been converted from ProPhoto to sRGB. Now the icons show correctly. Given that a similar phenomenon will occur in many types of web or mobile viewing, the clear moral of the story is to convert images to sRGB for mobile or web viewing. But that does not address the unpleasant previews seen when viewing wide gamut files through the Mac Finder. If Apple were to convert image thumbnails to sRGB when creating them, that would go a long ways towards solving this issue… except on wide gamut displays. So full color management is the only totally effective solution.

It seems quite clear that this is an OS X issue, so it may be corrected in either an OS X dot update, or in a major version of OS X (next up: OS X Mavericks). But given its low priority, as a wide gamut working space issue, there is no guarantee just when it will make the Apple fix list.

C. DAVID TOBIE has been involved in color management and digital imaging from their early development. David has worked to see affordable solutions put in place for graphic design, prepress, photography and digital imaging, and then taught users how best to utilize them. He has consulted internationally for a wide range of color-related companies, and is best known by photographers for his writing and technical editing of texts and periodicals for the photo industry such as Mastering Digital Printing, and Professional Photographer magazine, and his seminars on color and imaging at photographic workshop around the globe. David is currently Global Product Technology Manager at Datacolor, where he develops new products and features for their Spyder line of calibration tools. His work has received a long line of digital imaging product awards including the coveted TIPA award, and a nomination for the Spyder line of calibration tools. Much of David’s recent writing can be found at his photography blog: cdtobie.wordpress.com, and his samples of his photography can be seen at: cdtobie.com.