Converting Adobe RGB colour space to sRGB

Nikon D50I shoot photos on my Nikon D50 camera in the Adobe RGB colour space. This colour space has a wider gamut than sRGB, which is what all Digital cameras tend to default to these days. Using Adobe RGB allows my camera to record more colour than it ordinarily would if I were using sRGB.

The only annoying issue with using Adobe RGB, is that anyone looking at or using my photos in a non-colour space aware browser, program or printer will see a ‘pastey’, flat photo, because these ‘dumb’ programs simply assume that the image is sRGB. So whenever I upload photos to the web or send them off to other people, I need to convert them to sRGB.

This could be a rather tedious task, depending on the programs one has available. For example, in Adobe Photoshop, one has to open the image then ‘convert’ it to the sRGB colour space, then re-save the image. This is slow and frustrating, and can result in quality loss when the image is re-saved.

Poking around the net I found that there is a great little command line utility on my Mac that I can use to quickly batch convert a bunch of photos from Adobe RGB to sRGB. The utility is called “Scriptable Image Processing System” or “sips”. SIPS has the ability to convert the colour profile without having to re-save the image, hence avoiding quality loss. It also can batch-process, which is great.

So, here the command:

sips -m "/System/Library/Colorsync/Profiles/sRGB Profile.icc" *.JPG --out converted

What this does is: inside the ‘current directory’ convert the colour space of every image ending in .JPG to sRGB colour space and then output it to the ‘converted’ folder (you’ll need to create that). After this command has finished running, the ‘converted’ folder is now full of sRGB images. The whole process takes about 10-20 seconds for a hundred or so ~3MB images.

So all I do, is export the selected photos that I wish to convert, from iPhoto into a folder. I then run the SIPS command, convert the images, then email, upload or burn them as I please.

Of course what would be really nice, is if Apple were to add a “convert to sRGB” option to the export options in iPhoto. This should be really easy for them to do, given that they already have the ‘SIPS’ system included with the operating system.

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