Exporting images out of Lightroom is one of the simplest tasks imaginable. But what you may not realize or have thought about is what happens when you export images in a color space other than ProPhoto RGB. I bring this up because Lightroom by default uses a ProPhoto RGB color space with an sRGB tone curve. What this means in layman's terms is that while working up your images you are essentially working in a ProPhoto RGB color space which is huge compared to an sRGB color space. And there are subtle changes in your images if you export them in any color space other than ProPhoto RGB.

Don't ring the alarm bells just yet - this isn't a critique of Lightroom - this is just how it is. Let's say that you work up your image in Lightroom setting the white and black points using the option key as I wrote about in last weeks blog post. This allows you to set with great precision the white and black points of an image - in the ProPhoto RGB color space. When you export that image as sRGB and then open it in Photoshop you'll notice that your histogram is a little different than it was in Lightroom. You might even see some clipping in the shadows and highlights. This isn't rocket science. You just converted your precisely worked up ProPhoto RGB image to a smaller color space and because of that the histogram is going to change.

In some cases the change is so small that it is irrelevant. In other cases it isn't. Here is an example of one image that was exported as an sRGB file to be used online. You'll notice in the first histogram (from Lightroom) that there is ample room on either side of the histogram and all looks good. In the second histogram (from Photoshop's Levels dialog) of the same image in the sRGB color space we see that both sides are clipped. And in this case the difference is drastic. Though if you could see the sRGB image it doesn't look appreciably different on my monitor than the ProPhoto RGB version - mostly because my Apple Cinema Display only renders the sRGB color gamut. The image still looked just fine but I wouldn't want to send an image with this histogram to a client to publish in a magazine.

So the moral of this story is know what color space you are working in and where your images are going. This is also the main reason that I always export images out of Lightroom in a ProPhoto RGB color space and then in Photoshop I can convert the images to Adobe RGB or sRGB as needed but with a lot more control.

As an aside - if you want to work up your images in an sRGB color space with more control, Adobe Camera Raw (ACR) changes the histogram depending on which output color space you have chosen - because you can set this in ACR before you open the file into Photoshop.

As I said before this isn't a reason to abandon Lightroom - just one of those things to be aware of if you are exporting your images out of Lightroom into an sRGB color space. For many folks, you might not even notice any change in the images at all. Another workaround is to just leave a bit of room on either side of the histogram as you work those images up in Lightroom, then export the images and wait to make final histogram settings in the Levels dialog in Photoshop.

That's it for this session. See you next week.

Adios, Michael Clark