Picasa's hidden 'expert' features make it superb

I've discovered two hidden features that make Picasa suitable for serious amateurs and even, in some cases, professionals.

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Al Fasoldt's reviews and commentaries, continuously available online since 1983

Picasa's hidden 'expert' features make it superb

September 25, 2011

By Al Fasoldt
Copyright © 2011, Al Fasoldt
Copyright © 2011, The Post-Standard

While editing hundreds of photos of a recent journey, I became frustrated at the porkiness of my standard professional photo-handling software. The result of my dissatisfaction was a revelation.

Left with the feeling that my editing would take seven months to finish, I turned to Picasa, the free photo editor and image organizer from Google. I already know how to use Picasa's many features -- I teach a workshop on Picasa -- and I thought I had uncovered everything about the way the software works.

But overconfidence can be a fickle friend. After a close examination of the way Picasa exports photos and the way it adjusts dynamic range -- the range from very light to very dark -- I've discovered two hidden features that make Picasa suitable for serious amateurs and even, in some cases, professionals. I'll explain both of them. (If you don't already have Picasa, get it free from Google at http://picasa.google.com. It's available for Windows, not just Macs, and comes in a version that runs on Linux, too.)

The first hidden feature is amazing. To explain how it works, we have to look at Picasa's unusual editing process.

Picasa does all its work on JPGs. Ordinarily, that would be bad, because JPGs are compressed images with some of the picture content tossed away. An original JPG, the photo that comes out of the camera, is usually fine -- the first-time image compression in a JPG is very hard to detect -- but a JPG that's edited and resaved a couple of times starts looking rough and jagged.

But Picasa never does any of that resaving stuff. Instead, Picasa keeps a list of the changes you make (crop this much off the side, add this much red-orange to the image, increase the contrast 5 percent, that kind of thing) and applies those changes to an exact copy of your original whenever you view or print the photo.

And whenever you export the photo, too. That's the important point here, because the only way to get Picasa's image editing OUT of Picasa is to export the photo. So here comes the Big Kahuna of JPG Editing: Doesn't this create a resaved copy of the JPG with reduced quality, and therefore make all your efforts pointless?

Not at all. Or, more to the point, not if you use Picasa's unheralded "Automatic" image quality setting, shown in the screen shot here. As long as you use the original image size, the "Automatic" setting simply adds your changes to the original JPG as an overlay and saves the result. It is not "resaving" the JPG after editing; rather, Picasa is filtering the JPG through the overlay of your changes. The structure of the image, crucial to the way JPG compression works, is not touched.

You can then open the exported image in any other image program and save it as a TIF or PNG; both formats preserve the image in a lossless way. In other words, Picasa's editing is lossless in terms of what it does to the JPG, and Picasa's exported version is lossless too.

This is all but unknown outside of Google's engineering team.

The second hidden feature is Picasa's auto-adjustment method, used in the "I'm Feeing Lucky" and "Auto Color" buttons. To use it, first turn on the display of "overflow" or blown-out areas of the photo. Open the View menu, then choose the Display Mode menu. Make sure "Show overflow pixels" has a checkmark.

With that turned on, every photo you edit will show whether it has blown-out areas by highlighting them in red. To pull the brightness of just those pixels back from the blown-out stage, simply click "I'm Feeing Lucky" and then "Auto Color." I know of no other software that does this so automatically -- and so well.