Lightroom is great for getting the exposure or colour balance right, or for getting the horizon straight, but doesn't do many of the more complex things that Photoshop (or Photoshop Elements) will let you do (eg remove someone from the photo).
Can you get Picasa for the Mac? It can perform a surprisingly rich range of edits, and is free
Hmmm...I seem to be doing a lot more in Lightroom in terms of image processing. I've never used Picasa, but it looks like it's a wonderful free image editing program that handles many basic and slightly intermediate image editing tasks. Plus, it's available for Mac & PC.
Lightroom does all the things that Picasa does above, plus a lot more. Some of the big things that Lightroom does are local adjustments (using the "Adjustment Brush") and adjustment gradients (using "Graduated Filter").
I use the "
Adjustment Brush" to do local dodging and burning (ie. brightening and darkening different parts of a photo). Or, maybe someone's teeth are yellow but the rest of the photo is fine, so I might use the "Adjustment Brush" to whiten their teeth. (My wife laughs at me when I do this) Or, if someone's skin color is a little off due to lighting, I can use the "Adjustment Brush" to add a subtle color adjustment only to the skin to correct this.
I use the "
Graduated Filter" as a way to brighten or darken different sections of a photo. I'll use this for landscape photos, where the sky is pretty bright or the foreground is pretty dark. The graduated filter can darken the bright sky or brighten the dark foreground (similar to what a graduated neutral density filter would do, but maybe not quite as good). Sometimes with bounce-flash pictures, 1 side of the photo is somewhat brighter than the other. I can use the Graduated Filter to brighten the other side, so that the photo appears evenly-lit.
You can also do that wedding photography trick where you convert a photo to black-and-white, but leave some spot color on a particular object (like red roses).
You can also add vignetting for your wedding or portrait photos, or to draw your viewers' attention to the center of your photo.
Lightroom is also very useful for organizing & cataloging your images, too. That's a whole separate topic in itself!
I didn't think I'd turn out to be such a passionate Lightroom defender, but I just wanted to clarify that Lightroom does more than just "getting the exposure or colour balance right, or for getting the horizon straight". That's why I said earlier that Lightroom can do about 90-95% of my image processing needs. However, alan is still correct in that if you
*do* need heavy retouching, you'll need to bring your photo into Photoshop for those 5-10% of photos that need additional work.
and No I haven't loaded the software and won't. I don't need it.
