can select a group of photos and shrink them by 50%?

I have about 200 photos that are too large and I'd rather not manually reduce them all one at a time.

 

nice, thanks so much!

 

I'd vote for Irfanview, its batch conversion mode can do even far more than that. Free for private non-commercial use.

 

I would use that on windows, mac and ubuntu can do that by default...

 

I second the vote for IrFanView. You can even convert all the images from the command-line if you want, which is useful for batch scripting.