simplest way to open all images in a directory in Finder

If Preview is in the dock, you can drag and drop the folder onto the Preview icon to open only the pictures. I just tried this with a folder of images, wmv, mp4, and mov files and only the images opened in Preview.

You can open all the files with Quicklook by typing:

⌘+A then space

One approach is to sort by Kind and use the Shift key to select just the range that includes the images you want to open.

Another possibility is to use the spotlight search box in the corner of the Finder window to whittle down to the stuff you want by typing the file extension of interest.

Or if you are really motivated, you might whip up an Automator script and assign a dedicated keyboard shortcut.

I use the sort by kind option and shift select all the jpeg.

• ⌘+2 - enters list view
• scoll to the beginning (or end) of the pictures
• click once on the first picture
• scroll to the end (or beginning) of the pictures
• shift click the other end of the range
• ⌘+O - open them

If I find I have more than one extension or find myself doing this more than once, making a smart folder to select the files is the winningest move.

Rather than trying to do this in the Finder, I think you should consider a trial of a third-party image-processing program that provides a "Browser" for viewing large thumbnails of lots of images in a folder. I would suggest investigating the features offered by Adobe Photoshop Elements, GraphicConverter, and Google Picasa.