Rich,
I attended a class where it was suggested I shoot RAW+JPEG. (They also recommended Photo Mechanic.) My notes state that doing so allows for ease of emailing, (I assume if a fast turnaround is required), "etc." (whatever that means). I have read that others shoot RAW+JPEG for speed of browsing and selection.
Is there a performance difference in PM for RAW+JPEG vs. RAW? Is the quality of the image different in Preview or Contact Sheet different for RAW+JPEG vs. RAW? Are there other PM considerations in this regard?
Are there other reasons for shooting RAW+JPEG that I am missing?
Shooting RAW+JPEG is great when your JPEGs already look spot on since you have nothing more to do (no RAW development/adjustment needed). And for those times when the JPEG isn't perfect, you have the option of developing the RAW and adjusting it as needed.
Photo Mechanic can join the two images as a single item (and by default it does this) and in doing so it uses the JPEG of the pair for purposes of previewing and thumbnail generation. Photo Mechanic in general is not a RAW rendering application, meaning that when given a RAW photo, Photo Mechanic finds the embedded JPEG preview which is often half resolution, and uses that for previewing and thumbnail generation.
Some cameras like the Nikon D2X output a full resolution preview inside their RAW files, and as such there is virtually no difference in the preview quality in Photo Mechanic over shooting RAW+JPEG.
So if you shot RAW only instead of RAW+JPEG, the differences would be that your previews wouldn't look as sharp, and you can't do a Save as operation (in general this is true, but on Mac OS X 10.4.6 and higher we can indeed render many RAW formats). You can always extract the JPEG previews out of RAW files with a tool on the Tools menu.
There is a slight performance improvement in general when shooting RAW only in that since the JPEG previews embedded into the RAW files tend to be smaller than full resolution they can be scaled more quickly for thumbnails and previews. You may lose the ability to zoom in at 100% depending on your camera's JPEG preview size in its RAW files.
So it is really a matter of personal taste/workflow needs. If you shoot RAW only then you'll likely be spending a fair amount of time working with a RAW converter application. If you shoot RAW+JPEG then this time can be reduced somewhat. Your cards will fill up faster when shooting RAW+JPEG, and your ability to shoot long high-speed bursts will also be reduced. If you're a sports photographer then that can be a deal breaker.
HTH,
-Kirk
