Tying up Photoshop to scan is a very inefficient way to work.
Try using a dedicated scanning utility like VueScan or SilverFast.
VueScan, for instance, can be called from inside Photoshop and set up to open the image in Photoshop automatically.
Can't help you with CC, as I'm not a subscriber.
Well, if it doesn't work, it's very inefficent, yes. That is what I'm saying.
Also, as I've said, this is a problem that is found only within CC. Earlier versions are not effected by this problem.
While it's totally possible for me to go and use other software (I'm on a mac, so it's Image Capture for me) I find that it's actually less efficent for the person driving the software. I mean, I know I can set up Image Capture to punt scans over to Photoshop CC - that's trivial - but if I'm flicking between applications I might as well check my email, and then I'm answering some question from somebody, and then ten minutes has gone by and I haven't finished the scanning. So it kinda depends how you define efficiency.
If you use a scanning utility, you can continue to work on something else in Photoshop while you're scanning.
That's where the inefficiency comes in when you tie up Photoshop to scan. All versions of Photoshop are affected.
I'm on Macs too. VueScan and Silverfast are and have been available for the Mac.
I highly recommend that you check out Silverfast 8. It's a standalone app, but scans open in Photoshop CC. It has really great features for many scanning tasks, and is very efficient. The app is paired with your specific scanner, so before you buy, check out the demo. http://www.silverfast.com/get_demo/en.html
I took a look at Image Capture, and found it to be about as basic as it gets. Silverfast will save a lot of time retouching average-to-bad scans.
VueScan is a phenomenal value.
$ilverFa$t is indeed a bit more powerful, but its price for certain scanners is simply prohibitive.
What's the specific scanner/device you're using? What version of OS X? Is the driver up-to-date?
I agree with the prior posters. Personally, I do all my scanning in the background with the stand-alone scanner software. All TWAIN really does is call that software, so there’s no quality difference, plus you’re not locking Photoshop up just to doing scanning. You can retouch and edit images in Photoshop while you scan in the background – which I find is far more efficient.