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If you happen to be using a computer with a Core Duo processor (Not Core 2 Duo), every app is only running in 32-bit mode all the time, and the option won't show up.
Any chance you ran a tool like Monolingual to clear out unused languages and CPU architectures? Your Photoshop app is not the right size. I'd uninstall and reinstall it, then try again.
 
Whenever I set PS for 32-bit on the 2008 iMac in our lab, PS would crash every time it was launched. When I disabled 32-bit mode, PS ran fine. But of course that meant no TWAIN driver would work....
 
Preview works

Ran into same problem. Moved the twain driver from CS4 to CS5 and switched CS5 to 32-bit mode and was able to see the LIDE500F again under File > Import, but it kept crashing PS.

As an alternative to PS, you can use Image Capture, which is pretty basic. You can also import from Preview, which gives you the same basic interface as Image Capture.
 
LiDE80 not seen in anything

Tried all of the mentioned solutions: downloaded/installed the previously linked TWAIN driver, downloaded/installed CanoS can software, copied over TWAIN driver from previous install, set PS CS5 to open in 32-bit mode.

PS CS5 doesn't see the scanner (LiDE80) and no TWAIN driver shows up.

Image Capture doesn't see the scanner.

Preview doesn't see the scanner.

The only thing that does recognize the scanner is the PoS CanoScan software that came with the scanner that frequently crashes and has very few options for scanning that actually work.

Any other ideas? Any suggestions for scanners that actually work with Mac OS 10.6.5 & Photoshop CS5? Or scanners that have decent Mac software?
 
I got a Canoscan Lide 700F scanner on eBay. All I had to do was plug in the USB cable. My iMac immediately recognized it without installing any drivers. Works like a charm.
 
Considering the LiDE 700F ...

I got a Canoscan Lide 700F scanner on eBay. All I had to do was plug in the USB cable. My iMac immediately recognized it without installing any drivers. Works like a charm.

I saw the 700F on Apple's store. The reviews seem to agree with your experience with it. Would you mind telling me what version of OS you're using? I'm using 10.6.5.

Thanks!
 
The little details.

It seems very small - mine is 415MB. Do you have a cut down version?

I dont know if it will make a difference to you but...
i have had this same problem. (CanoScan 8600F)
i tried copying the plug in from the old PS4 to the new PS5 with no luck
i moved the old plug in back to the new PS5
i tested adding the scanner to the list of shared items in mac prefs, this went okay.
Still no twain in PS5
read this article and dicovered 32bit mode, Ahhhh.

QUIT PS5 BEFORE I GOT INFO ON PS5 APP IN APP FOLDER.

THE OPTION TO USE 32BIT MODE WAS AVAILABLE, SO CHOSE THIS OPTION.
CLOSED INFO WINDOW, STARTED UP PS5.
YIPPEEEE, IT WORKED.

Thanks for the advice. it worked for me
MacBookPro OS10.6.6 2.6GHz IntCore2 Duo 2.6 ghz 4GB 667MHz DDR2 SDRAM:p
 
No Solution....Ever.

I'm on a PC, but the answer, sadly, for everyone is that there is, and probably never will be, a way to get true 64 bit support for TWAIN.
There are CS5 TWAIN plugins for 32 bit and I'm guessing that is the reason that CS5 by default installs an extra 32 bit version on 64 bit machines.
The TWAIN people have stated, several times, that they have no plans to make 64 bit TWAIN drivers.
On W7 in CS5 you get this crappy little option called WIA, it has almost no user controls.
Hope there's something better for your Macs.

I just use the 32 bit version of CS5 when I scan.
Sucks, but what can you do?
 
Really Easy to fix Guys

I had the same problem.
Upgraded from CS4 to CS5, No scanner.
Also bought a new 3 in 1 (Cannon MG6250), installed drivers - still no scanner available in Photoshop CS5.

SO:

1. Moved my TWAIN plug in from CS 4 >Plugins>import/export to CS 5 >Plugins>import/export and still no scanner in Photoshop CS5.
2. Quit PS CS5
3. located the PS CS5 application icon in the finder
4. selected get Info
5. Ticked the "open in 32 bit mode" box.
6. Relaunched PS CS5

Hey presto, Ive got the scanner directly in Photoshop.
 
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