I have an Epson flatbed scanner that I share with another Mac. The scanner is connected by USB cable to the other Mac because the scanner is closer to that Mac. The two Macs are connected via Ethernet through a switch. I've had no problem sharing the scanner in this setup when both Macs are running Snow Leopard 10.6.8, but I can't get it to work when my Mac is running Mountain Lion 10.8.2. Is there a problem sharing when one Mac is running on 10.8.2 and the other is running 10.6.8?

There should be no issue sharing between Macs running different OS versions. If you have a problem using various peripherals, make sure that the appropriate drivers are installed on the Mac(s) from which you're trying to access the peripheral(s). In this case, make sure the Mac running Mountain Lion has the correct driver for the scanner (it may have been updated for ML, or it may need an update).

In addition to Alternaut's recommendations, double check the sharing settings on the Mac the scanner is attached to.

I just remembered something I ran into with a scanner after upgrading to OS X 10.8. After the upgrade the app I had been using to access the scanner apparently switched into 64 bit mode. Unfortunately the TWAIN drivers for my scanner are 32 bit only and I had to force the app to run in 32 bit mode in order to access the scanner. You should be able to in the Get Info pane for the app.

I tried that before making this post. I downloaded and re-installed 10.8.2 because I started with 10.8.1. I wanted the combo update and an updated driver from Epson on the App Store as an update. That gave me a fresh OS and driver, but it didn't solve the problem. Epson's tech support was not helpful (IMHO).

My best guess is that another update is needed. I can disconnect the USB cord from the other Mac and plug it into my machine and things work fine, but I can't get it to successfully do it through sharing. I may not know enough about sharing to do it right, but my settings were good enough to work perfectly when both Macs had Snow Leopard. The other Mac is staying with Snow Leopard for the sake of Rosetta.

Yesterday, I was desperate for a scan and the other Mac was very busy, so I restarted with Snow Leopard on my machine and made the scan. I then sent myself an email (with the scanned image attached) from Snow Leopard and quickly shut down. I then restarted from Mountain Lion and opened Mail. Voila! there was the message with its attached image. Frankly, that is NOT an effective use of resources, but it did solve an immediate issue.

Epson is not noted for keeping their drivers for older devices up to date with the rapid evolution of OS X, but that is their problem, not Apple's. That is a major reason why the Open Source Gutenprint was developed for printers and at least part of the reason Hamrick developed VueScan for Scanners. You might check VueScan's list of supported scanners to see if your Epson is on it and if so give VueScan a try. It has been highly recommended for years.

This is a problem I have seen with both Epson and Canon scanners. joemikeb hit the nail on the head; Epson and Canon scan software isn't 64-bit, so it doesn't always work on 64-bit systems.

What I have discovered is that the Photoshop scanner plugin for both the Epson and Canon scanners I've used isn't 64-bit, so I have to run Photoshop in 32-bit mode to make it work; and that the scanner drivers for scanner sharing also don't work in 64-bit mode.

Unfortunately, scanner sharing uses the same TWAIN driver that Photoshop uses. Unfortunately as well, there's no way to tell the network software to run in 32-bit mode. My understanding is that scanner sharing on recent versions of Mac OS X requires 64-bit drivers. In that sense, you're right that an update is needed...but the update needs to come from the scanner manufacturer. I don't see Epson or Canon going out of their way to create 64-bit driver software.

You may have something there. I went to Activity Monitor and it showed Image Capture as 64 bit. There was a related file with it that also is 64 bit, but I have no idea how to change them to 32 bit.

Also, I don't know where to find the Epson driver so I can check it. I'd think they all should be the same, but I'm no programmer--just a bruised user.

I have Photoshop CS4. Can I use that to get what I need? For example, could I use Photoshop instead of Image Capture? I run my stuff through Photoshop after I first make a file in Image Capture.

I don't know about the status of the plug-ins on my Photoshop, but I can follow instructions.

Select the Image Capture application and then press Command+i or Control Click on the application and select Get Info from the drop down menu. Then, with luck, in the Get Info window under General, there will be a check box labeled "Open in 32 bit mode". Close the Get Info window and relaunch Image Capture and it should be running in 32 bit mode. Hopefully that will solve your problem.

You may need to try the same trick on Photoshop. FWIW the app I am using is Graphic Converter.

OK. I have the Image Capture.app window open and under General there is: Kind: Application (but no mention of whether it is 32 or 64 bit), Size, Where, Created, Modified, and Version 6.2. No Get Info. Below that is More info (which is blank), then Name and Extension and Preview and Sharing and Permissions. That's it. No Get Info.

Photoshop CS4 shows Kind: Application (32-bit)

I can't guarantee this is exactly the same data path, but I attach to my scanner, actually a Brother Multifunction Center, over my WiFi network and the Brother 32 bit TWAIN drivers work perfectly as long as I am accessing TWAIN with an app running in 32 bit mode. The problem comes when I am using a 64 bit app to access the scanner through the 32 bit TWAIN interface.

Can I use Photoshop 32-bit to run the scanner and import or do I need separate software to run the scanner?

It sounds as if you have already done a Get Info and you are looking at the Get Info window. Since there is no checkbox for "Open in 32 bit mode" that means the app can only run in 64 bit mode

So you are either going to have to use something like the previously mentioned VueScan or an app capable of running in 32 bit mode. As I mentioned before, I use Graphic Converter but I would think your antique version of PhotoShop would either be 32 bit only or capable of running in 32 bit mode.

Yes, I revised one of my most recent posts to include the fact that Photoshop says it is 32-bit.

I'm still hoping to use the sharing feature since the cabling directly to my Mac is awkward.

Looking at the Activity Monitor on the "other" Mac, it shows Epson Scanner AND Image Capture as being 64-bit. I don't know what that means to this discussion, but I'd like your take on it.

My Mac also has the very same 64-bit apps.

Your confusion at this point is entirely understandable. Let me see if I can blow away some of the fog that may be obscuring your vision. Epson Scanner is the application provided by Epson to control and manage their scanner and I do not doubt that it is 64 bit on both machines. Unfortunately the Epson Scanner app is NOT what Image Capture, Photoshop, or any other "third party" app uses to access your Epson Scanner.

Like most of the other major scanner vendors, Epson is a member of the TWAIN Working Group. TWAIN is in essence a standard interface protocol with tightly defined gozintas and gozoutas supported by most scanner manufacturers, so applications can be written to use TWAIN independently of whether the scanner in use is an Epson, HP, Brother, or whatever. TWAIN is NOT a hardware level interface though so on the hardware side of TWAIN each manufacturer must write the hardware level data source code necessary to connect and converse with each of its scanner models. Vendor applications such as your Epson Scanner app may, or may not, bypass TWAIN and go directly to the hardware level. In fact there may be the equivalent of the TWAIN data source embedded within the vendor's application. Third party apps such as Image Capture, Photoshop, etc. on the other hand will almost always connect to the TWAIN interface.

TWAIN is in most cases on a Mac a Unix executable found in /Library/Image Capture/Twain Data Sources. On my system the specific Brother TWAIN data source is found in Brother TWAIN.ds. (Brother TWAIN.ds is a application package and requires using "Show Package Contents" to drill down into it.) Three or four levels down Inside that application package is the Unix exec file that provides the TWAIN interface. It is that Unix exec, not the application package itself you want to check to see if it is 32 bit or 64 bit and I strongly suspect you will find it is 32 bit — on both machines.

By-the-way some have said TWAIN means "Technology With An Interesting Name", others have asserted it means "This Was An Interesting Name", but neither is correct. Apparently the name came from a Rudyard Kipling quote [i]Oh, East is East, and West is West, and never the twain shall meet.[/i] in the TWAIN case it is referring to applications and scanner drivers.

Before I forget it, thanks JoBoy for starting this thread. It is interesting and more than once has sent me delving for additional information. I had no idea what the format of the TWAIN interface was or where it was located on my system and now I do.

NOTE:
gozintas is software engineer speak for Goes INTO
gozoutas is software engineer speak for Goes OUT OF

Thank you for the explanation. I came down with the flu yesterday and am not fit to ask lucid questions. I'll be back when my brain begins to function again.

Hope you get to feeling human soon. (I hope my flu shot worked.)

For what it's worth:

HP A-I-O PSC machines lose the WIRELESS scanning feature if running a computer/laptop through Time Capsule. One can still print remotely, however.

In order to user the scanner functions, the computer/laptop must be connected directly to the HP A-I-O PSC machine with a cable.

Note: Not sure if this only applies to HP or to only some of their models. But all the latest driver updates have NOT made my PSC's scanner work wirelessly through Time Capsule . . . although the printer will.