UPDATE: I reinstalled this scanner to use on my new Mac Air running OS Lion and Photoshop CS4 and the process was much faster this time. All you need is installing the driver and then the optional Photoshop plugin on this page - http://www.mustek.de/11/index.php/en/service-a-drivers-2/treiber-a-software/231-scanner/scanexpress/a3-usb-1200-pro
As soon as I did this and restarted Photoshop, it started showing File/import/Scanexpress USB 1200 Pro option. Although I did not eventually need it, here is another blog shedding some light on the topic - http://underdesign.wordpress.com/2011/04/04/getting-my-mustek-scanexpress-a3-tabloid-scanner-working-under-photoshop-cs4/
I had bought a Mustek A3 USB 1200Pro Scanner long long ago for scanning my larger than A4 pictures/paintings. The only problem – Mustek did a disgusting job on providing the right software for Mac. Although they provide something on a cd, those drivers do nothing on the Mac. Heck, you cant even detect the scanner.
If you Google, you would find that only software that will work is Photoshop. I tried that but although it detected, PS (I had CS3) would crash right as soon as you selected File > Import > ScanExpress A3 USB. After sifting through some google results, this is what worked for me:
Sunday 23rd August 2009 at 7:24 pm
I have found another option on this website:
2.- Click on “drivers” and then go to the first option and select your scanner-series (in my case is scanexpress series) and click “go”.
3.- Choose your scanner port : USB and then select your scanner from the list (mine is A3 USB 600Pro) and you’ll see a download option for MAC Driver 10.4~10.5
4.- Install the driver and open the Image Capture and find the TWAIN scanner.
5.- I’m using Photoshop CS3 and choosing File/import/Scanexpress USB 600 Pro..
I found this blessing of a comment here. And I had already followed all the steps mentioned on this blog before trying out this comment thing, so I dont know if those steps are required or not. I am also not sure if TWAIN drivers are finally required to get it working this way. But I had seen lot of people complaining that specially PS CS3 was troublesome and I eventually got it working on CS3 using Gabriels method. For CS, CS2 and CS4, TWAIN driver is supposed to work. So anyways, give original or Gabriel’s method a try and hopefully you wouldn’t end up wasting this awesome scanner trying to use with Mac. Also, I am running Snow Leopard and it worked. So, good luck and here’s my first oversize painting that I was dying to scan. Its just Version 1, more layers to come.