Sawasdee Kup. I'll have a go at answering your questions.
Forgive me if this is old hat to you guys but it’s all new and mystifying to me.
I’m just a hobbyist photographer and have a Hasselblad 500CM and a 500 EL/M. I'm considering a digital back to fit on either/both of them as here in Thailand shooting and developing film is difficult. As a retired pensioner finances dictate something around 12-16 megapixel and probably Phase One. I’m also looking at the Kodak DCS backs, both currently available on Ebay.
But this is where I get lost in this modern digital age!
Are these earlier backs tethered only or can they be used in the field?
Most people are currently advising against getting the Kodak DCS backs since you can no longer get support for them, eventho they are cheap, and they have a very limited ISO range.
Some digital backs are tethered only and some can be used "self-contained" in the field, and yet others can be used in the field, but they may be 2 box solutions - e.g., a digital back and an external hard disk. It depends on the model. Because there are so many different brands and models out there, I'll stick to PhaseOne since you mentioned you are like to go that way. All PhaseOne Pxx designated backs are self-contained units that require the insertion of a battery and a CompactFlash memory card for storage. You have your camera and the the digital back, and sync cable where appropriate and off you go, assuming your battery is charged. So this means, the P20, P20+, P21, P21+, P30, P30+, P25, P25+, P45, P45+, P65+ all are self-contained, and can be used tethered if you wish, or self-contained in the field.
Is it simply a case of bolting them on the camera, coupled with the appropriate sync cables, and off you go?
Essentially, they are designed replace the 120 rollfilm magazine. Remove the rollfilm magazine and you attach the digital back in the same way you would a film magazine. Then if you need a sync cable, attach that.
Where are the images stored?
As mentioned, there are different kinds of backs, but the PhaseOne Pxx model backs mentioned above store all the images as RAW files on a CompactFlash memory card. Like other digital cameras, the card is inserted into a slot designed for it that is covered by a door that has to be popped open to access it.
In the case of the earlier Imacon branded Ixpress digital backs and later the Hasselblad branded Ixpress backs, they stored their images on an external hard disk pack that you had to either sling over our shoulder or clip to your belt (I hope your belt is good at keeping your trousers up!). Other older backs like the Leaf Valeo backs also did use an external hard disk pack.
How are the images retrieved?
Often, you have 2 choices - you can remove the memory card from the back, insert it into USB CompactFlash memory card reader connected to your computer and import the files using the appropriate software, which would have been provided with the digital back. Otherwise, you can also connect the back to the computer with a Firewire cable, very much in the same way as you would to do tethered shooting if you so wished. Generally, the software provided detects the back when connected and Apple Macs and some PCs, the computer can also power the back, so that no battery is required. You can then use the provided software to copy the images from the back to the computer's hard disk and start editing.
What about synch cables for various lenses viz old style Compur and later CF. I have 50, 80 and 100 Compur’s and a 60 CF - is a dedicated cable needed for each?
As far as I know, they all use the same sync cable, since the sync cable connects to the X-flash sync PC socket on your lens. That raises a question - how do you connect your flash up to the whole setup? Well, with your lens' X-flash sync socket occupied by the sync cable for the digital back, you must connect your flash up to your digital back via the additional PC socket provided on the back for this purpose.
What problems will I experience as a newbie to this stuff?
You'll have to learn RAW image file workflow, learn the software, learn PhotoShop, and learn how to do whatever digital darkroom techniques your photographic vision requires. The files are also big, so you may have to upgrade your hard disk size and computer RAM size as well, if not the whole computer, in some cases...
In other words - how does it all work?
A bewildered old man would appreciate your guidance
I hope what I've written above helps and works for you as a starting point.
Kop-kun-kup.