controlling DSLR camera.

I will be using one of the arduino mega’s and want to control a dslr camera’s shutter which seems ok but i also want to tell the camera not to save the image on its sd card but to send it somewhere else, maybe to a raspberry pi or to a PC so that the pi/pc can project the image and save it to a storage device.

Will this be possible via the shutter control cable?

many thanks

Highly unlikely.
If it's a cannon you may want to investigate the MagicLantern project. It basically adds user defined functionality to the camera. Very interesting stuff. I was involved with it for a while myself but no longer have a cannon camera so lost interest.

If you are going to have a "raspberry pi or PC", why bother with the ARduino?

You will probably need to use USB to control the camera, so at the very least you will need the USB host shield.

But each camera is different.

Arduino can tell the camera to take a picture, but it can not tell it what to do with the picture once it's taken.
You can, however, use something like EyeFi to get the pictures out of the camera. I used them briefly a few years ago for time lapse and they worked okay-ish. I had some trouble with it operating reliably after a few weeks.