Hi
just to let everyone know, this process can be achieved with digital photography also.
Suppose you're shooting a low light event where flash is forbidden, and your maximum ISO on your digital camera is ISO 800. The camera is suggesting very low shutter speeds at ISO 800 at the biggest aperture u have (say f2.8), and u can't handhold that shot.
wat do u do?
you can switch to manual mode or use the exposure compensation dial to dial down one stop for shutter speed to the more handholdable shutter speed. Now naturally since you dial down a stop of shutter speeds, ur images are obviously going to be underexposed by 1 stop (asssuming in camera meter reading is accurate). Just keep on shooting.
When you get back home, run Photoshop, adjust curves for the first image until the image looks correct. Save the curve you just did, and then use Automate->Batch in photoshop, create an action that will apply this curve consistently across all images from that low light event shoot. If you do it right, that curve will consistently bring up all images by 1 stop. You have now effectively increased your camera's ISO at one stop to 1600. You've pushed your digital film by 1 stop.
Sometimes, depending on camera, it may be better to push low ISO to high ISO in photoshop using levels than actually shooting at the high ISO due to high level of digital noise. You will have to experiment to see which one is moer suitable for u.
The last paragraph may seem strange, until you realise that for films, it's the same. For example it has been reported that it is better to push Fuji Press 800 film to 1600, than shoot with Fuji's 1600 film - images turn out better.
