This might not be news to anyone more experienced than I, but I’ll post it anyway to wrap my head around the concept and maybe help out the next newbie to come along.
I recently lamented the overall poor quality of my first attempt at taking indoor punk show photos without a flash, in the typical low light of a dive bar. I knew this was going to be a challenge but I thought that by pushing 400 film to 800 I would get good results. Overall, most of the photos were very underexposed and the ones that were were very grainy and I could do very little Photoshop magic to pull any additional detail, without exaggerating the grain. At the time this frustrated me, but now that I’ve done a little research on pushing film it all seems clear to me now.
If you don’t know, pushing film involves two main steps. First, shooting a slower speed film as though it were faster, and second, developing it appropriately. That much I knew. But what I didn’t understand is that in fact, pushing does not do anything to increase the exposure in low light. In fact, all you’re doing is underexposing the film in the camera, and compensating for that underexposure by over-developing it.
When you load film into your camera, you set the ISO, perhaps at box speed. But if you’re pushing you will set it higher — 400 speed film could be set to 80o, for example. But this does not actually do anything to increase the exposure, actually the result is the opposite. Why? Well, what are the three things you can control when you determine the exposure of a film? The box speed of the film, for one; but this is set at the factory. The little dial on your camera does not adjust how the film was manufactured. Beyond that there is the aperture and the shutter speed. But those are exactly what you set them to.
So, setting the ISO dial on your camera doesn’t really change the exposure. What it does do is “fool” you and your light meter (and your auto settings if you have them) into thinking you have a faster film in your camera than you actually do. Your camera will tell you that a smaller aperture or faster shutter speed is OK for that film and lighting. But the camera “thinks” you have a faster film in there than you really do. Therefore, you photo will be underexposed. So the real pushing occurs at the processing stage, when the film is left to develop longer.
The longer development doesn’t compensate exactly for the underexposure, though. One reason, as I understand it, has to do with the way light works. We use terms like “bathed in light” and imagine light as being like a fluid, or like a coat of paint that we can cover something evenly with. In truth, however, light is more like a shotgun. Rays of light beam from a source in kind of a random distribution. Our brains are processing this continuously and we don’t perceive time nearly as fast as the shutter of a camera, so our eyes see a big enough sample that the randomness of the light evens out. But when we are talking about dim light, and collecting the rays that might hit a film in a tiny slice of a second…1/60, 1/125, 1/250, or even smaller…the randomness does not average out. Not every grain on the film will get hit with a roughly equal amount of light.
When the film is processed for longer than usual the disparity between the grains will be exaggerated. And if you do much tweaking with the contrast and such after the fact, you’ll probably make the grain pop even more. Unless you’re going for a very low-fi effect, you won’t have a lot of room to play around with it before your photos start to look like garbage.
So after all that, my take home lessons are: understand that setting your camera to a higher ISO does nothing but trick you into underexposing your images. If your light meter still says it’s going to be underexposed, it’s DEFINITELY going to be underexposed despite the pushing. Also be aware that you’re going to make the grain more obvious; if you don’t like the results you’ll either need a film that takes to pushing better, or just shoot a film with a faster box speed. Also be aware that the increased grain is going to tie your hands when it comes to post-processing, so you have to do your best to get the exposure right in the camera.
junkyard photo 