There is a joke that I can’t quite remember that involves a panda bear that eats, shoots and leaves, but this isn’t about that.
Several weeks back, I posted the image you see below in Sepia Mutiny. Prashant Mullick whose own fine blog on science I read from time to time chimed in to ask me to explain what I meant by “exposing for the leaves.” Trust me, there is nothing kinky about this.
Seriously, though, photographers have a series of options between the time they lift the camera to their eye and release the shutter. Each time we photograph, the choices range from what to photograph, what angle to photograph from, how to gauge the light and of course how to expose film or in this case a computer chip.
Cameras don’t make images, people do. Cameras are merely boxes that allow light in various quantities to enter into a tiny hole called an aperture and fall on either the film plane or a computer chip. While cameras have really turned into super-computers that can analyze every part of the scene and spit out a possible solution in a fraction of a nanosecond, in the end you as the photographer control whether to except or reject what that computer is merely suggesting.
I am going to assume that you already know the symbiotic relationship shutter speeds and apertures (also known as f/stops) have with each other. To go into that bit of photo-speak would take away from the simple explanation my friend Prashant expects.
Let me begin by saying that film or a computer chip has the capacity of rendering a range of tones – from shadows to highlights and everything in between. To what degree they do so and how successfully they are able to carry this out is perhaps the final determinant in making a picture. Film, for the most part, is forgiving. By that I mean, you can perhaps make an image three or four f/stops off and you could in theory still produce an acceptable print. Digital, so far, has been just the opposite. Your exposures have to be pretty much spot on or you get dull, flat images with obvious pixels (called digital noise) if the image is under exposed. Or, bright, shiny, impossibly white images if you have over exposed the scene. Being cognizant of your machine’s dynamic range is key to just about any process you end up using.
If you own a digital camera, try using it in near darkness and then again outside at around 12 noon. You’ll see what I mean. If you feel like your camera has cheated you out of a great image, think again. Remember you are in control. Thankfully, though, most digital cameras in the world today do a fair enough job at producing images without going haywire.
Now back to my image. Given that there is this range of highlights and shadows to deal with, I had a choice. Do I take a picture that emphasizes the empty, boring sky or these leaves with incredibly interesting markings and contours? You have to agree that it is a fairly easy decision in this case. There may be times when you may want to include both sky and leaves, but we can talk about that another time. Now I could have (and did) point the camera at the scene I wanted to capture and took a picture. I remember the intensity of the light in the sky confused the camera and made it think that there was just too much light in the overall scene. The camera then automatically cut the aperture down to where a resulting underexposure was recorded.
The gift of digital is that you can quickly assess the image and either accept it or reject it. I pitched the image and shot another frame. This time, instead of pointing the camera up where most of the sky was visible, I merely pointed towards the base of the leaves where it was really dark. What do you think the computer in the camera decided to do? Again, somewhat confused because it thought it had less light to work with, it increased the amount of light to be recorded. This time it was too darn bright. I pitched this overexposed image as well.
Finally, I pointed the camera to where I thought (and photography is very subjective) the camera would accept both shadows and highlights without going buck wild. I wish I had the exact readings for shutter speed and aperture, but whatever it was, it worked for me. Now, someone out there may complain that it’s still not perfect. That may be so. But I had arrived at a solution that I could accept and given the number of emails I have received about this image, so have others.
In the end, I wanted the leaves and leaves alone to be perfectly exposed, so I exposed correctly for the leaves and let the exposure for the sky to go beyond my little digital camera’s dynamic range. The sky became this impossibly stark white which means the camera did not record any pixels in that area (unnatural, some may say but everything is open to interpretation and rationale). No pixels means no digital information. The final result, however, was what I was going after.
Email me if you have any questions about this. But the best thing to do is to go out and shoot a few frames. Photography is about doing.