What’s missing from this photo? I’ll give you a hint: The camera was not in the cage when I took this shot. The fence is missing from the shot. The beauty of this shot is that, believe it or not, the fence is still in the shot – it’s between the lens and the birds – you just can’t see it thanks to the power of Depth of Field.
Try this little exercise: Set up your camera with a fairly wide aperture (f/4 or less) and focus on an object about 6 to 10 feet away (about 3 meters). Make sure you use manual focus. Now that you have an object in focus, take a sharpened pencil and place it in front of the lens just a few inches away. Now snap a photo – don’t trust your viewfinder – and look at your exposure (get it on your computer screen for better viewing). What do you see? You may see a blur, you may see a slight discoloration – but the pencil will nearly disappear, especially closer to the point. But generally, the pencil very nearly disappears. The wider the aperture, the less you will see evidence of the pencil.
Now imagine this effect with thinner objects, such as the wire in the fence in the shot above. The fence pretty much disappears. Or more specifically, it is incredibly out of focus. It is so close to the lens – and so far out of your depth of field – that it dissolves. What really happens is that the light (the view of the object across the room) passes on either side of the object before it is converged through your lens and onto your sensor or film. The light passing on either side of the object is carrying partial data which tells the full story, once combined. The side effect is that it may make your exposure slightly darker, but it won’t completely obscure the image. The worst case scenario is that it may create a blurry spot in the image if the obstruction is too large. If that’s the case, you can widen the aperture, frame the shot so the blur isn’t a distraction, or even take advantage of it for some fun effects.
So the next time you want to shoot through a fence or a similar, try this technique. No small obstruction should prevent you from capturing your shot.