This is a post for Flash Parker and my Flash Light Photography Expeditions. Head on over there!
Last week I wrote about three basic, and very broad ways in which to improve your photography. This week, we’re going to look more in depth at one of those; specifically, gear. Even more specifically, we’re going to talk about thousands of dollars of glass, and where we should be putting our hard earned big ones.
Simply put, the lens you should buy is the one that does the job you want it to do. I cannot recommend exactly which lens you should buy, as I don’t shoot like you. I can tell you that my Nikkor 85mm f/1.4 is one of the best lenses I own when used wide open. I can then tell you that it has pleasing bokeh. I can tell you that stopped down to f/2.8 it is tack sharp and very contrasty. I can also tell you that it is mildly heavy after shooting for a whole day, and that its screw-in hood can be a pain. However, what does this tell you? It tells you what makes this lens a good lens for me. Others may tell you that their Holga’s lens is the best they’ve used. So what should we look at when choosing a lens?
Aside from checking your bank account and clearing the purchase with your significant other, perhaps the first thing to decide upon is a focal length. The focal length of lenses has a lot of implications visually; including compression, angle of view, and depth of field.
Firstly, let’s look at compression. Longer lenses will tend to compress elements together, making them appear closer together. Whereas, wider lenses will do the opposite, making objects closer to the lens disproportionately larger than those further away. The wider a lens gets, the greater this effect. The longer a lens gets, the more the compression effect.
Similarly, wide angle lenses have a wide angle of view, and longer lenses have narrower angles of view. A 24mm lens will cause the subject to look much larger in relation to the background objects, and the wider angle of view will include many background elements. On the other hand, the 135mm lens will cut out much of the background, and the subject will appear closer to the background objects.
Another aspect of lens focal length is depth of field. Wide angle lenses inherently give deeper depths of field. Conversely, the longer a lens is, the narrower the inherent depth of field. For example, a 17mm lens focused two metres away from a 35mm film frame / sensor and set to f/5.6 will give acceptable sharpness between 0.9 metres and an infinite distance from the camera. However, a 135mm lens set up with the same parameters will give only a few centimetres of acceptable focus.
So, wide lenses offer greater depths of field, and a little or a lot of perspective distortion between foreground and background elements. For this reason, a lot of street photographers like to use lenses between 28 and 35mm. This allows them to get close to the action and slightly distort perspective to make certain elements stand out more. Longer lenses will give narrower depths of field and bring background elements closer together. This is why many portrait photographers prefer longer lenses like 85mm and 135mm for their portraits.
Below are some examples to illustrate this. In the portrait, I used a 135mm lens wide open at f/2. This enabled me to get a very narrow depth of field and bring the buildings in the background (approximately one kilometre away) apparently very close to my subject. Had I used a wide lens, my model would have been distorted as I would need to be very close, and the buildings in the background would appear so distant as to almost disappear. 
In this picture of a waterfall, a 24mm lens was used to give a very deep depth of field, and bring the rocks in the foreground into more prominence. If I had used the 135mm lens for this photograph, it would have been significantly different. The rocks in the foreground would appear much closer to the waterfall, which would appear larger in the frame. I would also have been neck deep in the ocean, which would have made for a much more rushed frame!
Other things to consider are things like sharpness and maximum aperture. A 50mm f/1.0 is a magnificent lens, of that there is no doubt, but do you need that speed? Could you use a 50mm f/1.8? It is approximately 1/50 of the cost in Canon’s line-up, it’s much easier to find, and is sharper and more contrasty wide open. A great resource for tests on lens sharpness and contrast is photozone.de.
One final thing to stress about lens choice is weight. A 70-200mm f/2.8 lens is heavy. Really. Do you need to trade in your 70-300 lightweight cheapy for that extra sharpness and speed? Think about what you shoot, and ask yourself if you need it.
In the end though, all technical considerations aside, sometimes you just want glass for its aesthetic appeal. I love the feeling my 50mm f/1.2 gives me, I wouldn’t trade it for the world. That is what is important to me.
So, look at a lens technically, physically, and emotionally. If it fits in your shooting style, then you can probably justify it.
Don’t forget to check this space over the weekend, we have a couple of new announcements coming up for all you folks in Korea!
