Why You/I Need An 85mm f1.8 Lens

April 09 02:07 2011 by Alexei Rivera Print This Article

Canon 85mm 1.8 USM and Nikon 85mm 1.8D

Sometimes, fast, really does mean fast. Lenses with apertures below f2.0 are considered fast. They let in more light, and you can take your pictures with shorter shutter speeds. Why do you need shorter shutter speeds? Because you do. (Photo credits: KenRockwell.com)

A kit lens can only do so much. Granted, it gives you a wide 18mm shot, albeit with slight barrel distortion (small fisheye effect) and some vignetting – and a 55mm “zoom” which is around the same amount of magnification as your eyes, not farther. So think of a kit lens as having no zoom at all. It can either see as much as your eyes can, standing at the same point, or can show more than your eyes by “zooming out” – it won’t zoom in.

The problem with your 55mm “eye-zoom” is that, your aperture goes down to a measly f5.6 – not at all very large, nor very fast. When taking pictures of subjects, just imagine that you need to be on 55mm zoom to take the same shot as your eyes frame it. If you want to go “faster” by opening up the aperture, you need to widen your zoom. At its widest 18mm, you can get an aperture of f3.5. This isn’t much, but is much better than the f5.6. However, 18mm is very wide. You need to be really close to the target to get them large enough in your frame – and that in itself is usually impossible when there are other photographers in the way.

Further, a wide shot at f3.5 still isn’t enough to allow you to take images at night even when a bunch of ambient lights are on. Your camera will (or you set it manually) take as slow a shutter it can to make a decent exposure of the environment. Well, what that means is blur. Lots of it.

This is why 85mm f1.8 lenses are popular. This isn’t the same as saying just a little bit of extra zoom on your kit lens and it’ll have the same effect, no. You’re comparing a 55mm f5.6 over an 85mm f1.8. Not only is it farther reaching, it also opens up larger. At 85mm, it is even faster than the fastest your kit can do at 18mm. What this means is basically: no tough time trying to get closer to the subject and blocking other photographers/audience/whatever, and being able to bring your shutter speed down, way down – and then blur goes away. (Well, except the creamy out of focus areas.) Simple, right?

Now only if they weren’t so damn expensive.