Prime lenses, the benefits, and why you should use them.

Advances in technology over the years has almost always been about convenience. Making it easier and faster to cook a meal, easier and quicker to go somewhere, things such as that. This is true in photography as well, especially with the digital revolution.

One thing that may never change though, thanks to the laws of physics and this world we live in, is that a zoom lens is a compromise. It is us giving in and asking something else to do the work our feet used to do while losing other things in the process. In many ways, this can be great. A traveling photographer documenting the events surrounding him will benefit from this. He can zoom in on a cow running amok in the streets of NYC and then zoom out to capture the entirety of the pandemonium.

But a photographer right beside him might get a much better photo of that cow, and here’s why. (A lot of this was written for the beginner to photography, if you’re aware of the terms you may want to skim some).

• Speed/Fast

when you hear that a lens is “fast,” what that means is that can open up the aperture quite a bit, letting in more light. Here is an example:

On the upper image, the lens has been opened wide, letting in more light. A larger opening in a pipe means more water can travel through, the same holds true for openings and light. This matters because the more light you let in, the faster of a shutter speed you can use. Mr. traveling zoom lens cameraman can’t open as large of a hole in his lens as the fellow beside him with the prime can, which means that his shutter speed will be slower (take longer to expose) and he will not be able to stop motion as nicely. (The more quickly you can expose a scene, the less movement you record, and the sharper the image *usually* is.)

The reason this matters in the prime vs. zoom argument is that because of the designs that zoom lenses have, a comparable prime lens will always be able to have a larger aperture opening. (Relatively anyway, it has to do with a relationship between the focal length and size of the opening that I won’t discuss now.) A $100 prime lens can shoot in conditions a $1,000 zoom lens can’t. If you’re shooting in low light situations, a prime lens will almost always give you more flexibility in what you can do and capture.

• Cost

As I said before, a $100 prime lens can usually beat a $1000 zoom lens. If you can live with the inconvenience of switching lenses when needing to cover a different focal length, a set of primes will give you advantages with nearly everything and save you money.

• Bokeh & Depth of Field

To put it simply, primes blur backgrounds beautifully. An essential part of portrait photography is deciding what will be in focus and what won’t be in focus. The more you can exaggerate the differences between the two, usually the better. This is something that happens usually when shooting  nearly wide open, f2.8 and below. (Smaller f-stop numbers mean a bigger hole. It’s confusing at first because it seems backward.)

This photo I took was shot with a Canon 50mm f1.4 lens @ f1.4 (1/500th sec and ISO 100) on a Canon 5D.

See how the background blends into this creamy, blurry goodness? This is a property of depth of field, in which a select plane of a photo is in focus and things closer and further from that plane become more and more blurred. When you open the aperture, make it large, that plane shrinks and becomes smaller. This means things that aren’t your subject become more and more blurred the larger you make the aperture opening. The lens designs of prime lenses allow for smoother background blurring, also referred to as bokeh. This photo, if shot at f4 at the same focal length, would lose some of the magical qualities that it has in its current form, as elements in the shot sharpen and become clearer.

A benefit of this narrow depth of field, other than the aesthetics of it, is isolating a subject. Blurring foreground and background elements in a photo forces the viewers eye to be drawn to the sharp, in focus areas of the shot.

• Sharpness

This is becoming more and more important as this mostly pointless megapixel war continues. You need a sharp lens to resolve well with those 24 megapixel sensors, or even more so with the 15 megapixel crop body sensors (pixels are packed even tighter together on a 50D compared to a 5D Mark II). A lot of things come together to determine resolving power of a lens. One I have noticed that effects things a lot is chromatic aberration. This is when you have color separation at areas of high contrast – you get a red line going one way and a blue line going another along the edge of a window, for example. Primes have simpler and superior optical designs, meaning less of this.

• Composition

I can go to any location, without my camera and lenses, and instantly know what each one will look like and how I would shoot someone there. I already know what the focal lengths 24mm, 35mm, 50mm and 85mm look like without having to have my gear. Shooting primes has allowed me to compose my shots better, zoom with my feet and get the distortion or lack thereof that I want in a shot by using the correct focal length for the situation. It might make more sense to back up and shoot with an 85mm lens over being close and shooting at 24mm, for example. I see a lot of people on flickr shooting snapshot portraits with wide focal lengths… it’s very rarely appealing, it rarely works. Not to say that it doesn’t or there’s times you shouldn’t, as it can be a useful effect.

To put it simply, a set of prime lenses will give you image quality that a zoom lens won’t, but it comes at the sacrifice of convenience. And yes, I’m one of those prime lens snobs the primes I currently own are the: Canon 24mm f2.8, Canon 35mm f2, Canon 50mm f1.4, Canon 85mm f1.8

I will likely update this over time, add things to it and tidy it up a bit, maybe post more comparison shots. Feel free to put your thoughts out there in comments below! Let me know if you agree, disagree, have any questions, feel I missed something, whatever.