Prime Lens Primer

If you are new to SLR photography you may be wondering what  prime lenses are. You may also wonder, why would I choose one over the typical zoom lens? Before getting into why you would choose one over the other let’s explore the major characteristics of each.

Zoom Lens:

– Zoom lenses cover the focal range indicated on the body of the lens. For example: 55-200mm. This lens is 55mm at the widest position, 200mm at the telephoto position, and covers the entire range of focal lengths in-between.

– Most entry to mid-range zooms are usually variable aperture. This means that as the focal length changes the maximum aperture changes as well. For example consider a lens which has an aperture listed as f3.5-f5.6; At the widest position the max aperture of the lens is 3.5, and as you zoom in the maximum is reduced to 5.6.

Prime Lens:

– Fixed focal length e.g. they do not zoom!

– Typically have wider maximum apertures e.g. f1.8

– Are often smaller than their zoom counterparts due to the lack of the complicated mechanical components needed for zooms.

Now that we have discussed the major differences, why would anyone want a prime lens?

Reason 1: Large Aperture:

If you want a lens with a wide maximum aperture lower than 3.5 the price for zooms in this range are quite a bit more expensive. Take for example the Canon 24-70mm f2.8 L II USM (which is over $2,000) versus the Canon ES 50mm 1.8 which is only $125! The cheaper prime lens even has a wider maximum aperture than the more expensive pro zoom lens.

 Reason 2: Fixed Aperture:

As mentioned before many non-pro zoom lenses are variable aperture. This is fine for most general purpose photography, but becomes a major pain when using the camera in manual mode. For example: Shooting in manual mode with a variable aperture lens you zoom out to 55mm @ f3.5, you set the shutter speed and ISO appropriately set to get the correct exposure. Now, if you zoom into the telephoto position (f5.6) your image is now  underexposed by 1-1/3 stops!

Reason 3: Sharpness

Prime lenses tend to be sharper throughout the frame when compared to zoom lenses. It much easier for a lens to be sharp at a fixed focal length, than sharp at many focal lengths.


If you are just starting out, your camera probably came with a kit lens. Something like an 18-55mm f3.5-56 zoom lens. A great prime lens to add to your bag would be a 50mm 1.8. Both Nikon and Canon have a version of this lens for just around $100 USD. If you have a crop sensor camera like a Nikon DX series or Canon EOS 6D/7D you may want to look at a 35mm prime lens. 35mm on a crop sensor camera has roughly the same field of view as a 50mm lens on a full frame camera. Many consider the 50mm lens one of the best lenses to learn with because it forces you to “zoom with your feet” and explore new angles that you might not have considered if you simply zoomed in with a telephoto lens.

Here are a few great prime lenses to get started with:


50mm: Canon EF 50mm f/1.8 II Standard AutoFocus Lens

35mm: Canon EF 35mm f/2 IS USM Lens

If you have a little more to spend the Canon 50mm 1.4 USM is a fantastic lens! It is what I currently use with the Canon 5d Mkii. It has slightly better build quality than the 1.8 and nearly as good bokeh as the much more expensive 50mm 1.2L.


50mm*: Nikon 50mm f/1.8D AF Nikkor Lens

35mm: Nikon 35mm f/1.8G AF-S DX

*Note for Nikon Shooters: Some newer camera bodies do not support autofocus AF-D lenses. Check this page for lens support for your camera body.

Leave a Reply