I have been in photography long enough to remember when the quality of zoom lenses was so far inferior to single focal length lenses (AKA “fixed lenses”) that most serious photographers would not use zooms, in spite of their obvious convenience. But today, the quality of modern zoom lenses is excellent and they do have an important place in every modern photographer’s camera bag. So there must be other reasons to use single focal length lenses. For me, there are four very good reasons:
1. SIZE: Single length lenses are almost always smaller and lighter than the more complex zoom lenses. The shorter the focal length, the smaller they are – even an EF 200mm f/2.8L II lens is significantly smaller and lighter than an EF 70-200mm f/2.8L zoom lens. Smaller lenses are easier to hold steady and take up less space in your camera bag.
2. MAXIMUM APERTURE: No current Canon zoom lens has a maximum aperture under f/2.8. However, all except three of the current 31 fixed focal length lenses 200mm and under have maximum apertures f/2.8 or faster, as of August 2015 (The three exceptions? Two TS-E lenses and the EF 180mm f/3.5L Macro lens). This gives the photographer greater control over depth of field and access to higher shutter speeds, which is especially important in low light conditions.
3. MINIMUM FOCUSING DISTANCE: Single length lenses focus as close or closer than their zoom counterparts — and macro lenses extend the minimum focusing distance even more. An EF 100mm f/2.8L Macro lens gives an excellent portrait perspective and an extended focusing range to get that perfect composition.
4. PRICE: In many cases, single lenses are lower in price than zoom lenses. With simpler optical designs, there is no need to resort to complex optical formulas of “L” lenses. As an example, you can purchase an EF 28mm f/1.8 USM lens, an EF 50mm f/1.8 STM lens and an EF 85mm f/1.8 USM lens for roughly $1,050.00. On the contrary, an EF 24-105mm f/4L IS zoom lens will cost you only about $50 less at $999. All three fixed length lenses are 2-1/3 f-stops faster (f/1.8 vs. f/4), don’t take up much more space than the single zoom and you still have a wide angle, telephoto and normal focal length lens represented in your camera bag. However, the benefit of the zoom lens is that the focal length range of the three fixed lenses are comprehensively represented in one lens.
The Key to Composition: "Thinking" Like Your Lenses!
There is a discipline to single lens shooting. A zoom lens allows you to stand in a specific spot and compose your picture by zooming the lens, rather than first visualizing how you want the photograph to look. I do it a different way. I have taught myself to look at a scene and see it the way my lenses see it. I then move myself into the correct position to take the photograph I have pre-visualized for the lens I have selected. I have learned to “think” like my lenses see. Instead of zooming a lens, I move myself into the perfect place. Once you have learned to “think” (and see) like your lenses, the extra “‘in-between” focal lengths you get with a zoom lens will no longer be as important.
Do You Need Image Stabilization?
Because fixed length lenses are smaller, they are easier to hold steady and have larger maximum apertures, which allow you to use higher shutter speeds. These two factors substantially lower the need for Image Stabilization (IS) — although it’s still a very welcome feature, in recent fixed focal length lenses like the EF 35mm f/2.0 IS or EF 24mm f/2.8 IS. Long telephoto lenses will still greatly benefit from IS, but today all current Canon single length lenses 300mm and longer (except the EF 400mm f/5.6L) are available only in IS versions and some shorter lenses now also come with Image Stabilization.
How to Start
You can start by purchasing an inexpensive zoom lens (one may have come with your camera kit) or by renting a zoom lens. Select some representative samples of photographs you plan to take and zoom the lens. Pay particular attention to what you feel are the “most pleasant compositions” or the ones that “feel right” to you. Then note the focal length position of your zoom. After a few sessions, you should get a feel for which focal lengths have become your favorites and you will start to “think” like your lenses. From there, you’re ready to invest in the single length lenses that fit your new way of seeing and thinking. The more you shoot, the better your photographs will get.
In conclusion, zoom lenses add weight, cost and complexity to your camera/lens system and you do not necessarily need all the “in-between” focal lengths that zoom lenses provide. You simply need to learn to “see” like the single length lenses you have chosen for your system and “think” about the photographs you are taking. Your photography will improve and your back will feel a lot better at the end of a long shooting day.