prime vs. zoom

I am often being asked why do I carry so many heavy lenses with me while "most people" use only one camera with one lens. People who are asking such questions are either beginners in photography or not photographers. Anyway, since it is the majority of people around me, they let me think about basic issues. One of them is the choice between lenses with fixed and variable focal lengths — between so-called "prime" and "zoom" lenses. With regard to current state of optical technology, and as most people who are serious about photography, I generally prefer the first to the second. I think all experienced photographers would know why, while for the others, the difference between zoom and prime lenses, as well as their advantages and disadvantages are explained in many books and articles, and demonstrated by countless comparison tests and reviews. This article shouldn't be another profound analysis but only a statement of my personal attitude to zoom and prime lenses and their use in nature photography. I just want to write down my thoughts about this not only for readers but also for myself.

advantages of zoom lenses

1) The photographer doesn't need to change his position to compose the image.

If it isn't macro photography, the wildlife photographer has usually a quite limited freedom to choose his position. The subject can be high on a tree, it can be shy or dangerous, there can be physical obstacles (such as water) between the photographer and the subject, etc. In quite many situations, the photographer can't adjust the frame composition by moving himself towards or back of the subject. Images taken in such cases with a prime lens will need to be cropped in software if the subject was too distant. If it was too close, the composition will be too tight. Therefore a suitable zoom lens should be generally ideal for wildlife photography.

2) With a zoom lens, there is no need for frequent changing of lenses.

To adjust the focal length, the photographer has to change several prime lenses while one zoom lens can remain mounted all the time. In the field, using only one lens means less risk of damage for the equipment, less dust, dirt and moisture getting into the camera, and first of all — no time loss for lens changes. Also carrying of two camera bodies with different prime lenses is not necessary.

3) Zoom lenses are compact.

One zoom lens takes much less space in the bag than several prime lenses covering the same focal length.

4) A zoom lens is not as heavy as several prime lenses that have the same focal length combined.

Usually we need several focal lengths — one for landscapes, one for distant wildlife, one for close-ups, etc. With prime lenses, a separate lens is necessary for each kind of subject. Two or three such lenses would, of course, be heavier than a single zoom lens.

advantages of prime lenses

1) Better image quality, particularly, better contrast, resolution, and saturation.

In the theory, the image quality (IQ) of prime lenses should be better because they have less optical elements than zoom. Nowadays, it is, of course, a huge generalization. To claim this, one has to compare only lenses with similar quality. Some high-end zoom lenses may provide IQ that will be on par or even better than of some prime lenses. However, everyone who had some experience with both kinds of lenses would know that the image obtained with a quality prime lens will usually be more crisp than with its zoom counterpart. (There are exceptions even here: Just think about AF-S Nikkor 14-24 mm 1:2,8G ED which is a zoom lens but nowadays regarded as the best wide-angle lens for SLR, i.e. with image quality better than of AF Nikkor 14 mm 1:2,8 D ED which is a prime lens.) Better IQ of a bare lens makes the use of teleconverters with prime lenses possible. This is an additional benefit for wildlife photography. Better resolution makes also greater cropping of images possible. In wildlife photography, the focal length is never enough. Even with the longest lens, there would always be situations when the subject would be too far and too small. If the resolution of the lens (i.e. optical resolution) and of the sensor (i.e. digital resolution) allow it, the image can be cropped. Therefore, a very long high-resolution lens and a very large camera sensor will always be preferred.

2) Prime lenses are usually "faster", i.e. have larger maximum aperture than zoom.

This is not only an advantage when you use a teleconverter. To achieve a higher shutter speed in low light, it is better to use a wide aperture than a higher light sensitivity (ISO number). For wildlife photographers who usually have to handhold the camera and to shoot moving subjects, a high shutter speed is very important. Another nice effect of wide aperture is better separation of the subject from background and artistic background blur (so-called "bokeh").

3) Some special lenses are only prime.

Some manufacturers produce lenses of some types only as prime. So Canon has no zoom lenses with a focal length greater than 400 mm. Also no 1:1 macro lenses are produced by this company. In wide-angle range, lenses with some focal lengths are available only as prime lenses. There are even lens types, such as tilt & shift, that don't exist as zoom lenses at all.

arguments that do not work for me

1) A prime lens will make you a better photographer.

The authors of some publications mention a didactic value of prime lenses among their advantages, meaning that a prime lens forces a photographer to move in order to compose an image and makes him think about composition. This sounds idealistic and naive, and, when the subject is a wild animal, even absurd. First, one should ask the question why moving towards or back of the subject is better than keeping the same distance and zooming. I would agree if it has to be a fitness exercise for the photographer, otherwise I don't see any advantage for developing photographic skills, as those writers want to convince us. Second, the use of a prime lens doesn't necessarily require movement from the photographer because one can change the composition of an image afterwards by cropping it during postprocessing. With modern high-resolution image sensors it is usually possible when a large size of the image isn't a requirement. And honestly, I don't see why thinking about composition at the location should be better than afterwards — in a "digital darkroom", when it isn't going about preserving the maximum resolution, i.e. the size of the image. But in cases when that latter issue is important, it is the zoom lens that helps because it increases the chances for a better composed image in the field — when the movements of the photographer are usually restricted by natural obstacles, safety considerations, wildlife protection rules, etc. — and hence saves pixels from cropping. Finally, since a zoom lens is just a lens with several focal lengths, a photographer can use it like a prime lens: He can choose one focal length that suits the subject and move around to achieve a good perspective.

2) A prime lens is smaller and lighter.

This is true if the photographer is working with only one focal length. For the entire range of one zoom lens, several prime lenses of several hundred grammes each are necessary. Together they would be much more bulky and would exceed the weight of the zoom lens many times. Of course, someone who prefers prime lenses would not have all of them and usually would carry each time only the lens for the particular subject he is going to photograph. But, although a single prime lens is normally smaller, it is rarely much lighter than a zoom lens. The EF 14mm 1:2.8L II USM prime lens and the EF 16-35mm 1:2.8L II USM zoom lens showed in the title picture of this article have the same weight of about 640g. Okay, there is no Canon prime lens with 16 mm focal length, and 14 mm is not the same. But even if we take for comparison a lens whose focal length is within the range — EF 35mm 1:1.4L USM, it would not be much lighter. This lens weighs 580g.

3) Prime lenses are cheaper.

This may be true if you look at the price for a prime lens of only one of focal lengths covered by a zoom lens. Indeed, if you take a 200 mm lens of equivalent quality and compare it with a zoom lens that has 200 mm at one end, you would see that it costs much less. For instance, in late 2010, the minimum price for EF 200mm 1:2.8L II USM was 695 € while EF 70-200mm 1:2.8L IS II USM was offered for at least 1.850 €. However, a single prime lens can't replace a zoom, and two or more prime lenses of similar quality as the corresponding zoom will cost more.

conclusion

Clearly, the advantages of zoom lenses make them better for nature photography, particularly for wildlife. However, since it is the image quality that really matters, the generally lower IQ of zoom lenses reduces their advantages over prime lenses. As most other nature photographers, I prefer image quality to anything else and am always looking in a certain focal length range for the sharpest lens. Unfortunately, this will more likely be a prime.

Generally, I would be glad if there were a good zoom lens in super tele range that I could use instead of two expensive prime lenses. My dream zoom lens is a Canon L lens of similar quality as the now popular EF 100-400mm 1:4.5-5.6L IS USM but with even more reach — 300-600 mm — maximum apertures of f4 - f5.6, to an affordable price and with reasonable weight and size. Such a lens would be perfect for shooting from vehicles (cars, boats) or hides, i.e. in situations when the photographers can't change the working distance. In all other cases, particularly for landscape and macro photography, I would still prefer a prime lens.