Lenses and Optics

Optimus Prime

Published February 1, 2009

Today’s topic is prime lenses, those lenses that (GASP!!!) don’t zoom!

Wait, don’t leave. This is really worth your time. (OK, those of you who already shoot entirely or mostly with primes can leave, there’s probably not much for you here.)

About 10 times a week, in discussing the best lens for the job with a customer, I’ll suggest a prime. Generally if the customer is a pro, they immediately go “great idea, I’ll take it.” If the customer is newer to photography, though, they are often flabbergasted. Some get really quiet and go “you mean it doesn’t zoom at all?” Others may admit they’ve heard of people shooting with those but just don’t think it would work for them. Usually I try not to be persuasive, but when I start talking about prime lenses, I can’t help it sometimes. And almost every customer that tries a prime lens is back a few weeks later to try another.

So why in the world would people use those inconvenient prime lenses? A lot of reasons:

  • Wider apertures and narrow depth of field
  • Superior sharpness and contrast
  • Lower cost (well, sometimes)
  • Some would add ‘that special prime look’ which is true, but may be a combination of the factors above.

Zooms versus primes

If you set your watch back say 30 years, we wouldn’t be having any discussion at all: Zoom lenses were for not-too-serious amateurs and vacation snapshots. Prime lenses were the stuff of professionals and serious photographers. That’s because all zoom lenses are compromises: In prime lenses all of the elements were designed to bend light rays entering at a certain angle to provide a sharp focus on the film (remember this was way back). In a zoom lens, certain elements inside the lens move away from each other when the lens is zoomed, changing the angle of light rays passing through the lens. The other elements did the best they could to keep up, but they couldn’t focus the light rays as sharply as a prime throughout the zoom range. Since then, computer aided design programs, multiple elements in multiple groups, aspherical elements, rear focusing elements, and a host of other improvements have made a world of difference. Top of the line zooms are now nearly as sharp as top of the line primes, and about as sharp as cheap consumer grade primes. Lets emphasize that: in general, top of the line zooms are about as sharp as consumer grade primes at the same aperture. Most zooms, however, still have a ‘sweet spot’, a focal length where they are sharper than the rest of the zoom range.

Aperture difference

So zooms have closed the sharpness gap with primes quite a bit, although not entirely. So much so that the convenience of a zoom (which is huge, I don’t mean to belittle it) makes them far more popular than primes. Why carry 3 lenses and have to change them, when a zoom will cover the whole range? Well, the major reason is aperture. The very best zooms have an aperture of f/2.8 and are sharp at that aperture. The very best primes have apertures of f/1.2. Just in case you’re aperture challenged that’s more than two full stops of difference: f/1.2 to f/2.8 is greater than the difference of f/4 to f/8. A shot at f/1.2 needs only one-fourth of the shutter speed that is required at f/2.8. On the ‘consumer grade’ front the difference can be larger: A good consumer zoom will usually be f/4-5.6 (slower at the telephoto end) but often requires you to stop down to f/5.6 to f/8 to get good sharpness. A consumer grade prime will generally be f/1.8 or perhaps f/2 and usually is sharp (at least in the center) wide open.

Of course the next question is ‘do you need that aperture’? The obvious answer is “No”. Otherwise everyone wouldn’t be carrying around a zoom, now, would they? But sometimes you need it. Try shooting indoor sports with an f/5.6 zoom (Yeah, we know you did. Don’t be ashamed, everybody tries it once). Or taking pictures of the family inside on a dark winter night. Yoda said it best about aperture impaired lenses: ’Afraid of the dark, you will be. Wanting more aperture then, will you.”

So most of the time you don’t need extremely wide aperture. But will you want it? Yep. Yessir. Yes indeedy. We don’t need wide aperture lenses most of the time, but we all love the narrow depth of field they can give: that 3-D effect that lets the subject jump out from the background like this (also known as bokeh).

Notice as the girl’s picture shows you have to pose carefully at these apertures—the earrings are already quite out of focus. The depth of field is that narrow. If the head is tilted very much you’ll get one eye out of focus (which is sometimes a nice effect, and you can always say you meant to do it that way.)

Price difference

Here’s perhaps the biggest reason to own a prime or two, after you’ve ‘collected the whole set’ of zooms and have 10mm to 400mm covered. They’re (relatively) cheap. Lets say you’ve got a nice set of consumer zooms, but your kid has started playing basketball and you need something with enough aperture to get those action shots (OK, the action may not be too fast in 4th grade, but its coming). The standard answer is a 70-200mm f/2.8 zoom. Prices range from $1100 (Canon non IS) through $1700 (Nikon VR) to $1900 (Sony 70-200mm f/2.8 and Olympus 35-100mm f/2.0). Ouch. So how ’bout we consider giving up the zoom, maybe do a little cropping of our shots and consider an 85mm f/1.8 ($350 for Canon, $390 for Nikon).

Or perhaps you just occasionally need a fast lens for some indoor shooting: family shots, museums where flash isn’t allowed, a club where your favorite band is playing. You might get by with a 24-70mm f/2.8 zoom ($1100 Canon, $1400 Nikon, $1700 Sony). You’ll probably do better with a 50mm f/1.4 prime though (Canon, Nikon, Olympus, Sony each about $350 ).

The very best primes can be as expensive as the best zooms though: A Canon 85mm f/1.2 will drop you about $1,800, a Sony 135mm f/1.8 about $1400, or an Olympus 150mm f/2 about $1900.

Look and feel

Obviously this is largely subjective, but there are a number of prime lenses that are widely renowned as being exceptionally good: not only sharp, but with great microcontrast and that ‘special’ look that other photographers ask “what did you shoot that with” when they see your prints (notice I said prints. Its hard to appreciate how good these lenses are on a web page). If you want to see just how great a photo can be, here’s some recommendations:

Roger Cicala
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Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Lenses and Optics
  • Clayton Taylor

    Hey, Roger – as always, it is fun to re-read your older posts. I was thinking that it might be cool to update this post with, at the very least, your current Honor Roll of primes. I would be interested to see which ones listed here remain on the 2019 list. I’m betting that a LOT has changed in (gulp…) 10 years!

  • I like this article. FYI: the lens links at the end are broken.

  • I suggest the Nikkor 50 mm f 1.2. It has a wonderful 3D touch

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