Zoom or fixed focal length lens?

[IowaLizard]

I'm looking to buy a new lens and I'm wondering, should I get a zoom lens or a fixed focal length? Which is really more practical?

[Andy]

For most forms of photography, a zoom is by far the more practical. 10yrs ago, zoom lenses were optically inferior to fixed (prime) lenses by a considerable margin, but they have become better all the time. A zoom lens makes it easier to perfectly frame your subject without having to physically move yourself.
If you know exactly what distance the subject is going to be with most of your photography, the slight optical advantage of a prime lens maybe worth considering... but for the most part, zooms make sense.

What focal lengths were you thinking about?

cheers,
Andy

[yelvertoft]

It all depends on what kind of photography you are going to do with it.

Primes give sharper results, though as Andy has said, this difference is reducing all the time. Primes usually (but not always) also have wider maximum apertures, allowing faster shutter speeds in lower lighting conditions.

These benefits have to be weighed against the advantages of zooms, namely that you effectively have a whole bundle of single focal length lenses packaged into a single item. This benefit is not to be dismissed lightly.

The ability to reframe your composition quickly and easily with a zoom may mean you get the shot with a zoom. Having to swap prime lenses to get the length you need may mean the opportunity has gone.

Regards,

Duncan

[Tannin]

Some homespun rules of thumb, passed down from father to son for many generations in my family. Or possibly some rules that I make up as I go along - you decide.

Rule 1: For long-lens work, primes are better. When you are doing the sort of photography that needs a long lens - birds in particular, but also many other things - you are practically never as close as you want to be. If you have a zoom, you are practically always at maximum length anyway, and wishing it was longer still, so why not just use a prime in the first place?

For any given budget, a prime will always outperform a zoom. The same for any given weight or bulk contraint. In short, if in practice you are not going to zoom in and out (and with a long lens you don't), then there is no reason to buy a zoom, and every reason to buy a prime.

Rule 2: For shorter work - anything once you get into the long-normal, normal, wide, and ultra-wide categories, zooms are enormously more capable of doing what you want to do. These shorter lenses are easier to manufacture too, which means (to me) that while the 400mm class zooms are clearly not as good as primes, when you get down to 100mm and 50mm and 20mm and maybe even 10mm lengths, the picture quality a decent zoom delivers is so damn close to that delivered by a prime that the difference isn't worth worrying about. Buy the zoom and you can take a whole swag of different sorts of pictures. It won't cost you too much either: the big lens makers turn out so many zoom lenses in the wide to normal lengths that they are surprisingly inexpensive - and short primes are rare these days, which is no doubt why few manufacturers bother introducing new models or improving old ones. (When was the last time Canon introduced a new prime lens in the wide to normal range? A long, long time. In fact the only lens you could even vaguely put in this class would be the EF-S 60mm macro, which on a 1.6 crop body (the only sort you can use it on) is clearly in the mild telephoto class.)

Rule 3: Primes make you more creative. It's true! With a zoom you stand in one place and fiddlle about zooming in and out until you think you have a shot. (One dead-set giveaway that you don't really have a worthwhile shot at all is when you find yourself taking two shots from the one place, one zoomed in and the other zoomed out. London to a brick they are both destined for culling room as soon as you face reality and admit to yourself that they are rather pointless shots - scenes in search of an idea, not ideas in search of a scene.)

Lately I've been needing to do a lot of stuff in very poor light. When it gets bad enough, the 18-55 is the first to head bagwards, followed by my beloved little 10-22 - now there is a lens to dream with - and the seldom-used 60mm macro lens comes into play - at f/2.8 it's the fastest lens I own, and though 60mm is way too much for what I'm shooting (nature), it's that or get into the car and drive home.

And, you know, having to work with one focal length, and one at least three times longer than I'd usually use for these same places - I'm an ultra-wideangle junkie - really brings to the fore your most important bit of photographic equipment and makes it work both hard and productively.

(Most important part of your kit? The 60mm prime lens? Nope. Your brain - never, ever leave that behind when you pack your bag.)

Seriously, I really, really enjoy working with just the 60mm macro - close to 100mm in 35mm equivalent terms remember - and although it makes me sweat and swear and grumble about the light, and wish I had a Sigma 30mm f1.4 instead, or an optically impossible 10-22mm f/2.0, I actually start thinking hard about what it is I'm trying to achieve, and producing better pictures than I would have done with a zoom.

One day, just to see what comes of it, I'm going to go out, on a perfect day with perfect light, with just one prime lens and nothing else.

[Leif]

It is true that some primes are better than any equivalent zoom, but some of the pro-grade zooms can equal many primes, and even better them. I know from first hand experience that the Nikon 12-24 F4 zoom equals the 24mm F2.8 prime in normal use. By all accounts the Nikon 17-35mm F2.8 zoom at least matches the equivalent primes throughout the zoom and aperture range. And from what I have read, the Nikon 200-400mm AFS F4 zoom is superb. My old Nikon 75-150 F3.5 zoom is very sharp with low distortion and CA.

Where zooms fall down:

Cheaper ones tend to be mediocre at wide apertures, with poor corners.
Cheaper ones have slower maximum apertures.
Most are more susceptible to flare.
Most will have more distortion than a prime.
Most are not as good at close focus as a prime, and most are not so good on extension tubes.

In addition zooms have more elements, and are more complex due to the need to zoom and focus. Hence they tend to suffer more from mis-collimation. The number of brand new zooms that show problems straight out of the box is shocking. Even pro-grade ones have considerable sample variation.

These days manufacturers are putting most effort into designing zooms rather than primes. Most primes are old designs, and some such as the Nikon 28mm F2.8 are decidedly mediocre. So no, you can't simply say that zooms are bette than primes.

That's enough rambling from me.

Back on the ranch ... you didn't say what focal length you were thinking about. Or which brand.

Leif