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07-17-2008, 04:24 PM   #1
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Neophyte question


It seems that using a variable focal length lens (eg a 80-200mm or whatever) is more versatile than using a fixed one (eg 135mm); so, why use a fixed when all you need, when going outdoors to shoot, is a variable that will offer you more choices in both subject and composition. Am I totally wrong in making such an assertion? I'd like to know what rationale, other than compulsive lens buying syndrome, goes into choosing either a fixed or a variable focal length... or both.


07-17-2008, 04:40 PM   #2
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Conventional wisdom has been that the IQ on the primes is better than on the zooms. As the lens manufacturing technology has improved, so has the IQ of zooms. Overall, primes tend to be faster in speed than zooms, as well, but there are some zooms out there that do rival the primes in IQ (the *50-135, for example). At least in Pentax-land, many of the primes are a lot smaller in physical size than the zooms are and that makes them attractive to people who prefer to carry a lighter-weight setup.

In my own kit, I have both. The zooms are great for convenience and the primes I have, I have for specific purposes (the 50/1.7 for low light and the DA35 and A100/4 for macro/close up shots).

If you plan on building your kit with zooms, I recommend that you get the fastest lenses that you can afford in each range that you want to cover. While not critical, a constant aperture lens is desirable, especially when you're using the lenses at their long end.

If you need recommendations for specific lenses, either prime or zoom, you've come to the right place. If you browse through the current and previous threads, you can get a good idea of which lenses people around here really like and why.

07-17-2008, 04:44 PM   #3
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It used to be that prime lenses (single focal length) were optically superior to zooms. I'm not so sure how true this is anymore. There has been a heck of a lot of production research put into zoom lenses over the past dozen or so years to make them better, and very little (by comparison) done with primes.
Many prime lenses are still based on very old optical designs dating back a hundred or more years.
Still, a lot of people prefer prime lenses, and often, even if a zoom has better hard resolution numbers, primes can still have better secondary qualities such as brighter aperture or rendering proberties.
As an example, the 50-135mm zoom, as good a lens as it is, is two stops slower than the 50/1.4 and the 85/1.4. If speed in this range is important, then the prime lenses will be the better choice.
07-17-2008, 05:32 PM   #4
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It's very true that zooms have closed the gap quite a bit. But there are a couple levels of zoom to consider.

The typical 'consumer zoom' such as the DA 50-200mm or Tamron 70-300mm is quite good but just can't compare in the quality of a prime in the same range. The prime will beat it in all respects, sharpness, speed, bokeh and any other small variables. These zooms generally fall in the under $500 catagory but there are exceptions*.
A middle category might be something like the Sigma 50-500. very good quality but has some compromises like speed and sharpness.
Higher end zooms such as the DA* series, the Sigma 70-200 f2.8, *Tamron 28-75 f2.8 and so on will come very close to prime image quality across the range. For shooters that put a lot of emphasis on bokeh (background blur) a zoom will not generally perform as well. The primes will often produce a smoother background and smoother highlights. A prime, as others have said will also be faster.

All that said, many pros now shoot with the higher end zooms all the time and get excellent results with these new generation lenses. I took one weekend course and the Pro had 3 lenses. A prime macro, a wide zoom and a mid range zoom. She had 5 camera bodies and almost no lenses. The work created was stunning with a very simple kit.

The one area that primes will always out perform a zoom is in the long end. A Sigma 500 f4.5 is an incredible lens and there are few zooms in this range and the few that are there are not as good in most cases (at least from current shelf stock not counting the few rare discontinued Pentax long zooms).

Choose your zooms carefully and they can do just about all you'll need. Add a good Macro prime if you like that sort of stuff and you have a good kit.

07-17-2008, 05:44 PM   #5
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I think it is all a question of money (what you want to spend), convenience (zoom with th elens vs step back or change lenses), and speed (at most focal lengths)

In my experience, below perhaps 150mm High quality primes can be between 1 to 2 stops faster than zooms.

Examples are things like the F1.4 85mm, F1.2 and F1.4 50mm lenses, etc. It is possible to get a prime well below the minimum F2.8 that seems to be it for zooms. This gives you atvantage in the case of low light, and better conntropl of ddepth of field, but at a price.

at 200mm, there are several high quality zooms, such as the Sigma 70-200 F2.8 where both speed and quality rival a prime. above 200mm, you generally don't get amything faster, but you can get primes at 300mm F2.8, 400mm F2.8 etc. They are very expensive, but there is nothing to match them.

I have, over the years collected 14 lenses, 7 zooms and 7 primes.

Zooms go on vacation, I have 4 specific ones (the other 3 are now somewhat redundant) giving a range from 10mm to 200mm, and a 2x TC.

My primes are for low light, & portrait, (50mm F1.4 105mm F2.8) light weight medium telephoto (135mm F2.5) and two long ones 300F4 and 400F5.6 for wild life.
07-17-2008, 06:45 PM   #6
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Zoom with your feet!

Zooms are convenient but can make us a little lazy. Using fixed focal length lenses may make us
work a bit harder to get just the right framing, but that often pays off with better composition.

07-17-2008, 07:16 PM   #7
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Another reason for using prime lenses is because they often control lens flare better than zooms.
07-17-2008, 07:58 PM   #8
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QuoteOriginally posted by ChrisPlatt Quote
Zooms are convenient but can make us a little lazy. Using fixed focal length lenses may make us
work a bit harder to get just the right framing, but that often pays off with better composition.

That's pretty much the way I feel. Prime lenses force me to think about the kinds of shots I can take with the lens and make the most of the situation. which often results in a better composed shot.

07-18-2008, 05:11 AM   #9
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I don't buy the almost spiritual "a prime makes me frame the image better" hocus pokus.

For me, it boils down to weight and speed. A fast zoom is still 2.8 and all constant 2.8 zooms are heavy and large. Compare the 16-50/2.8 with the 21mm 3.2 pancake, it's like night and day.

I find WA zooms the most useful as speed is not so important (f/4 is fine) but on longer lenses, fast zooms are enormous.
07-18-2008, 05:52 AM   #10
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QuoteOriginally posted by ChrisPlatt Quote
Zooms are convenient but can make us a little lazy. Using fixed focal length lenses may make us
work a bit harder to get just the right framing, but that often pays off with better composition.
Zooming with your feet IS dangerous !!!

07-18-2008, 07:03 AM   #11
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When they come out with the 17-85mm f/1.4 zoom, I'll sell off my primes. Until then I'm sticking with my 30mm f/1.4 and 85mm f/1.8
07-19-2008, 10:21 PM   #12
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Some great foto'er, I forget who, said, "The best wide-angle lens is three steps back." That doesn't always work in small spaces or at a cliff's edge. Yeah, zooms make us lazy, but they can help capture an otherwise-unobtainable image. Primes make us work and think and move around and look closely. Manual lenses in unmetered cameras make us learn to judge distance and light. A funky Weston meter and my late lamented 1934 Retina (loaded with ASA-32 Pan-X film) taught me photography, and after a while it was an extension of me -- *I* was the automation system. Autofocus zooms let us concentrate on image and action, and ignore many of the finer points of technique.

I guess it's a matter of speed. How long do we spend setting up? Are we taking pictures or making pictures? The longer it takes to capture an image, the more time we have to contemplate and ponder just what we're doing. Maybe it's like the difference between fast food and slow food, between motoring and biking and walking.
07-19-2008, 10:30 PM   #13
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QuoteOriginally posted by TaoMaas Quote
Another reason for using prime lenses is because they often control lens flare better than zooms.

Let us not forget the issues with distortion. New zooms are better, but the wide range super zooms almost all suffer from barrel, pincushion, or mustache distortion throughout most of their range.
07-20-2008, 05:47 AM   #14
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One thing that you can do with primes that can be hit-or-miss with zooms is to get decent results if you need to crop. The other day, I noticed this when I was working on some pics I had taken with the DA35. Here are a couple of examples of what I mean...

If you can't quite get in quite close enough with your prime, don't fret, just crop!


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