Fixed (non-zoom) lenses - why?

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Itti

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Itti
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Just wondering what are the reasons for having a fixed-focus lens?
I hear the image quality is a little better but I think there must be more to it than that, surely?
 
fixed lenses are also usually much faster (F1.2 - F/1.8 etc), as well as offering a better IQ overall, some people swear by them, especially thouse who specialise in portraiture.
 
As Wez has mentioned, the speed is the main factor, but in the case of wide angle fixed lenses, they are normally more compact and have smaller filter threads.

Having said that, you would be carrying 2 or 3 lenses instead of just the one. So it's down to personal choice really.
 
Sharper & faster are the advantages.

Rather than picking a place and zooming with the lens if you rely on your feet you have to think a lot more about how that would affect the shot
 
Smaller.
Lighter.
Faster.
Better image quality.
More robust.
 
cheaper, smaller, larger aperture, better IQ, more reliable...and more fun
 
Why is it easier to make a wider aperture for a fixed lens than for a zoom then?
 
Itti said:
Why is it easier to make a wider aperture for a fixed lens than for a zoom then?
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Aperture is a ratio of the diameter of the hole through which light passes and the focal length of the lens.

This is why long lenses don't have such wide apertures as the diameter has to be huge meaning every piece of glass has to have a large aperture making the lenses very heavy and very expensive.

With a zoom lens you have more internal glass anyway, and to give it a wider aperture whilst retaining quality and not making it too heavy is difficult, so a compromise has to be reached - I think 2.8 is the widest any zoom lens goes (canon 70-200mm and 24-70) giving a nice balance between versatility and quality
 
If you need convincing, get a nifty fifty. (nickname for a Canon 50mm f1.8) Costs about £70. Shoot with that for a week and see what it does.
 
AliB said:
If you need convincing, get a nifty fifty. (nickname for a Canon 50mm f1.8) Costs about £70. Shoot with that for a week and see what it does.
Click to expand...

haha good idea, that was my first prime and I'm firmly convinced now I got a bunch of primes:naughty:
 
If I ever got a fixed lens it would be a nifty! But there's quite a bit of other kit I "need" before I get that far, lol! I was just curious :)

Thanks for the explanations Rick and midgen :)
 
huanjia said:
haha good idea, that was my first prime and I'm firmly convinced now I got a bunch of primes:naughty:
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Me too, it's a slippery slope and once you get down to f1.4, f1.2 territory it gets a bit pricey too!

I'm still on the "cheaper" variants with 35mm f2, 50mm f1.8, 85mm f1.8 and 100mm f2.8. But I'm getting some good results with them so until the beanstock grows................:D
 
Take two comparable lenses...the EF200/2.8L and the EF70-200/2.8L

The 200 prime has 9 elements whilst the 70-200 zoom has 18 elements. It's fair to assume that each element induces some aberrations (hopefully very minor ones) and therefore logic would say that the 70-200 zoom would have double the amount of disturbances to the light path and hence the image projected onto the sensor is inevitably going to be inferior....that's the cost of flexibility.

Bob
 
Previously it was a case of poor quality and weight and speed of zooms.
As technology progresses, these differences get less and less.
A single focal point is still faster and possibly smaller, but the delta is getting less and less.
I'd stick with the zoom lens, and try One single focal-lenght. A nifty-fifty one. If you have a canon dslr, Kerso on the classifieds is doing a good deal on them.

Ekso
 
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