Primes?

[Rob MacKillop]

I've seen a few mentions of lenses being primes. What does that mean?

 

[Pete Askew]

Hi Rob, it means they have fixed focal length (often of lengths such as 20, 24, 28, 35, 85, 135, 200 etc), ie they are not zoom lenses. They are usually grouped as either wide angle (eg 20 - 28 mm), normal (35 - 85 mm) and telephoto (> 85 mm) with ultra wide angle being < 20 mm (eg 14 mm) and super telephoto being > 600 mm. There are also fish-eye lenses that have a circular field of vision even on a normal negative / sensor and come in around 6 mm. But the important distinction is that they have a fixed focal length and do not zoom. This often means that the lens is less compromised in its design and often you can gain higher quality at a larger aperture and lower cost.

Hope that helps.

 

[Paul Lange]

Fixed focal length as opposed to zoom lenses. They have less glass elements, are faster (lower aperture number) and generally are much sharper. 50mm (or 35mm for a crop frame sensor) is the most popular.

 

[Rob MacKillop]

Now I know. Many thanks

 

[Pete Askew]

This might be interesting also Rob.

http://www.realphotographersforum.c...s-exposure-part-1-understanding-aperture.html

 

[Rob MacKillop]

Pete - are you saying a super zoom is not the same as a regular zoom? I'm a wee bit confused there.

 

[Pete Askew]

Sorry, that was a typing error. I'll correct it. It should have said super-telephoto. Actually these are not what I would call real terms as with both super-wide and super-telephoto the design of the lens is not so different from standard wide and telephoto types but you do see it used to refer to those lenses towards the extreme ends of the ranges. There are also super-zooms and these again operate in the extremes so instead of zooming over the range 24-70 mm they might do 18-300mm. Hence super zoom. Convenient but often highly compromised.

 

[Paul Lange]

Some zooms are better than others (and usually cost a lot more) but I have been told that for a zoom take 10% of the max focal length and add 10% onto the min focal length and consider that your usable range. It seems to bear out on my zoom lenses. I'll stick my neck out and say, sports and wildlife photography aside, people will get much more out of photography if they use primes whenever they can. I had a 18-105mm that was quite good but when I replaced for a 35mm prime I didn't miss it very much and enjoyed taking photos and the results much more.

I find zooms are useful for portraits though due to the convenience of being able to zoom in and out easily.

 

[Rob MacKillop]

OK. And thanks to the link to the aperture explanation, which I've now read and commented on.

Oh dear, I feel a new addiction coming on...well, I have enough musical instruments now! Unfortunately, photography can be an expensive addiction...