primes?

[roadkill]

I know I may sound like a dumbass... but what are/is primes when referring to lenses?

 

[nicfargo]

they are lenses that have no zoom. Zoom lenses have a range that they can cover, for example 24-70mm. A prime would be 50mm. You cannot zoom...if you're too far away you must physically get closer to your subject.

 

[Helen B]

That's the most common meaning these days. A lens with a fixed, or nearly fixed, focal length. Some lenses do vary their focal length a little as they are focussed, but they are still called primes.

The other meaning, much less common nowadays, is the main lens in a combination. For example you could have a lens fitted with a teleconverter, a wide angle converter, a varifocal converter, an anamorphic (squeeze) lens, a close-up lens (aka diopter) or other supplementary lens. The main lens would be referred to as the prime lens in that case.

Best,
Helen

 

[EOS_JD]

Helen
Name a prime lens that varies it's focal length that is a prime? I think you may be confusing that the barrel may extend when focusing but this is different from focal length which remains constant.

Prime = Fixed Focal Length
Zoom = Variable Focal Length

 

[Happy Hour]

Helen
Name a prime lens that varies it's focal length that is a prime? I think you may be confusing that the barrel may extend when focusing but this is different from focal length which remains constant.

Prime = Fixed Focal Length
Zoom = Variable Focal Length

I believe Helen was referring to the distance when a lens focuses. Like my 50mm macro, depending on the subject when focusing it can lock on at 1 foot away or zoom in to 2 inches from the subject before it actually locks focus. Therefore the distance changes depending on where it focuses.

 

[Helen B]

No, I'm referring to the focal length of the lens.

Helen
Name a prime lens that varies it's focal length that is a prime? I think you may be confusing that the barrel may extend when focusing but this is different from focal length which remains constant.

Prime = Fixed Focal Length
Zoom = Variable Focal Length

OK, so what would you call these three current AF Micro-Nikkors: the 60 mm, the 105 mm and the 200 mm? They all achieve their closest focus by shortening their focal length. The focal length cannot be changed independently of the focus setting. There may be other 'prime' lenses with internal focussing that change their focal length while focussing.

There are a number of high-end motion picture prime lenses (eg Zeiss UltraPrime) that change their focal length while focussing. Think about those focus pulls you see in the movies. If the lens had a fixed focal length, you would see a slight zoom effect as the focus was pulled. We call it 'breathing', and good MP lenses should control it, particularly the wide angle lenses.

Best,
Helen

 

[roadkill]

what's the point of a prime? Seems like a lot of money to spend (500-3000 dollars) on a lens that you have to physically move your body to get correct and accurate focus.

 

[roadkill]

give me a zoom any day

 

[keith204]

what's the point of a prime? Seems like a lot of money to spend (500-3000 dollars) on a lens that you have to physically move your body to get correct and accurate focus.

sharp and fast

 

[roadkill]

happy hour, I don't understand. Sorry. If what I understand these folks to be saying is true, when you have a fixed lens like that there is no playing room in regaurds to focus. Am I off track? All I own are 18-55 Nikkor and 70-300 Quantaray

 

[roadkill]

Are there fixed lenses with AF?

 

[roadkill]

Keith...what is sharp and fast about having to reposition yourself everytime you want a new shot?

 

[roadkill]

I don't frown upon primes. I just don't understand. Sorry.

 

[keith204]

Keith...what is sharp and fast about having to reposition yourself everytime you want a new shot?

you sound closed-minded.

AF - yes, primes often have AF. Most now do.
Sharp - most of the time, you can get a sharp prime for far less than a zoom of that sharpness (look at the Canon 50mm f/1.8, very sharp for only $79)
Fast - find a f/1.4 zoom lens. Not possible. With 1.4 you can shoot in much darker situations, and get better bokeh. Also, a 50mm 1.4 lens is only $299.

I agree that this sounds silly from a beginner's standpoint, but as you venture more into photography, you will understand the value of prime lenses.

 

[chris]

Most primes produced these days have AF. They generally have greater maximum apertures than zooms and so can be used in lowlight situations where a zoom may require the use of flash or a tripod. The designs are usually simple compared with a zoom which makes them relatively cheap to produce and light in weight. Prime lenses are well corrected giving exceptionally sharp images with minimal distortion whereas the performance of many zooms deteriorates at the extreme ends of the range. The large apertures permit narrow depth of field to separate the subject from the foreground or background. The large apertures help when focussing in poor light.

Enough on reasons to use a prime instead of a zoom, except that having to move around to get the field of view you want makes you investigate scene more and look for more interesting angles than just turning up looking at a scene and framing it using a zoom.