Prime lens benefit?

[tcd2004]

I've been reading a lot about people shooting with prime lens' and i was wondering what the benefit is. Im obviously not very familiar with aperture and im still waiting for my rebel field guide to get here so i can start reading. i read a lot of good things about the canon 50mm f/1.8 and since it's cheap i was wondering if i should pick it up. What are the benefits/sacrifices of having the aperture fixed? Right now i have the kit lens and a 17-300mm lens both by canon with a digital rebel. Thanks!

 

[jrynash]

Prime lenses have fixed focal lengths (zoom), not fixed aperatures.

See this, for example:
http://www.cambridgeincolour.com/tutorials/camera-lenses.htm

I've been reading a lot about people shooting with prime lens' and i
was wondering what the benefit is. Im obviously not very familiar
with aperture and im still waiting for my rebel field guide to get
here so i can start reading. i read a lot of good things about the
canon 50mm f/1.8 and since it's cheap i was wondering if i should
pick it up. What are the benefits/sacrifices of having the aperture
fixed? Right now i have the kit lens and a 17-300mm lens both by
canon with a digital rebel. Thanks!

 

[rayfound]

Prime lenses K.I.S.S.

They do not have any of the complexity required to allow adjustment of focal lengths (zooming). There need not be any of the optical comprimises made to allow "good enough" performance, at various focal lengths, instead, they just have to be dialed in to their one focal length.

Also, they typically have much larger maximum apertures. This is likely the biggest advantage, as it allows one to use the lens in lower light, and/or utilize a shallow depth of field effect, for subject isolation.

 

[tcd2004]

my mistake, like i said, i am pretty new at this. so when there is f/(insert number here), is that relating to aperture or focal length? I thought the the mm number was focal length...

 

[rbhun]

A zoom lens (one with a variable focal lenth) is a much more complex optical element than a prime lens. Primes (fixed focal length lenses) generally have 4-6 glass elemnts in them, while zooms have something like 15 or even more. This should give you the basic idea. Primes will always have a huge advantage (and naturally, a disadvantage of not being able to zoom...). A prime lens' construction has to face much less compromises, and its generally easier to 'tune' a glass to one given focal length. Primes are usually 'breathing' less, meaning that they do not (or to a lesser degree) change their actual focal length while focussing.

Prime lenses are usually faster (having a largest aperture of 1,8 or 1.4, sometimes even lower, while only the best zooms can open up to 2.8), smailler and lighter. Some special lenses, like ultra-wide or ultra-tele, macro and tilt-shift lenses are generally primes.

So primes are better, however recent years brought zooms with qualities closing on on prime lenses. Today, average users will not need primes, maybe with the exception of the all-beater 50mm f/1.8 (regarding value). If you want the best of the best, get a prime, but if you are happy to give up a little quality for a lot of flexibility, get a zoom.

That being said, walking out with a prime (or two) is a very interesting photographing experience, and opens up a lot of new possibilities.

Balazs

 

[hopkinsg]

f/ = aperture... 1,1.4,2,2.8,4,5.6,8,11,16,22,32,45,64. Lower the #, the bigger the aperture

mm would refer to the focal length of the lens. so 50/1.8 would be a 50mm focal length with a maximum aperture of 1.8 . a 17-50/2.8 would mean it's a zoom lens from 17-50mm and that the maximum aperture anywhere in that range is 2.8 .

18-55/3.5-4.6 would mean that at 18mm the maximum aperture is 3.5, and at 50mm the maximum aperture is 4.6

--
Gary H
http://www.pbase.com/hopkinsg

 

[wibbs]

My list of advantages for primes:
1) Usually capable of shooting at a wider aperture
2) Usually lighter
3) Usually better optical qualities at the given focal length

The most significant to me is the wider aperture. Why do I care about that? Two reasons:

1) I can shoot in lower light (wider aperture means more light gets through to the sensor) without flash where I couldn't with a zoom.

2) Wider Aperture means smaller DOF - I happen to love this effect for photos of people in busy environments. If you want to see some excellent examples, joe_mama in the SLR lens forum is particularly good at this. He recently posted some samples with his 50/1.2L:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=23978546

 

[jgb]

Used to be that primes were sharper than zooms; that's not necessarily the case today.

Primes will be faster (have a larger max aperture) than zooms; this allows you to control depth of field better than with most zooms.

Primes are usually a bit more compact than a zoom that covers the same focal length.

Primes are usually less expensive, but not always.

Primes are more likely to have better bokeh if that's important to you.

Good luck,

jgb

I've been reading a lot about people shooting with prime lens' and i
was wondering what the benefit is. Im obviously not very familiar
with aperture and im still waiting for my rebel field guide to get
here so i can start reading. i read a lot of good things about the
canon 50mm f/1.8 and since it's cheap i was wondering if i should
pick it up. What are the benefits/sacrifices of having the aperture
fixed? Right now i have the kit lens and a 17-300mm lens both by
canon with a digital rebel. Thanks!

--
Galleries: http://www.pbase.com/jon_b

 

[tcd2004]

Thanks for the info so far, maybe i will pick up that prime lens and play around with it. That being said, i'm still a little confusedon the whole aperture thing. I know its just me being a novice and i havn't taken the time to read about it but everyone on here is usually easier to understand then a manual. what are the downfalls of having a fixed aperture? and on my kit lens for example the aperture is variable so what effects would i get of making it bigger or smaller? Thanks again for all the help

 

[Gerrit Smit]

if you are happy to give up a little quality for a lot of
flexibility, get a zoom.

For me as a amateur shooter ( family shots, vacations ), there's really NO quality diference between the 50mm f/1.8 Canon Prime lens and the 18-50mm f/2.8 EX DC Macro Lens by Sigma.

The only advantage the f/1.8 lens has, is that I can shoot in very low light conditions, but I never use this, because indoor lowlight, asks for wide-angle shots. With 50mm you can hardly get a whole person on your picture, even if you step back. In my small house, if I step back to get everyone on the picture, I hit the wall ...

So, why buy a 50mm f/1.8 lens if you never use it? Or maybe use it only 0.01% of the time? The only reason I can think of ( again, for my personal use !!!! ) is because it's cheap, very, very cheap ( the Sigma zoom I have was 6x more expensive ) and a lot of fun to play with once in a while.

 

[jgb]

Virtually no lens available today has a fixed aperture. Primes have a fixed focal length, not a fixed aperture.

What you are talking about is whether the maximum aperture varies with focal length. For instance, the 18-55 (kit) lens has a maximum aperture of f3.5 when used at 17mm, but a maximum aperture of f5.6 when used at 55mm. There is some potential advantage to lenses that maintain the same max aperture at all focal lengths. These by definition are all zoom lenses (i.e. you can change the focal length of the lens). Primes have one max aperture since they have one focal length.

Regards,

jgb

Thanks for the info so far, maybe i will pick up that prime lens and
play around with it. That being said, i'm still a little confusedon
the whole aperture thing. I know its just me being a novice and i
havn't taken the time to read about it but everyone on here is
usually easier to understand then a manual. what are the downfalls
of having a fixed aperture? and on my kit lens for example the
aperture is variable so what effects would i get of making it bigger
or smaller? Thanks again for all the help

--
Galleries: http://www.pbase.com/jon_b

 

[pretzelb]

Thanks for the info so far, maybe i will pick up that prime lens and
play around with it. That being said, i'm still a little confusedon
the whole aperture thing. I know its just me being a novice and i
havn't taken the time to read about it but everyone on here is
usually easier to understand then a manual. what are the downfalls
of having a fixed aperture? and on my kit lens for example the
aperture is variable so what effects would i get of making it bigger
or smaller? Thanks again for all the help

As the other poster said I think you're confused on either the apeture vs the focal length or the max value of the aperture. I'm an extreme novice too so I know how hard it can be.

The prime lenses have a fixed focal length. If you put the camera to your eye with a 50mm prime and the person's face you are trying to take is cut off at the top then you have to either move yourself or your subject to fit them in the frame. This is sometimes called framing with your feet. With a zoom lens you just turn a dial and you can adjust the frame (within the limits of the zoom). The turning of the dial adjusts the focal length.

Now I'm not entirely sure because I haven't owned a zoom in a while but I think when you do adjust the zoom your aperture will change to compensate. Someone please correct me on this (sorry, I'm a novice too). So if I'm correct, that means with a prime you aperature COULD be fixed simply because your focal length is fixed. But you are still free to change to an aperture value available to the lens at will.

So why is that good? Well for me it saved my DSLR habit (not sure if that's good or bad). I was going to switch to P&S but instead I sold my crappy zoom lenses and got the 50mm f/1.8 prime. This gave me one less variable to think about with my shots. Everytime you change the focal length the variables change and not being able to change the focal length simplified it for me. Shortly after getting the 50mm f/1.8 I picked up the 85mm f/1.8 also (which is really nice).

As others have said the prime lenses are usually cheaper, sharper, and almost always lighter. In addition I think they're like training wheels because the lack of a zoom eliminates a lot of variables.

I hope I'm somewhat right on my explaination. I'd hate to make this worse for you. But I was in your shoes not so long ago so I'm eager to help if possible.
--

Misc equip : Canon 610, Canon 400D, Canon 10D (about to sell), EF 50mm f/1.8 II, EF 85mm f/1.8 USM

 

[tcd2004]

so if it has a fixed aperture, can the aperture value not be changed at all from the camera settings? and how exactly would the picture change if taken at different apertures if possible?

 

[pretzelb]

so if it has a fixed aperture, can the aperture value not be changed
at all from the camera settings? and how exactly would the picture
change if taken at different apertures if possible?

Maybe I'm not understanding your question. The aperture isn't fixed on a prime lens. The focal length is fixed. I apologize for not being clearer.

Different apeture values ARE possible. As far as I know all lenses can change the AV. As to what that does take a look at this link and try lesson #4. The interface is a bit goofy but it's not too bad. The image samples should help.

http://images.photoworkshop.com/rebelxtlessons/interface.html

This link talks about prime vs zoom
http://photonotes.org/articles/beginner-faq/lenses.html#zoomprime

but this is the entire list of topics
http://photonotes.org/articles/beginner-faq/

See if any of that helps.

--

Misc equip : Canon 610, Canon 400D, Canon 10D (about to sell), EF 50mm f/1.8 II, EF 85mm f/1.8 USM

 

[BAK]

This stuff gets complcated, and sometimes the camera companies don't help make it easier to understand.

Focal length of a prime lens means that the only way to change how much the lens "sees" is to walk closer or back away. A zoom, instenad, let's you change the focal length, and get more or less int eh shot, without moving your feet.

"Fixed" aperture relates only to the maximum aperture of certain zoom lenses.

Evey lens has a maximum aperture. With a prime lens, it is whatever it is, at the only focal length of the lens.

With most zooms, the maximum aperture is NOT fixed. As you zoom the lens, the maximum aperture changes. For instance, it may be f2.8 at 24mm, and f4.5 at 135mm, and at different values in between.

On an expensive zoom lens with a fixed maximum aperture, it is always, for instance, f2.8, whether at 18mm or 50mm, or on a different lens, at 70mm or 200mm.

With ALL lenses, (rare exceptions you don't need to know about) there are lots of other apertures available that are smaller than the maximum.

BACK TO THE ORIGINAL QUESTION

DISCIPLINE -- when you are taking pictures for fun, or for mental stimulation, having a prime lens (fixed or single focal length) forces you to think and look and study the light, and move yourself to the right spot for the good photograph. You learn to leave the shots the focal length does not work for -- a 50mm lens is a poor lens for a soccar shot on the other side of the field -- and you learn to spot the shots the lens is good for.

EASIER FOCUS -- most/many prime lenses are faster (have wider maximum apertures) than zooms. The wider the aperture, the less the depth of field. The less the depth of field, the easier it is to tell whether or not you are in focus.

EASIER PICTURE TIMING -- depending on the light in the location, the wider aperture of a prime makes it easier to see the subject. If you are looking for an elusive smile, for instance, it's easier to see, and then press the shutter release, with a faster (brighter) lens.

BETTER LOW LIGHT PICTURES -- a faster (wider, brighter) lens lets you use a higher shutter speed, minimizing subject blur and camera shake in low light.

SHARPER -- maybe, probably, depending on what it is being compared to. I have three 50mm lenses; a Canon 50mm f1.8, a Sigma 24-135 and the Canon 18-55 kit zoom. 8x12 prints from all three are pretty close to identical at f8 and f11, but the 50mm prime is better, obviously, at f2.8 and f2, because these settings are not on the two zooms.

BAK