primes?

[roadkill]

Thank you Chris. Well said and extremely informative. Appreciate it.

 

[Happy Hour]

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

Well I was only referring to my 50mm macro. (my other primes are not the same) On my 50 If I am taking a close up of just your eye, threw my viewfinder it is exactly where I want it, then when the camera auto focuses the focus ring will slide out close to 3 inches (in some cases) if it locks focus that far out my shot is now too close so I have to back up, Changing my focal length.

 

[Helen B]

I have far more primes than zooms. The technical reasons have already been explained well, but there are also the aesthetic reasons already touched upon. When you change the focal length, whether by zooming or by switching lenses, you change the perspective of the image. Some of use prefer to maintain a consistent perspective in our work, and therefore we stick to one focal length for one kind of photography, or one project.

Best,
Helen

 

[Dubious Drewski]

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

My Asahi 50mm prime does it. It's not alot, but it's definately happening.

 

[Socrates]

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.

Large apertures at reasonable cost.

I have a 50 mm f/1.4 and an 85 mm f/1.8. I also have several rarely-used zooms.

 

[Socrates]

give me a zoom any day

When I'm forced to use a zoom, I consider it a failure.

 

[Dubious Drewski]

Wow, roadkill, you post alot of half-thoughts. Half of these posts are yours!

Anyway. Primes have their uses! You get wider aperture, lower cost, usually better overall optics (less lens elements), etc.

Plus using a vintage prime makes your camera look dead sexy.

 

[Stratman]

And in almost ALL instances, a prime will have better IQ than a zoom.

 

[Snyder]

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.

haha, stupid noob. Primes were used by some of the top photojournalist. And even still to this day. I use them aswell.

 

[chris_arnet]

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

pretty much answered it. Ill bet you my 20D cant find a zoom as fast and sharp as most 50mm primes.

 

[DSLR noob]

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

how about the lens itself focuses really sharp? Did you even think of that as the (more obvious) meaning he meant by sharp? The cheapest prime by Canon, ($75 for 50 1.8) can easily be sharper than an L series zoom lens costing $1,500.

Fast, once again, not the literal meaning, as in "I get my shots fast by zooming in and clicking." fast. But rather, "Te large f/1.4 aperture lets me take a picture at 1/60 of a second in a room where I would need a shutter speed of 1/10 or slower (causing blur) with my zoom lens." fast.

Next time, try and take our posts seriously, rather than being so close minded as to worrying about walking a little bit. It's healthier, and will often make you think harder about what you're trying to do, resulting in better photography.

If someone came up to me and said "Quick, pick one and it's yours! A Canon 40D with every Canon L series Prime in current production, or a 1D Mk III AND a 1Ds Mk III with every L series zoom in current production?" I'd take the package with all the primes. It ranges from a 14mm 2.8 to an 800 5.6 IS lens and the quality is too good to pass up.

 

[EOS_JD]

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



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

OK Helen. I hold up my hands and beg for forgiveness. :hail:

I did know about the motion picture lenses but didn't consider it as "photography" however that said I should have known that macro lenses change their focal length slightly!

Apologies

However for any other prime......

As has been noted above Primes generally have larger apertures than zooms allowing photography in very low light where using a zoom would not be possible. They are also generally lighter as well (although primes with very large f1.2 apertures are pretty large). And sharpness (especially macro lenses) cannot be matched by zooms. Not sure the cheap 50 f1.8 is sharper than my L zooms though but it's pretty close.

 

[Helen B]

Well, to be fair, not that many macro lenses change their focal length. I have more macro lenses that are true fixed focal length than variable focal length. In the Nikon macro prime line I think that it's only the recent AF Micro-Nikkor lenses that shorten their focal length. It helps them to achieve 1:1 without excessive extension, helps them to autofocus more quickly and improves illumination a little (the f-number is lower at 1:1 than it would be if it had a fixed focal length, for example the AF Micro-Nikkor 60 mm f/2.8 ends up as an f/5 instead of an f/5.6 at 1:1).

I just try to be as accurate as I can be when I post, that's all.

Best,
Helen

 

[Socrates]

Well, to be fair, not that many macro lenses change their focal length. I have more macro lenses that are true fixed focal length than variable focal length. In the Nikon macro prime line I think that it's only the recent AF Micro-Nikkor lenses that shorten their focal length. It helps them to achieve 1:1 without excessive extension, helps them to autofocus more quickly and improves illumination a little (the f-number is lower at 1:1 than it would be if it had a fixed focal length, for example the AF Micro-Nikkor 60 mm f/2.8 ends up as an f/5 instead of an f/5.6 at 1:1).

I just try to be as accurate as I can be when I post, that's all.

Best,
Helen

I submit that this is not a valid example because the change in focal length is not an intended feature but, rather, a byproduct of an engineering issue. You may recall Nikon's first effort at automatic exposure with shutter priority. Quite simply, it didn't work. Their engineers had to "tweak" the shutter speed during the exposure because they couldn't set the aperture as accurately as they wished.

 

[Helen B]

Their focal length varies, and they are generally considered to be primes. It seems quite simple. Why complicate it?

Best,
Helen