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DPChallenge Forums >> Hardware and Software >> Why are fast lenses more expensive?
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 12/12/2006 04:05:57 PM · #51
Originally posted by Gordon:
Originally posted by Spazmo99:
I have the Tamron... It changes length when zoomed, the barrel rotates when focusing, it's nowhere near as sturdily built and it's certainly not weather sealed.


I hate hate hate the variable length/ rotating barrel lenses.


The Tamron lens barrel does NOT rotate.
 12/12/2006 04:19:27 PM · #52
Originally posted by Gordon:
Does it let you focus manually when in auto focus mode ? That's another nice L feature that I don't think was mentioned. The internal focusing is also a nice feature, for most of them. Particularly if you are using a circular polariser or doing close-up work.


No, you cannot manual focus in AF mode. It does, however, have an internal focus design where the front element does not rotate. It's the focus ring that rotates when it auto focuses, not the front element so using a polarizer isn't a problem at all. And if I remember correctly, the 24-70mm f/2.8L also has a lens barrel that extends and retracts when zooming.

Edit for grammar.

Message edited by author 2006-12-12 16:21:08.
 12/15/2006 10:55:51 PM · #53
Nikon ED=Extra Dollars Canon L=Ludicrus
I just thought that up a while back when my buddy Steve bought a cannon L.
Back to the original post about what's a fast lens. In simple terms you can think of light sort of like water. It takes a certain quantity of light on the sensor with digital cameras to get the image exposed right. Call it a tea cup full.
You can pour that amount thru a hole the size of a soda straw, but it takes a while, or a long exposure, slow shutter speed. This would simulate a slow lens.
You can pour that amount thru a hole the size of a tennis ball relatively much faster, and have the same result in a much shorter time, a quick exposure, or fast shutter speed. This would simulate a fast lens.
It's bubbaneering physics, but that's about how I learned it.
The glass, like diamonds, is more expensive and tricky to manufacture and machine in larger pieces.
When you look a digital image at full screen, think about the number of sensor sized dots it would take to cover the screen, then think about all the details in each spot on the screen that size, and wonder how they get the light to go to the right place on the sensor as well as they do. They also manufacture many more of the lower priced lenses than they do the high end ones, so smaller production runs = more $ per unit. I picked up a 1.4/50mm manual nikkor in perfect shape at a pawn shop with leather case and metal shade for $20 recently. Luck, and patience helps a lot when shopping for good glass.
12/16/2006 12:08:35 AM · #54
Originally posted by scalvert:
Originally posted by Gordon:
Originally posted by Spazmo99:
I have the Tamron... It changes length when zoomed, the barrel rotates when focusing, it's nowhere near as sturdily built and it's certainly not weather sealed.


I hate hate hate the variable length/ rotating barrel lenses.


The Tamron lens barrel does NOT rotate.


The barrel doesn't, but the focus ring does. My bad.
12/16/2006 01:26:50 AM · #55
Originally posted by Gordon:
Originally posted by Spazmo99:
Originally posted by Gordon:

I hate hate hate the variable length/ rotating barrel lenses.


I don't necessarily like that part of it, but it wasn't worth another $1200 to be rid of it. Should my photography become a profitable enterprise, I'll probably reconsider buying the "L".


Does it let you focus manually when in auto focus mode ? That's another nice L feature that I don't think was mentioned. The internal focusing is also a nice feature, for most of them. Particularly if you are using a circular polariser or doing close-up work.


Not all L lenses allow FTM focussing, though.
 12/16/2006 02:29:24 AM · #56
Originally posted by Gordon:
Originally posted by Spazmo99:
Originally posted by Gordon:

I hate hate hate the variable length/ rotating barrel lenses.


I don't necessarily like that part of it, but it wasn't worth another $1200 to be rid of it. Should my photography become a profitable enterprise, I'll probably reconsider buying the "L".


Does it let you focus manually when in auto focus mode ? That's another nice L feature that I don't think was mentioned. The internal focusing is also a nice feature, for most of them. Particularly if you are using a circular polariser or doing close-up work.


No, it doesn't, well, you can turn the focus ring, but the motor is engaged and it's not a good idea to do all the time. Full time Manual focusing not a feature exclusive to "L" lenses either. My 85 f1.8 allows it as does my Sigma 12-24.

None of those issues are bothersome enough that I would spend for the "L".
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