Basic question about fast/slow lens


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red_ryder

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#1
Why call a lens with a small maximum aperture a slow lens? Why call a f/1.4 lens a fast lens? It doens't make sense to me. Aperture has nothing to do with speed right? Isn't aperture just the size of the hole that lets light in? The shutter speed is controlled by the body of the camera.
 

#2
red_ryder said:
Why call a lens with a small maximum aperture a slow lens? Why call a f/1.4 lens a fast lens? It doens't make sense to me. Aperture has nothing to do with speed right? Isn't aperture just the size of the hole that lets light in? The shutter speed is controlled by the body of the camera.
Aperture bigger more light goes in ? So shutter speed will be faster when compared to a lens with smaller aperture ? :dunno:
Eg. 135 F2 shoot at 1/100 while 135 F4 will be at 1/25 in the same lightning conditions ?
 

sulhan

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#3
red_ryder said:
Why call a lens with a small maximum aperture a slow lens? Why call a f/1.4 lens a fast lens? It doens't make sense to me. Aperture has nothing to do with speed right? Isn't aperture just the size of the hole that lets light in? The shutter speed is controlled by the body of the camera.
Haha...

Many possible analogy and explanation through times....

Imagine a boat with a large hole.....and a boat with smaller hole....which sinks faster...?

In the photography sense which will allow more light in a particular shutter open/close instance...? obviously alens with a larger aperture.

Also as mentioned...allowing faster shutter speeds given the requirement of "desired exposure"...not changing ISO...

rgds,
sulhan
 

Jul 30, 2005
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#9
ortega said:
ditto the above and also the fast lens makes your money disappear faster as well
*choke* *cough* erhum haha easy ortega dun scare away potential buyers haha they help us to bring prices down :bsmilie:
 

litefoot

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#10
majere2sg said:
Not really.. a 50mm f1.8 is a fast lens.. :bsmilie:
For a 50mm no. 50mm f/1.0 is fast. ;p ;p ;p
 

litefoot

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#12
Oh another thing, you need to fast a lot inorder to buy "fast" lenses.
 

student

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#13
majere2sg said:
no no.. 50mm f1.8 is fast.. 1.4 is faster.. 1.0 is fastest :bsmilie:
No, No,...

0.95 is the fastest of the fastest!:bsmilie:
 

Cactus jACK

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#16
f1.8 is fast
f1.4 is faster
f1.2 is faster-er
f1.0 is fastest
f0.95 is the fastest of the fastest

all know your lenses here... but all fail your england!!! :bsmilie:
 

Jan 23, 2005
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#17
red_ryder said:
Why call a lens with a small maximum aperture a slow lens? Why call a f/1.4 lens a fast lens? It doens't make sense to me. Aperture has nothing to do with speed right? Isn't aperture just the size of the hole that lets light in?
You're absolutely correct. "Fast lens" is slang, but unfortunately in common use.

[QUOET]The shutter speed is controlled by the body of the camera.[/QUOTE]

"Shutter speed" is another of these expressions. With a few exceptions, the parts of a mechanical shutter move at a speed that is independent of exposure time. Exposure time is controlled by a variable delay between the shutter opening and closing process, not by the speed (velocity).

To make the trinity complete, the term "film speed" is obviously also nonsense.
 

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