April 21, 2014, 11:11:36 AM

Author Topic: Photo jargon question: f/stops  (Read 1989 times)

SJTstudios

  • Rebel T5i
  • ****
  • Posts: 150
    • View Profile
Photo jargon question: f/stops
« on: January 10, 2013, 12:12:22 PM »
Hey guys quick question.

"Does anybody know why the name of the lens includes the widest aperature (f/...)?"

Why not the smallest, or the sharpest?

canon rumors FORUM

Photo jargon question: f/stops
« on: January 10, 2013, 12:12:22 PM »

Drizzt321

  • 1D X
  • *******
  • Posts: 1645
    • View Profile
    • Aaron Baff Photography
Re: Photo jargon question: f/stops
« Reply #1 on: January 10, 2013, 01:09:28 PM »
Hey guys quick question.

"Does anybody know why the name of the lens includes the widest aperature (f/...)?"

Why not the smallest, or the sharpest?

I don't exactly understand the "Why the smallest, or the sharpest", but the fastest lens I've heard of is probably f/0.95, of which there are a few. Probably the best known current production lens is the Leica 50mm, but Canon had a 0.95 50mm back in the day.
5D mark 2, 5D mark 3, EF 17-40mm f/4L,  EF 24-105mm f/4L IS USM, EF 135mm f/2L, EF 85mm f/1.8
Film Cameras: Mamiya RB67, RB-50, RB-180-C, RB-90-C, RB-50, Perkeo I folder, Mamiya Six Folder (Pre-WWII model)
http://www.aaronbaff.com

Timothy_Bruce

  • Rebel T5i
  • ****
  • Posts: 116
    • View Profile
Re: Photo jargon question: f/stops
« Reply #2 on: January 10, 2013, 01:32:54 PM »
Because it is a relevant fact about the lens.

Would they not do that you would have to search far more to know if the 16-35 or 17-40 is capable of gathering more light and why the 16-35 is double the Price ;)

paul13walnut5

  • Guest
Re: Photo jargon question: f/stops
« Reply #3 on: January 10, 2013, 02:14:34 PM »
It's indicative of brightness, lenses are usually at their best stopped down a bit, so max aperture lets you know the starting point, also in most modern af systems the faster the max aperture the better the af performance, regardless of shooting aperture.

Minimum aperture can cause it's own problems, particularly when considering that dslrs of different sensor sizes and generations have different pixel pitch, the effects of aperture limited diffraction mean that the desirable minimum aperture can vary vastly between say a 1100d and a 7d or even between a 5d and a 5d3.


Drizzt321

  • 1D X
  • *******
  • Posts: 1645
    • View Profile
    • Aaron Baff Photography
Re: Photo jargon question: f/stops
« Reply #4 on: January 10, 2013, 02:22:40 PM »
It's indicative of brightness, lenses are usually at their best stopped down a bit, so max aperture lets you know the starting point, also in most modern af systems the faster the max aperture the better the af performance, regardless of shooting aperture.

Minimum aperture can cause it's own problems, particularly when considering that dslrs of different sensor sizes and generations have different pixel pitch, the effects of aperture limited diffraction mean that the desirable minimum aperture can vary vastly between say a 1100d and a 7d or even between a 5d and a 5d3.

Ah, I'm glad someone was able to figure out what the OP was trying to ask. I apparently couldn't.
5D mark 2, 5D mark 3, EF 17-40mm f/4L,  EF 24-105mm f/4L IS USM, EF 135mm f/2L, EF 85mm f/1.8
Film Cameras: Mamiya RB67, RB-50, RB-180-C, RB-90-C, RB-50, Perkeo I folder, Mamiya Six Folder (Pre-WWII model)
http://www.aaronbaff.com

rs

  • 6D
  • *****
  • Posts: 513
    • View Profile
Re: Photo jargon question: f/stops
« Reply #5 on: January 10, 2013, 05:13:11 PM »
It's indicative of brightness, lenses are usually at their best stopped down a bit, so max aperture lets you know the starting point, also in most modern af systems the faster the max aperture the better the af performance, regardless of shooting aperture.

Minimum aperture can cause it's own problems, particularly when considering that dslrs of different sensor sizes and generations have different pixel pitch, the effects of aperture limited diffraction mean that the desirable minimum aperture can vary vastly between say a 1100d and a 7d or even between a 5d and a 5d3.
Spot on. Most lenses, even the ones which are very sharp wide open hit their sweet spot around f8, and most current FF canon SLR's suffer from diffraction around f11, most current crop Canon SLR's suffer from it from around f7. So whether a lens stops down to f16 or f32 is less relevant than its max aperture.

It's similar to how simple engines specs are engine size and max power. Not how much power is delivered when the engine is at its smoothest, or how little power it can deliver before stalling.
5D II | 24-70 II | 70-200 II | 100L | 40 | Sigma 50/1.4 | 40D | 10-22 | 17-55 | 580 EX II | 1.4x TC II

Menace

  • 1D Mark IV
  • ******
  • Posts: 925
  • New Zealand
    • View Profile
Re: Photo jargon question: f/stops
« Reply #6 on: March 07, 2013, 03:01:05 AM »
It's indicative of brightness, lenses are usually at their best stopped down a bit, so max aperture lets you know the starting point, also in most modern af systems the faster the max aperture the better the af performance, regardless of shooting aperture.

Minimum aperture can cause it's own problems, particularly when considering that dslrs of different sensor sizes and generations have different pixel pitch, the effects of aperture limited diffraction mean that the desirable minimum aperture can vary vastly between say a 1100d and a 7d or even between a 5d and a 5d3.
Spot on. Most lenses, even the ones which are very sharp wide open hit their sweet spot around f8, and most current FF canon SLR's suffer from diffraction around f11, most current crop Canon SLR's suffer from it from around f7. So whether a lens stops down to f16 or f32 is less relevant than its max aperture.

It's similar to how simple engines specs are engine size and max power. Not how much power is delivered when the engine is at its smoothest, or how little power it can deliver before stalling.

+1
5D III | 6D
50 1.2L | 85 1.2L II | 100 2.8 | 400 2.8L IS II 
24-70 2.8L II | 70-200 2.8L IS II

canon rumors FORUM

Re: Photo jargon question: f/stops
« Reply #6 on: March 07, 2013, 03:01:05 AM »

RGF

  • 1D X
  • *******
  • Posts: 1196
  • How you relate to the issue, is the issue.
    • View Profile
Re: Photo jargon question: f/stops
« Reply #7 on: March 08, 2013, 07:17:14 PM »
Hey guys quick question.

"Does anybody know why the name of the lens includes the widest aperature (f/...)?"

Why not the smallest, or the sharpest?

The definition of the F is the focal length divided by the diameter of the aperture.  This tells the maximum light gathering ability.

Mt Spokane Photography

  • 1D X
  • *******
  • Posts: 7714
    • View Profile
Re: Photo jargon question: f/stops
« Reply #8 on: March 08, 2013, 10:14:34 PM »

I don't exactly understand the "Why the smallest, or the sharpest", but the fastest lens I've heard of is probably f/0.95, of which there are a few. Probably the best known current production lens is the Leica 50mm, but Canon had a 0.95 50mm back in the day.

 
Lenses are named by largest aperture simply because its the largest aperture that determines the value of the lens (assuming its a normal quality lens).   The smallest aperture does not really cost anything, but it limited since image quality gets pretty poor at extreme small apertures.  For larger the film or sensor sizes,  smaller apertures can be used, so its relative.
 
The Zeiss 50mm f0.7 is one of the fastest lenses.
 
"Carl Zeiss Planar 50mm f/0.7 is one of the largest aperturelenses in the history of photography. The lens was designed and made specifically for the NASAApollo lunar program to capture the dark side of the moon in 1966.
Stanley Kubrick used these lenses when shooting his film "Barry Lyndon", which allowed him to shoot the scene only by candlelight.[
In total there were only 10 lenses made. One was kept by Carl Zeiss, six were sold to NASA, and three were sold to Stanley Kubrick."
http://en.wikipedia.org/wiki/Carl_Zeiss_Planar_50mm_f/0.7

Zv

  • 1D X
  • *******
  • Posts: 1036
    • View Profile
    • Zee-bytes
Re: Photo jargon question: f/stops
« Reply #9 on: March 08, 2013, 10:49:20 PM »
So that we know the most important feature of the lens - how much light it lets in. No point in knowing how it performs stopped down, most lenses are sharp stopped down. That is useless info. Its like saying hey this sports car can also cruise at 60mph. Who cares about that? We wanna know the max speed! Same with a lens the max "speed" relative to aperture size. So we know a f/1.4 will allow for some fast shutter speeds compared with narrower apertures at the same light level. Also we can tell by the wide aperture that it is possible to achieve a shallow depth of field and hopefully some pleasing out of focus areas. All important considerations when buying a lens.

Also the sweet spot for any model of lens may vary copy to copy. That info could be misleading.
« Last Edit: March 08, 2013, 11:09:35 PM by Zv »
5D II | 7D | EOS M + 22 f2 | 17-40L | 24-105L | 70-200 f4L IS | 135L | Samyang 14mm f/2.8 | Sigma 50 f/1.4

Drizzt321

  • 1D X
  • *******
  • Posts: 1645
    • View Profile
    • Aaron Baff Photography
Re: Photo jargon question: f/stops
« Reply #10 on: March 09, 2013, 01:15:18 AM »
So that we know the most important feature of the lens - how much light it lets in. No point in knowing how it performs stopped down, most lenses are sharp stopped down. That is useless info. Its like saying hey this sports car can also cruise at 60mph. Who cares about that? We wanna know the max speed! Same with a lens the max "speed" relative to aperture size. So we know a f/1.4 will allow for some fast shutter speeds compared with narrower apertures at the same light level. Also we can tell by the wide aperture that it is possible to achieve a shallow depth of field and hopefully some pleasing out of focus areas. All important considerations when buying a lens.

Also the sweet spot for any model of lens may vary copy to copy. That info could be misleading.

Actually, it's not useless. Some lenses might perform better at f/5.6 than f/8, although some of that depends on the recording medium (different sensors/film). However, often a faster lens (wider aperture) will let you stop down a bit (say, f/1.4 -> f/2.8) while still being fast, and improving quality. Also faster glass tends to be of higher quality, and better designs all of which contribute positively to the image quality at any aperture.
5D mark 2, 5D mark 3, EF 17-40mm f/4L,  EF 24-105mm f/4L IS USM, EF 135mm f/2L, EF 85mm f/1.8
Film Cameras: Mamiya RB67, RB-50, RB-180-C, RB-90-C, RB-50, Perkeo I folder, Mamiya Six Folder (Pre-WWII model)
http://www.aaronbaff.com

bycostello

  • 1D Mark IV
  • ******
  • Posts: 910
    • View Profile
    • London Weddings
Re: Photo jargon question: f/stops
« Reply #11 on: March 09, 2013, 02:17:09 AM »
its a dof issue...  unless ur a landscape photographer u not really bothered the other end and all lenses tend to go to f22

canon rumors FORUM

Re: Photo jargon question: f/stops
« Reply #11 on: March 09, 2013, 02:17:09 AM »