Why do older camera lenses have faster F-stops?

Started Apr 14, 2013 | Discussions thread
EinsteinsGhost
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Re: f1.8 equivalents...
In reply to HumanTarget, Apr 17, 2013

HumanTarget wrote:

EinsteinsGhost wrote:

Joseph S Wisniewski wrote:

Dave Luttmann wrote:

Joseph S Wisniewski wrote:

EinsteinsGhost wrote:

Joseph S Wisniewski wrote:

Yes, because it's micro four thirds, and the DOF and you need f0.9 to have the light gathering and DOF equivalent of the "plastic fantastic" $100 f1.8 lenses on FF. So, some old "cine" lenses get reincarnated.

DOF yes (at same FOV), exposure no.

Exposure yes.

Cut the sensor area into a quarter of what it was, and you have 1/4 of the photons in the picture, so you need to throw 4x the light at it to get the same results. Just like in the film days, when tri-x was probably my most shot film on the 4x5, while tech pan was one of my favorites on 35mm.

Physics is a bear.

Exposure...no.  I get the same shutter and aperture rating using a FF camera at iso 100 and f8 as I do on an m43 body.

exposure...no.

Exposure... yes.

Come on Dave, you've shot many different film formats and different digital formats. Do you shoot the same ISO in all formats?

No, it doesn't. The f-stop equivalence applies to DOF, not to exposure.

It applies to both.  You're confusing exposure and image brightness.  Less DOF implies a greater exposure, all other things being equal.

Nope.Here's an image taken with a small sensor camera (4x crop), at 200mm FF equivalent:

Sony F828, ISO 64, 51mm (200mm equivalent), f/2.8 (f/11 equivalent), 1/800s

Are you going to tell me that a FF camera will get this same exposure with a 4-stop faster shutter speed (1/12,800s) at same ISO and f/11?

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