Why do older camera lenses have faster F-stops?

Started Apr 14, 2013 | Discussions thread
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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... 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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