Lens size

nseika

Mu-43 Veteran
Joined
Nov 22, 2010
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Jakarta, Indonesia
Real Name
Lois
From the internet, there is this two premises
- Minimum size for front lens element is focal length / max aperture
- Smaller sensor system such as m4/3 could have smaller lens design than full frame

How does these two premises fit each others ? Same fatness but less volume ?

Thanks for the answer. Just being curious :)
 

Hikari

Mu-43 All-Pro
Joined
Nov 26, 2010
Messages
1,531
From the internet, there is this two premises
- Minimum size for front lens element is focal length / max aperture
Not really. You also need to take field of view and acceptable level of vignetting into the equations. Wide-angle lenses will always have a front element larger than the f-number would suggest.

- Smaller sensor system such as m4/3 could have smaller lens design than full frame
Optics to a certain point is a geometric problem. Given an equal angle of coverage, angle of view, and design, an m4/3 lens will be smaller. But, like most generalizations, that can be taken so far.

How does these two premises fit each others ? Same fatness but less volume ?

Thanks for the answer. Just being curious :)
Both length and diameter can be reduced to a point.

Then there are other considerations. Physically, a 4x5 135mm lens is smaller than a 35mm 135mm lens. That is just because the way the cameras are made--a 4x5 does not need a helical focus mechanism nor does the lens construction have anything to do with lens-to-image plane distance (4x5 cameras have bellows).

A few more thoughts. A lens can be shorter than the focal length would suggest--that is what a "telephoto" is--or longer, a reverse telephoto. You do not need to change the lens to sensor distance to focus, you can do that by changing focal length--that is what an IF (internal focus) lens is.
 
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