Archived posting to the Leica Users Group, 2007/01/01

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] WTB : Noctilux (UK)
From: lug at (Steve Unsworth)
Date: Mon Jan 1 03:17:31 2007

Richard, but if that was happening then photographing the white wall I
mentioned would show different exposures for the two lenses, and it doesn't.

Remember that the aperture is the ratio between focal length and iris
diameter - so the aperture on a 35mm lens @ f1.4 is physically smaller than
f1.4 on a 50mm lens.


On 1/1/07 11:10, "Richard" <> wrote:

> Steve, I could be wrong, but think of it this way: the exposure value for
> the mid-tone must be the same, but the total number of photons gathered
> must be larger for wider angle lens.
> At 03:04 AM 1/1/2007, Steve Unsworth wrote:
>> I'm sorry Tina, but I don't get this. Imagine you were photographing a 
>> white
>> wall that filled the viewfinder for both the 35mm and 50mm lenses. The
>> exposure for each lens would be identical - i.e. both lenses would have 
>> the
>> same shutter speed / aperture. You can't say that because a lens is wider 
>> it
>> somehow sucks in more light at a given aperture - if that was the case 
>> hand
>> held meters wouldn't work over a range of focal lengths.

In reply to: Message from richard-lists at (Richard) ([Leica] WTB : Noctilux (UK))