Archived posting to the Leica Users Group, 2003/02/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
At 9:30 AM -0800 2/14/03, Jacques Bilinski & Barbara Bradbury wrote:
> > I'm sure this has been covered but why would you test a lenses/bodys focus
>> using a wide angle @ infinity? Wouldn't you want to use a tele @ the
>minimum
>> focusing distance ???????????????????????????????????????????
>>
>
>You want to do the test at infinity rather than a close focus distance in
>order to test the lens/body compatibility independantly of the rangefinder
>adjustments. Rangefinders in RF cameras easily get out of adjustment if the
>camera is banged, and this won't play a part in the test if you do it at
>infinity.
>
>You want the widest aperature lens you have in order to minimise the depth
>of focus (i.e. depth of field inside the camera at the film plane).
>
>Focal length doesn't matter, contarary to what is often written on this
>list. Best lens for this test is a Noctlux.
Focal length can make the test easier because if the flange - film
distance is 1mm too large, the lens will be focussed at a shorter
distance; with a wide angle lens this distance will be significantly
closer to the camera than with a longer focal length lens, and thus
the discrepancy will show up. As I mentioned before, if the
discrepancy between the Hexar and the Leica bodies is as large as
some have said, a 35 lens would focus at about 6m instead of
infinity. A Summilux wide open would show this discrepancy easily. A
Noctilux would focus at about 12m with the same film - flange
discrepancy; that is why it is easier to see with a wideangle lens.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
- --
To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html