Archived posting to the Leica Users Group, 2003/12/14
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At 9:26 AM +0000 12/14/03, Frank Dernie wrote:
>So much for all the bullsh*t about angle of incidence at the sensor
>then eh! If the last element is almost touching the sensor the angle
>of incidence will be very large unless, I suppose, the periphery of
>the lens element is not used but then why would it be there?
>Frank
>
>
>On Sunday, December 14, 2003, at 08:16 am, Eric Welch wrote:
>
>>A MUCH shorter focal length. And have you seen the diagram of the
>>internals of the Digilux2? The last element is almost touching the
>>sensor. With longer focal lengths, and a shutter in the way, you
>>have your answer.
>>
>>On Dec 13, 2003, at 9:56 AM, eric wrote:
>>
>>>The body and lens dimensions look so very M rangefinder.
>>>So again - Why can't they design a digital M body?
>>>I know it has been discussed at length about angles of incidence and sensors
>>>not up to the task - but what is so different about the digilux 2 that
>>>precludes designing a body to accept M lenses?
>>Eric
>>Carlsbad, CA
Well Frank, the fact that the rear lens element is almost touching
the sensor has almost nothing to do with whether the angle of
incidence is high or not. With a lens designed for digital use, the
design usually attempts to include a rear element or group that
'straightens out' the incident rays; such elements are often placed
relatively far back in the lens. I would think that this would be the
case. The lens design would include a collector group at the front, a
zoom group possibly combined with a focussing group, and then, at the
back, a rectifier group that will reduce the angle of incidence. This
the way most digicam lenses are constructed.
Lenses designed for film cameras, especially rangefinder cameras,
don't need to have the light rays descend on the film
perpendicularly, and therefore aren't designed that way because doing
so creates other problems. Have you noticed the rather severe
distortion that most digicam lenses have? This is one of the
consequences. In a couple of years this will probably get worked out,
but for now it is a problem.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
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