[Leica] M Lenses on GF-1

[henningw at archiphoto.com (Henning Wulff)]

Basically, it refers to lenses with exit pupils at infinity. For some 
purposes, double sided telecentricity is desired, which means that 
the entrance pupil is infinitely far behind the sensor.

Some sites with explanations, and also about some of the problems and 
disadvantages of telecentric lenses:

http://www.edmundoptics.com/technical-support/imaging/what-is-telecentricity/

https://www.schneideroptics.com/pdfs/industrial/telecentric_lenses.pdf

http://en.wikipedia.org/wiki/Telecentric




At 5:06 PM -0500 4/14/10, George Lottermoser wrote:
>I'd think extreme retrofocus designs to achieve maximum perpendicularity.
>
>Regards,
>George Lottermoser
>george at imagist.com
>http://www.imagist.com
>http://www.imagist.com/blog
>http://www.linkedin.com/in/imagist
>
>On Apr 14, 2010, at 4:48 PM, Jeffery Smith wrote:
>
>>  I don't really recall Olympus's exact wording. I think the only 
>>way to get perpendicular light rays to hit would be to have a very 
>>large diameter rear element, and still they would not be actually 
>>perpendicular, but maybe more perpendicular.
>>
>>
>>
>>  On Apr 14, 2010, at 4:22 PM, Henning Wulff wrote:
>>
>>>  The vignetting of the 45-200 is due to the attempt by Panasonic 
>>>to keep the lens as small as possible, so vignetting appears at 
>>>wider apertures due to cutoff of off-axis rays. If the vignetting 
>>>were due to light rays hitting the sensor at a too steep angle, 
>>>the aperture wouldn't make a difference. Also the latter is an 
>>>issue with shorter lenses where the rear exit pupil is too close 
>>>to the sensor. Not an issue with the 45-200.
>>>
>>>  As I mentioned before, the vignetting doesn't bother me since the 
>>>lens is only for digital use, and the software that I use 
>>>certainly has no problems fixing the vignetting if so desire.
>>>
>>>  BTW, that Olympus claim is not true; I'm not sure they actually 
>>>said that. Their lenses are 'more telecentric' than those of most 
>>>other manufacturers; true telecentricity causes so many problems 
>>>that it's really not worth it except for certain industrial uses.
>>>
>>>
>>>
>>>>  Is the vignetting due to the light rays hitting it at less than 
>>>>a perpendicular angle? One of Olympus's big selling points on 
>>>>their lenses is that the light path is exactly parallel to the 
>>>>APS-sized sensor behind the lens.
>>>>
>>>>  Jeffery
>>>>
>>>>
>>>>  On Apr 14, 2010, at 3:05 PM, David Rodgers wrote:
>>>>
>>>>>  I don't doubt what you're saying. I'm just a bit mystified how a lens
>>>>>  can vignette on a sensor that's half the size of film that it was
>>>>>  designed to cover. That hasn't been my experience with M lenses on 
>>>>> Micro
>>>>>  Four Thirds. I actually have to use Lightroom to add a little forced
>>>>>  vignetting because in many cases I like that look.
>>>>>
>>>>>  I'm also perplexed at how Contax G lenses can be materially better on
>>>>>  Micro Four Thirds than are Leica M lenses, or even CV lenses for that
>>>>>  matter. While I haven't used all on Micro Four Thirds I have used them
>>>>>  all on film and for the most part they're all pretty good. Thus I'm
>>>>>  curious as to why the performance would be so different on Micro Four
>>>>>  Thirds. What kind of adapters are you using?
>>>>>
>>>>>  The main issues I see in using Lumix lenses versus Leica M lenses on 
>>>>> the
>>>>>  GF-1 is that Lumix lenses have AF and Leica M lenses don't. It's easy 
>>>>> to
>>>>>  miss focus, particularly with the longer lenses wide open. A focus
>>>>>  assist LED in the viewfinder would be a nice feature to have.
>>>>>
>>>>>  Dave R
>>>>>
>>>>>
>>>>>  -----Original Message-----
>>>>>  From: lug-bounces+drodgers=casefarms.com at leica-users.org
>>>>>  [mailto:lug-bounces+drodgers=casefarms.com at leica-users.org] On 
>>>>> Behalf Of
>>>>>  Simon Ogilvie
>>>>>  Sent: Wednesday, April 14, 2010 3:03 PM
>>>>>  To: lug at leica-users.org
>>>>>  Subject: Re: [Leica] M Lenses on GF-1
>>>>>
>>>>>  I've used a variety of Leica and Voigtlander M lenses on a G1, and
>>>>>  also a couple of Contax G lenses (45/2 and 90/2.8).  Without exception
>>>>>  I found the M lenses disappointing with either smearing, vignetting or
>>>>>  other faults.  The Contax G lenses however are superb on the micro 4/3
>>>>>  format and I much prefer the 90 to the 90 Summicron and the 45 to my
>>>>>  (now sold) 50 Summilux.
>>>>>
>>>>>  I've also been a bit disappointed with the performance of the
>>>>>  Panasonic 45-200.  I haven't checked but it's possible most of the
>>>>>  shots I've taken have been at or close to full aperture, so the
>>>>>  vignetting at the long end is very noticeable.  It also doesn't appear
>>>>>  very sharp at the long end either.  Maybe the upcoming 100-300 will be
>>>>>  better - I hope so.
>>>>>
>>>>>  _______________________________________________
>>>>>  Leica Users Group.
>>>>>  See http://leica-users.org/mailman/listinfo/lug for more information
>>>>>
>>>>>
>>>>>
>>>>>  _______________________________________________
>>>>>  Leica Users Group.
>>>>>  See http://leica-users.org/mailman/listinfo/lug for more information
>>>>
>>>>
>>>>  _______________________________________________
>>>>  Leica Users Group.
>>>>  See http://leica-users.org/mailman/listinfo/lug for more information
>>>
>>>  --
>>>    *            Henning J. Wulff
>>>   /|\      Wulff Photography & Design
>>>  /###\   mailto:henningw at archiphoto.com
>>>  |[ ]|     http://www.archiphoto.com
>>>
>>>  _______________________________________________
>>>  Leica Users Group.
>>>  See http://leica-users.org/mailman/listinfo/lug for more information
>>
>>
>>  _______________________________________________
>>  Leica Users Group.
>>  See http://leica-users.org/mailman/listinfo/lug for more information
>
>
>_______________________________________________
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>See http://leica-users.org/mailman/listinfo/lug for more information

-- 

    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw at archiphoto.com
  |[ ]|     http://www.archiphoto.com