[Leica] Re: A lens question for technophiles

[durling at cox.net (Mike Durling)]

Getting to this late.  I'm not familiar with this model, but Arri cine 
cameras are basically SLRs.  On the classic models there is a rotating 
mirror that reflects light into the viewfinder when the shutter is 
closed.  The lenses have a fairly long focal distance so I suspect that 
the angle of the light rays to the film or sensor is fairly straight.

Mike D

Lawrence Zeitlin wrote:
> While browsing through the web, I came across the Arri (motion picture 
> camera) newsletter describing the D20 demonstration back allowing Arri 
> cine cameras to be retrofitted for video capture.
> 
> http://www.arri.de/news/newsletter/articles/09211103/d20.htm
> 
> One of the features of the D20 is that the frame size is the same as 
> that of normal 35 mm motion picture film, 18 x 24 mm. This allows normal 
> cine lenses to be used with the same field of view and focal range as 
> with film. This gives rise to several questions relevant to the Leica M8 
> and 4/3 lens concepts.
> 
> Motion picture frame size is about the same sensor size as that being 
> used in current digital DSLRs and the M8 and fractionally larger than 
> that used in the 4/3 system. The 4:3 cine aspect ratio is exactly that 
> of the 4/3 system. How does Arri use normal cine lenses with normal back 
> focus on a sensor this size without suffering all the image deleterious 
> effects so carefully described in the Leica literature. Similarly the 
> 4/3 literature describes the system as providing almost vertical impact 
> of light rays on the sensor. Obviously that cannot be the case with the 
> Arri approach. How does Arri sidestep the issue of light ray angularity 
> on the edges of the field? The web site didn't give the information but 
> surely someone on the LUG knows.
> 
> My Olympus Pen F SLR camera uses the exact same film size (1/2 frame) as 
> the Arri camera. The lenses are normal and compact. The camera, with 
> lens, is Leica LTM sized. The pictures are excellent. Wouldn't it be 
> nice to have a DSLR of similar dimensions?
> 
> Incidentally, for those concerned about the multiplication ratio between 
> frame or sensor sizes, a full frame 35 mm camera produces images only 
> 1.33 times larger than a 1/2 frame camera despite the fact of having 
> twice the film area. Further about 90% of the 1/2 frame area is used to 
> produce an 8" x 10" print while only 83% of the full frame negative is 
> used to product the same print.
> 
> While I don't dispute that bigger frame sizes in both film and digital 
> produce better image quality, the difference in quality is not always 
> proportional to the difference in area between frame sizes. If that was 
> the case, 35 mm would never have been adopted since a Zeiss Ikonta, with 
> a 36 sq. cm. image, folds into a package the same size as a Leica M with 
> an 8.64 sq. cm. image. So let's admit it, the desire for a full frame M 
> or DSLR digital sensor is based on convenience for existing lens 
> utilization rather than image quality. I suspect that the same is true 
> for DSLR cameras using the 4/3 format or the APS-C format.
> 
> Larry Z
> 
> 
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