[Leica] Re: A lens question for technophiles

[lrzeitlin at optonline.net (Lawrence Zeitlin)]

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