Re: [Leica] image quality and format

[Ken Iisaka <kiisaka@pacbell.net>]

Erwin wrote:
> Now the format. A 35mm negative has an area of 864 square
> millimeters. To make the 6x6 format comparable, we need the same 2:3
> ratio for the Hasselblad negative and that is 38x56mm or 2101 square
> millimeters. So the Hasselblad has an advantage of 2.5 times for
> area. That implies that the same object that fills the frame in the
> Leica case, will fill the frame in the Hasselblad case with an
> advantage of  2.5 times. So now we have the situation that one square
> millimeter of image area in the Leica case has 2.5 square millimeters
> in the Hasselblad case. Assume that we need the limit of 40 lp/mm for
> the object details when taking the picture with the Leica. We need
> only 16 lp/mm for the Hasselblad picture to cover the same detail at
> the equivalent resolution. So OF COURSE the Hasselblad negative has a
> big advantage.

Actually, Hasselblad requires not 16 lp/mm but 26lp/mm (40 lp/mm * 36 mm
/ 56mm) to captures the same amount of information.  lp/mm is a unit in
one dimension only.  Alternatively, Hasselblad lens needs to perform as
well as a Leica lens at 40 lp/mm, at only 26 lp/mm.

With a more square, conventional 4x5 aspect ration photographs, the
comparison turns in favour of Hasselblad further: the usable negative
area from a Leica would be 24x30mm, where you could use as much as
45x56mm from a Hasselblad negative.  In this case, Hasselblad lens has
to perform at 21 lp/mm (40 lp/mm * 30mm / 56mm) to equal Leica at 40
lp/mm.

However, this comparison is only useful in certain picture taking
situations, or on a bench.  Leica is capable of capturing images not
possible with any other.  There is no equivalent of an M6 with Noctilux,
period.