[Leica] Noctilux DOF Film vs M8

[hoppyman at bigpond.net.au (Geoff Hopkinson)]

Len it IS a very interesting issues for M8 users and subject to quite a lot
of discussion in the Leica forum, some more objective than others! When you
mention focus shift and back focus, firstly are you talking about each lens
shot wide open or the sharpest plane moving as you change the aperture?
That is two separate things, I think.
LFI reports Leica's position as that the focus shift when stopping down a
little has always been there (with fast lenses) but is more detectable with
the M8 due to several factors. Purportedly, only the 50 asph and the 75AA
that shares its design are immune.
What apertures are you testing all of those lenses at? You are testing I
think, at 8 feet? The comparison could only be valid at the same aperture.
I have heard about the infinity point adjusting in the M8 body, but the
shimming is new to me. The DoF of each lens cannot change at the same
aperture and focus distance surely. Certainly you could shift the focus
point with either method. What works in practice may have theoretical or
actual disadvantages I would think?
No question but that I am noticing missing focus with the 50 asph using it
close-up stopped down to f4 or so. I did the same on my M7. I think that it
is operator error. The 1.25 magnifier seems to help. 
Cheers
Geoff
http://www.pbase.com/hoppyman/e
http://gallery.leica-users.org/v/gh/

-----Original Message-----
Subject: [Leica] Noctilux DOF Film vs M8

This is a very interesting issue. I don't know if anybody has  
mentioned what happens to the depth of field of the Noctilux, or any  
other lens, in a Leica film camera versus the M8 digital camera. It  
seems that nobody complains about the focus on a film body but all  
kinds of complaints on the M8, especially the Noctilux, Summilux Asph  
and the 75mm Summilux. Is there a difference? Yup, there sure is. I  
tested 16 leica lenses for depth of field at a distance of 8 feet. I  
tested 13 of the lenses with film using a .85 MP and compared the  
results to those taken with an M8 and a 1.25 Leica magnifier.

In every case the DOF shifts away from the camera with the M8. In  
other words the lens appears to back focus. The worse lens for this  
shift is the Noctilux. But even on a film camera it is barely in  
focus. The typical back focus shift of any 50mm Leica lens is about 4  
to 5 inches at 8 feet with the M8. The backward shift of the Noctilux  
is between 8 and 9 inches. This puts the focused point of the  
rangefinder outside the depth of field of the lens. The other thing I  
noticed is the DOF is better centered on the older LTM lenses then on  
the newer lenses. I don't know if this is a quality control problem  
now or if the focus point test has changed. I tested 7 LTM lenses,  
the Xenon, Summarit, Summitar, Summicron Coll, 50 Elmar RS, 90 Elmar  
and 135 Hektor. The focus point nicely stayed within the DOF on both  
cameras. Of the M lenses the best is the 1st 50mm Summicron rigid  
version followed by the current 50mm Summicron.

I verified my results with a second M8. The MP body is one year old  
and purchased new. I also sent my Noctilux and 75mm Summilux to DAG  
for focus adjustment even though the lens is still in warranty. I'm  
also shooting more with film these days.

Len



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