[Leica] Noctilux DOF Film vs. M8

[freakscene at weirdness.com (Marty Deveney)]

Every camera lens you can buy is loaded with abberrations, even the 50/1.4 
and 75/2 asphs from Leica which are probably among the best you can 
currently buy.  Some abberrations are more obvious than others.  As Henning 
noted, perfection is a long way off.

Focus shift is important in all optical systems where spherical abberrations 
are the main limiting factor for resoltuion.  This is the case for the 
Noctilux.  At going from f1 to f2 the Noctilux focus shifts 74 microns 
closer than the gain in depth of field.  Between f2 and f5.6 the shift is 
120 microns greater than depth of field.  This is enough to visibly lower 
contrast in enlarged prints due to slight softening.  Resolution is harder 
to assess, but Erwin makes it clear that it was visible on the test bench.

I've always been sceptical about Erwin Puts' independance.  Leica has his 
'Leica M lenses - their Soul and Secrets' (a stupid title if ever there was 
one) on their website (for example, on the Noctilux page 
http://en.leica-camera.com/photography/m_system/lenses/2182.html click 
'Know-how' to open the .pdf).  This document mentions nothing of focus 
shift, only describing the imaging characteristics of the Noctilux when 
stopped down with reference to the figures from his website with adjusted 
focus.  No mention of focus shift.  That smells like advertising to me.

If Leica design and build a 50/0.95, they have much better technology 
available to them than they did in the 1970s when the 50/1 was designed.  
They can include one or more aspheres more easily and can include a floating 
element.  These will assist in managing focus shift by limiting spherical 
abberration.  I cannot, however, imagine how they can build such a beast 
without it being even heavier than the Nocti, unless they lighten the 
barrel.  The prospect of such a lens is pretty exciting, even if the 
additional speed is only minimal.  A full stop to f0.7 would be 
unmanageable, for any number of reasons - can you imagine the size of such a 
thing?

Most of the shots in my Russia gallery (URL below) were shot with the 
Noctilux; one notable exception being the photo of the guy sitting near the 
boats (St P XXXV) on the eighth page; the loss of contrast in the upper 
third of the photo is definitely from flare that was characteristic of my 
former 50/2 Summicron, which did this often.  I enjoy the Noctilux 
immensely, but its limitations are real.  Mine doesn't focus very well on my 
M8 at all, but it's fantastic on my film Ms.

M


Gallery:
http://gallery.leica-users.org/main.php?g2_itemId=7617

Most people can only judge of things by the experiences of ordinary life, 
but phenomena outside the scope of this are really quite numerous.
        Shen Kuo - 'Dream Pool Essays'


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