[Leica] M8 upgrade - 90 Cron APO focusing problems now question

[cummer at netvigator.com (H&ECummer)]

Hi Len,
How good of you to do this testing in a systematic way! For my fast  
lenses, 50 Lux and 35 Lux, they both focus well enough on both film  
and digital bodies.
Only the 90 Cron APO gives me trouble.
Cheers
Howard

>
>
> Date: Sat, 13 Dec 2008 16:47:26 -0500
> From: Leonard Taupier <len-001@verizon.net>
> Subject: Re: [Leica] M8 upgrade - 90 Cron APO focusing problems now
>       Question????
> To: Leica Users Group <lug@leica-users.org>
>
> Aram,
>
> Actually it is true. Because of the back focus issues I had with my
> M8 I decided to test 11 lenses for DOF first with a film camera, then
> with an M8, (actually two M8s). Every one of the 11 lenses showed the
> center of the DOF shifted to the back when going from film to sensor.
> The shift was greatest with the faster lenses and also with the more
> telephoto lenses. In a couple cases the DOF shifted enough so the
> point where I focused was either at the very edge or outside of the
> DOF. The worst lens was the Noctilux followed by the 50 Summilux Asph
> followed by the 75 Summilux. I found the most accurate focus was with
> lenses built in the 50s, like the 50mm Summicrons and even the 1.5
> Summarit. My 90mm AA was fine. But every Leica lens I have tested has
> a focus shift when going from film to digital. The shift with 8 of
> the 11 lenses was acceptable.
>
> Len