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

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

Hi Aram,
Film has a bow in it as it sits in the camera but the surface of the  
M8 CCD is perfectly flat. At f2.0 my Cron (although within spec  
according to the Schmidt repair department) is mismatched enough with  
my M8 that it back focuses. On my film camera (M4) the bow in the film  
compensated for the back focus. Expressed another way - there is a  
tolerance for correct focus in the depth of film which is not there  
for the flat single plane of the CCD. Hence lenses need to be more  
accurately adjusted for the M8 than for film cameras.
Perhaps come experts will weigh in on this.
Cheers
Howard
On 14 Dec 2008, at 3:38 AM, lug-request@leica-users.org wrote:

> Message: 22
> Date: Sat, 13 Dec 2008 11:09:36 -0800
> From: "Aram Langhans" <leicar@q.com>
> Subject: [Leica] M8 upgrade - 90 Cron APO focusing problems now
>       Question????
> To: <lug@leica-users.org>
> Message-ID: <BLU121-DS3010D2ED63D287290714FD4F60@phx.gbl>
> Content-Type: text/plain; charset="windows-1250"
>
> Question.  I am not an M user, but am curious.  How can this be?   
> How can a
> lens focus properly on a film camera but not on the digital M?  If  
> this
> happened with every lens, I could understand that - something out of  
> whack
> with the camera.  But if other lenses that worked on a film camera  
> also work
> on the digital M, why would one lens behave this way?
>
> Aram, the curious R user.