Archived posting to the Leica Users Group, 2007/09/01

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Subject: [Leica] Re: do it yourself back-focus adjustment..."
From: len-1 at comcast.net (Leonard Taupier)
Date: Sat Sep 1 10:57:11 2007
References: <98A0D67D-CE25-48F3-84D2-A34BBA5BEC1C@mac.com> <002001c7ec8b$e5295910$6400a8c0@corp.nortel.com> <5DDF2A59-8784-410E-9C7C-C56C8073DAB1@mac.com>

Bob,

I used the Leica Forum procedure as well but I was more rigorous than  
you were (and the forum) in the following two areas.

1. I did not use a flat target against the wall. That just tells you  
if you are in focus or not and not what the DOF is after each  
adjustment. I lined up about 20 CD's in their holders and positioned  
about 45 degrees to the film (sensor) plane of my M8. I also placed a  
12" ruler in front of the CD's and focused at the 6" point on the  
ruler. It looked like this:

http://tinyurl.com/3dtys4

2. After every adjustment I took 3 photos, wide open, closed two  
stops, closed 4 stops. This way I would know if there was any focus  
shift. I also used 7 lenses and took the 3 shots with every lens  
after each adjustment.. The lenses I used were the 50mm Noctilux,  
75mm and 50mm Summilux, 50mm Summicron, 90mmAA and 90mm macro and  
35mm Summicron. This exercise was performed over two day and took  
over 8 hours to complete. I believe the adjustment was made 4 or 5  
times in order to get it right with all of my lenses. That's about  
100 photos total.

The three lenses that were off the most were the Noctilux, the 75  
Summilux and the 90AA.

The end result was all my lenses are in focus except for the 135mm  
APO 3.4 at infinity. I don't care about that. I also found that  
photos look much better if the DOF is centered in front of rather  
then behind the target focus point. As an example if I take a tight  
portrait wide open and focus on the eyes, the nose will be in focus  
and the hair out of focus. That is my preference.

Len



On Sep 1, 2007, at 1:12 PM, Robert Rose wrote:

> Vick,
>
> The original idea to do this came from the Leica Forum.  Look there  
> if you want to find a more rigorous approach to the problem.
>
> Bob
>
> On Sep 1, 2007, at 4:33 AM, Vick Ko wrote:
>
>> Okay, now I understand.
>>
>> You are adjusting the RF arm.  I anticipate that it only takes a  
>> very very
>> small amount of adjustment.  If the adjustment is large, then you  
>> will end
>> up affecting the infinity alignment of the RF image.
>>
>> Congratulations on discovering this method.
>>
>> regards
>> Vick
>>
>> -----Original Message-----
>> From: Robert Rose [mailto:robert.rose@mac.com]
>> Sent: Saturday, September 01, 2007 2:33 AM
>> To: Leica Users Group
>> Cc: vick.ko@sympatico.ca; Leonard J Kapner
>> Subject: do it yourself back-focus adjustment..."
>>
>> Vick,
>>
>> We had a thread on this around March or so.  I had posted some  
>> samples and
>> how to do it at:
>>
>> http://gallery.leica-users.org/v/rjrose/focus/
>>
>> Bob Rose
>>
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information


In reply to: Message from robert.rose at mac.com (Robert Rose) ([Leica] do it yourself back-focus adjustment...")
Message from vick.ko at sympatico.ca (Vick Ko) ([Leica] RE: do it yourself back-focus adjustment...")
Message from robert.rose at mac.com (Robert Rose) ([Leica] Re: do it yourself back-focus adjustment...")