[rollei_list] Re: Bright Screens

Maxwell screens come with DIY instructions, but a surprising number of people 
put screens in upside down – two of my Rolleis came that way.  

I've always had Krikor or Mark Hansen install the screens and colimate the 
lenses at the same time.  Mark says that the majority of TLRs he works on need 
this (he does Rollei & Zeiss).  

IMO lens calibration should be done by a tech who has a colimator & doesn't 
just eyeball the focus on a piece of ground glass.  But you could do the latter 
yourself.  

Krikor's Rollei colimator sets lenses so 60' = infinity; Mark, Infinity = 
infinity.  I've heard that some techs put a piece of film in the camera for 
'average curl,' while some use a piece of mirror, for absolute flatness.  
Apparently there are diffferent approaches to this.

Kirk

Subject: [rollei_list] Re: Bright Screens
From: starboy0@xxxxxxxxxxxxx
Date: Tue, 3 Jan 2012 17:17:17 -0600
To: rollei_list@xxxxxxxxxxxxx



Kirk,
Were you able to install the Maxwell grid screen yourself?  Thought I read 
somewhere the focussing mechanism needs to be recalibrated which can be 
problematic.
Thanks,
Bob



On Jan 3, 2012, at 5:03 PM, Kirk Thompson <thompsonkirk@xxxxxxxxxxx> wrote:





Not a further thought, but a previous one that didn't make it into your summary:
Bill Maxwell makes two types of focusing screens: plain ones with grids, and 
others with split-image focusing aids. User reports in this thread and 
elsewhere have spoken more favorably of the former.  
'Additional data': Maxwell himself recommends the plain grid screen. When 
you're ordering by phone, he can go on at some length about this.  
Maxwell seems to offer the split image screens just because people keep asking 
for them.  Just a guess: prior to autofocus, the majority of DSLRs had a 
split-image focusing aid.  In the absence of experience, people have perhaps 
tended to ask for what looked familiar.  That was my own mistake, until I tried 
the plain-grid one.  
KirkTo: rollei_list@xxxxxxxxxxxxx
From: cuffe@xxxxxxx
Subject: [rollei_list] Re: Bright Screens
Date: Tue, 3 Jan 2012 22:13:17 +0000

This is a wonderful summary in a complex area where opinions are divided. As a 
group I would expect our powers of observation to be particularly good, hence 
the diversity of opinion indicates to me that there may be something deeper 
going on here than just a subjective diversity of opinion. I'm trying to think 
of some optical reason why one type of screen could suit some users better than 
others.The factors I'm coming up with are in order of significance:Ability to 
close focusMaximum pupil diameter, as it affects the depth of field available 
for the eye to accommodate.After these two I find myself considering usage 
patterns which might affect users perceptions of utility.Here again  I list 
these in my perceived order of importance:Preferred viewing distance i.e with 
magnifying lens up to the eye or truly at waist level.The relative importance 
of center and peripheral image areas,A users knowledge of and customary use of 
auxiliary features such as micro prisms, or grid lines for aligning the image.
Has any one any further thoughts on this or data to add?
All the best
Laurence Cuffe


                                          
                                          

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