Archived posting to the Leica Users Group, 2012/07/22

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Subject: [Leica] Some technical speculations re: rangefinder
From: jsmith342 at gmail.com (Jeffery Smith)
Date: Sun, 22 Jul 2012 17:53:06 -0500
References: <CAF8hL-EMSebH=YGfXU=qpuVyMbZxGjfH9cebK-BNVAS6oCMMkQ@mail.gmail.com> <p06240809cc308b2b92c9@192.168.1.103> <CAF8hL-H0Pne4ev8Q4Du2WD+8tGafOVa2YQ4r-m7qtzda+iBK-Q@mail.gmail.com> <p0624080ccc3121a4d6cf@192.168.1.103> <CAE3QcF4sTKjyGFWTgNf8xry==V0Cj3BpXvjtxxKA15ujBREc-A@mail.gmail.com> <8AE125E92F06484E99813B22B29761CB@syneticfeba505> <p0624080ecc315993f2df@192.168.1.103> <CAF8hL-FObtdfK56O7Ho_kQiG5SJxdfE9ykYD+w1Z_j6Zb5mcXQ@mail.gmail.com> <024301cd6830$74943000$5dbc9000$@earthlink.net> <p0624080fcc322fee2fb0@[192.168.1.103]>

In Nikons, I think that was called a K-Screen. 

Sent from my iPad

Jeffery L. Smith
New Orleans, Louisiana
USA

On Jul 22, 2012, at 17:40, Herbert Kanner <kanner at acm.org> wrote:

> If you remember film SLR cameras, they all had a focusing aid in the 
> center of the screen, implying that just focusing on a ground glass was 
> sometimes difficult. The first kind I saw were a couple of shallow crossed 
> prims in the center, giving the effect of a split image rangefinder. Years 
> ago, I did a calculation that I don't think I'm competent to repeat now, 
> but the calculation showed that the image separation of the simulated 
> rangefinder was equivalent to that of a true rangefinder whose base was 
> the diameter of the lens aperture--i.e. piss poor. Then a better thing 
> showed up, a large cluster of micro prisms in the center. The hand shake 
> of even the steadiest photographer was enough to make an out of focus 
> image shimmer. However, on a tripod, this system was useless.
> 
> So, a viewfinder display derived from the image on the sensor would be at 
> best equivalent to that on a ground glass. To be practical, this would 
> have to be supplemented by a display of the kind of signal that actuations 
> auto-focus systems, for example, an indication of local contrast, which 
> decreases when going out of focus.
> 
> Herb
> 
> 
>> Can't be THAT hard.  It would amaze you what can be done in SW, and then
>> implemented in HW.
>> 
>> If you make it a priority of your design team......
>> 
>> But let me go back to basic RF cameras.....
>> 
>> If you employ LiveView in the VF ( which I believe is called EVF or
>> something like that), and you use a really good LCD/LED display for the
>> image, you are basically looking through a SLR camera. Better than that is
>> the fact that you are actually looking at the "film" plane .  No more out 
>> of
>> focus adjustment cameras or lenses.... WYSIWYG.  Period. Make the LCD a
>> really good one, and it would make a surprisingly good focusing system.
>> Noctilux capable.....
>> 
>> Did I mention cheap?  I should have.....
>> 
>> And the implementation of AF is pretty easy, but then again, how do you 
>> make
>> the M mount lenses move in and out for focusing?  Move the mounting plane?
>> 
>> Personally, I like the idea of an EVF.....
>> 
>> I do not like the idea of a big honking rear mounted LCD that is my 
>> primary
>> focusing and viewing device... Ii think those are insufficient to promote
>> good technique.
>> 
>> Let's just hope Leica actually makes a M10 at a price point we can
>> afford.... God knows, the M9 MSRP was way above mine.....
>> 
>> ( Thanks John.....!)
>> 
>> Frank Filippone
>> Red735i at earthlink.net
>> 
>> 
>> 
>> 
>> _______________________________________________
>> Leica Users Group.
>> See http://leica-users.org/mailman/listinfo/lug for more information
> 
> -- 
> Herbert Kanner
> kanner at acm.org
> 650-326-8204
> 
> Question authority and the authorities will question you.
> 
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information


In reply to: Message from richard at richardmanphoto.com (Richard Man) ([Leica] Some technical speculations re: rangefinder)
Message from richard at richardmanphoto.com (Richard Man) ([Leica] Some technical speculations re: rangefinder)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Some technical speculations re: rangefinder)
Message from tedgrant at shaw.ca (tedgrant at shaw.ca) ([Leica] Some technical speculations re: rangefinder)
Message from richard at richardmanphoto.com (Richard Man) ([Leica] Some technical speculations re: rangefinder)
Message from red735i at earthlink.net (Frank Filippone) ([Leica] Some technical speculations re: rangefinder)
Message from kanner at acm.org (Herbert Kanner) ([Leica] Some technical speculations re: rangefinder)