Archived posting to the Leica Users Group, 2015/11/04

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Subject: [Leica] The SL
From: sonc.hegr at (Sonny Carter)
Date: Wed, 4 Nov 2015 21:51:24 -0600
References: <> <>

Subject movement trumps wide open aperture.

from my iPad

Sonny Carter

> On Nov 4, 2015, at 9:36 PM, Frank Verizon1 <red735i at> wrote:
> All true , but nothing trumps the sccuracy of a fully wide open aperture
> Frank Filippone
>> On Nov 4, 2015, at 10:22 PM, Geoff Hopkinson <hopsternew at> 
>> wrote:
>> Yep didn't forget that. I was attempting to explain that if the lens was
>> already at the shooting aperture (like an M lens for example) it may be
>> that an EVF can still display a bright enough image for focussing (that is
>> your EVF brightness is controllable).
>> Focus at the shooting aperture of course defeats any focus shift (for
>> example from f/1.4 to f/4). Much depends on what you are shooting I 
>> imagine.
>> Just played with this on the XT1 and the Summilux 50 ASPH down to f/8.
>> However personally I have never found DoF preview sufficiently precise or
>> particularly useful in any camera at all from the 70's forward. I may be 
>> an
>> outlier there ;-)
>> ---------- Forwarded message ----------
>> From: Frank Filippone <red735i at>
>> To: "'Leica Users Group'" <lug at>
>> Cc:
>> Date: Tue, 03 Nov 2015 22:35:51 -0800
>> Subject: r
>> Yes, all true.....but you forget that DOF is, for example at F8, greater
>> than at F2.  So focusing is much less precise without auto stop
>> down..........
>> Frank Filippone
>> Red735i at
>> Do I have it right that the desire for automatic diaphragm control is for
>> focus at maximum aperture then stopping down to shooting aperture at the
>> moment of exposure?
>> Doesn't the use of the EVF potentially permit the finder brightness to be
>> controlled? If the lens is stopped down (ie not operating with auto
>> diaphragm) of cause the image arriving at the sensor is what is used for
>> focussing. So the desire for auto diaphragm control comes from the OVF
>> systems?
>> M lenses of course are already being employed with the initial SL units in
>> the field.
>>> You can get autoexposure only if the camera knows what the open
>>> aperture and the taking aperture are. If the lens does not generate
>>> those info, then some kind of manual system is needed
>> Autoexposure with TTL metering in apertured-preferred mode is simple with 
>> no
>> auto-diaphragm, no data other than light, ISO and shutter speed is needed.
>> With TTL metering and an automatic diaphragm the camera needs to know the
>> difference between open aperture and working aperture.  It does not need 
>> to
>> know what the actual open aperture is or the actual working aperture, only
>> the difference.  Any other data is extra and can be used for the user's
>> convenience, but is not required for autoexposure function.
>> Cheers
>> Geoff
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>> Leica Users Group.
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Replies: Reply from george.imagist at (George Lottermoser) ([Leica] The SL)
In reply to: Message from hopsternew at (Geoff Hopkinson) ([Leica] The SL)
Message from red735i at (Frank Verizon1) ([Leica] The SL)