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

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Subject: [Leica] The SL
From: red735i at (Frank Verizon1)
Date: Wed, 04 Nov 2015 22:36:28 -0500
References: <>

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
> _______________________________________________
> Leica Users Group.
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Replies: Reply from sonc.hegr at (Sonny Carter) ([Leica] The SL)
In reply to: Message from hopsternew at (Geoff Hopkinson) ([Leica] The SL)