[Leica] The SL
Sonny Carter
sonc.hegr at gmail.com
Wed Nov 4 19:51:24 PST 2015
Subject movement trumps wide open aperture.
from my iPad
Sonny Carter
> On Nov 4, 2015, at 9:36 PM, Frank Verizon1 <red735i at verizon.net> 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 gmail.com> 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 verizon.net>
>> To: "'Leica Users Group'" <lug at leica-users.org>
>> 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 verizon.net
>>
>>
>> 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
>> http://www.pbase.com/hoppyman
>>
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>
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