Archived posting to the Leica Users Group, 2014/03/21

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Subject: [Leica] Vignetting in FF digital Ms
From: hopsternew at gmail.com (Geoff Hopkinson)
Date: Sat, 22 Mar 2014 01:16:14 +1000
References: <07856C10-1788-4FF9-8E79-E985BBE9578A@bex.net> <CAE3QcF7ooA_L93xrEO15FkTveONTs4FFUSNaYjXar50MQmL1XA@mail.gmail.com> <2F0AB1B4C1E04BD6A46AF7D25BAF13B7@syneticfeba505>

Sorry master! I will go and shoot more instead ;-) ;-)
I got some vignette for ya right here!
http://www.pbase.com/hoppyman/image/154913493


Cheers
Geoff
http://www.pbase.com/hoppyman


On 22 March 2014 01:05, <tedgrant at shaw.ca> wrote:

> Geoff Hopkinson OFFERED:
>
> Gee Geoff I didn't know you were describing my ARGUS A2 1950 model! ;-) ;-)
>
>
> " <hopsternew at gmail.com>
> To: "Leica Users Group" <lug at leica-users.org>
> Sent: Friday, March 21, 2014 6:40 AM
> Subject: Re: [Leica] Vignetting in FF digital Ms
>
>
>  Well now Howard that is quite a topic you have broached ;-) Before Dr Ted
>> reminds me that only content matters ultimately (as is true of course) I
>> shall dive in.
>>
>> For some attempt at clarity (post brevity not being my strength!) I will
>> just talk about the specific hardware you mentioned, although the
>> principles are more generally relevant.
>> Wide open the lens you mentioned has 2.5 stops of vignetting. How much of
>> that do you consider ought to be corrected out? There's no wrong answer of
>> course just preference.That is what you got with positive film previously
>> though.
>> The camera corrections are also non-aperture dependent. That is to say
>> that
>> a single (compromise aperture value I guess)  (less vignetting when
>> stopped
>> down) is corrected for because neither the  M9 nor the M (typ 240) can
>> reliably determine the exact aperture used due to the legacy designs. A
>> new
>> system (S & X for example) and I guess T? is not so limited. By brightness
>> sensor value comparison estimate the M full frames might be within say a
>> stop/stop and a half or two at worst. If the (single) correction value per
>> lens was set at that for the worst case (wide open) you would get
>> over-correction at smaller apertures. Actually odd lighter corners and at
>> the expense of increased noise/ more loss of dynamic range there to do so.
>> All correction is a compromise with some loss of quality in those corners.
>> That may or not matter at all or be noticed.
>>
>> The camera is also making significant correction for every image for basic
>> homogeneity because the 1954 fundamentals were just never designed for
>> optimum use with a sensor.That includes asymmetric colour shift which is
>> an
>> optical reality with all systems more or less (Italian Flag) as well as so
>> called red edge syndrome. That fundamental is why M digital sensors have
>> their unique microlens arrangements in the first place and why the legacy
>> wides in particular are compromised when adapted to other systems' sensor
>> (Sony being the current prominent example).
>>
>> Phew, that ought to kick the discussion off, or get filtered out because
>> my
>> name is on the top!  ;-)
>>
>>
>>
>>
>>
>>
>> Cheers
>> Geoff
>> http://www.pbase.com/hoppyman
>>
>>
>> On 21 March 2014 21:50, Howard Ritter <hlritter at bex.net> wrote:
>>
>>  In doing some preliminary exploratory shooting with my new M240 and the
>>> previous-generation 35mm Summilux ASPH, I encountered the inevitable
>>> severe
>>> fall-off of illumination at the corners, as I expected. What I did not
>>> expect was that the M's built-in lens correction feature would reduce
>>> this
>>> by only a subjective 50% or so, leaving a prominent and very
>>> disappointing
>>> degree of vignetting still to be seen.
>>>
>>> I realize that this can be easily corrected in post-processing, e.g.
>>> Lightroom, PS, and DxO, but my question is WHY? Why would Leica
>>> engineers,
>>> after recognizing the problem, creating a software correction to it, and
>>> deciding to incorporate that correction into the FF M digital camera,
>>> then
>>> proceed to implement it in such a half-assed fashion? Clearly a full
>>> correction is straightforwardly implementable in post-processing, so why
>>> not write the firmware to accomplish it rather than hobble it to perform
>>> a
>>> half-correction?
>>>
>>> Anybody know the reasoning behind this? Or am I missing some feature that
>>> would actually give full correction? And when correcting for this in
>>> Lightroom etc., what do most of you do? Let the camera do its bit and
>>> then
>>> finish it, or simply dispense with the built-in correction and do
>>> everything in LR? Will LR and the other software suites with built-in
>>> corrections for various lens and body combinations even perform properly
>>> with the M's built-in correction applied?
>>>
>>> Thanks for any suggestions.
>>>
>>> --howard
>>>
>>>
>>> _______________________________________________
>>> Leica Users Group.
>>> See http://leica-users.org/mailman/listinfo/lug for more information
>>>
>>>
>> _______________________________________________
>> Leica Users Group.
>> See http://leica-users.org/mailman/listinfo/lug for more information
>>
>
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Replies: Reply from ric at cartersxrd.net (RicCarter) ([Leica] Vignetting in FF digital Ms)
Reply from tedgrant at shaw.ca (tedgrant at shaw.ca) ([Leica] Vignetting in FF digital Ms)
In reply to: Message from hlritter at bex.net (Howard Ritter) ([Leica] Vignetting in FF digital Ms)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Vignetting in FF digital Ms)
Message from tedgrant at shaw.ca (tedgrant at shaw.ca) ([Leica] Vignetting in FF digital Ms)