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

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Subject: [Leica] Vignetting in FF digital Ms
From: ric at (RicCarter)
Date: Fri, 21 Mar 2014 12:09:04 -0400
References: <> <> <2F0AB1B4C1E04BD6A46AF7D25BAF13B7@syneticfeba505> <>



On Mar 21, 2014, at 11:16 AM, Geoff Hopkinson <hopsternew at> 

> Sorry master! I will go and shoot more instead ;-) ;-)
> I got some vignette for ya right here!
> Cheers
> Geoff
> On 22 March 2014 01:05, <tedgrant at> wrote:
>> Geoff Hopkinson OFFERED:
>> Gee Geoff I didn't know you were describing my ARGUS A2 1950 model! ;-) 
>> ;-)
>> " <hopsternew at>
>> To: "Leica Users Group" <lug at>
>> 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
>>> On 21 March 2014 21:50, Howard Ritter <hlritter at> 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 for more information
>>> _______________________________________________
>>> Leica Users Group.
>>> See for more information
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In reply to: Message from hlritter at (Howard Ritter) ([Leica] Vignetting in FF digital Ms)
Message from hopsternew at (Geoff Hopkinson) ([Leica] Vignetting in FF digital Ms)
Message from tedgrant at (tedgrant at ([Leica] Vignetting in FF digital Ms)
Message from hopsternew at (Geoff Hopkinson) ([Leica] Vignetting in FF digital Ms)