Archived posting to the Leica Users Group, 2014/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 >> > > > --- > This email is free from viruses and malware because avast! Antivirus > protection is active. > http://www.avast.com > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >