Archived posting to the Leica Users Group, 2014/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search];^) ric On Mar 21, 2014, at 11:16 AM, Geoff Hopkinson <hopsternew at gmail.com> wrote: > 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 >> > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information