Archived posting to the Leica Users Group, 2008/04/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Steve, the bit coding correction is basically only significant for wides. With coding but no filter the firmware corrects for some vignetting effect known from that lens. With filter but no coding the magenta effect from IR sensitivity is defeated but you may see a cyan corner effect. With filter and coding (plus setting in menu), the vignetting and the cyan corner effect from the filters is corrected. Each of those issues may or may not be significant for you dependant on subject, photographic style and personal taste. Presence of either of these effects does not cause catastrophic problems. For some styles it may not concern you at all. Two free filters for each M8 you buy. Tony Rose, for one has deals on extra filters. I don't know US pricing. In Australia each lens costs AUD 341 total for shipment to Germany, coding and return. Cheers Geoff http://www.pbase.com/hoppyman/e http://gallery.leica-users.org/v/gh/ -----Original Message----- Subject: Re: [Leica] IMG: the episode in which Hoppy becomes a criminal On Apr 23, 2008, at 9:22 PM, Henning Wulff wrote: > At 6:37 PM -0700 4/23/08, Steve Barbour wrote: >> On Apr 23, 2008, at 5:42 PM, Tina Manley wrote: >> >>> At 08:33 PM 4/23/2008, you wrote: >>> >>>> so the coding has nothing to do with outcome or photo quality, just >>>> puts the lens into the exif...is that correct? >>>> >>>> >>>> Steve >>> >>> I read somewhere - I can't find it now - that the coding would >>> optimize the performance of the lens - addressing known vignetting >>> and color balance issue, particularly with wide angle lenses. >> >> >> rings a bell for me too Tina, but is this true ?! >> >> Somehow I wonder if it turned out to be speculation. >> >> >> Steve > > The coding provides vignetting correction for most lenses, but this > is of course more important for wide angle lenses. For lenses > shorter than 35, coding is definitely of benefit as it corrects for > the 'cyan corners' caused by the steep incoming angles of light > which causes 'frequency shifting' on lenses equipped with the UV/IR > cut filters. so it appears that the problem and therefore the coding benefit is seen with color, and only with UV/IR filters... Is this cited somewhere in Leica's technical support as I searched without success. Steve > > > The filters are interference filters, and do their job by the > interference of reflected radiation within the coating layers of the > objectionable wavelengths. When the angle gets steeper, the > incorrect wavelengths get cut; in this case the deeper red and not > just the IR wavelengths, therefore the cyan colour. > > If the camera knows the lens characteristics, it can do some pre- > processing on raw as well as jpeg files and counteract this > undesirable effect, and give consistent colour response across the > whole frame. The Wide Angle Tri-Elmar would be unusable with an IR/ > UV cut filter without such coding. > > The EXIF data on lens and focal length is just a side benefit of > this. Vignetting is also easy to correct in software if desired. > > I wouldn't bother sending perfectly functioning lenses in to get > coded if it weren't for this correction that the camera does. I have > a 28 Summicron where the cyan corners are just detectable, so I will > send in the lens at some point, but 35 and longer won't get sent in. > > -- > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information best, Steve "I never wanted to be famous" http://www.blurb.com/bookstore/detail/186890 _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information