Archived posting to the Leica Users Group, 1998/05/27
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> >I recall that all versions of the 2.8/21 are retrofocus. The Russian >Russar MR-2 is not retrofocus and, of course, does allow metering, so it IS >possible to design a non-retrofocus 20mm lens which will allow metering. I >seem to remember that the Canon 19mm also allows metering on an M6, as does >the non-retrofocus 8/15 Zeiss Hologon. > >Marc Hellio all, PMFJI but it seems to me that all this talk about lens designs is rather irrelevent in the real world: sure, view camera wide angles are true wide angles and very wonderful but to get the best from them you need the centre grad filters to match. BUT surely the situation in 35mm photography is different. You are not normally using a tripod and f16 is not the usual f-stop for 35mm shooting, centre filters are an inconvenience at least and TTL metering would be impossible with such lenses. Hence the Hologon 15/16 is just an interesting special usage/exotic lens that has a market in the 3 figures max amongst professionals* world wide. Oh yes - I had a Canon 19mm lens once and thought it was awful - lots of flare and fuzzy corners but very nice colour. Nice viewfinder though! A non-retrofocus lens offers the theoretical advantage of a simpler design and hence better manufacturing consistency plus smaller size but vignetting is really a problem especially with exposure-sensitive colour transparency film. The simpler design precludes the use of filters or TTL metering or wide maximum apertures. Leica's practical choice to go for a semi-retrofocus 21mm design offers the possibility to improve the vignetting and TTL metering situation without going to quite the extreme of SLR lenses which have to be more complex and larger to accommodate the mirror. OTOH they cannot enjoy floating elements since such innovations cause a slight change in focal length at different distances and would play havoc with the RF coupling precision. All cameras and all lenses represent a compromise and those who search for perfection must first understand the specific requirements for the situations they face then assess the options available - not the other way around. There is no perfect lens. Rgds Adrian *FWIW a professional is IMHO somebody who produces photographs to order. A great photographer OTOH is somebody whose style dictates what is ordered. Money is a sticky, smelly substance that oozes in the general vicinity of both the above and not necessarily in the wallet of the photographer... Adrian Bradshaw Photojournalist Shanghai, China