On Sep 25, 2013, at 2:02 AM, Alexandru-Cristian Sarbu <[email protected]> wrote:
> On Tue, Sep 24, 2013 at 10:19 PM, Godfrey DiGiorgi <[email protected]> wrote: >> ...However, neither M nor F mounts are ideal for 24x36mm digital >> sensors—they can be made to work, but ideally a lens mount for a digital >> sensor should be larger diameter relative to the format and a shorter >> registration distance ... > > It might not be ideal, but they work pretty well; surprisingly, the M > mount has more issues due to the small registration distance > (requiring offset microlenses to compensate). The M mount has a short registration, but the lenses designed for the M mount were not originally designed for a digital sensor. That's the issue there, not the short registration. The reason a short registration distance is favorable to digital sensors is that you can design the lens to have more elements behind the primary nodal point to help re-direct the light path across the image field to intercept the sensor orthogonally. This was not a consideration in designing lenses for use with film, and for compactness reasons (amongst others) RF film camera lenses were designed with very tight primary nodal point to imaging plane distances. SLR film camera lenses had to clear the swinging mirror, which was the primary reason for the deep mount registration and fostered lens designed that were 'naturally' more akin to digital sensor lens designs. >> Canon was roundly dissed when they obsoleted the FL/FD mount in the 1980s >> and thereby obsoleted many owners' expensive lens collections. However, they >> were prescient in developing the EOS mount which is huge diameter (about >> 51mm) and a relatively short (44mm) register. The change has stood them in >> good stead in the long term, although it cost them a lot of customers once >> upon a time. > The large diameter should help at least in making large aperture > lenses; but the registration distance is a mere mm and a half away > from Pentax'. Yes, there are only so many degrees of freedom when you have to clear a large, swinging mirror. >> Olympus ... worked with Kodak and developed the FourThirds mount.. This lens >> mount is the only one in production that actually has the ideal sensor >> size/diameter/register depth combination for digital capture SLRs and lenses >> up to f/1.4 aperture settings. The Micro-FourThirds design is essentially >> the same ... > > Which is interesting, because unlike the "inadequate dinosaurs" (F and > K) that mount it's now dead and buried - FourThirds lens owners being > supposed to jump to the new mirrorless EM-1. > I'm not aware of any Olympus FourThirds lens larger than f/2 - though > Panasonic made a 25mm f/1.4. The FourThirds SLR lens mount is hardly "dead and buried". The full range of Olympus FourThirds lenses, consumer/high grade/super high grade, is in production and is 100% compatible with Micro-FourThirds camera use via four available dedicated adapters. I used my FourThirds SLR lenses interchangeably with Micro-FourThirds lenses as long ago as 2008 when the Panasonic G1 was released. The only thing that was different between using the lenses on SLR-FT vs mFT bodies was the auto-focus performance, because the SLR bodies of necessity supported PDAF (which is what the SLR lens line was designed for) and the mFT bodies of necessity supported CDAF focusing protocols. Micro-FourThirds mount design is the same, with a reduction in diameter to match the shorter register and enhance compactness of the bodies. The Olympus E-M1 model introduces PDAF sensels on chip to provide both focusing protocols, so if anything FourThirds SLR lenses are now more "alive" than ever. FourThirds SLR bodies are no longer in production, but the FourThirds SLR lenses have a long future in front of them. Of course they will be phased out as mFT lenses of comparable focal lengths and features replace them, but that's hardly dead and buried in the sense of "not being able to be used" implies. Olympus stuck with f/2 as their fastest offerings, even though the SLR mount was designed for up to f/1.4. I have no issue with that—their SHG f/2 zooms are the best in the industry, out-performing most of the best primes ever made. BTW, I neglected Sony NEX E-mount and Samsung NX mounts, which are other, more recent lens mounts designed for interchangeable lens digital cameras exclusively. Neither Sony nor Samsung have gotten much of a reputation for top notch lenses in these mounts as yet, despite their relationships with Zeiss and Schneider respectively, though some of the latest offerings are really very good. The Zeiss 35mm lens for Sony NEX is terrific, amongst others. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
