On Wed, Sep 25, 2013 at 6:27 PM, Godfrey DiGiorgi <[email protected]> wrote: > > 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.
In theory, I agree - but for compatibility reasons I don't expect this to change. Does it mean the future lenses should be designed in the same manner? > > 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. Precisely; it was a coincidence but the "old" lenses - the better ones - are working quite well for digital sensors, because of this. With the large focal range specific to a DSLR, using offset microlenses would not be an option. The telecentricity Olympus loudly promoted was a natural characteristic of the classic SLR lenses. > >>> 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. I'm afraid it is; with no new FourThirds lenses since 2008, and the 2010's E-5 being replaced by the EM-1, as Olympus says. Maybe not "buried", but they're definitely phasing it out. Being able to adapt your lenses on another mount doesn't change this. > > 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. Your lenses might be "alive" and see good use on whatever cameras you have, but the mount isn't; sorry. > > 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. They surely have some excellent zooms, I'll give them that. > > Godfrey Alex -- 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.
