huh? the main advantage of a dedicated M42 DSLR body would be full support of auto aperture function that is NOT being supported with any DSLRS at this point via M42 adapters.
Secondly, you obviously have never used autoaperture M42 lenses in the autoaperture mode or you would know that not having to flip awkward lensmounted aperture switches to open & close the aperture every single time you want of focus and compose ( which is far more often than just taking a meter reading)and then again every time you want to make an exposure is nowhere near user friendly or ergonomic or intuitive or whatever you want to call it then when you dont have to that clunky, slow, error prone non-sense because the aperture function is fully AUTOMATIC. The autoaperture function is so important to ANY SLR camera design that the vast majority of all SLR lenses and bodies made since early 60's have it. It is far more important than ANY metering modes or metering at all. This is the SOLE reason for making a M42 dedicated DSLR, metering could be same as GB on Pentax Kmount bodies is now with K/M lenses because it would work with ANY M42 lens. Yes, the very last generation M42 lenses did have some open apeture metering modes available with certain lenses on certain bodies, but unlike the autoaperture function, these open aperture metering systems were nearly all propriatary and you had to buy same brand lenses as your body to get that function. I would not expect a whole bunch of totally different DSLR M42 bodies to be made to do that and for only a very few M42 lenses that could even do it in the first place. M42 DSLR body would almost certainly be a so-called "universal" M42 body with auto-aperture and NO open apeture metering function. And it would still be very useful for the millions of high quality M42 lenses out there. P.S. I am not infatuated with the M42 lenses, I have been using them for over 30 years, and still love using some of them. That's not infatuation by definition. jco -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Cory Papenfuss Sent: Wednesday, February 21, 2007 7:54 PM To: Pentax-Discuss Mail List Subject: RE: 85mm f1.8 SMCT on ebay : $400+ On Wed, 21 Feb 2007, J. C. O'Connell wrote: > YOU are the one confused here. ALL autoaperture > M42 lenses have "open-aperture auto aperture" (your > term, not mine), that's > what auto aperture ISs by defintion. The lens aperture > stays open all the time during focus and composition > and only stops down during the moment of exposure. It then reopens > immediately and automatically after the exposure is made. The vast > majority of M42 lenses are auto apeture models. Yes, there are/were > some presets, some semi-automatics, and some manuals > with regards to the aperture function but the vast > majority of them (M42) are full auto-aperture. > > The reason I say you are confused is you are associating > the metering directly with the autoaperture ( someone else was doing > the same thing too, but its a mistake ) because the metering technique > is independent of the auto aperture function. Most M42 bodies do stop > down metering, but this is only temporary, during the metering > function itself, and the lens goes back to normal autoaperture > functioning once the proper meter reading is made ( if the body even > has metering, or you choose to use it, or choose to > take another meter reading). > > OPEN APERTURE METERING- which is what I think you > are referrring to ( which is not the same thing as > auto apeture), is where you can take meter readings > without stopping down the lens. That is not as > common as autoaperture, but it is not as needed > or useful as autoaperture is either. All open aperture metering lenses > have autoapeture function too, but not all autoaperture lenses have > open aperture metering function. I am not advocating a dedicated M42 > DSLR be produced for open aperture metering, I am advocating > one to get the AUTOAPERTURE function, which most > M42 lenses support, and which is sorely lacking when > you mount M42 lenses on any current DSLR including > Pentax's via a M42 mount adapter ring. > > jco > My confusion of terminology was primarily induced by your rabid infatuation with auto-aperture M42 lenses. I figured you must have *meant* open-aperture metering because that would be the main advantage of such a body. Auto-aperture with automatic stop-down metering still has the major problems of: - Meter inaccuracy due to angle on incidence - Meter inaccuracy due to falling off the end of metering range while stopped down. - Manual focus aids ineffective at apertures smaller than 5.6-8 or so. - Sticky apertures (LOTS of 'em on these old suckers... still work fine for manual stopdown metering, but not fast enough for auto) Automatic aperture with stop-down metering does not address any of these rather large problems. All it does is save one from having to flip a switch between focusing and pressing the button. The meter will work fine in 'P' mode once stopped down like that. Even more intuitive and "automatic" then the GB kludge for K/M lenses. -Cory -- ************************************************************************ * * Cory Papenfuss, Ph.D., PPSEL-IA * * Electrical Engineering * * Virginia Polytechnic Institute and State University * ************************************************************************ * -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
