24 Jan 02, Frantisek Vlcek <[EMAIL PROTECTED]> wrote: > > Tim wrote (a technical theoretical treatise on aperture > blades closing down speed etc)
Sorry, I didn't mean to be boring... it just comes naturally to engineers. It's what we do best. ;-) > TE> BTW, "Shutter Release" is a misnomer... it's really a mirror release. > TE> Then "mirror-up" triggers the shutter and "shutter-closed" triggers the > TE> mirror return. The aperture goes along on the mirror's ride. > > Not a misnomer, as you can (and in many cameras have) a separate > mirror-release, vis Pentax67. The shutter is what counts, you expose > with the shutter not mirror. :) Are you referring to mirror lock-up? I have several Pentax bodies equipped with MLU and one is apart on my work bench right now, repairing a sticky MLU. In a SLR body MLU just moves the mirror up in advance of the drive mechanism. It doesn't side-step the exposure sequence or create a direct connection between the release button and the shutter. The release button still triggers the mirror mechanism which triggers the shutter. Then you say, "The shutter is what counts...". Absolutely, I agree whole heartedly. That was my point (step 2 / the shutter fires) is the only part of the cycle that affects shutter/exposure speed. We are in violent agreement ;-) > TE> I'm probably being too literal here, but I think saying more blades limits > TE> fast motordrive frame rates assigns the cause to the wrong link in the > TE> chain. But, if you're having trouble moving a box containing a horse and a > TE> fly, it's kind of hard to blame your difficulties on the fly. > > > Tim, you have got it theoretically great. My simple argument > against your theoretical thoughts is this: > > at the time automatic aperture got into lenses (Auto-Taks and > others), all the auto lenses changed the number of blades from > many to fewer, AFAIK. And I got it from people who are very > knowledgable in photographic and lens history. > > So I guess the lens makers must have had some very good > reason why they did so :-) Hmmm... I'm still not tracking with you (understanding or agreeing with you). First, I dont recall the thread referring exclusively to auto aperture lenses. I understood the statement to say the number of blades limited shutter speed and motordrive frame speed. Sorry if I missed the message where it took a sudden turn to auto-aperture. I'll try to pay more attention. Second, the auto-aperture mechanism doesn't open-close the diaphragm... much less at shutter speed. It only sets the limit stop. When the mirror is released, the mirror mechanism drives the diaphragm to close down to the stop that was preset by the auto-A mechanism. Then releases it to open via it's own spring power. The auto-A mechanism does not power the stop-down-up action. Third, I'm sure the lens makers had some very good reasons for deleting blades and I'd be curious to know what they were. But I wouldn't leap to a conclusion about what they were. Like, maybe, controlling cost or making room for the auto-A mechanism? But since the auto-aperture mechanism only sets the stop, the number of blades shouldn't affect the load applied to it. and 24 Jan 02, Frantisek Vlcek <[EMAIL PROTECTED]> added: > TE> I'm probably being too literal here, but I think saying more blades limits > TE> fast motordrive frame rates assigns the cause to the wrong link in the > TE> chain. If you're having trouble moving a box containing a horse and a > TE> fly, it's kind of hard to blame your difficulties on the fly. > > 2nd, you forgot friction. period. No, I didn't forget friction in the aperture diaphragm at all... or mass, inertia, etc, etc... Nor did I forget friction and all those elements in the mirror mechanism. My point was that all the power factors affecting the rapid movement of the diaphragm are dwarfed by the similar factors in the mirror. The diaphragm is the fly in my analogy. I like a good discussion/debate once in a while, if that's what this is. It's hard to tell in e-mail and smiley faces only go so far. I wouldn't mind kicking this around with you for awhile if you wish. But I sense some irritation in your response and this subject isn't worth poisoning the air on the PDML. If I've touched a raw nerve in you, I'd be happy to accept a rebuttal and let this end. We have a common interest, not a bone of contention. Have a beer on me. I'll reimburse you via PayPal and then we can move over to that message thread. ;-) Best regards, Tim - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
