1st, sorry for the amount of same & similar messages I sent to list
yesterday with this subject :( I was having trouble with a filter I
configured wrong, and it copied the message into my outbox again. Mea
culpa!
Friday, January 25, 2002, 1:56:11 AM, Tim wrote:
TE> 24 Jan 02, Frantisek Vlcek <[EMAIL PROTECTED]> wrote:
>>
>> Tim wrote (a technical theoretical treatise on aperture
>> blades closing down speed etc)
TE> Sorry, I didn't mean to be boring... it just comes naturally to engineers.
TE> It's what we do best. ;-)
Tim, you were not boring at all! It was
very comprehensive. I didn't mean by my words that it was boring!
[...]
TE> Are you referring to mirror lock-up? I have several Pentax bodies equipped
TE> with MLU and one is apart on my work bench right now, repairing a sticky
TE> MLU. In a SLR body MLU just moves the mirror up in advance of the drive
TE> mechanism. It doesn't side-step the exposure sequence or create a direct
TE> connection between the release button and the shutter. The release button
TE> still triggers the mirror mechanism which triggers the shutter.
No, I was only thinking that at least Pentax 67 and some other,
adapted 6x6 bodies (Kievs) have separate mirror release. On the 67
it's electronic, on the kievs it's mechanical. I don't know if it
sidesteps the normal mechanism or not :(
[...]
TE> only part of the cycle that affects shutter/exposure speed. We are in
TE> violent agreement ;-)
;-))
TE> First, I dont recall the thread referring exclusively to auto aperture
[...]
I am sorry, its my fault - I didn't mean auto-aperture lenses like
Pentax K-A series. I meant autoaperture as opposed to manual aperture
(ie Auto-Takumar opposed to Takumar) and its derivatives like pre-set
aperture.
[...]
TE> Third, I'm sure the lens makers had some very good reasons for deleting
TE> blades and I'd be curious to know what they were. But I wouldn't leap to a
Me too ;) I am of course not sure about the cause. I was told this,
and it made sense.
[...] And I wrote:
>> 2nd, you forgot friction. period.
TE> No, I didn't forget friction in the aperture diaphragm at all... or mass,
TE> inertia, etc, etc... Nor did I forget friction and all those elements
TE> in the mirror mechanism. My point was that all the power factors affecting
TE> the rapid movement of the diaphragm are dwarfed by the similar factors in
TE> the mirror. The diaphragm is the fly in my analogy.
I still think friction plays a major role, but I don't have much
technical background, so it's not based on any technical insight
unfortunately. I think so just because many of the pre-set lenses I
have, which sport 18-bladed diaphragms, have harder to turn rings,
even if the blades are completely cleaned (which I did on some of
them) or clean from start. It could be other cause, but from my look
on the aperture mechanism in these lenses, that's my opinion on it.
TE> I like a good discussion/debate once in a while, if that's what this is.
TE> It's hard to tell in e-mail and smiley faces only go so far. I wouldn't
TE> mind kicking this around with you for awhile if you wish. But I sense some
TE> irritation in your response and this subject isn't worth poisoning the air
TE> on the PDML. If I've touched a raw nerve in you, I'd be happy to accept a
TE> rebuttal and let this end. We have a common interest, not a bone of
TE> contention.
Tim, please accept my sincerest apology! I am very sorry that my post took
a more argumentative tone. My only excuse is it was night and I was
tired and hungry! ;-) I feel ashamed.
TE> Have a beer on me. I'll reimburse you via PayPal and then we can move over
TE> to that message thread. ;-)
If you come to Prague someday, I will be glad to treat you a beer or
two!
Tim, I like your attitude very much - it would be good if it was more
widespread on internet discussion lists! Unlike the perpetual flame
wars on most of them (with PDML being most of time an exception).
Back to diaphragms - I see you have good knowledge in repair, what
have you found a best way to clean oiled blades? I always had to
remove them completely and clean one by one, but putting it all
together was a major pain in the a**, calling for making wood forms to
hold it while assembling! Especially the 18-blades one! Is there a
trick to it which isn't shared with us amateurs :) ?
And could just wiping the exposed but not disassembled diaphragm with
cotton and ether/isopropanol or other solvent help, at least some?
Thanks!
Best regards,
Frantisek
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