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12-11-2009, 02:11 AM   #16
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Thanks everyone!

Conclusion is that without my modification, it is not possible to get automatic exposure on K-x with this kind of lens- which could be considered a minor flaw.

Stefan

12-11-2009, 03:29 AM   #17
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Somebody correct me if I'm wrong, but I was under the impression that the lever in question was what stopped down the lens. If it is removed won't the lens just stay open all the time?
12-11-2009, 04:04 AM   #18
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QuoteOriginally posted by Steve Beswick Quote
Somebody correct me if I'm wrong, but I was under the impression that the lever in question was what stopped down the lens. If it is removed won't the lens just stay open all the time?
Isn't it the other way around. When you hold a lens in your hand it stops down when the aperture ring is turned. When you mount the lens the lever in the camera holds the lever in the lens (and aperture) wide open regardless of the aperture setting. Only when taking a picture your camera body releases the lever to stop the lens down to the value selected from the aperture ring. When the lever is removed from the lens it works just as when not mounted.
12-11-2009, 05:57 AM   #19
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QuoteOriginally posted by 16N64 Quote
Thanks everyone!

Conclusion is that without my modification, it is not possible to get automatic exposure on K-x with this kind of lens- which could be considered a minor flaw.

Stefan
Stefan

this "minor flaw" began long before pentax digital cameras.

In the late 1990's, almost 20 years after the introduction of the program series of cameras and the KA mount, pentax decided that there was no longer need to fully support the origonal K mount in full automatic mode and deleted the aperture coupling from their cameras, making them much simpler mechanically, while retaining the ability in most bodies to still meter with manual lenses.

while many have complained that the "crippled K mount" is a flaw, I have to remind you that with Canon, you can't even mount their manual focus lenses and with Nikon, on all but a few of the bodies, while you can tape pictures, there is no metering AT ALL

The fact that pentax offers metering capability and some functionality with lenses that are between 25 and 60 years old should be viewed as a bonus. Not a flaw.

It is like complaining that your CD player cannot accept 8 track tapes.

12-11-2009, 08:29 AM   #20
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Thanks Lowell!

I am perfectly happy with my K-x, and still happy how I got the "crippled K-mount " to cooperate by crippling my lens too. All what you say about Canon and Nikon confirms for me that my decision for Pentax was the right choice - but still exposure metering with a manual lens is only restricted by firmware here, and that is not a bug, not a malfunction, but a minor unconvenience, and I hope this issue could perhaps be addressed in a future firmware upgrade.

Stefan
12-11-2009, 08:54 AM   #21
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QuoteOriginally posted by 16N64 Quote
Thanks Lowell!

I am perfectly happy with my K-x, and still happy how I got the "crippled K-mount " to cooperate by crippling my lens too. All what you say about Canon and Nikon confirms for me that my decision for Pentax was the right choice - but still exposure metering with a manual lens is only restricted by firmware here, and that is not a bug, not a malfunction, but a minor unconvenience, and I hope this issue could perhaps be addressed in a future firmware upgrade.

Stefan
stefan

while there may be a firmware restriction there is also a hardware restriction

K mount lenses, have a different aperture activation lever behavior than KA mount lenses.

On K mount lenses the activation lever is essentually an on off switch, where as the KA mount lenses it can be easily controlled to set the aperture in precise increments for exposure control. As a result, even if somehow the relationship between maximum and minimum aperture could be input and controlled, the number of increments in the control lever would be different for each F stop, leading to more and more inconsistent exposure control as the lens is stopped down. I suspect this is why pentax has not enabled the feature of entering the max and min apertures for the lens, and then let the camera try and control it. The K mount lenses were not designed with this in mind.


FYI I believe the KA mounts have the aperture area change linearly with position, such that the change in f stops (i.e. E.V differences of 1, 2, 3 are linear with movement) as oppposed to diameter on K mounts
12-11-2009, 09:46 AM   #22
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I bought two lens with that pin cut. One is M and one is A.

M lens:
when I stop down the problem is that the viewfinder darkens, so I have to focus with the lens wide open and only after that to slow down. Also, the green button is useless, since the camera will measure exactly the light that enters when pressing the green button.

A lens:
it works as a M lens, because in A position, the body do not recognize the apperture due to missing pin. All I write for M lens also apply to A.


Afterall, it`s not such a big deal to have not those pins, you just have a new manual lens.
12-11-2009, 10:20 AM   #23
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It is always a good laugh

Watching us all discuss how to use these darn manual lenses.

I always leave these threads more confused than when I started reading, and rethinking if I have been using all 25 of my manual lenses wrong for the last 3 years

Luckily this time, my K20 is in for service, so I can't re-check to see what I have been doing wrong.

But Forget all this nonsense... where are the photos?

That is all I care about!

Maybe I need my 11th 50mm lens


Last edited by Igilligan; 12-11-2009 at 10:32 AM.
12-11-2009, 10:37 AM   #24
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the only lenses I have ever considered "castrating" so to speak, are two lenses that I would like to use but can't (until my flanged adaptors arrive)

I have a vivitar (by Kino - Kiron) 24mm F2 in Nikon AI mount, and a Kiron 28mmF2 in Minolta MD mount.

one was free the other cost an incredible $5.00 Both had stuck aperture blades (now fixed), and I am going to turn them into K-Mount preset lenses.
12-11-2009, 11:04 AM   #25
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To the OP...

You should not have had to castrate the lens. Here are the instructions to use for non-A contact K-mount lenses...
  • In your setup menu confirm that "Using aperture ring" is set to "permitted"
  • Choose your desired f/stop on the lens
  • In "M" mode, take a stop-down meter reading using the"green" button. This should momentarily close the aperture, allowing the meter to read and should set the body to the appropriate shutter speed.
  • Take the picture
  • Note that in any mode other than "M", the camera will NOT actuate the aperture lever, meaning that the exposure will be done wide open.
All this stuff is in the camera manual, though it is pretty well hidden.

Steve
12-11-2009, 11:34 AM   #26
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QuoteOriginally posted by stevebrot Quote
To the OP...

You should not have had to castrate the lens. Here are the instructions to use for non-A contact K-mount lenses...
  • In your setup menu confirm that "Using aperture ring" is set to "permitted"
  • Choose your desired f/stop on the lens
  • In "M" mode, take a stop-down meter reading using the"green" button. This should momentarily close the aperture, allowing the meter to read and should set the body to the appropriate shutter speed.
  • Take the picture
  • Note that in any mode other than "M", the camera will NOT actuate the aperture lever, meaning that the exposure will be done wide open.
All this stuff is in the camera manual, though it is pretty well hidden.

Steve
Steve

his complaint is that with K mount lenses, he wants to use Av mode only, and not M mode.

He believes it is a firmware issue only and is not aware that the K mount lenses do not have a properly calibrated and linear (exposure) movement of the aperture activation arm. As a result he is willing to give up the green button and open aperture focusing for the convenience of Av mode like a preset or M42 lens
12-11-2009, 04:07 PM   #27
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QuoteOriginally posted by Lowell Goudge Quote
Steve

his complaint is that with K mount lenses, he wants to use Av mode only, and not M mode.

He believes it is a firmware issue only and is not aware that the K mount lenses do not have a properly calibrated and linear (exposure) movement of the aperture activation arm. As a result he is willing to give up the green button and open aperture focusing for the convenience of Av mode like a preset or M42 lens
That sounds strange! I like my M42 lenses a lot, but prefer pre-set or auto diaphragm to full manual! Oh well, to each his own.

Steve

BTW...I reviewed the OP's comments. He still does not understand that the body does not trigger the aperture lever in other than M mode for non-A lenses. I suspect that he will figure it out on his own...hopefully before he mangles any additional lenses.
12-11-2009, 06:16 PM   #28
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I did that to an SMC-M 28/f2.8

I cut off the aperture lever. The lens has very sticky aperture blades, and I felt it would cost more to repair then the lens is worth.

So I removed the lever, and now use the lens in AV mode only.

It makes for a great street lens. Stop it down, and set it to its hyperfocal length, and just shoot away.

I wouldn't do this to a functional lens though.
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