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08-05-2012, 05:36 AM   #1
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Pentax 67 - 1:2,4 105mm - Aperture problem

Hello everybody!

I have a problem concerning setting the aperture: Normally the lever on the lens is set to "MAN." and by turning the aperture ring the aperture should visibly change. When pulled down to "AUTO" the aperture should close down to the highest number, showing you the maximun DOF.

When I got the lever set to "MAN." and turn the ring, nothing happens, the aperture stays always wide open. When I now push the lever down to "AUTO" the aperture changes depending on where my aperture ring is set, for example: when the aperture is set to 22 and the lever is set to "MAN." nothing happens, the aperture blades are wide open - when I now push the lever down, the aperture will close corresponding with 22. This is the same for every Stop.

When I lock the lever to "AUTO" I am able to manually change the aperture by turning the ring. That way I am obviously not able to check for the DOF because the lever is already on "AUTO" and when I release the lever the aperture will open wide up again.

So far I don't know yet if the aperture will stay where it's set (locked on "AUTO") when releasing the shutter.

The only hint I got so far was when the mirror was locked up. If that's the case the aperture setting works the normal way: when the lever is set to "MAN." the aperture changes by turning the ring...

I am rather puzzeled by this behaviour and also new to this system. I don't want to try much more because I am afraid to ruin something. I suspect the issue to be within the lens rather than on the body - so far I don't have a different lens to test.

I would really appreciate your help on this! Thank you!

Regards!

08-05-2012, 07:06 AM   #2
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I have tested if the aperture will actually stay as set when releasing the shutte in the abnormal setting that I have my aperture in: it will stay as set - which is good but still not normal...
08-05-2012, 07:32 AM - 1 Like   #3
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I think you might be misinterpreting how the diaphragm switch is supposed to work, so let me try to explain it:

Let's assume the lens is mounted on your camera, as if it isn't, the aperture ring setting should always correspond to size of the aperture diaphragm.

In MAN mode, the viewfinder will darken as you stop the lens down using the aperture ring, and you will see the true DOF.
In AUTO mode, the viewfinder will not darken, and the lens will not stop down until you take the shot. However, a lever inside the lens does transmit aperture info to the camera so that it can meter properly (aka you've got open-aperture metering).

Hope this helps!

Adam
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08-05-2012, 07:32 AM - 1 Like   #4
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The mode shown is the mode you are in. If you cover up man, you are in auto.

08-05-2012, 09:55 AM   #5
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Ok! Thanks for the fast response! So, I was mistaking the modes...and everything works as you explained.

"Let's assume the lens is mounted on your camera, as if it isn't, the aperture ring setting should always correspond to size of the aperture diaphragm."

As if it isn't? What do you mean by that?

Why would anyone use AUTO and not be able to see what his aperture will do to the outcome?

Regards!
08-05-2012, 09:58 AM   #6
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One more thing: will it make any difference to the correct metering if I use MAN or AUTO?
08-05-2012, 03:48 PM   #7
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QuoteOriginally posted by Josias Quote
Why would anyone use AUTO and not be able to see what his aperture will do to the outcome?
Because AUTO was not intended to be a DOF preview lever. Manual mode was for that. AUTO means auto diaphragm, so that you can set the aperture and meter without the lens being stopped down.
QuoteOriginally posted by Josias Quote
One more thing: will it make any difference to the correct metering if I use MAN or AUTO?
Metering in manual should only be done when the connection between diaphragm and meter is broken ( such as when you use the helicoid extension tube). Metering with an auto lens like the 105 in manual mode without the connection break I just mentioned is a mistake.
08-05-2012, 04:40 PM   #8
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Mhhh... I guess I just have to learn how to handle this machine and get another light meter because for now (one roll) I metered in MAN - which made the most sense to me because only than the lightmeter within the prism will change to the changes made on the aperture in a logical way, at least from my perception. Do you know where the light is actually metered? Is it the white circle on top? Because if so I am mistaken about my perception which was based an a metering within the prism...

So if I would meter with an external device, it would be correct to have the lens set to MAN right?

Regards

08-05-2012, 04:42 PM   #9
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I could just wait for the outcome of the film ant try all sorts of ways... But you know...
08-05-2012, 05:14 PM   #10
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QuoteOriginally posted by desertscape Quote
Metering in manual should only be done when the connection between diaphragm and meter is broken ( such as when you use the helicoid extension tube). Metering with an auto lens like the 105 in manual mode without the connection break I just mentioned is a mistake.
Yep unless if you have a flakey TTL meter. My 67 TTL meter will work in AUTO mode for a few shots then stops working, it will then only work in MAN mode. Removing the lens, then the prism and remounting them does not help. This happens every time I go out shooting with any lens; sometimes I can get through most of the roll, sometimes only one shot. I finally gave up and got a hand held meter! I’ll send the TTL to Eric one of these days to see if he can fix it.

Phil.
08-05-2012, 06:11 PM - 1 Like   #11
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QuoteOriginally posted by gofour3 Quote
Yep unless if you have a flakey TTL meter.
gofour3 is right...
QuoteOriginally posted by Josias Quote
I metered in MAN - which made the most sense to me because only than the lightmeter within the prism will change to the changes...
... that sounds like either the switch in the camera is not connecting or the first half of the meter is not operational. The TTL has two circuits to activate the meter, but it is not uncommon to have the AUTO side fail over time.

As desertscape pointed out, but additionally... AUTO comes from when cameras earlier had simple aperture functions and with the invention of SLR cameras the change of the f-stop meant that the you would get a dimmer image in the viewfinder, the invention of the "auto-aperture" allowed viewing and focusing in the brightest possible situation and then automatically close the aperture down for the picture to be taken. So the normal behavior of AUTO on a P6X7 is to be held open/wide. MAN or manual is the stop-down mode and should allow for viewing in the set aperture selected. On a P6X7 or P67 or P67II, the MAN mode when locked in will engage a small lever inside the lens to push in on a small stem within the camera's lens lock pin. That pin will flip the voltage of the meter to "stop-down" mode or other words the alternate meter circuit. You may want to make sure the contacts on the camera body are clean to see if the AUTO mode is actually not working or just not connecting...see below...


Also, you may want to review the procedure on attaching the TTL and setting the lens to avoid any mishaps with the index and chain that links the lens aperture setting to the TTL if you have not already.
08-06-2012, 03:02 AM   #12
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I think I was not expressing myself clearly. Set to AUTO, the light meter will actually change according to the changes made on the aperture ring even though not seen visibly through the the lens (change of the aperture). So that is all in good condition - it works as you are describing. Still - I can't make too much sense of metering in AUTO: You are not able that way to see what the aperture does to the DOF, you can only focus and take a guess of the outcome. Why would the metered light be same when once set to AUTO on an aperture set to 11 and once on MAN. set to 5.6 (same light condition)?

The only thing I am really concerned about is how to meter proper using MAN - would a handheld or external light meter be ok with that?


PS: If I was to be concerned about focusing with the most light possible I would just open the aperture, focus, and than set aperture to the desired value... It seems like this systems logic is beyond me...

Regards!
08-06-2012, 03:52 AM   #13
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I see, its not all that simple, regading the aperture values in MF and lightmeters normally working with 35mm values, is that correct?

So basically I just want to figure out how to meter properly in the best way possible (external device better than TTL?)

Just for my understanding on metering in AUTO: First, I could focus in AUTO, giving me all the light, than I could switch to MAN setting my desired aperture and checking for the actual outcome of the DOF, now I would change back to AUTO and do the metering setting only the shutter speed - would I now have a correct metering given that the lens is an auto lens and that it is conected properly to the lever of the body?
08-06-2012, 04:06 AM   #14
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With MF I meant medium format!
08-06-2012, 06:18 AM   #15
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Josias, you seem to have the workflow down... Focus while in AUTO and light meter (if it is still accurate) to get an exposure solution, flip to MAN to check you depth of field and then shoot either in AUTO or MAN.

However, based on the above...

QuoteOriginally posted by Josias Quote
...set to AUTO on an aperture set to 11 and once on MAN. set to 5.6...
...which is right?

You are relying on the following event... reading from AUTO and relying on the synchronization of the of the Chain-Tab-Potentiometer to TTL meter circuit
OR
the MAN and the alternate circuit of the TTL to get the reading.

Have you checked the TTL against a trusted hand-held meter to see if the TTL is still calibrated properly?

For example, I've calibrated (no recommending you do-it-yourself) my meter to match in both AUTO and MAN mode and have not had any problems with exposures. Prior to calibration was a reading that was usually about 2 stops different every time.


Last edited by MysteryOnion; 08-06-2012 at 06:27 AM.
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