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01-20-2010, 02:04 PM   #1
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Question m42 Takumar dSLR

Okay guys I have an m42 Takumar f1.4 50 mm lens and 2 types of k-mount adapters and an *ist DL DSLR. I am confused about one thing. I have found info on "stop down metering" and it works, that the AE-L locks the shutter speed when pressed. But.... is the lens aperture supposed to stay wide open and then "stop down" for the instance that I press AE-L and or take the photo? If the lense is set to "auto" the aperture will stay wide open and a little button the back of lense will close the aperture down to the ring setting, is my camera supposed to trigger that button? Maybe I am confused because the discussions about "stop down metering" are about different types of lenses with the correct aperture "arm" that catches the camera mechanism? As it is I can only manually stop down the camera, so AE-L is kind of pointless since I have to close down the aperture to the desired setting before taking the photo and it will meter then. Am I missing something? Or will my m42 Takumar not “stop down” automatically for the instant that I am metering and taking a picture? And if this is the case what is the procedure for taking a picture? Frame the picture and focus with the apperature wide open and then close it down and shoot?

01-20-2010, 02:21 PM   #2
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There is nothing in the K mount camera to press in the M42 aperture pin. Therefore, if you are in Auto mode on the lens, the only available aperture is wide open.

This is where the Manual mode comes in. To meter/shoot, you close down the lens via the aperture ring to where you want it - and then either trust in Av or do the manual 'stop down' (in this case nothing is stopped down because the lens is already stopped down) to set exposure.

On a K-M lens, the stop down metering will indeed stop down the lens, and the camera will also stop down the lens at exposure time.
01-20-2010, 02:31 PM   #3
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Welcome to the forum Big Jonnee.

M42 lenses attached to your *ist DL don't need to be stop-down metered as they are already 'stopped down' by the physical aperture setting on the lens aperture ring. Shooting with M42s is explained here: https://www.pentaxforums.com/forums/pentax-lens-articles/3800-can-i-use-m42-s...unt-d-slr.html. This is quite different to the function of K and M lenses on your camera (see here: https://www.pentaxforums.com/forums/pentax-dslr-articles/32-can-i-use-k-m-len...ist-ds-dl.html)

Not sure if you're aware of this article but it may be worth a read: https://www.pentaxforums.com/forums/pentax-lens-articles/59287-shooting-manua...x-dslrs-f.html

AE-L only offers a lock of the exposure settings for the scene you meter, and remains locked unless you release the shutter or the specified metering time elapses.

Lastly, this thread should be in the Beginner's Q&A section.
01-20-2010, 04:29 PM   #4
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QuoteOriginally posted by Ash Quote
Welcome to the forum Big Jonnee.

M42 lenses attached to your *ist DL don't need to be stop-down metered as they are already 'stopped down' by the physical aperture setting on the lens aperture ring. Shooting with M42s is explained here: https://www.pentaxforums.com/forums/pentax-lens-articles/3800-can-i-use-m42-s...unt-d-slr.html. This is quite different to the function of K and M lenses on your camera (see here: https://www.pentaxforums.com/forums/pentax-dslr-articles/32-can-i-use-k-m-len...ist-ds-dl.html)

Not sure if you're aware of this article but it may be worth a read: https://www.pentaxforums.com/forums/pentax-lens-articles/59287-shooting-manua...x-dslrs-f.html

AE-L only offers a lock of the exposure settings for the scene you meter, and remains locked unless you release the shutter or the specified metering time elapses.

Lastly, this thread should be in the Beginner's Q&A section.
Not completely true. M42 lenses are wide open until something pushes the aperture pin. Since there is nothing in a modern dslr to do that, the lens will NOT stop down, regardless of the aperture ring.

For use on manual extension tubes and bellows, all Pentax M42 lenses that I am aware of had an Auto/Manual switch. In auto mode, the lens works as I described above. In manual mode, the iris follows the aperture ring setting. If the lens has a switch, and if the switch is set to manual, it will stop down as you turn the aperture ring.

Some, but not all, non-Pentax M42 lenses have such a switch. In the absence of the switch, the lens can only be used wide open, unless you modify the lens or come up with something to keep the pin depressed. For this reason, I pass on these lenses.

K-mount lenses are just the opposite. Take a k-mount lens off the camera and it will stop down as far as it can. Take an M42 lens off the camera, and (if the switch is in Auto, or there is no switch), it will stay open.

01-20-2010, 06:12 PM   #5
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thanks!

sorry for being such a noob I don't even know there is a noob section. one more question though while i have your attention. In aperture priority mode the shutter time will only go up to 1.5" and won't go any higher which leads to entirely under exposed photos in real low light.
maybe this is just a crappy limitation of my 3-4 yr old *ist DL? But with a regular lens in aperture priority the shutter goes all the way up to the maximum 30". I can manually set it higher, but that is a shoot in the dark so to speak. Anybody know if this is just a limitation or is there a fix? Thanks again!
01-21-2010, 04:39 AM   #6
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QuoteOriginally posted by noblepa Quote

Some, but not all, non-Pentax M42 lenses have such a switch. In the absence of the switch, the lens can only be used wide open, unless you modify the lens or come up with something to keep the pin depressed. For this reason, I pass on these lenses.
Not completely true.....

Lenses with preset aperture mechanisms (double rings) can be used at any aperture.

For the OP:

Regarding the 1.5 second thing, just switch to "M" mode and you should be able to access all shutter speed settings. You will need to do a few test shots to get the right speed. Use the review screen to check your results, and also refer to your histogram as it is a very handy tool.
01-21-2010, 06:03 PM   #7
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QuoteOriginally posted by noblepa Quote
Not completely true. M42 lenses are wide open until something pushes the aperture pin. Since there is nothing in a modern dslr to do that, the lens will NOT stop down, regardless of the aperture ring.

For use on manual extension tubes and bellows, all Pentax M42 lenses that I am aware of had an Auto/Manual switch. In auto mode, the lens works as I described above. In manual mode, the iris follows the aperture ring setting. If the lens has a switch, and if the switch is set to manual, it will stop down as you turn the aperture ring.

Some, but not all, non-Pentax M42 lenses have such a switch. In the absence of the switch, the lens can only be used wide open, unless you modify the lens or come up with something to keep the pin depressed. For this reason, I pass on these lenses.

K-mount lenses are just the opposite. Take a k-mount lens off the camera and it will stop down as far as it can. Take an M42 lens off the camera, and (if the switch is in Auto, or there is no switch), it will stay open.

There is a simple cure for this problem. I push the apature pin in manuslly and use a center punch and a hammer to put a small dimple next to the pin to keep it depressed then it is stopped down with the apature ring to what ever setting you desire. jim
01-21-2010, 10:47 PM   #8
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QuoteOriginally posted by jmc7104 Quote
There is a simple cure for this problem. I push the apature pin in manuslly and use a center punch and a hammer to put a small dimple next to the pin to keep it depressed then it is stopped down with the apature ring to what ever setting you desire. jim
This is absolutely true, and a fairly simple fix. This is the kind of modification that I was referring to. However, some users may not be comfortable taking a center punch and hammer to their lens.

Also, if one happens (like me), to still enjoy using my M42 lenses on my Spotmatic, as well as my K10D, this solution is less than optimal. It would render the auto aperture function unusable. I realize that the OP does not seem to be asking that, however.

And Mike, I completely forgot about preset lenses. Actually, preset lenses are every bit as useful on a dslr as are the later auto aperture models, since both must be used in manual mode, anyway.

01-22-2010, 09:17 PM   #9
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QuoteOriginally posted by noblepa Quote
Actually, preset lenses are every bit as useful on a dslr as are the later auto aperture models, since both must be used in manual mode, anyway.
They're actually more useful on a DSLR than the later versions, IMO, as the second aperture ring on most of these (at least on most pre-set Takumars) allow you to easily shift between wide open focusing & stopped down shooting apertures effortlessly..... one of those instances in which "outdated" technology actually surpasses the the later "improved" models.
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