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02-28-2008, 05:34 PM   #1
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M42 and aperture?

Good afternoon:

I am sure this is answered already but I couldn't find it. I have a K100D Super and I recently acquired a 50mm M42 screw mount lens for it. I have an adapter from my older film cameras and it mounts and takes great pictures - especially for $12.

Anyway, is there a way to have the aperature stop down when taking pictures? It seems to only work at 1.9 and this is great as that is why I bought a fast lens but there may be time I want to shoot at 8 or 16.

Any ideas or help would be greatly appreciated!

Stan

02-28-2008, 05:41 PM   #2
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Sorry for posting in the wrong thread area
02-28-2008, 06:14 PM   #3
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Nope, no automatic stop down for you! You have to stop down using the aperture ring. That's the sucky part about using M42 lenses.
02-28-2008, 07:04 PM   #4
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The lens needs to either:
a) Have an automatic/manual switch
b) Be a preset lens, where you set the aperture, focus/compose, then rotate a ring to close the blades.

If your lens doesn't have either of these things, it cannot stopdown...in which case, you have a full-time f/1.9 lens unless you tape down or otherwise modify the pin in back.

Stop down metering isn't bad...I'll get a close reading in Av then switch to M.

02-28-2008, 09:30 PM   #5
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QuoteOriginally posted by ryan s Quote
in which case, you have a full-time f/1.9 lens unless you tape down or otherwise modify the pin in back.
what i did to my M42 lens is i glued (epoxy type) that pin so i am now able to do stop down metering...
02-29-2008, 06:03 AM   #6
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QuoteOriginally posted by praxxis Quote
what i did to my M42 lens is i glued (epoxy type) that pin so i am now able to do stop down metering...
Does your lens not have an Auto-Manual switch? All you have to do is press the pin in and set the switch to Manual. I can't imagine under what circumstances you would have to glue the thing in place.
02-29-2008, 09:28 AM   #7
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Fujica ST lenses are M42 thread, but are auto-only in addition to having the little protusion for communicating with the camera. Just off the top of my head...

I wouldn't modify a lens, personally...
02-29-2008, 05:34 PM   #8
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I was thinking of the additional and practically invisible pin on the later generation Takumars. Never occured to me he was talking about the aperture coupling pin.

02-29-2008, 09:23 PM   #9
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QuoteOriginally posted by praxxis Quote
what i did to my M42 lens is i glued (epoxy type) that pin so i am now able to do stop down metering...
I would go for a reversible solution: metallic tape rather than epoxy the aperture pin into the lens.
03-04-2008, 02:10 PM   #10
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Thanks everyone - I haven't had a chance to try it all out but I am going to look at the taping option and use of the manual button.
03-07-2008, 06:50 PM   #11
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hi this thread caught my eye because i just bought an M42 50mm SMC Takumar Macro with a Real Pentax Adapter, although it hasn't come in yet and i have a k100d

from the many articles i read, i thought the stop down doesn't work at all? so when i shoot i can do the following
1. use Av mode
2. set the aperture to the brightest
3. focus
4. stop down
5. take picture

but after i read this thread, i'm getting that if i set the lens to "Auto" ... and tape down this pin, the lens can stop down if i half press the shutter button? or did i totally misread this post :S
03-07-2008, 07:16 PM   #12
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I don't believe Auto mode on an M42 lens will ever work because the DSLR has no ability to press in the button that stops the lens down. Setting it to Manual is basically the same as being in Auto with the pin taped/glued down.

So, you can either...
Shoot in Av (wide-open only)
Shoot in Manual, and press AE/L to have the camera meter properly

You can, of course, focus at the largest aperture in order to have more brightness then set it to the desired aperture, but that's optional.
03-08-2008, 12:06 PM   #13
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^^Right

You can meter in Av as you stop down, but without EV compensation, it will start to overexpose because the cam is used to taking the "average" of what it sees in the mode. Eg...when you increase the aperture number on an electronic lens, the cam does some black magic and calculates shutter speed.

When the lens is closed down, the cam sees it as darker so it makes the shutter speed slower because of the "averaging" effect.
06-12-2008, 07:03 PM   #14
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QuoteOriginally posted by Mike Cash Quote
Does your lens not have an Auto-Manual switch? All you have to do is press the pin in and set the switch to Manual. I can't imagine under what circumstances you would have to glue the thing in place.
sorry for my verrrry late reply... and sorry for not telling that my M42 lens is a Yashica (Yashinon) type so there's no auto/manual switch...


QuoteOriginally posted by Canada_Rockies Quote
I would go for a reversible solution: metallic tape rather than epoxy the aperture pin into the lens.
i also tried the metallic tape but noticed that it seems the aperture pin pushes the tape little by little and i'm afraid that the tape falls-off inside my camera and then stick in my sensor that'll cause me much trouble...
06-12-2008, 09:43 PM   #15
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sglj3: When I first bought my K20 and Tamron 17-50, I went searching Ebay for a fast 50mm Prime. But I was new to this game then and bought a Yashinon 50mm 1.9 just like you did. The Ebay seller claimed, in large letters in the ad for this lens, that it worked on Pentax DSLRs.

Now, I did not know any better, trusted him, and bought the lens. When I learned what you are talking about here, that you could only use it wide open, I contacted the seller. He told me I needed to stick a tooth pick in the aperture pin to enable use on the K20. I told him this was unreasonable, that he advertised it would work on the Pentax DSLRs. He accused me of making an uniformed purchase—said I should have done more research before I bought the lens.

Anyway, he refused to take the lens back and even threatened that if I gave him negative feedback, he would also give me negative feedback as a buyer—this really bothered me, but I ditched the lens and went on to learn as much as I could. I now own about 15 Pentax primes, from A & M series to SMC Takumar and Auto Takumar. But, with all I went through on this lens, it seemed the toothpick idea was the best idea. However, I did not want to risk any damage to a $1300 DSLR for a $20 lens so I moved on. However, I have since encountered others who have met with this problem and it appears the toothpick remedy is very popular. You can try this, since it works and is temporary-- just realize if a piece breaks off it may get on the sensor or possibly even worse jam itself into a moving piece somehow.

PS A short time after this horrible dealing with the Ebay seller, Ebay changed their policy and stopped sellers from using this strong-arm tactic to artificially inflate a seller’s reputation.

Regards,


Ernest


"Humanity subdues inhumanity as water subdues fire."

Mencius 6A:18
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