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02-28-2008, 05:42 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, 05:51 PM   #2
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That's why you have the term stop down metering. That means you have to change the aperture and find the correct exposure by pressing the green button in M mode. So usually, you will focus using at wide open, then stop down.
02-28-2008, 06:03 PM   #3
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I think I understand the concept of stop down but when I press the shutter release the aperture does not close - should it? The Lens has a manual stop down button for preview.
02-28-2008, 06:17 PM   #4
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You have to switch that button to manual mode (it's basically for old camera that doesn't have auto exposure mechanism). The stop down pin on these old lenses doesn't work with modern camera. That's what i mean stop down metering.

02-28-2008, 06:31 PM   #5
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QuoteOriginally posted by sglj3 Quote
I think I understand the concept of stop down but when I press the shutter release the aperture does not close - should it? The Lens has a manual stop down button for preview.
You have to manually stop down the lens before you press the shutter release.

I like to use the Av mode with my M42 lenses. I focus with the lens wide open, manually stop the lens down, select the aperture, press shutter release. Using this method I do have to add some EV compensation, or the shot is underexposed. But it works well and for me is easier then using the cameras manual mode and pushing the AE-L button to meter the shot.

HTH

02-28-2008, 06:33 PM   #6
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Thanks - I will just have to get used to using so many fingers to take the pictures then
02-28-2008, 06:40 PM   #7
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There are custom settings that I recall that I need to setup with my K100D, I have a blog post where I drop down two settings:

Setup with Pentax M42 mount lens - Hin's Tech Corner

And recently I attempted to modify a M42 lens to K mount with some success, it is documented in this blog post

How to convert Pentax M42 to K mount lens - Hin's Tech Corner

Warmest,
Hin
02-28-2008, 06:45 PM   #8
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THX Hin - I actually had looked at your conversion post and it is something I might consider...

02-28-2008, 07:07 PM   #9
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sglj3,

If you have any troubles with the exposure try shorting all the cameras auto focus contacts with a piece of tinfoil or something that conducts electricity.
If your screen shuts off right after you press the menu buttons try the same thing as well.

Some people have to with all their screwmount lenses. I only have to with one, which covers those contacts with it's base.
02-29-2008, 06:11 AM   #10
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I've done umpteen thousand shots with M42 lenses on my K100D. The process is not complicated:

1. Set to Av mode and lens switch on "Manual"
2. Focus
3. Spin aperture to desired setting
4. Go mashy-mashy on the shutter thingy

Two things that make a world of difference are 1) installing a split-prism focus screen and 2) start from a default of about f4 when focusing and know how to find your aperture by counting the clicks. In the viewfinder you get a constant and instant DOF preview as you shut down the aperture and all you have to do is sort of keep an eye on the shutter speed to make sure you don't shut down the aperture so much that you get a shutter speed too slow for what you're shooting at the moment.
02-29-2008, 08:27 PM   #11
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Though all the troubles and fuss with M42 adapters

Warning on Bower M42 adapter - Hin's Tech Corner

I won't hesitate a bit to use my M42 lens. I love them! Ever since I work with M42 lens, I find myself liking my Pentax dSLR more. Not that I have a problem with AF, when I go out and shoot with manual focus and stop down metering, I come to appreciate the AF more though I frequently try to push myself not to rely on it as much as I can afford to. Due to the noted problems of jammed adapter on my K100D body, I highly encourage others to go with the Pentax genuine M42 to K mount adapter. I got a used copy and it makes a big difference when I tried the genuine adapter on M42 lens.

Here is one site that I admire the author for his constant input of information from Pentax lens to macro and flash, it is a great read on his 5D review using a couple of M42 lens

jr-worldwi.de: Photography: Technic

His Canon 5D review using (SURPRISE) a lot of M42 lens
jr-worldwi.de: Photography: Technic

and many of his Pentax lens include M42 mount
jr-worldwi.de: Photography: Technic

Few of my favorite M42 photos


Prakitcar 28-70 zoom


Prakitcar 28-70 zoom


Prakitcar 28-70 zoom


Schneider 135mm f/3.5



Warmest,
Hin

Last edited by hinman; 02-29-2008 at 08:37 PM.
03-04-2008, 02:09 PM   #12
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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.
03-04-2008, 03:02 PM   #13
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QuoteOriginally posted by aegisphan Quote
So usually, you will focus using at wide open, then stop down.
In the old manuals for the screw-mount cameras, especially before the advent of the semi and fully auto lenses, Pentax called this "Bright Field Focusing."

And yes, you should have the lens on the (M)anual setting since the camera does not have a way of actuating the automatic stop-down pin

woof
03-04-2008, 03:25 PM   #14
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Av mode

think i'm going looking for some pra......
no, it'll just drive the price up..
03-04-2008, 07:59 PM   #15
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QuoteOriginally posted by Mike Cash Quote
I've done umpteen thousand shots with M42 lenses on my K100D. The process is not complicated:

1. Set to Av mode and lens switch on "Manual"
2. Focus
3. Spin aperture to desired setting
4. Go mashy-mashy on the shutter thingy

Two things that make a world of difference are 1) installing a split-prism focus screen and 2) start from a default of about f4 when focusing and know how to find your aperture by counting the clicks. In the viewfinder you get a constant and instant DOF preview as you shut down the aperture and all you have to do is sort of keep an eye on the shutter speed to make sure you don't shut down the aperture so much that you get a shutter speed too slow for what you're shooting at the moment.
I have occasionally used the Av method but more often, I run into underexposure program with various lens and depending on lens, I need to dial in different Ev compensation, some go to as high as +2 Ev and I have since given up trying the Av mode. Instead I use the M mode with AE-L for stop down metering in K100D. I think it is the green button in K10D. In M mode, I just dial in the shutter time with adjustment depending on the previous shot. And I seem to get used to the default focusing screen thought that viewfinder in K100D is not great but reasonable in manual focusing. I think K10D will be better in that regard.

Thanks,
Hin
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