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02-03-2009, 03:51 PM   #1
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Something wrong in using this M lens?

Just picked up an M 28 f/2.8 lens, my first manual lens.

I just want to make sure I'm doing this right: M mode, turn the A ring to the chosen aperture, shutter half way down, press the AE-L (on the K100D) to set the speed, and take the shot?

Seems like the shots are coming out dark. Can I see and vary the speed with an M lens?
Brian

02-03-2009, 04:11 PM   #2
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you dont need to press teh shutter half way, just press the ae-l button, it will meter, then press the shutter to take a picture

thats one

two, when you step down meter you are using spot metering, keep that in mind

three, if its dark, just reduce the shutter speed, after all, you are in M mode
02-03-2009, 04:23 PM   #3
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I presume you've changed the setting in the custom menu about using the aperture ring? You need to turn that on.

Otherwise, you may be encountering what many people have found--that while the old K and M lenses often have wonderful build and optical quality, metering on our latest DSLRs can be tough. I am new to manual focus lenses, but have picked up 3 of them lately (2 M lenses, and one A lens). The M lenses are very nice, but I still need to work on getting the metering right. Mind you, it's been winter while I've been testing them out and been mostly indoors, but it definitely takes some getting used to.

With the K and M lenses, once you set the aperture on the lens, you'll need to adjust shutter speed once you stop down with AE-L (green button on my K200) if you want to get more light. The onboard flash is not that helpful as it fires full throttle. Alternatively, the A lens I have can be used with the AV setting (when the aperture on the lens is set to A), and is much easier to properly meter. That's why the A lenses are generally more expensive than the K or M lenses.

You'll need to experiment with this. The older lenses require some work, but they're definitely pretty fun to use, and can produce great photos.

And you can always check out this thread at dpreview for some pictorial advice.

http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=24921509
02-03-2009, 05:23 PM   #4
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A few minor clarifications and additions:

If he hadn't set the option to use the aperture ring, he'd get no picture at all.

Half-pressing the shutter *is* often necessary to wake up the meter. You don't have to do it before every shot - just when the viewfinder info display goes dark. At least, that's how I remember it being on my DS. My K200D seems to respond to the Green button even when the meter has expired, but my DS would do *nothing* when pressing AE-L unless the meter was active (which you could tell because the viewfinder display was also active). I wouldn't be surprised if the K100D wasn't similar. It doesn't hurt to try AE-L first. But If you don't hear the stop down happening - and it's unmistakablewhen it does - then do a half-press to wake up the meter.

"M" lenses *can* use spot metering, but the default if you weren't already using spot metering is to use center-weighted metering.

While in many cases center-weighted metering will produce a *brighter* exposure than multi-segment (because the camera can't protect highlights as well), there are no doubt scenes where the opposite is true. I long ago switched to center-weighted metering fulltime (eg, for for my DA lenses) because I got tired of having to keep readjusting to a new metering method every time I changed lenses.

You ask if you can see and vary the speed - well, of course. After hitting AE-L, it displays the speed in the viewfinder. Turning the dial changes it. No different from how "M" mode works with other lenses - and that's a big part of why I also switched to using "M" mode fulltime.

BTW, unless you have the K2000 (which lacks DOF preview), you can also get a "live" meter reading by doing a DOF preview. I use that a lot. Hit the green button to get an average reading of the scene, then do DOF preview and point directly into the shadows and into the lights to see how they register. That helps me decide if I need to override the camera's suggestion.

02-03-2009, 08:43 PM   #5
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To add to Marc's comment about changing the shutter speed, the net result on my K200D is Manual mode more or less functions as Aperture priority with the command wheel changing shutter speed and acting as a very handy and easily set exposure compensation. Very nice.

I do have to press the shutter button half-way to wake up the meter in my K200D before the green button will work.

Finally, I'm not convinced the stop-down metering process gives an accurate meter reading at smaller apertures but I haven't found documentation on how the current Pentax meters function. They're intended to take a reading at full aperture with the lens aperture lever or the lens electronics telling the camera what the current aperture selection is. In stop-down metering the camera is forced to make an approximation from a reading taken at partial aperture. It's possible the custom menu selection for allowing the use of lens aperture rings changes the program for the meter but I'm not sure. I'm not surprised though when I must retake a shot with an increased or decreased shutter speed.
02-04-2009, 10:07 AM   #6
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QuoteOriginally posted by B Grace Quote
I do have to press the shutter button half-way to wake up the meter in my K200D before the green button will work.
Interesting. I had assumed so too, because I knew it was true on my DS, but I tried it out just before posting yesterday and couldn't get the green button to not work. Of course, if the whole camera has gone to sleep - not just the meter - then you need to wake it up.

QuoteQuote:
Finally, I'm not convinced the stop-down metering process gives an accurate meter reading at smaller apertures
This is definitely a widely-reported problem on the K10D, apparently related to the focus screen and other issues that don't seem to affect the Kx00 or *ist series. I did a test series with my K200D an M135/3.5, ponting at a scene and running through the green button sequence and taking a shot at each aperture ring setting. The results were as consistent as one could possibly hope for - all exposures came out within about a quarter stop of each other.

It's possible, of course, that individual lenses might have aperture rings that are not entirely accurate in smaller apertures. And it's also possible that if you repeated my experimented in something other bright sunlight, the total amount of light entering the camera would be below the threshold for what the meter needs.

QuoteQuote:
It's possible the custom menu selection for allowing the use of lens aperture rings changes the program for the meter but I'm not sure.
Wow, that's a possibility I've never heard raised before! I kind of doubt it - the camera knows when the aperture ring is being used anyhow, so no need to change the metering behavior for all lenses just because you've enabled this setting. But of course, actually using the aperture ring *does* switch you to center-weighted metering if you had been using multi-segment.
02-04-2009, 10:45 AM   #7
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Thanks Marc, Gooshin et al. I should have figured out that I could reset the speed with the wheel after setting it with the AE-L button, it just never occurred to me.Also, good tip that the AE-L button alone sets the speed without the half-push on the shutter, that makes it just that much easier to handle.
Brian
02-13-2009, 02:42 AM   #8
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QuoteOriginally posted by Marc Sabatella Quote
You ask if you can see and vary the speed - well, of course. After hitting AE-L, it displays the speed in the viewfinder. Turning the dial changes it. No different from how "M" mode works with other lenses - and that's a big part of why I also switched to using "M" mode fulltime.........you can also get a "live" meter reading by doing a DOF preview....Hit the green button to get an average reading of the scene, then do DOF preview and point directly into the shadows and into the lights to see how they register. That helps me decide if I need to override the camera's suggestion.
On a K200d, I have been using the optical DOF preview to check the exposure readout while twisting the aperture ring of an SMCP-M lens or using the wheel to adjust the shutter speed. The theoretically "correct" readout is shown as 0.0 in the viewfinder, though one can overexpose or underexpose in fractions of an EV. I am treating this as the digital equivalent of the green orange and red leds in the MX viewfinder. Mostly I don't touch the green button when I use this method. Am I missing out on something?

02-13-2009, 03:40 AM   #9
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chhayanat

Your metering method is perfect.

The green button method is simply doing what you do manually by adjusting the shutter speed.
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