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11-20-2007, 12:58 AM   #1
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SMC M lens + K100D = no aperature control?

Hi folks,

I purchased a few M lenses and absolutely love them. The only problem is that when I'm using these M lenses with my K100D, I'm finding that, even though I change the aperture value on the ring, the background doesn't focus or defocus any differently at all.

I have the "Using Aperture Ring" custom option set as permitted, as well as "AE-L button on M exposure" to Tv shift (Although I don't think this function has any bearing on this problem).

Any help would be greatly appreciated!

11-20-2007, 01:14 PM   #2
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That's strange. If you're moving the aperture ring on the lens, then the aperture should surely be changing when you take shots. I'm thinking about getting some cheap M lenses myself, so I'll keep an eye on this thread to see what the experts say.
11-20-2007, 01:31 PM   #3
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QuoteOriginally posted by dugrant153 Quote
I'm finding that, even though I change the aperture value on the ring, the background doesn't focus or defocus any differently at all.
Do you mean while you're looking through the viewfinder? If so, have a look while changing the aperture on any other lens - there should be no difference with them, either. The aperture remains wide open until you either take the photo, use the dof preview (the little lever on the shutter), or use stop-down metering. When you stop down to meter or do dof preview, you should hear the aperture closing, and if you look through the viewfinder, you should notice the scene get darker, particularly if you're well stopped down. I hope I haven't entirely misunderstood your problem!

Julie
11-20-2007, 05:34 PM   #4
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Yep. What foxglove said.

Lens stays open unless your camera is in the act of taking a picture. So you can't see a difference through the viewfinder, but the image actually captured will inherit the appropriate attributes.

11-20-2007, 06:59 PM   #5
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What foxglove and Avant said. Also you can see the aperture stops down if you use the depth of field preview. You will see the blades close down to the apropriate aperture value.

cheers
11-20-2007, 07:13 PM   #6
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Don't forget you must shoot in "M" mode. I believe that Tv or Av mode will leave your aperture wide open on M lenses.
11-21-2007, 12:48 AM   #7
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thanks for the replies, I actually figured it all out just after posting this thread. (my bad!)

Anyways, here's the thing with Pentax SMC-M lenses. Using my K100D, if you shoot in Av mode, the lens will always been in the 'widest open' aperature value. That means that, even if you twist the aperture ring from F1.7 to F22 or whatever, the aperture value will remain the same: wide open (in my case, always F1.7).

juice, you got it right on the nose. You have to be in 'M' mode in order to use the aperture ring. Here's how you take a shot with an M lens, with controllable aperture (using the aperture ring on the lens):

1) Twist ring to desired aperture value.
2) Manually focus on your object. (no autofocus on this bad boy!)
3) Press the AE-L button (if I'm correct, this meters the light and adjusts your shutter speed).
4) Press the shutter button and take the picture.

This is a very involving process, but I actually kind of find it rewarding. This technique makes me think about the picture, what I'm metering on, what's my aperture value, etc. So if you're considering an M lens, make sure you know this technique cuz you'll be using it with all the M lenses. If you don't like the idea of manually metering with the AE-L button, go for a Pentax A manual lens.

At first, I was put off by having to press an extra button. But... there's something about doing all the stuff manually that's really rewarding. And that extra button has made the photo experience that much more challenging... and fun.


To everyone who's replied so far, thanks for the info! I just realized I have just summarized all your replies! oops!
11-21-2007, 02:14 AM   #8
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I use a lot of M and "K" lenses. I agree with all that has been said so far. One further method i sometimes use with the K10D (not sure if this applies to K100D too), is when in M mode turning the DOF preview on also activates the light meter. Hold the DOF preview on and as you turn the aperture ring or adjust the shutter speed you will see the meter reading change.

11-21-2007, 07:50 AM   #9
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QuoteOriginally posted by pschlute Quote
Hold the DOF preview on and as you turn the aperture ring or adjust the shutter speed you will see the meter reading change.
I do this too - I find it much easier than using the AE-L button. You can meter various areas of the scene and choose your aperture/shutter speed based on that. Hm, rather like what I did with the old needle meter on the K1000! I get a certain Luddite pleasure out of making an advanced digital camera behave like one of the most basic, classic cameras.

Julie
11-22-2007, 12:22 AM   #10
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strangely enough, I can't get the DOF preview method to work. the AE-L method seems to work for me just fine so far

maybe it's because I have a K100D?
11-22-2007, 04:42 AM   #11
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The DOF preview method works fine on the K100D - provided of course you've set preview to optical. I have a K100D and use it a lot - I have several M lenses.

Actually, I'd really like to be able to switch quickly between the two preview methods without going into the menu - perhaps a feature for the K100D Extra Special that I'm sure is just round the corner
11-22-2007, 09:35 PM   #12
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Using M series lenses has worked fine for me with the 100 Super, once you have the camera set up for the M lens. I also agree with some of the earlier comments that actually having to make the settings will make you feel more involved with the picture taking process. Obviously an M series lens is not your first choice for fast moving subjects.
11-22-2007, 11:10 PM   #13
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great info guys..Thanks
11-23-2007, 12:17 AM   #14
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actually, sometimes I prefer the M lens with fast moving subjects, as it can be difficult to autofocus on an object. By the time I switch from AF to MF, I might've missed the shot, whereas if I started out as MF, I could've focused properly, pressed the AE-L button to meter, and got the shot. Where this is most prominent is in darker areas (ex: indoor arenas) where the autofocus tends to take a lot longer to focus properly... and I find that it sometimes even doesn't focus properly! (is this a K100D bug?? hmmm...)

Never knew about the 'optical preview' option! I can see the meter reading now. I'm finding it a bit foreign, though, as it doesn't adjust the shutter speed to the light being metered. The AE-L button method sets the shutter speed to the light in that situation, and I like that. But that's just me.
11-23-2007, 01:41 PM   #15
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QuoteOriginally posted by dugrant153 Quote
I can see the meter reading now. I'm finding it a bit foreign, though, as it doesn't adjust the shutter speed to the light being metered. The AE-L button method sets the shutter speed to the light in that situation, and I like that. But that's just me.
It's just another option, maybe more familiar to those of us who started on a really basic camera. With the K1000, I'd point it at the subject, and change shutter speed and aperture as needed to get the little needle in the middle. Now on the K100 I flick the dof preview on, and change the shutter speed and aperture until the meter reads "0.0". Same effect in the end! And it does allow you to meter various parts of the scene - I'll often check the darkest and brightest areas just to see how under- or overexposed they are, and sometimes adjust accordingly. Occasionally an average meter reading just doesn't cut it.

Julie
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