Using aperture ring?

audiobomber · 10-06-2008, 05:06 PM

I RTFM but I'm still confused. I have my K20D set to allow manual aperture settings. If I take the lens out of auto aperture mode, and set the ring at a selected manual aperture, I'm getting erratic results.

In Av mode with the aperture ring on my FA 50mm set for f1.4, it didn't show the aperture before the shot (F---), but it took a photo at f1.4, 1/2000s. When I moved the aperture ring to f22, it still used f1.4, 1/2000s. In Program mode and mechanically set to F22, it took a photo at f2.8 and 1/1000s. I have a 28mm A lens that is doing a similar thing. No matter what aperture I set mechanically, it takes the photo at f4. I've tried P and Av modes. What am I doing wrong?

*Canada_Rockies* · 10-06-2008, 05:11 PM

Originally Posted by audiobomber

I RTFM but I'm still confused. I have my K20D set to allow manual aperture settings. If I take the lens out of auto aperture mode, and set the ring at a selected manual aperture, I'm getting erratic results.

In Av mode with the aperture ring on my FA 50mm set for f1.4, it didn't show the aperture before the shot (F---), but it took a photo at f1.4, 1/2000s. When I moved the aperture ring to f22, it still used f1.4, 1/2000s. In Program mode and mechanically set to F22, it took a photo at f2.8 and 1/1000s. I have a 28mm A lens that is doing a similar thing. No matter what aperture I set mechanically, it takes the photo at f4. I've tried P and Av modes. What am I doing wrong?

You can only use Av and M and Bulb with a manual aperture ring. I use M myself, but I grew up on manual cameras, so it's not that a big deal to me. Av will not stop the aperture down, and will expose always with the lens wide open. (eg f/1.4)

Wheatfield · 10-06-2008, 06:24 PM

Originally Posted by audiobomber

I RTFM but I'm still confused. I have my K20D set to allow manual aperture settings. If I take the lens out of auto aperture mode, and set the ring at a selected manual aperture, I'm getting erratic results.

In Av mode with the aperture ring on my FA 50mm set for f1.4, it didn't show the aperture before the shot (F---), but it took a photo at f1.4, 1/2000s. When I moved the aperture ring to f22, it still used f1.4, 1/2000s. In Program mode and mechanically set to F22, it took a photo at f2.8 and 1/1000s. I have a 28mm A lens that is doing a similar thing. No matter what aperture I set mechanically, it takes the photo at f4. I've tried P and Av modes. What am I doing wrong?

To use the aperture ring, you need to set the camera to "M" and press the green button after setting the aperture. The camera stops the lens down, takes a meter reading at the set aperture and sets the shutter speed accordingly.
My own experience with this is that the camera does a reasonable job of getting it right in bright light and moderate apertures, but it seems to run out of accurate metering range fairly quickly, so if you are stopping down a lot, or are shooting in dim conditions, you may want to either use a hand meter or check your review screen frequently.

Also, the way the aperture cam works was altered when they made the change from M to A (IIRC, A series and later is a non linear movement), and I don't believe the K10 or k20 is capable of giving a really accurate exposure with A lenses using the aperture ring.
I get very good exposures with pre A lenses, but the few times I have experimented with later lenses the exposure have been kinda all over the place.

audiobomber · 10-07-2008, 06:26 AM

Thanks Wheatfield. Lots of good info there. I'll try M mode and see how it goes.

*Canada_Rockies* · 10-07-2008, 01:52 PM

There is another way to use the M mode. I generally prefer it myself, but it is a bit more complex and slightly slower. I find it to be more the way I work. I use the depth of field stop down on the power switch. This stops the lens down, meters, and displays the Exposure scale in the finder and on the top LCD. That way it is simple (for me) to allow for exposure compensation using the scale in the finder.

It does require me to hold the switch with my forefinger and to move the front (shutter) e-dial with my middle finger. Then release both and move my index finger to the shutter release to take the image. It is a bit slower that way. However, once it is done for a particular situation, there is not need to repeat the exercise. This holds true for the green button approach as well.

I have found with my M lenses that only certain stops meter correctly, so I shoot at only those stops (8 through 16 on my 400, for example). This ensures that my meter is giving me a correct result. As I have seldom used stops other than these on the 400, it is not a penalty to me. At f/5.6 (wide open) the meter is off by 1 stop, and above f/11 it is out as well.

Using the green button approach would again only be accurate between f/8 and f/11 on my M 400, and would set the shutter speed to the one corresponding to the center 0 on the scale. I find it handy to have the over/under scale visible when I am "selecting" a shutter speed.

As another poster is fond of saying "Your mileage may vary".

audiobomber · 10-07-2008, 02:22 PM

Originally Posted by Canada_Rockies

There is another way to use the M mode. I generally prefer it myself, but it is a bit more complex and slightly slower. I find it to be more the way I work. I use the depth of field stop down on the power switch. This stops the lens down, meters, and displays the Exposure scale in the finder and on the top LCD. That way it is simple (for me) to allow for exposure compensation using the scale in the finder.

When I hit the dof switch, my camera goes into Live View mode. I tried the Green button method and it's very simple to use. I'll try working with it and see how aperture affects exposure the way you've done, so I can add compensation if needed.

*Canada_Rockies* · 10-07-2008, 03:31 PM

Originally Posted by audiobomber

When I hit the dof switch, my camera goes into Live View mode. I tried the Green button method and it's very simple to use. I'll try working with it and see how aperture affects exposure the way you've done, so I can add compensation if needed.

Yes, my method only works when the power switch goes into a viewfinder depth of preview stop down. Sorry I did not make that clear. It is a menu setting, if you wish to try it out.