I have owned a 67II with AE finder for around a year now. Most all of the shots I've taken with it have been metered at wide open aperture. It seems to be doing a good job with exposure in that mode.

Something I have noticed is that when I lock down the DOF preview the exposure drops off. Sometimes as much as -1 stop. I don't beleive this should happen since the camera knows the aperture ring setting. I brought it in for an adjustment early under warranty. When it came back repaired and calibrated it still acted the same.

I only make these comparisons in central emphasis or spot modes. If you have the camera in full frame average wide open it will shift to central emphasis when you stop down. This invalidates the comparison.

My question, now that you've suffered through this: Has anyone else noticed this? Is it normal? Do I need to find a warranty shop that knows what they are doing?

-- Chuck Bernards (chuckb@hevanet.com), March 14, 2000

Answers

Chuck, I noticed the same thing with my P67. Before I had taken pictures with it I was playing with all the functions and saw that exposure readings were different when the lens was stopped down, comparet do wide open. I called Pentax asked which reading was correct. My question was relayed to someone that I did not talk to, then the answer was relayed back to me. Hopefully the answer is right.

I was told that when a lens is attached directly to the body, metering should be done wide open, and that stopped down readings would be inaccurate.

Stopped down metering should be done only when an accessory is added, such as an extension tube, that breaks the metering chain. The inner bayonet extension tubes are called 'automatic', but they are automatic only for stopping down the diaphram when the picture is made. These tubes don't have the linkage necessary for wide-open metering, so metering should be done stopped-down when they are used.

For what it is worth the T6-2X tele-converter (this is the older one, black) has linkages for both automatic diaphram control and metering, so metering can be done wide open when it is attached between the lens and body.

This situation seems odd to me. You would think you would get the same meter reading whether metering is done wide open or stopped down. I'd like to hear from others on this too. Bob

-- Bobby Mahaffey (mahajen@prodigy.net), March 14, 2000.

Hmmm,

I don't like the sound of that very much. I havn't used the tubes yet but It sounds like I better bracket a wide range with them. At least it appears to consistently underexpose stopped down. It even does it with the aperture ring dialed wide open! One of those newfangeled accurate TTL meter thingy's would sure be nice...

-- Chuck Bernards (chuckb@hevanet.com), March 14, 2000.

Chuck, I hope I didn't mislead you about the use of extension tubes. If you use tubes, then the proper way to meter is stopped down, with the DOF preview lever engaged, and metering should be accurate. It's only when the metering chain isn't broken, i.e. when the lens is attached directly to the camera, that you should NOT use stopped down metering.

If you use tubes, and meter stopped down to the working aperture, then your exposures should be right, and you shouldn't have to bracket wildly. If you shoot slide film a little bit of bracketing won't hurt, whether you are metering stopped down with tubes (or some other accessory that breaks the metering chain), or wide open with the lens attached directly to the camera. I usually bracket + and - 1/2 stop with slides, plus one right on the meter, and the middle one is usually right. Bob

-- Bobby Mahaffey (mahajen@prodigy.net), March 15, 2000.

Bob,

Thanks for the reply. I'll be pleased if that's true. I'll check it out on my next roll.

-- Chuck Bernards (chuckb@hevanet.com), March 15, 2000.

I noticed the same thing, and the difference of readings differ from one lens to another. I have tried two 135mms, with one the reading does not change much (less than 1/3 stops) and with the other the reading goes 2/3 stops over, both stopped down to f/32. Upon inspection, the second lens does have a visually smaller apature when stopped down to f/32 in comparison to the first one.

Therefore, my theory is that the meter is doing the right work, but for many P67 lenses the actual apature is not very accurate closed way down. Thus the light is not reduced to the exact amount prescriped by the differences of number of f-stops, and thus the meter readings, already accounting for the changing apature settings, differ.

-- Leping Zha (leping@tamri.com), March 20, 2000.

Leping,

I don't think so. I see a shift in shutter speed when I work the depth of feild preview, even with a wide open lens. Try it with various lenses and your aperture ring set wide open.

-- Chuck Bernards (chuckb@hevanet.com), March 20, 2000.