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05-02-2011, 02:42 PM   #1
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K-7: metering when it's dark, and with interval shootign

I've just had a few days away (lucky me) where the stars were clear.

One evening I set my K-7 up on a tripod, and because I've not used it before, I used the interval timer to shoot once a minute for an hour - I did it as an experiment really.

Unfortunately it has exposed every shot the same, which as it was getting darker is not ideal - most of the shots are massively under exposed. The shots were taken between 21:40 and 22:40, during which time it got significantly darker, but each one has the same exposure - 1/2 sec @ f4.

Does the interval timer always do the same exposure for every shot? Or is there a way to change it? The manual isn't much use for this.

Also, and possibly related, I've noticed that the meter is generally quite poor if it is very dark anyway - I've tried in the past to take pictures of my daughter sleeping and had to switch to manual as the meter was way out, and even if I put the lens cap on the camera won't set a shutter speed of more than 6 seconds. Is this right? I'd have thought it could set one down to 30 secs?

Any advice much appreciated as ever.

05-02-2011, 03:53 PM   #2
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This might help.

Ultimate Exposure Computer

Scroll down to see an exposure value chart and an exposure factor relationship chart.

This won't help with interval shooting, but it will empower you to decide on the exposure rather than relying on your camera.
05-03-2011, 06:58 AM   #3
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Thanks - I'm quite happy taking control of the camera, and I know roughly what exposure I expect the camera to select - hours playing with my Prakticas with no film in them as a kid taught me that - there was some advantage to not being able to afford film from my pocket money all the time!

I was just a bit surprised that

a) given a dark scene, the meter in the K-7 seems totally flummoxed

b) the metering on interval shooting appears to be fixed to the same as the first shot.

I wondered if other K-7 owners have the same experience?

The interval shooting feature is not much good if you have to keep adjusting the exposure manually, but it may be that my camera is just very reluctant to give a proper reading in the dark. It's still under warranty so I'd like to find out if it is a 'feature' or a fault!
05-03-2011, 09:07 AM   #4
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A camera's meter operates on the assumption that the scene it is metering averages out to 18% gray. This is not unique to the K-7, or to Pentax cameras--they all work that way. If a scene is brighter or darker than 18% gray, the photographer needs to adjust exposure accordingly.

05-03-2011, 12:49 PM   #5
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Ah I know that, although I think the matrix mode is a wee bit smarter, I'm just trying to establish if my meter works correctly.

Even if I cover the lens and viewfinder it won't give an exposure of more than 6 seconds, which seems odd as it can accurately time exposures up to 30 seconds. All my other SLRs have used longer shutter speeds when appropriate.

There is no way that 0.5 seconds /f4 /ISO800 is anything like accurate for a scene lit only by stars!

I just want to know if interval shooting is supposed to take all the shots with the same exposure (in which case it seems pretty pointless) and if my meter is behaving out of character from other K-7s.

I've had a few SLRs, and none have been as reluctant as the K-7 to use a long shutter speed where appropriate.
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