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09-05-2011, 10:49 PM   #1
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Long exposure metering on K200D

This weekend I used my K200D with a K24, Tak 35/3.5 and a A50/1.7. It was an overcast day and I used an ND filter for long waterfall exposures. Every time it was off by 2-3 stops possibly more. It wasn't an issue since I was photographing waterfalls and I could retake the photo as many times as I wanted until the exposure was right. But it distracted me and I feel like I was making unrelated composition mistakes. I remember this happening once before but I haven't had any other problems that I remember. But it was usually sunny and I was taking 1 second exposures instead of 4-6 seconds.

So I'm just wondering if this is normal. I can accept that since this isn't normal usage.

09-05-2011, 11:57 PM   #2
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It's tough when your calculations don't work out the way the are suppose to. Is it underexposing or overexposing? You might have to do a controlled test indoors with various time lapses. It may be possible the sensor can no longer handle the longer exposure time accurately.
09-06-2011, 08:41 AM   #3
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Taiwan? Small world...

Underexposing. It's not an old camera though except in technology terms. I bought it in July with 3600 clicks on it. I haven't doubled that number yet but it won't be too long.

I was actually planning on playing with this in a more controlled way and see if there is a certain point where it goes haywire.
09-06-2011, 12:29 PM   #4
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I don't know how many stops your ND filters is (maybe an nd8 by the sounds of it?). Anyway, when you put the ND filter on, think of it like turning the lights out. Anything beyond around 1 second required exposure and most meters will start to become inaccurate - it will either be a case of the experimenting you're doing to get it right, or figure out the regular exposure, use M mode and compensate the required number of stops to get proper exposure. If I'm wrong someone let me know!

09-06-2011, 05:23 PM   #5
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QuoteOriginally posted by pxpaulx Quote
I don't know how many stops your ND filters is (maybe an nd8 by the sounds of it?). Anyway, when you put the ND filter on, think of it like turning the lights out. Anything beyond around 1 second required exposure and most meters will start to become inaccurate - it will either be a case of the experimenting you're doing to get it right, or figure out the regular exposure, use M mode and compensate the required number of stops to get proper exposure. If I'm wrong someone let me know!
this is kind of what I was thinking and I was wondering if this was actually true for other users. Or if there was something else I could be doing with the camera for it to meter correctly or if I need to just figure out the exposure thru trial and error like I did.
09-06-2011, 05:29 PM   #6
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Sounds like you are probably shooting in manual mode. I would recommend taking a meter reading with the ND filter off, then when you put it on, increase your exposure time to compensate for the correct number of stops for the filter. ND2 = 1 stop, ND4 = 2 stops, ND8 = 3 stops. So if your original metering was a 1 second exposure, and you add an ND8 filter to your lens, then increase your exposure time to 8 seconds. Does that make sense? It might help your meter stay more accurate since it could operate using all available light.
09-06-2011, 10:04 PM   #7
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I think the manual specifies the metering range down to 0EV, which I think corresponds to 1sec. at f1 iso100. It may be that behind your ND filter, exposure is below 0EV, which could give the inaccurate meter readings.

I'd try arpaagent's method. Another approach is trial and error. If you set Preview Method (Custom Setting 18) to Digital Preview and select Histogram for Digital Preview in the Playback menu, the trial and error method may be faster than removing/replacing filter. Just rotate the On/Off/Preview switch to Preview and the image with histogram overlay will be displayed. The image will not be saved, unless you then press the fn key. Adjust shutter speed per histogram results and try again.
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