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09-07-2014, 09:07 PM   #1
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K20d slow exposure/meter coupling

Recently out shooting at night in very low light, around 2-8 sec, f2.8, iso800-1600 would be about the correct exposure.

My K20d however would not meter/expose below about 1/10th sec f2.8 iso 1600-3200. Or 1.3 second at iso 400. In P mode.

Below around that point it just flashes to show low exposure, and if I fire the shutter just gives me a black 'image.' So it is actually firing at the settings it shows on the screen.

By comparison, my old film Super A will flash to warn low exposure but if shutter is fired, will get a pretty correct or correct exposure down to 15 seconds at f1.7 on iso 400-800. It will sometimes flash a 1-2 second shutter speed warning but actually fires at several seconds on P mode.

So I get that there is a meter coupling range, but I've noticed many cameras with a P mode will shoot a longer range that seems to exceed the coupling range, I assume by cumulative metering during exposure but I may have that wrong.

I'm wondering if my K20d is malfunctioning or does it actually not have the ability to shoot below its official coupling range at all? Why would my Super A have a better meter/shutter than a K20d?

Any idea anyone?

09-08-2014, 03:48 AM   #2
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QuoteOriginally posted by culturalproduct Quote
Recently out shooting at night in very low light, around 2-8 sec, f2.8, iso800-1600 would be about the correct exposure.

My K20d however would not meter/expose below about 1/10th sec f2.8 iso 1600-3200. Or 1.3 second at iso 400. In P mode.

Below around that point it just flashes to show low exposure, and if I fire the shutter just gives me a black 'image.' So it is actually firing at the settings it shows on the screen.

By comparison, my old film Super A will flash to warn low exposure but if shutter is fired, will get a pretty correct or correct exposure down to 15 seconds at f1.7 on iso 400-800. It will sometimes flash a 1-2 second shutter speed warning but actually fires at several seconds on P mode.

So I get that there is a meter coupling range, but I've noticed many cameras with a P mode will shoot a longer range that seems to exceed the coupling range, I assume by cumulative metering during exposure but I may have that wrong.

I'm wondering if my K20d is malfunctioning or does it actually not have the ability to shoot below its official coupling range at all? Why would my Super A have a better meter/shutter than a K20d?

Any idea anyone?
There is a limit of EV where camera can't meter. I mean any camera. When you reach that, you have to find out what are the good settings to achieve the proper result for your chosen scene. For that, I suggest manual (M) mode or aperture priority mode (Av) - and experimenting until you get the proper look for the photo.

Regarding the behaviour of the camera in P mode, I'm not sure, but it worth checking what setting you have in the Custom menu "Program Line". Maybe it is set to "Hi speed" and the camera can't reach the preset values for that - or maybe there is a limitation in P mode - and you reached the "limit".

I suggest you to try the same situation in full manual (M) mode. I never use P mode, so I can't speak about that, but I'm 100% sure that there is no such a limitation in M or Av - as I've used my K20D in many situations below the level of light where the camera can't meter anymore, for example in caves, dark forest...
09-08-2014, 07:31 AM   #3
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The specifications for the K-20D lists the meter range from 0 to 21 EV. You could calculate the limits at a given ISO from that. But as pointed out above the limits can be modified by the program line.

For extreme exposures it is often best to use a hand-held meter and manual mode.
09-08-2014, 08:12 AM   #4
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Thanks for the replies. So yes, the camera can shoot if set manually and get an exposure in very low light (ignoring issues like noise etc).

I just wondered why my Super A, and other film SLRs I've checked again in the last 24 hours, seem to be able to meter correctly well below their stated EV range, in P mode at least. In M mode everything seems to be limited by its EV range. I don't have any other brands of DSLR to compare anymore, but I do remember using my D1x and D2x at least, in very low light and they would expose apparently correctly, even though it was below their stated EV range.

It just seemed strange to me that my K20d couldn't do what a 30 year old program camera could do. So I thought maybe it is a malfunction.

Conversely, why is it that those older cameras will meter below their EV range?

09-08-2014, 08:16 AM   #5
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QuoteOriginally posted by culturalproduct Quote
Any idea anyone?
As noted above, the meter sensitivity range of your K20D is 0-21 EV(100). Below that range the meter is not linear and the display will blink indicating so. 0 EV(100) is f/2.8 @ 8s exposure. At ISO 400 for the same aperture that would be a 1/s exposure. So the short answer is that you are attempting to use automated metering in light below the meter's range. There is nothing wrong with your camera. The meter on your Super Program is even less sensitive with a range of 1-19 EV(100).

Solution? Shoot in M mode using your best estimate of exposure times or use one of several available hand-held meters offering extended light sensitivity.


Steve

---------- Post added 09-08-14 at 08:27 AM ----------

QuoteOriginally posted by culturalproduct Quote
I just wondered why my Super A, and other film SLRs I've checked again in the last 24 hours, seem to be able to meter correctly well below their stated EV range, in P mode at least.
You must have a very special Super A. My Super Program (same camera) goes into blinky mode at about 1 EV(100). The shutter will still release and a good photo may still be rendered (most negative films have great dynamic range), but the exposure was not determined by a "correct" metering of the scene.

I put quotes around the word "correct" for a reason. For night scenes, it is seldom the photographer's intent to generate an image that looks like it was taken in full daylight (histogram centered). I would suggest using one of the exposure charts for typical subjects instead of depending on your meter. Using your K20D's spot meter in M mode on the brighter parts of the scene is another option.


Steve

Last edited by stevebrot; 09-08-2014 at 08:27 AM.
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