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03-23-2010, 03:23 PM   #1
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K-x Av mode shutter speed question

Hi all,

I took a road trip to Sequoia National Park this past weekend, and took about 250 pictures all with the kit 18-55 lens in Av mode.

however, not sure if snow or sky affecting anything, my K-x used really high shutter speeds (1/3200, 1/2500 etc) resulting in under exposed photos.

I was using spot metering, could this be the reason?

also, would shooting in P mode resolve this under exposure problem?

thanks in advance

M

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03-23-2010, 03:44 PM   #2
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The meter was fooled by the snow. You could have dialed in 1.5 to 2 stops extra EV.
03-23-2010, 03:52 PM   #3
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Spot metering is a tricky thing to do; you have to know what you are doing to use spot metering correctly (with proper exposure). Even in this case, taking snow scene generally requires +EV to compensate with matrix metering. But if you metering on the dark spot, you will get over-exposured picture.
03-23-2010, 04:12 PM   #4
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In my limited experience it makes a lot of difference where you expose of. If the lightmeter in the camera exposes for the snow in the picture above and takes that as a reference point the darker parts of the photo can be rather underexposed and the shutter speed will be relatively hight. Spot metering perhaps will only make that effect stronger.

But that doesn't really explain why the whole picture is underexposed. With snow in the picture I use the EV-compensation (+2) to get natural looking white snow. For landscapes I use center weighted metering, expose for a suitable reference point, lock that with de AE-L button and compose the picture.

Anyway, there are people on this forum far more capable then me. Perhaps they have better answers! The book Understanding Exposure by Brian Peterson is mentioned a lot as a good way to guide for these sort of questions.

Good Luck!

03-24-2010, 03:41 AM   #5
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The cameras meter is designed to expose to 18% grey. This gives best results for images where there is a range of colours and even lighting.

In snow scenes the camera will do what it is designed to do and render the snow as 18% grey. Using spot metering will only make things worse as you are not allowing the dark areas to be taken into consideration by the meter.

You need to apply compensation (increase exposure) in this instance to achieve correct exposure. You will find the opposite happens if you shoot a predominantly dark scene...the camera will overexpose unless you reduce exposure through compensation.
03-24-2010, 07:32 AM   #6
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Unrelated to your original inquiry but in response to your statement about the camera choosing high shutter speeds:

That correlates to what you had your ISO set to. Lower ISO will give you lower/slower speeds. (Less sensitivity needs longer exposure.)

In an outdoor scene with plenty of light, not such a critical issue, but I always shoot at the lowest ISO anyway, 100. However, I say this because in case you find yourself in a situation in Av mode (or any mode) where your shutter speeds are getting too slow for comfort, bump up the ISO.
03-24-2010, 09:17 AM   #7
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hi everyone,

thank you all for informative replies.

regarding metering usage, is it useful to use center weighted metering for portraits and multi-segment metering for landscape? are there situations where one metering method would be more useful than the other?

regards,
M

03-24-2010, 09:50 AM   #8
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QuoteOriginally posted by macky112 Quote
hi everyone,

thank you all for informative replies.

regarding metering usage, is it useful to use center weighted metering for portraits and multi-segment metering for landscape? are there situations where one metering method would be more useful than the other?

regards,
M
You need to learn all about your metering modes. Each of them has its benefits. Using the wrong one will over/underexpose your scene.

If your pics aren't coming out with the right exposure, it's possible that using another setting will correct the problem.

This is a long learning process, but it will help you get your image more to your liking.

Or, you can just go for manual mode and let your eyes do the metering. That will take longer, though, in certain situations, but be better for others.
03-24-2010, 10:10 AM   #9
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QuoteOriginally posted by macky112 Quote
hi everyone,

thank you all for informative replies.

regarding metering usage, is it useful to use center weighted metering for portraits and multi-segment metering for landscape? are there situations where one metering method would be more useful than the other?

regards,
M
It all depends on what you want the outcome (picture) to be. I generally use multi-segment to start with as it tends to provide the most accuracy on the overall exposure. But that may not necessary be what you want as you sometimes you may want to deliberately under-expose or over-expose for certain situation. You can use + or -EV to do the fine tuning or you can change to either Center-weigh or spot metering mode depending on the situation. It is all part of the learning process as you get your eyes trained to just knowing what to use.
03-24-2010, 10:13 AM   #10
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QuoteOriginally posted by macky112 Quote
hi everyone,

thank you all for informative replies.

regarding metering usage, is it useful to use center weighted metering for portraits and multi-segment metering for landscape? are there situations where one metering method would be more useful than the other?

regards,
M
The short answer:

Yes.

For example, let's say you're going to shoot someone against a bright white background. If you use multi-segment, the camera is going to interpret that bright white as 18% grey, and lessen exposure to bring everything to that 18%. The background stays white, but your model was ALREADY close to 18% grey, so that less exposure UNDEREXPOSES him. This is what happens with snow scenes, where the common problem is underexposure.

If you use center-weighted metering and keep the subject in the viewfinder guides, your meter doesn't "see" the white background at all--it's as if it doesn't exist--and you get correct exposure for the subject. (Spot metering is even more targeted.) However, the white may now appear UNDEREXPOSED.

It's a real balancing act and involves some trade-offs at times. That's why perfectly exposed models against perfectly exposed backgrounds involve lighting the elements separately, but that's nothing for you to think about now.

I use center-weighted all of the time, even when doing scenics (rare for me) because I shoot in manual and can always bracket anyway.
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