Underexposure

Finally, after much wait, Canon replaced my 1D MkII with a new (refurbed) N version

I've been taking a few test pictures, and I thought that I was getting a lot of underexposed shots, usually by about 2/3rd of a stop or so. I double checked my EV, and it's at 0.

Here is an example taken of a pretty much white wall using evaluative metering, with the histogram in the top right. Is this what I should be getting?

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That looks about right to me. The camera won't meter a solid white wall that well. You'll find snowy scenes on a cloudy day will turn out grey as well.

When the camera sees all white, it assumes everything is grey and adjusts the exposure to get grey.

You should be adding a bit of EV in these situations.

Edit.. Just for fun, I shot a PURE bright white freshly painted wall with my 10D.. EV=0 Here it is below

Um, is that a white wall with an old custom white balance setting?

Dave

I respectfully disagree with Jim T.

The camera, if the frame is full of a wall lit evenly, should bring the exposure to the middle, regardless of the wall being white, green, or brown. That histogram should be right in the middle, especially with a 1 series. Also, since the color is rather even, I am not sure why there are three peaks in the histogram and not one like the gray example below it.

Looks like his camera is underexposing a bit. I would double check all settings again. No matter how experienced one is, a double check cannot hurt.

canoflan wrote in post #2367891
I respectfully disagree with Jim T.

The camera, if the frame is full of a wall lit evenly, should bring the exposure to the middle, regardless of the wall being white, green, or brown. That histogram should be right in the middle, especially with a 1 series. Also, since the color is rather even, I am not sure why there are three peaks in the histogram and not one like the gray example below it.

The camera uses a reflective light meter, which assumes your target is neutral gray. A neutral gray (18% gray) target will give you a spike that is to the left of the center of the histogram. A 13% gray card will give you a spike right in the middle of the histogram. Try it yourself if you have an 18% gray card handy.

You'll get the same results even if you use a handheld reflective meter and plug the readings into your camera.

So if you put a gray card next to the wall you'll see that the card, of course is darker. According to Ansel Adam's zone system, the gray card should fall (by definition) on zone 5, whereas a white wall will generally fall on zone 7.

But the camera doesn't know what's in front of it. It reads the wall, thinks its a gray card, and chooses settings that will make it look like a gray card. Accordingly, your histogram and your picture both show exactly that result.

So you can get the exposure right a few different ways. First, you can recognize that the wall is about 2 stops lighter than 18% gray, and use +2 stops exposure compensation. (Snow and sunlit sand are similar; caucasian skin is about 1 stop lighter than 18% gray).

You can also meter off a gray card to show the camera exactly what middle gray should look like under that lighting -- then use those settings to take a picture of the wall.

Or you can use an incident light meter, which would have to be a handheld meter -- but incident meters evaluate the light falling on the subject, rather than the light reflected off the subject itself.

As far as the three spikes, I can't say -- certainly your red, green, and blue spikes can fall in different places depending on the color of the wall, but with a uniform color the RGB composite curve should just have one spike.

DrPablo wrote in post #2367938
The camera uses a reflective light meter, which assumes your target is neutral gray. A neutral gray (18% gray) target will give you a spike that is to the left of the center of the histogram. A 13% gray card will give you a spike right in the middle of the histogram. Try it yourself if you have an 18% gray card handy.

You'll get the same results even if you use a handheld reflective meter and plug the readings into your camera.

So if you put a gray card next to the wall you'll see that the card, of course is darker. According to Ansel Adam's zone system, the gray card should fall (by definition) on zone 5, whereas a white wall will generally fall on zone 7.

But the camera doesn't know what's in front of it. It reads the wall, thinks its a gray card, and chooses settings that will make it look like a gray card. Accordingly, your histogram and your picture both show exactly that result.

So you can get the exposure right a few different ways. First, you can recognize that the wall is about 2 stops lighter than 18% gray, and use +2 stops exposure compensation. (Snow and sunlit sand are similar; caucasian skin is about 1 stop lighter than 18% gray).

You can also meter off a gray card to show the camera exactly what middle gray should look like under that lighting -- then use those settings to take a picture of the wall.

Or you can use an incident light meter, which would have to be a handheld meter -- but incident meters evaluate the light falling on the subject, rather than the light reflected off the subject itself.

As far as the three spikes, I can't say -- certainly your red, green, and blue spikes can fall in different places depending on the color of the wall, but with a uniform color the RGB composite curve should just have one spike.

^ what he said.

knowing how to meter and the different types of metering is essential.

Ok, here is a picture taken of a white piece of printer paper. It still looks a little low to me. No?
It's about 100 on the RGB values.

0 EV, Evaluative Metering

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stop shooting white/black. it will not properly meter it. it wants it to be middle gray. so yes, its under exosed, as if you think about it, it is. go and shoot a gray card, green grass, the dark blue part of a sky, the palm of your hand etc.

drisley wrote in post #2368093
Ok, here is a picture taken of a white piece of printer paper. It still looks a little low to me. No?
It's about 100 on the RGB values.

You've actually proven my point quite well.

Again, the camera's meter thinks anything you point it at is a gray card.

If you point it at a white wedding dress, it will think it's a gray card.

If you point it at a black tuxedo, it will think it's a gray card.

So it will choose settings to make it look like a gray card.

But you know that a white wedding dress is brighter than a gray card, so you need to give the scene more exposure. And you know that a black tux is darker than a gray card, so you need to expose less.

Your camera just did a great job at making your white piece of paper look like 18% gray. It did its job. Now try it using +2EV exposure compensation. Or try it by metering off a gray card and using those settings to shoot the paper.

Ok, thanks guys. Im not sure why I suddently thought the cam was underexposing. Maybe it's because I was shooting at high ISO's and I prefer to keep things "to the right" as much as possible.

Unless you're shooting in full manual mode and ignoring the light meter, the camera will use reciprocity calculations to give you the exact same exposure. So if you have your camera in Av mode at f/2.8 and the camera meters 1/125 at ISO 200, it will automatically change the metering to 1/60 at ISO 100 and 1/250 at ISO 400. It's just compensating for the change in ISO to produce the same exposure.

Under many conditions just blind metering is fine. But there are times when you want to intentionally modify exposure, like increasing exposure for sand or decreasing exposure for sunsets.

Aside from metering incorrectly, have you checked the accuracy of your chip yet? All chips are slightly off, and need exposure compensation. Go out in full sunlight where the eposure will be 1/ISO @ f/16 ans shoot a white t-shirts with wrinkles in it, a grey card and a wrinkled black (not faded black) cloth or shirt and shoot from 2 stops under to 2 stops over exposed, then look at them in Photoshop, find the one that has the best middle grey/white, black combo and see that the exposure was.

It it were 1/250 at f/16 ISO 200 then your chip is off by 1/3 stop. So you have to correct it by setting EV to +1/3.

Well, if you have a gray card, I don't think you should be using the sunny 16 rules unless you can't get into the same lighting as your subject. You should just meter off the gray card instead. It's also well known that different handheld meters can be off by 1/3 or 1/2 a stop, and that's more likely to be the case than a sensor problem post-metering and post-exposure. Fortunately a 1/3 stop discrepancy is almost never important unless it's in the extreme highlights or shadows, and you can correct it in Photoshop (even if you're shooting JPEG it's easy to correct a 1/3 stop discrepancy).

DrPablo wrote in post #2369755
Well, if you have a gray card, I don't think you should be using the sunny 16 rules unless you can't get into the same lighting as your subject. You should just meter off the gray card instead.

But he's not sure if his meter is accurate, so the sunny 16 rule will give him a guidline to fugure out if his meter and chip are accurate.