exposure compensation

Hi how do you know when you should be using this? I genrally shoot in manual mode and genrally dial setting so as get the marker in view finder on zero. So if i do that do you still need compensation as i keep seing pics such as widlife ie tiger where ex comp has been used to bring out the blacks more.
Now is this something the photographer instinctivly knows or knows by looking at data. Ie lets say got marker on zero take a pic pic looks ok but look at histogram and a bit light on the left dark side . How much would warant ex comp?
Cheers shane

The camera always assumes you meter off a mid-gray object, because it will put that object in the middle of the histogram, no matter what.
For example, if you meter off of a black cat, the camera will bump the exposure so much so the cat will get in the middle of the histogram, and will appear as a mid-gray cat.
If you meter off a white sheet of paper, again it will appear mid-gray, centered on the histogram.
Ofcourse, we won't agree with such situations, so here comes the EC we add. It's a matter of the photographer being aware he didn't meter off of a mid-gray object, and take action accordingly.
The best way is obviously metering off a gray card, which will set the tones in their right places, yet not always practical.

ninjaboy wrote in post #6557332
Hi how do you know when you should be using this?

Experience.

ninjaboy wrote in post #6557332
I genrally shoot in manual mode and genrally dial setting so as get the marker in view finder on zero.

If you really set the needle on 'zero' for every shot, then working in M mode is not worth the effort. Just shoot in Av or Tv mode with 'zero' EC dialed in and you will get exactly the same shot every time with less effort.

M mode is really best used when you are explicitly going to ignore the meter shot to shot. You might use the camera meter (or the histogram, or an external meter) to pick your settings in M mode to start but after that most users of M do not change unless conditions change.

Chasing the needle around in M mode is really the same thing as shooting in Av mode except that you have inserted yourself in the process without changing the outcome.

JefferyG, Would that not depend on the metering mode that you are in?

When I use spot metering on critters, I try to center that needle without regard for the background.
Shooting at 1/1000 @ f/2.8, I adjust that needle by using the ISO. Is there a different/better method?

chauncey wrote in post #6558277
JefferyG, Would that not depend on the metering mode that you are in?

When I use spot metering on critters, I try to center that needle without regard for the background.
Shooting at 1/1000 @ f/2.8, I adjust that needle by using the ISO. Is there a different/better method?

Whatever metering mode you are in, if you adjust aperture, ISO and shutter speed to center the meter you will get the same shot that you would have gotten had you used the camera in Av mode with no exposure compensation.

Now, as to the second part of your question, yes, if you are locking in aperture and shutter speed and adjusting ISO for exposure compensation then M mode is the best way to work. This is because Av and Tv modes have come to us from film cameras where you had to change film rolls to change ISO.

What a smart camera company might want to do is recognize that exposure is a three variable system in a digital camera. Thus instead of locking one parameter (Av - lock aperture, Tv - lock shutter) there should really be three modes. These three modes should have you pick two and drift the third.

Aperture Mode - you pick shutter speed and ISO and the aperture is adjusted.
Shutter Mode - You pick aperture and ISO and the shutter speed is adjusted.
ISO Mode - You pick shutter speed and aperture and the ISO is adjusted.

And EC should be available in all three modes.

Is this what you're referring to?
Have yet to try it out on my Ds3.
Sorry for Hijack!

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chauncey wrote in post #6558798
Is this what you're referring to?
Have yet to try it out on my Ds3.
Sorry for Hijack!

No, safety shift only steps in when the camera needs to adjust the 'floater' setting beyond what is possible in Av or Tv modes. What I described would simply let you always choose which of the three variables you want moving in the auto metered modes.

But if you'er in a low light situation and want/need that lens wide open and a fast SS (locked in), it would allow you ISO to "float", right?

Or am I completely FOS?

chauncey wrote in post #6560048
But if you'er in a low light situation and want/need that lens wide open and a fast SS (locked in), it would allow you ISO to "float", right?

Or am I completely FOS?

You are not FOS, the Canon camera simply lacks the ability to automatically 'float' the ISO value...you have to find and set that manually.

To use exposure compensation effectively, you have to understand how an exposure meter works. Conventional wisdom states that the meter exposes for 18% gray* and assumes that the average scene is equivalent to that. Of course, Evaluative Metering is designed to more intelligently read the scene and meter according to the bright/dark zones of the scene, and the other exposure modes adjust accordingly.

Appropriate compensation means understanding that if a scene is predominantly dark such as an animal with black fur, as an example, you need to add negative exposure compensation since the metering system will provide an exposure reading to render the fur as a medium gray. Similarly, and white animal or scene would require postivie EC to make sure the white is rendered as white and not as a gray.

*While 18% gray is usually noted as standard, other sources indicate it is actually closer to 12% and based on luminosity and not gray in modern exposure meters.

Mark_Cohran wrote in post #6598445
To use exposure compensation effectively, you have to understand how an exposure meter works. Conventional wisdom states that the meter exposes for 18% gray* and assumes that the average scene is equivalent to that. Of course, Evaluative Metering is designed to more intelligently (?!?!)read the scene and meter according to the bright/dark zones of the scene, and the other exposure modes adjust accordingly.

Appropriate compensation means understanding that if a scene is predominantly dark such as an animal with black fur, as an example, you need to add negative exposure compensation since the metering system will provide an exposure reading to render the fur as a medium gray. Similarly, and white animal or scene would require postivie EC to make sure the white is rendered as white and not as a gray.

*While 18% gray is usually noted as standard, other sources indicate it is actually closer to 12% and based on luminosity and not gray in modern exposure meters.

This brings up an interesting experiment, to see just how smart/stupid the programming in Evaluative really is...Shoot a scene with a very bright area up high and a very dim area down low, which mimics the real world. First with the camera upright, then turned to Portrait orientation, then with the camera turned upside down! and see how the exposure varies. One might suspect that the scene, shot with the camera upside down, might result in a very different interpretation by Evaluative, compared to the scene with the camera in the conventional orientations! because the samples programmed into the logic do not have 'sky low, dark area high' built into the logic.

I would do that for a white balance shot, but to figure exposure on cars, I prefer to chimp a white to the right.
Need an exposure crutch?

Wilt wrote in post #6598505
This brings up an interesting experiment, to see just how smart/stupid the programming in Evaluative really is...Shoot a scene with a very bright area up high and a very dim area down low, which mimics the real world. First with the camera upright, then turned to Portrait orientation, then with the camera turned upside down! and see how the exposure varies. One might suspect that the scene, shot with the camera upside down, might result in a very different interpretation by Evaluative, compared to the scene with the camera in the conventional orientations! because the samples programmed into the logic do not have 'sky low, dark area high' built into the logic.

You're probably right - and in Evaluative Metering, exposure is biased toward the active focus point, which may not be what you want as either.

ninjaboy wrote in post #6557332
Hi how do you know when you should be using this? I genrally shoot in manual mode and genrally dial setting so as get the marker in view finder on zero. So if i do that do you still need compensation as i keep seing pics such as widlife ie tiger where ex comp has been used to bring out the blacks more.
Now is this something the photographer instinctivly knows or knows by looking at data. Ie lets say got marker on zero take a pic pic looks ok but look at histogram and a bit light on the left dark side . How much would warant ex comp?

Shane, I think some posters have missed the point a little bit.

The main point I want to make is that Exposure Compensation (EC) feature does not function in Canon SLRs while in Manual (M) mode.

Putting the EC feature aside, a good photographer really has to know how to use a light meter under a variety of situations. Merely pointing a light meter (whether it is built into a camera or a handheld meter) at a scene and blindly accepting the "centered needle" reading it provides will work in simple situations - those that don't have any extremes of contrast, etc. However, the world is full of scenes that need careful metering and it is those situations that require skill with a light meter.

Film and digital cameras can only capture so much of what we see, relative to light intensity. It's easy to have a scene with the difference between the brightest and darkest portions of the scene so great that the film or digital camera cannot capture the whole range of brightness. The extreme range of light levels that can be captured by either film or a digital camera is called "latitude".

I will often measure the brightest and darkest portions of a scene and determine what the difference is. Assuming that the difference is within the capability of the film (or the digital camera) that I am using, then I will calculate the mid-point exposure setting and dial that into the camera. If the contrast of the lighting is too great for the medium I am using, then I will determine what I want to do about it. Sometimes, the answer is to put a little more light into the darker portion of the scene (with a reflector or a light source). At other times, I merely choose which end of the lighting spectrum is more important for the image and tweak my exposure settings accordingly.

Knowing how to control exposure in less-than-perfect situations is one thing that really separates the skilled photographer from the rest of the crowd. Today's camera manufacturers try to program their cameras to deal with these situations but it's virtually impossible for an automated camera to do what a skilled photographer can do in the tougher lighting situations.

Fortunately, we have a tool for digital photography that helps with the contrast problem, but it only works for static scenes. That's called HDR - High Dynamic Range - imaging. One would make two or more images of the same scene with different exposure settings and combine them in post-processing.