Canon 20D Metering Question.

[Mercycreek]

Hello all. I'm so glad I found these forums. I'm in dire need of a good kick in the right direction. Let me start by saying that the 20D is my first real camera but I'm not entirely new to photography. Does that make sense?

I'm a graphic designer by trade and I utilize a camera when needed in the design process, but I have had a desire to pursue photography as both a hobby and a profession for quite some time. I have an educational background in photography and videography so I'm aware of the tradition and philosophy involved. My problem currently lies in the technical understanding of the Canon 20D's metering system.

I understand what metering is and how it used, but I'm not sure how to analize the metering of the 20D. I have studied the manual until I'm blue in the face. All it defines for me is the three metering modes. I don't find anything that tells me how to read what the meter gives me and how to translate that into proper settings. Heck, all I know is that the camera has a metering system.

Does the meter just read what ever I point the camera at and adjust the small arrow under the exposure compensation bar to let me know how well exposed that particular point is or am I really missing something? I really want to get past this bit of a rut and actually put the camera to proper use. I just don't understand how to read the 20D's metering system and how to make the adjustment from what it gives me.

I truly hope I'm making sense. Any feedback would be greatly appreciated.

Thank you for reading.

-brandon-

[Andy_T]

Hi Brandon,

welcome to the forum!

Actually, the only time when you really have to put the metering into all the considerations yourself is when you are using M(anual) mode.

When you use any of the other modes (T, A or P), the camera does what is necessary to get a decent picture. You pick the aperture in A mode, and the camera meters the available light and selects the appropriate shutter time. The only thing you basically have to do is to observe (based on the figures displayed in the viewfinder) that the shutter time selected is not too slow to get a good shot (e.g. 1/125 second when you are using 50 mm of focal length).

If that would be the case, then you have to open up the aperture or increase the ISO.

When the camera is not able to select something that makes sense (e.g. you set 1/500 second in T mode but it is too dark and you only have a f/4.0 lens), then the parameter selected by the camera will be flashing. This tells you to select something else to get a properly exposed picture.

In the 'automatic' modes and 'P', it's even easier, as the camera selects all the parameters to give you a decent exposure.

Hope that helps you.

The advantage of the digital camera is that you can actually try it out to your heart's content, as you don't have to pay for films or prints (unless the pictures are good and you really want to print them)

Best regards,
Andy

[Mercycreek]

Well... Now I feel that I'm even more confused.

The literature I have been studying (Outdoor Photography) puts a strong emphasis on metering in order to obtain the best shot. I do tend to work in the full manual setting so as to learn the workings of exposure and the camera fully at the same time. Perhaps I'm making this more difficult than it is. I'm just not sure how to be in control of the metering of the camera because I don't know where to look for the reading.

Based on what I'm reading through right now if I meter on one subject I should get a reading different from another subject that is lighter or darker. I just want to be in control so as to get the exposure I want with a well defined lighting in the image. As above, I just don't understand where the meter reading is on the 20D and how to implement the information it gives me. I do work in the full manual setting.

I do appreciate the feedback, Andy. thank you. ;)

-brandon-

[Andy_T]

Hehe,

then my solution would be to start with one of the other modes and see what the camera gives you. That way, you get a feeling which shutter speed and aperture the camera would select in different lighting situations.

Nothing better than some kind of starting point for your own experiments in full manual mode - but this is just my opinion. I am most likely not much of a help, as I normally don't use full manual mode, but rather 'A' mode (and adjust the exposure compensation based on the histogram of a test shot if I would like the camera to get the photo a bit brighter or darker )

Finally, the result the meter will give you also would also depend on the metering mode ... depending on the mode selected more or less of the motive will be taken into consideration for the brightness of the picture.

Best regards,
Andy

[PacAce]

Well... Now I feel that I'm even more confused.

The literature I have been studying (Outdoor Photography) puts a strong emphasis on metering in order to obtain the best shot. I do tend to work in the full manual setting so as to learn the workings of exposure and the camera fully at the same time. Perhaps I'm making this more difficult than it is. I'm just not sure how to be in control of the metering of the camera because I don't know where to look for the reading.

Based on what I'm reading through right now if I meter on one subject I should get a reading different from another subject that is lighter or darker. I just want to be in control so as to get the exposure I want with a well defined lighting in the image. As above, I just don't understand where the meter reading is on the 20D and how to implement the information it gives me. I do work in the full manual setting.

I do appreciate the feedback, Andy. thank you. ;)

-brandon-
What mode do you want to take your pictures in? If in Manual mode, the scale at the bottom serves as an exposure meter. When the "needle" is dead center, the camera is telling you that the exposure you're getting based on the set shutter speed and aperture is dead on. If the needle is off to the left, then the exposure you're getting from the camera settings will underexpose the shot by however many stops the needle is off from center. If it's to the right, you're overexposing by the the number of stops the needle is off from center. In either case, you will need to adjust the aperture and/or the shutter speed to get the needle to the middle of the scale if you want to use the exposure the camera is recommending. If you want to underexpose or overexpose a little from what the camera recommends, then you'll need to set the camera so that the needle is off center by however many stops (or fraction thereof) you want to compensate the exposure with.

If you are using the other Creative Zone modes, such as Av or Tv, the needle will always be in the center and will not change. The camera will set the exposure for you automatically. If the needle is not in the center, then that means that you have set the exposure compensation (EC) and the camera will under- or overexpose by however many stops you have set EC to.

[Mercycreek]

So I'm basically making this more harder than it is?

If I work from the other modes I will tend to get a good shot and if for some reason I need to compensate for the exposure I could switch to full manual to correct that?

Pretty much what you're saying is that the camera does the work itself?

An example of my plight would be that sometimes I have landscape images where the sky is blown out and the foreground has a decent exposure... my understanding is that metering would make the adjustment to get everything in proper exposure. Is this understanding faulty?

I'll begin playing with the other settings and learn to see it work, instead of trying to disect a problem with such intensity.

I think I've got a lot to learn.

-brandon-

[Mercycreek]

Leo,

That put it into the words I needed to hear. I truly appreciate it. Now that gives me another question.

In full manual as I move the camera around with the shutter half depressed the needle moves based on how "light" an object is in the view finder. Metering doesn't really affect anything but exposure does it? It won't have some grandious effect on the way light is displayed? Perhaps this sounds odd, but I'm just trying to understand the perspective I already have and what areas of it are wrong and what I need to change.

Again. You put that into the format and words I needed. Thank you.

-brandon-

[HJMinard]

If I work from the other modes I will tend to get a good shot and if for some reason I need to compensate for the exposure I could switch to full manual to correct that?

Yes. Or you could utilize EC (exposure compensation) within the mode that you're in (Av, Tv).

Pretty much what you're saying is that the camera does the work itself?

It certainly can if you want it to. Use Av and choose your aperture, or Tv and choose your shutter speed, and the camera will do the rest (in most conditions) amazingly well.

An example of my plight would be that sometimes I have landscape images where the sky is blown out and the foreground has a decent exposure... my understanding is that metering would make the adjustment to get everything in proper exposure. Is this understanding faulty?

No, not faulty, but there are limitations. The camera's sensor has a limited dynamic range and can only handle so much contrast. In some cases you will need to use a graduated neutral density filter to prevent the sky from overexposing.

[Todd Jacobsen]

Leo,

That put it into the words I needed to hear. I truly appreciate it. Now that gives me another question.

In full manual as I move the camera around with the shutter half depressed the needle moves based on how "light" an object is in the view finder. Metering doesn't really affect anything but exposure does it? It won't have some grandious effect on the way light is displayed? Perhaps this sounds odd, but I'm just trying to understand the perspective I already have and what areas of it are wrong and what I need to change.

Again. You put that into the format and words I needed. Thank you.

-brandon-


Greatest gift the digital camera provides the photographer is instant feedback. For focus, you have the thumbnail. For exposure, you have the histogram. The learning curve between film and digital is logrithmic. What used to take YEARS to learn, now takes months...

[PacAce]

You're welcome, Brandon.

In full manual as I move the camera around with the shutter half depressed the needle moves based on how "light" an object is in the view finder. Metering doesn't really affect anything but exposure does it? It won't have some grandious effect on the way light is displayed? Perhaps this sounds odd, but I'm just trying to understand the perspective I already have and what areas of it are wrong and what I need to change.

You are correct. In Manual mode, as you move the camera around, you will see the needle moving around. That's the camera telling you that with the aperture and the shutter speed currently set on the camera, your exposure will be just right (needle in the middle), underexposed (needle towards the left) or overexposed (needle towards the right). If the needle is in the middle, depress the shutter fully and you'll have what the camera thinks is a well exposed picture. However, bear in mind that YOU may not think that the picture is well exposed. Since the camera will always try to make everything mid-gray in tone, a light colored subject in a lightly colored background will come out underexposed. Knowing this, you would have to make sure that your purposely overexpose by setting the needle a little to the right by however many stops you need to properly expose the lightly colored subject. And, of course, you influence where the needle ends up by adjusting your shutter speed and/or your aperture and, I might add, your ISO.

In the other creative zone modes, you will need to use EC to compensate for the exposure.

Of course, you won't see any change in what you see in the viewfinder as far as the scene is concerned because you're viewing it with the aperture wide open. But, as someone already pointed, with digital, you can take the shot and review the image and the histogram to see if you got the exposure right.

[Mercycreek]

No, not faulty, but there are limitations. The camera's sensor has a limited dynamic range and can only handle so much contrast. In some cases you will need to use a graduated neutral density filter to prevent the sky from overexposing.

I was sure that was the real answer I'd get. I've been eyeing a few filters. The first ones on my list are a polarizing and a graduated neutral density.

Thank you for the answers. I truly appreciate the input. ;)

-brandon-

[Mercycreek]

Leo,

Thank you. It make smore sense now. What I realize is that a lot of my original understanding of the camera was initially true. I was just a bit confused by different sources of information that I have been consuming as of late.

I would like to ask one more question if that is ok. I'm interested in furthering my understanding of metering by looking into information concerning the "zone system". Are there any good web based information pools on the subject?

Thank you again, Leo.

-brandon-

[Mercycreek]

Thank you. I'll be putting those areas of the camera to greater use now. ;)

-brandon-

[robertwgross]

The bright sky-dark foreground scene is hard to get right. It does not seem impossible, but it is difficult to get right the very first time.

Your camera has about three metering methods, and each of those averages light over a different area. Let's just suppose that you are using Evaluative. If the camera "sees" a scene with bright sky and dark foreground, it might average that all and pick a middle value for exposure solution. That might be still too bright for the sky and too dark for the foreground. Let's try another mode, centerweighted. If you aim that center circle just a little above the horizon, then the meter sees brightness, and it may pick an exposure solution to tone that down, which may or may not be what you wanted. On the other hand, if you aim the center circle just a little below the horizon, then the meter sees darkness, and it may pick an exposure solution to brighten that up, which again may be suboptimal.

So, for the difficult scene, the meter may not be perfect automatically. That is where the human eye can help. Shoot one frame with the center circle too high, and read the histogram as a result. Then shoot one frame with the center circle too low, and read the histogram again. Now, you are approaching the end result by successive approximation.

In "P" mode of exposure, you can use that same solution and vary aperture for depth of field control. Or, if you don't like the solution, you can vary it up and down with exposure compensation.

You've got a ton of tools there to work with, and it remains a challenge to choose the right tools to apply.

---Bob Gross---

[slin100]

The way I interpreted the OP's post was a question about the differences between Evaluative, Center-Weighted Average and Partial metering. Bob Gross is on the right track.

[Mercycreek]

This is such a help Bob. Thank you so much. I can't express in words how relieved I am that I pretty much made it more complicated than it was. Thank you again.

-brandon-

[cmM]

Basically, the 20D's TTL metering works by trying to average the data and coming up with the exposure needed to get proper exposure. Proper exposure in camera language means an average of 18% grey.
•Evaluative metering (or matrix) looks at the entire image(split up into a matrix) and averages.
•Center weighed calculates exposure for the entire image, but calculates exposure which is more ideal for the center
•Partial metering: only the center of the frame is metered, and everything else is not taken into consideration.