Metering vs. using a light meter?

I am still relatively new to photography and do not have a light meter. I'm reading a lot and experimenting with different techniques using a 5DM3 and shooting with natural light or studio lights.

I'm not sure if this makes sense? How effective is it to put the camera into P mode and meter off the subject, take the f-stop and shutter speed, switch to manual and plug those values in? Curious to hear your thoughts on this? Can this be used instead of a light meter? What else can I look into?

Thanks.

Well you can but not really. Your camera's light meter is a reflective meter. It meters light reflected back to it from your subject. All modes are subject to the same physics reflected of light. The camera's light meter is designed for an even balance of reflected light. A scene with 50% snow and 50% tar will produce an acceptable exposure. 100% snow or %100 tar requires exposure compensation by the operator.

The only way to improve on that is by using an incident light meter. This meter is positioned in front of your subject and evaluates the light that falls onto the subject. They can be costly. The inexpensive option is a grey card.

Do the following to understand what your meter is doing, and how it can FOOL you...

Under indoor lighting, take three items of clothing...a white shirt, a black (or verrrry dark brown), and a medium (not too light, not too rich) green. Try not to cast a shadow on the target items while you are metering...

1. Meter so that the green target is all you can see in the viewfinder, and note the light reading.
   
2. Meter the white shirt so it is all you can see in the viewfinder, and note the light reading.
   
3. Meter the black items to it is all you can see in the viewfinder, and note the light reading.
   

• it tries to make a mid-tone area to be 'middle grey' (the tone which is midway between black and white tones)
  
• it tries to make a white area to be 'middle grey'...which gives LESS exposure than it should, so as a result white comes out 'grey'!
  
• it tries to make a black area to be 'middle grey'...which give MORE exposure than it should, so as a result black comes out 'grey'
  

You do have a light meter. Problem is, it was programmed by a geek at Canon who thinks everything should be gray. Look at this: Post #47
So you usually can't " take the f-stop and shutter speed, switch to manual and plug those values in."

Try this & see how it works for you: Need an exposure crutch?

PhotosGuy wrote in post #18249864
You do have a light meter. Problem is, it was programmed by a geek at Canon who thinks everything should be gray. Look at this: Post #47
So you usually can't " take the f-stop and shutter speed, switch to manual and plug those values in."

Try this & see how it works for you: Need an exposure crutch?

LOL. A geek at Canon. Excuse while I go wipe the tear from laughing.

The thing about M mode is you can set your exposure up for the conditions. It takes a bit to wrap your head around it but very effective. Grass or dense green leaves are very close to the mid grey or grey card I talked about.

One day when out shooting expose for grass or trees in front of you. Basically get the meter at the middle no matter what your ISO, shutter speed or aperture is set at. Then take a picture of a bird or plane in the sky and you will get a good exposure. This how you maintain correct exposure. Pros and amateurs use M and set up to maintain consistent exposure shooting sporting events, etc. They are not exposing off the turf but you get the idea. There are many approaches to this.

It's not always that easy to get the incident light meter into the area where you subject is being lit - that's critical if it is not in the same light as you are. Even if you can, it will make a difference whether the subject reflects a lot of light or only a little. You can learn to use an incident light meter, and take the necessary variables into account (you can't always believe the setting it tells you) or evaluate the information from the (reflected ) 100s of thousands of light meter readings all over the image in your camera - aka the histogram, after learning how the metering modes work - either way, you need to learn how to adjust the first input you get from any measuring device baed on the specific conditions (i.e. EC). For constant light settings where the "average" subject is close like a studio or a cloudless or totally overcast day, the incident light meter is a pretty reliable method but by no means the only one A partly cloudy day with back birds and white birds is quite a challenge where you will need to understand the variables whichever meter you use

That is the issue with incident light meters. As far as the OP's original question. I shoot in Av mode almost all of the time unless I have a flash on indoors. I have no issue with M mode. I just correct correct the exposure compensation as needed for the scene.

digital paradise wrote in post #18249869
LOL. A geek at Canon. Excuse while I go wipe the tear from laughing.

+1. The Geek squad is at Best Buy. C'mon, people!

Proper exposure is proper exposure. It doesn't matter how you get there, light meter, camera meter, sunny 16 rule, experience, or even just guessing. Mode (M, Av, Tv, P, B) is irrelevant to exposure, also.

An ISO of X, shutter speed of Y, and aperture of Z, all yield the same photo, no matter how you got there.

Bassat wrote in post #18249974
Proper exposure is proper exposure. It doesn't matter how you get there, light meter, camera meter, sunny 16 rule, experience, or even just guessing. Mode (M, Av, Tv, P, B) is irrelevant to exposure, also.

An ISO of X, shutter speed of Y, and aperture of Z, all yield the same photo, no matter how you got there.

Correct exposure is everything. There are no short cuts.

There's no point in setting the camera to P mode, read the values, remember them, go to M mode, dial them in and take the picture.

You can just as well dial in the time you like, then zero the meter by dialing in an appropriate aperture and take the picture. It will be just as bright, or dark.

apersson850 wrote in post #18250202
There's no point in setting the camera to P mode, read the values, remember them, go to M mode, dial them in and take the picture.

You can just as well dial in the time you like, then zero the meter by dialing in an appropriate aperture and take the picture. It will be just as bright, or dark.

^
one of the 'automatic' modes simply means that the camera sets itself... TO THE NUMBERS INDICATED IN THE VIEWFINDER...which anyone can do in Manual mode! There is absolutely NOTHING magical and mysterious in any of the Auto modes including 'P'.

With the camera's meter, you're measuring the brightness of the different parts of the scene. With an incident meter, you're measuring the source of light that's illuminating the scene. So in both case, you end up with a value or values which you will use to adjust the cameras settings.

Now the camera, using its own meter, makes some calculations to get the average brightness of the scene, then uses this as its base or middle value. It makes the assumption that the dynamic range of the scene is not too wide and not too narrow. When that's true, you'll get a good exposure. When it's not, you'll get over exposure or under exposure. But you would then adjust your camera settings to compensate for the incorrect assumption and take another picture.

I've never used an incident meter, but believe it also makes assumptions when providing camera settings, such as the sensitivity of a sensor and it's dynamic range. But since it uses just one measurement, it more accurately captures tones as we observed them. However, this may not be desirable in all cases. Maybe there is a dark object but I want to make it appear brighter to make its detail more visible.

The cameras meter is programmed to take a happy shot. A nice day with a green grass, trees. some clouds, maybe a mountain and some people. Nicely balanced which is what the majority of shooters want to do. Then you have the serious hobbyists and pros who learn about it and take it to the next level.

My wife (who has a better eye than I) only knows where the shutter button is but understands about issues while shooting backlit people.