The Light Meter, Pt.2 How the Camera Exposes an Image

Hi and welcome to my blog.  Today I am going to shed some light on, how your camera exposes an image and why it gets it wrong a lot of the time.  I also wanted to show why a light meter is an invaluable tool to determine the proper exposure.

A camera measures light that comes in through the lens and tries to assign it a specific value.  That value is a shade of grey 1/2 of the way between black and white and it is called 18% grey.  A camera uses that middle grey as it’s reference point, represented by a little mark in the viewfinder in the center of the exposure scale and is most often shown as the number 0. (- 3- -2- -1- -0- -1- -2- -3 +).

Have you ever filled the frame of your camera with a white piece of paper?  What about a black piece of paper?  Better yet, an unknown value of dark grey piece of paper?  How do you know when you have the correct tone that represents the exact tone of dark grey?  What about if you are using flash?

Every camera/lens/sensor combination reads light differently, and there isn’t any way to calibrate exposure inside the camera.  Lets say you are using aperture priority mode, this means the camera picks the shutter speed, and you need to accurately expose a subject that has a specific tone.  Do you think the camera can do this?  Well, I made a video to show you how a camera works.  In the video I use a dark grey piece of paper as the reference tone.  This is to be reproduced and you might be interested to know what happens.

Thanks for taking time to read my blog. If you have any questions or comments please feel free to post them below. I will answer them as soon as I can. I hope you have a great day. Thomas Shue

Please remember this video is not intended to be definitive I am not claiming this video is the ONLY way or even the BEST way to understand how a camera exposes a scene or subject. I am merely offering my thoughts on camera exposure and offer this video only because it might be helpful to someone to understand more about their camera.