What is the Difference Between and Incident and Reflective Light Meter?

Great Question:
In the test, there was a question that asked:
“T or F
An incident light meter is the type of meter built into most 35mm cameras today.”

Please explain why this is false.  Thank you!!

Hello and thank you for your questions

There are two types of light meters – incident and reflective. Let’s talk about the reflective one first.

Reflective Meter:
A reflective light meter is the type that is in your camera. It reads the light that reflects off of surfaces you are metering. A reflective light meter can be fooled as to what the correct exposure will be due to some surfaces being more bright or dark. A reflect meter takes whatever you are photographing and converts all the tones to 18% gray. So if you are photographing a white wall, the meter does not know it is white. It will give you are reading to make the wall 18% gray. As you want the wall to be exposed like it is white, you will need to open up (brighten) your exposure by two stops.

Conversely, if you are photographing a scene that is mostly black or dark brown/red/blue/green/purple/orange, the meter is still going to give you are reading for 18% gray. Fortunately, you are smart and can use this consistent meter reading and make adjustments by closing down your exposure (letting in less light) by two stops so that your 18% gray tones will get darker.

The best way to really cover your bases with important photos that have challenging lighting conditions is to bracket your photos – one taken at what the meter gives you, one or two taken at a stop or two underexposed (less light), and one or two taken a stop or two over exposed (more light). (In some challenging light situations, I will bracket my shots and then combine them later so that I have the exposures I want for each area which I brush in later in Photoshop with layers – but that is a different lesson.)

Incident Meter:
The other type of light meter is an incident light meter. This type of meter is handheld. You place it in the area of light that is most important for you to get correct in your photograph. An incident meter will measure the amount of light that falls directly on it. This is the same amount of light that would fall on your model/scene. The incident light meter will give you an 18% reading also, but as it measures the actual light falling on its sensor,you do not have to worry about making adjustments for light/dark environments or subjects.

Here is a link to an article on both meters that goes into the details a little differently:

https://www.digitalphotomentor.com/the-difference-between-reflective-and-incident-metering-and-how-they-work/ (Links to an external site.)Links to an external site.

Let me know if you have further questions you want clarification with.

Take care,

Tutorial on how to use the in-camera meter of Canon’s Rebel T2i

Tutorial on how to use the in-camera meter of Canon’s Rebel T2i
To use the meter in your camera, turn it on and press the shutter button down half way.This will “wake up” the camera and activate your meter.Image of Rebel T2i showing shutter release button
Looking through your viewfinder, you will see a few numbers at the bottom but you are only really interested in these at this moment:

  • The shutter speed
  • The aperture
  • The meter
  • The ISO

Rebel T2i viewfinder screen

If you look carefully in the image to the right, you will see that the meter has a green line at zero. When using the meter in the camera, you have the choice to adjust the shutter speed, aperture, and/or ISO settings to get the lit line in your camera to “zero out”.In this case, the exposure at ISO 100, 1/125 of a second at f/8 should give a neutral exposure.Rebel T2i meter on zero
If the aperture is closed down to f/11 (one stop less light) the meter will give a read out that the exposure is one stop under exposed by making the lit line show up under -1.Rebel T2i meter showing one stop under
When the lit line is all the way to the left the camera is telling you that the exposure us at least two stops under exposed.(Same is true if the lit line were all the way to the right – only it would be at least two stops over exposed.)In either case, you may have to do a bit of adjusting of controls before you can get the lit line back to the zero position.

Rebel T2i meter showing two stop under

Remember, you are trying to get the lit line to fall back under the zero for a neutral exposure.Rebel T2i meter on zero
Once you have mastered how to control you meter, be sure to read this web page on how make the meter work for you if you are metering white or dark subjects.