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,

A little bit more about apertures, shutter speeds, and ISO settings

For the Chair assignment you will need to turn in one stop manually bracketed images.  This means that you will be submitting a total of six images.  Three for each of the two scenes (objective and subjective).  Don’t use the auto bracket, I will know.  It is easy to shoot in manual, so please learn to do this correctly.Mode dial of a camera set to M for manual
Stops are just a measure of how much light is coming into your camera.Let’s think about it by looking at the size of the aperture hole in your lens.When you open up the hole in your lens one stop, you are letting in twice as much light.  When you close down one stop  you are letting in 1/2 the amount of light.  Depending on which way you adjust your lens opening, you will always be doubling or halving the amount of light that can enter your camera for every stop you move.

f/4 aperture hole
Twice as much light as f/5.6
f/5.6 aperture hole
Half as much light as f4Twice as much light as f/8
f/8 aperture hole
Half as much light as f5.6Twice as much light as f/11
f/11 aperture hole
Half as much light as f/8Twice as much light as f/16
f/16 aperture hole
Half as much light as /11
Now let’s apply this thought to actual numbers.
Go get your camera, I’ll wait………………………………..
Got it?  (Go get it!)
OK.  For now, don’t worry about the other dials, let’s just look at the aperture dial.   You should have numbers on it that look like this, but probably not all of these numbers:

f/1, 1.2, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45

If you don’t know where these numbers are at on your camera, then turn it on and push the shutter button down half way to wake the camera up.  Your LCD (liquid crystal display) will light up if your camera is on.  Now gentle and slowly start turning dials until you see these numbers (along with a lot of other numbers in between – don’t worry about those now, I’ll come back to them.)Some cameras require you to hold an Av button down (see third image below) while you gently turn the dial.Do you see these numbers?  That is your aperture dial. It is telling you that you want the hole in the lens to be a specific size.

Shutter release and dial on top of camera
Some dials are on the top of camera

aperature dial on the back of a canon camera
Some dials are on the back of the camera

Av button on back of camera
Some dials require holding down to Av button to activate the aperture change

OK, set the dial so that your aperture is at f/8.

Camera LCD set at f/8 at 1/250 of a second with an ISO of 200

Now close down the aperture one stop (-1) by turning the dial to f/11.  Congratulations!  You just stopped 1/2 of the amount of light from entering your camera.

 Camera LCD set at f/11 at 1/250 of a second with an ISO of 200

OK, go back to f/8 please.

Camera LCD set at f/8 at 1/250 of a second with an ISO of 200

Now open up your aperture one stop (+1) by turning the dial to f/5.6.  Congrats again!  You have now let in twice the amount of light into your camera then f/8 and four times the amount of light than f/11…. and eight times the amount of light than f/16!

Camera LCD set at f/5.6 at 1/250 of a second with an ISO of 200

Each number listed above is one stop of light.  It either halves of doubles your light each time you turn it a full stop.
Now, let’s quickly talk about those other numbers in between.  More than likely you will have two numbers in between each stop.  They may go something like:F/8, 9, 10, 11, 13, 14, 16
Sometimes half or double the amount of light is too big of an adjustment.  In these cases, you can turn the dial to one of the numbers in between to move 1/3 of a stop.  For example:  If you were at f/8 and closed down to f/10, you would be letting in 2/3 OF A STOP less light.  Not a full stop, but 2/3s of the way there.   Same goes for opening up your exposure too, but I think  you are getting the idea now.  If not let me know!  (Oh, BTW, you will not be tested on 1/3 stops, but you will be tested on FULL STOPS – like those listed at the top.)
OK, so that is the idea of a stop.  A unit of measure that either halves or doubles the amount of light you will let into your camera when you trip the shutter.  Pretty simple.You should also know this too….

f/5.6 aperture hole
Twice as much light as f/8
f/8 aperture hole
Half as much light as f5.6Twice as much light as f/11
f/11 aperture hole
Half as much light as f/8
The shutter speed works in full stops too.  Wake up your camera again and start turning dials until you find number that look like these (with other numbers between them).

1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000

(Depending on your camera, you may or may not have a “1/” above the bottom numbers. For example, it may say 1/2, 1/4, 1/8…)
Did you find them?  Good, this dial controls how long your shutter will be open.  It’s pretty simple – 1 second, 1/2 a second, 1/4 of a second…  Notice how I am halving the amount of time here?  That is because your shutter is based off the 1 stop idea too, which is brilliant.  Photographers are not known for their long division skills, so keeping the math easy is greatly appreciated.
Pie charts showing a second, half second, quarter second, eigth second
The extra numbers are just 1/3 of a stop control like the aperture has.
Can you start to see how these two can play with each other for exposures?  If you take away one stop with the aperture, you can increase your time one stop with the shutter’s speed.
The last thing in your camera that works off the 1 stop rule is the ISO of your camera.  It goes like this:

100, 200, 400, 800, 1600, 3200

The ISO determines how sensitive your sensor is going to be with the light you have.  800 is very sensitive and can shoot in dark areas more easily than 100.  800 also has a greater chance of noise though… but we will get into all that later.  I just wanted to let you know it was there.
One last-last thing.
Set your camera to ISO 200 at f/16 at 1/250.  If you are shooting with your subject in bright sunny light, this is a good exposure to start with.  Using your aperture only, what would this corrected exposure be?  Remember, you are opening the hole in your camera one stop………………………………………………….Camera LCD set at f/16 at 1/250 of a second with an ISO of 200
Did you get ISO 200 @ f/11 at 1/250?  If so, then you got it right. If you did not get this, go back and look how this happened.

Camera LCD showing f/11 at 1/250 with 100 ISO

When you bracket, your exposures could look like this in SB on a bright sunny day:
(Remember, Santa Barbara usually has a marine layer that is blocking 1 stop of light that reaches us.)

Camera LCD set at f/8 at 1/250 of a second with an ISO of 200

ISO 200 @ f/8 at 1/250 = 1 stop over (+1)
One stop too bright

Camera LCD showing f/11 at 1/250 with 100 ISO

ISO 200 @ f/11 at 1/250 = normal
Correct Exposure

Camera LCD set at f/16 at 1/250 of a second with an ISO of 200
ISO 200 @ f/16 at 1/250 = 1 stop under (-1)
One stop too dark
You could use the shutter to make the bracket it too – like when you are shooting images for HDR processing (you’ll have to look it up, we are not covering it in class.)
In this case, your exposure would look like what?

ISO 200 @ f/11 at 1/___ – 1 stop over (+1)

ISO 200 @ f/11 at 1/250 – normal

ISO 200 @ f/11 at 1/___ – 1 stop under (-1)
If you are more of a visual person, check out below.


Camera LCD showing f/11 at 1/250 with 100 ISO


I tried shooting manually, but my images were all black.

Hello,You mentioned on my post to be using the manual mode on my camera. I tried using it for several hours on my Canon EOS 60D, and it would not take pictures. When it did, the images were all black and I tried working with it but the problem persisted. Could you please help me resolve this issue?
Thanks for emailing me.  I would love to help you.
If you images are black, this means you are not getting enough light to your sensor.  To get more light you need to do one of three things.
  1. Open up the aperture hole in your camera lens so that it is wider.  You would move it from f/16 towards f/11 or more for f/8.
  2. Slow down your shutter speed. This means you would move from 1/125 of a second to 1/60 or even slower at 1/30.
  3. Increase your ISO setting so that it is higher.  This means you would go from 100 to 200 or even more at 400.
So now that you know you what your three options are, let’s put this information into practice.
Go get your camera and turn it on.
Next rotate the dial on the top so that it is set in the “M” mode for manual control.
Go outside during the day where it is bright or find a bright room.
Hold your shutter release 1/2 way down and look through the viewfinder.
There will be a meter that will light up at the bottom of your viewfinder.  It will look similar this one below that is telling us that it is one stop under exposed.  (See how the black line is below the number one on the negative side of the line?)
meter-1-under (1)
If you were outside, photographing something in the bright sun, you can get your meter to look like the one below by setting your exposure to ISO 100  f/16 @ 1/125 of a second.
This is called a normal exposure when the line is below the triangle.  Depending on how bright the sun is during the time of day, if there is haze or are clouds, you may have to move you aperture, shutter speed, or ISO setting to make the normally exposed image, which is fine.  You are in control, so feel free to play with it.
Once the line is in the center, click your aperture or shutter three times one direction to see how the line moves.  If it goes to left and is under the -1, then you are one stop under exposed.  Snap off a frame here.
meter-1-under (1)
Lastly move your dial six clicks in the opposite direction to let in more light and you will have your one stop overexposed shot too for the bracketing assignment.
Play around with it and let me know how this goes for you.
Just a quick test, how many stops over or underexposed is the image below?
Hope this helps,