02. What Is Exposure in Photography?

When it comes to photography, ‘exposure’ is a term you’ll hear often. Quite simply, exposure refers to the brightness or darkness level of an image.

We can control the exposure of an image using the two main mechanical functions of a camera: shutter speed and aperture. Using these two functions, either individually or in combination, allows us to control the amount of light that reaches the sensor to record an image, as you see me demonstrate in this video.

Shutter speed

Shutter speed refers to the length of time the shutter remains open when recording an image. The slower the shutter speed, the longer the shutter stays open, allowing more light to reach the recording medium. Faster shutter speeds mean the shutter stays open for a shorter duration and less light is recorded.

Shutter speed

Aperture

Aperture refers to the opening in a lens through which light passes before reaching the recording medium. The greater the size of the hole, the more light passes through, and vice versa. Aperture is recorded in f-stops and shown as f1.2, f5.6, f16 etc. The lower the number, the larger the aperture and the more light that can be recorded.

Aperture and shutter speed

To correctly expose an image, you need to find a balance between both shutter speed and aperture, which you can do by using your camera in Manual mode while referring to the built in light meter (as you would have seen in the video above).

We can add or subtract stops of light by changing the aperture or shutter speed. A change in any setting that doubles or halves the amount of recorded light is known as a one stop change. For example, a change from 1/125 to 1/250 will decrease the exposure by one stop. Opening the aperture from f16 to f8 will result in a two-stop increase.

By controlling these settings yourself using Manual mode, you’ll have the greatest amount of control over what your final image looks like.

The exposure seesaw

When it comes to adjusting your settings, try to think about exposure as a seesaw. If you change either shutter speed or aperture, the other will have to be adjusted accordingly to maintain that balance. For example, if you increased your shutter speed by two stops, you would have to open your aperture by the same amount.

Exposure Seesaw
Let’s take an example of photographing on a hazy day, where the correct exposure is at 1/125, f8. This is equal to 1/250, f5.6, because the shutter speed has been increased by one stop, but the aperture has also been opened by the same amount. The faster shutter speed cuts out more light, but the larger aperture allows in more light. This ensures the exposure remains the same.
Exposure Seesaw
In the same conditions, the combination of 1/250, f11 would result in an underexposed image. This is because the shutter speed has been increased by one stop and the aperture has been closed by one stop. Both changes result in a reduction of one stop of light each, darkening the image by two stops in total. To maintain the correct exposure, if the shutter speed was increased by one stop, the aperture should have been opened by one stop.
Exposure Seesaw
Also in the same conditions, the combination of 1/60, f5.6 would result in an overexposed image. This is because the shutter speed has been slowed by one stop and the aperture has been opened by one stop. Both of these changes allow for more light and result in an overall two-stop increase in exposure. To maintain the correct exposure, if the shutter speed was decreased by one stop, the aperture should have been closed by one stop.

Determining the correct exposure

Once you’ve understood aperture, shutter speed and one-stop changes, the next thing to understand is how to get the right exposure. This is a question that comes up a lot and is something many photographers struggle with.

There are a couple of technical ways that can help guide you with achieving the best exposure, but essentially you should determine exposure based on the creative look you’re going for.

One of the features you can use to help you is your camera’s built in light meter, which you can see through your viewfinder. Most cameras have a meter from -3 to +3 stops, with 0 indicating the ‘correct’ exposure (this is according to your camera). Anything to the left of 0 (in the minus) is considered to be under-exposed and anything to the right (in the plus) is considered to be over-exposed.

ExposureOverexposed imageUnderexposed image

Light meters in different camera brands can look slightly different, but essentially they all tell you the same thing. For more examples of in-camera light meters, please see the complimentary e-book.

The histogram is another way to judge exposure, but unlike your camera’s light meter, you can only use this after you’ve taken your picture. A well exposed image will have a histogram that is evenly spread from edge to edge without any gaps. The left side of the histogram represents the blacks and shadows in an image and the right side represents the whites and highlights.

Histogram

You can view the histogram for an image on your camera or in photo editing software.

camera histogram view

Here you can see a histogram on the back of a camera.

It is important that you don’t get too caught up in what your light meter or histogram are telling you as often the scene you’re photographing can confuse your camera. For example, your camera might think a shot of a white cat in the snow is overexposed and overcompensate until you have a grey cat on grey snow, the same way it might also struggle with something like a black dog on a black blanket and try to increase the exposure until you have a grey dog and grey blanket.

Remember that it’s your image and you should make the creative decisions, not the camera. Over time, with practice, you’ll be able to better judge what exposure you want and how to achieve it.

All content © Copyright Karl Taylor Education.

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Comments

  1. I’m having so much joy watching these essential videos, thanks so much for putting them together. See you in the community; this membership was well worth the price of admission.

  2. Hi Karl. One thing I don’t understand is how F4 and 5.6 are half apart. It’s 3 clicks on my camera. 1/3 stops. Wouldn’t F4 to 5.6 be a stop?

  3. dmzbennett@icloud.com

    Hello Karl and thank you for this fantastic website of knowledge. I am a beginner working towards becoming a professional Photographer. I started watching your videos on YouTube first. Out of all the videos I watched on YouTube, I really am inspired by your work. I was trying to purchase the lifetime package but I couldn’t wait any longer so I purchase the monthly package. I see that I have to know the lingo of photography. One thing that I get confused on is exposure.

    1. Hi, thank you and you’ve come to the right place. As you are doing work your way through the ‘Essentials’ section before you progress into ‘Lighting Theory’ and that will give you a good grounding. If you have any questions they will usually be answered in the class or the next class along but if not then drop a comment and I’ll do my best to answer it. Cheers Karl.

  4. Karl, your subscriber Norseman here . . . over the years of introducing folks new to photography I’ve often had the great good fortune of being able to pull out one of my older Hasselblad V-system lenses to show them how the aperture and shutter speeds are on parallel interlocking rings on the lens barrel where the relationship of aperture changes and shutter speeds lock in to interact and arrive at the, apparently dying, concept of Exposure Value. It’s always gratifying to see the smile of realization on their faces when the interaction of aperture and shutter speed is so illustrated and simplified.
    Though I continue to be amazed at my wondrous H-system lenses, I do miss the old classic red tabs of Depth of Field on the V-system lenses . . . and I don’t hesitate to use those lens barrels and red tabs to teach about Depth of Field for new folks. Ahhh, the nostalgia . . . .
    BTW, bless you and your amazingly talented staff for your site and your ongoing contribution to photography. We, every one of us, never know so much that we can’t benefit from more experienced hands and others’ experiences. I’ve become known for encouraging people to seek out your site for explanations and illustrations. Please extend a very sincere Thank You to all of your staff, every one of them. You guys simply ROCK !

    1. Hi Norseman, yes that would be such a great way for people to see it and understand it. It’s a shame everything went electronic! Thank you also for your kind words about our platform, we think we’re doing a great job but it’s always nice to hear it from our customers, I will pass on your sentiments to the team. 🙂

  5. Hi Mr. Karl, just registered last night and starting to watch some videos. I want to start in basic just to understand more about photography. Thanks and Godbless

  6. Hi Karl,
    I want to know how to get exposure balance while shooting on studio lights. This video only demonstrate the use of exposure scale with continuous light. Please tell me that after connecting studio lights how camera scale tell us that what is correct exposure with the flash fire.

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