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Exposure: How Bright is Your Photo Going to Be? How Do You Know? How Do You Fix It?

Updated: Jan 10

What does it mean when a photographer talks about "exposure"? There are (as usual for the English language) multiple definitions of exposure. For our purposes, we are going to talk about the technical definition of exposure in photography. Exposure is defined by Adobe as "the amount of light that reaches your camera’s sensor, creating visual data over a period of time." (Source) This is a very accurate summary of exposure, but how do you know what "exposure" your camera has and why should you care?


Exposure Meter

In your camera there is most likely a diagram that looks kind of like a ruler. It has one side that has positive numbers on it (these indicate "over exposure") and negative numbers (these are "under exposure". The diagram usually looks something like this (without the red arrows):

Most modern cameras (in my experience) have this nifty little tool in it. It's probably one of the tools in a camera that I rely on the most. This meter tells me how dark or light the photo will come out after I hit that shutter button. If the meter is giving me a "+1" indication (how it indicates this depends on the camera), that means that I probably need to make the photo darker. On the other side of the meter, if the camera is telling me that the subject is "-2", then that means that I need to increase the exposure to make the resulting image brighter. The light meter isn't always 100% accurate, but that is only a concern in the rarest of occasions. During my career and training in photography, I have never encountered a situation where the light meter wasn't at least mostly accurate.


So, how do you change the meter? There are three main ways that a photographer can shift the exposure. Aperture, shutter speed, and ISO. If you are interested in more detail, you can learn more in other posts.



Aperture

Aperture covers how wide the lens will open after the camera shutter button has been pressed. In this case, the lower the aperture on the camera, the more it will increase the light meter reading. On the other side, the higher the aperture, the more it will lower the meter. While this can be quite helpful for changing the meter, remember that it can also impact the focus and structure of the image that you create.


Shutter Speed

Shutter speed is quite literal. It covers how quickly the camera lens opens and closes. The higher the number, the faster the lens. In this case, the faster the lens the less light the camera takes in, and the darker the image. So, if you set the camera at 1/2500 of a second, the image might be pretty dark. Therefore, the meter might read as "-2". In order to fix this without impacting the aperture, you have to lower the shutter speed. Sometimes this can be tricky, given what photo you're trying to create. The lower you go, the more likely you are to miss your target. The lowest I've ever gone without risking shaking or missing the subject is 1/60 of a second, but I was talking a photo of a set of leaves. There is not much motion in leaves. I've known sports photographers who set their cameras at a minimum of 1/2000 of a second, never lower. In order to keep that those sports photographers often compensate for it by using a lower aperture.


ISO

You may have noticed that I almost never talk about ISO, and that's because I almost never change it. This is true for most photographers I know. I set my camera's ISO at 400 and rarely switch to 800. I almost never go to any other setting, unless I really have to. Most photographers I know set their ISO at a certain measurement, and never change it. This is because a higher ISO can cause an effect called "grain" or "noise". It's this strange effect where a photo looks like sand is spattered on the image. The higher t5he ISO, the more likely this is to happen. That's why the only people I know who regularly use ISOs higher than 1600 are all photographers specializing in night skies.


I hope you found this post helpful. See you again soon!

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