The 500 rule is a guideline for how to determine if your subject will be exposed correctly when using an on camera flash. An off-camera flash can also be used, but it’s important to understand that this does not change the 500 rule calculations. You may have heard of the “rule of thirds” or “golden ratio,” which are both guidelines for composition in photography. There are no rules about what you should shoot, but understanding basic principles like these can help you make decisions about where to focus your attention.
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What Is The 500 Rule?
The 500 Rule is a camera setting that guarantees a good exposure of the stars and Milky Way while preventing “star trails.” If you exceed the 500 rule with your shutter speed, the stars in your photo will appear as star trails (rather than dots).
500 divided by your focal length is the number of seconds you can leave your shutter open before getting a correctly exposed photo.
You want to underexpose your shot slightly, which means aiming for a longer shutter speed than what’s calculated using the 500 rule. Your goal with this method should be to capture any movement in your scene while keeping everything else properly lit and exposed. It takes some practice and patience! This can also be used when photographing sports or other fast moving objects that require high ISOs: like many nighttime scenes, these subjects often benefit from long exposures so it’s important not to lose sight of that when exposing your shot.
500 Rule Example
Let’s say you’re photographing the stars with a 50mm lens on a full-frame camera at f/11 for 20 seconds, ISO 500. The 500 rule tells us this is an acceptable exposure because it will render everything in our frame properly exposed, allowing us to get more detail in both the sky and landscape below (the Milky Way). If we only expose for 16 seconds using our shutter speed dial instead of 20 seconds, two things happen: first, there is less light hitting our sensor so noise becomes more apparent. Second–and most importantly–because the 500 rule guarantees proper exposure of key elements within your image like bright stars while also ensuring movement won’t occur in the rest of your scene, we’ll start to see star trails in our image. This is because 500 / 16 = 31.25 and anything above 30 seconds starts to show very apparent star trails (which can be cool if that’s what you’re going for!). You should also check out our 600 rule photography guide for more context.
500 Rule For Different Camera Bodies
Below are a few applications of the 500 rule for different camera bodies.
Full Frame Camera
A full frame camera’s 500 rule requires you to set your camera to ISO 3200 or 6400, with a shutter speed of 500 divided by the length of your lens. If you’re using a 50mm lens, for example, your shutter speed would be 10 seconds (500 / 50 = 10). If you’re using a 24mm lens, your shutter speed will be 21 seconds (500 / 24 = 21 approximately).
Crop Sensor Canon Camera
Because a Canon crop sensor camera has a crop factor of 1.6, you must include it in your calculation. Then it becomes this: 500 / (focal length x 1.6) With a 50mm lens, for example, the time is 6 seconds (approximately).
Crop Sensor Nikon Camera
Because the crop factor for a Nikon crop sensor camera is 1.5, you simply divide 500 by this figure: focal length x 1.5 For example, with a 50mm lens, it would be 500 / (50 x 1.5) = 7 seconds.
Ideal Shutter Speed Settings For 500 Rule
Below is a table outlining the ideal shutter speed settings you should use when incorporating the 500 rule for shooting photos:
