What is the 500 Rule in Photography?

If you’re into night sky photography in any way then it’s only a matter of time before you run across somebody talking about the “500 Rule” – sometimes referred to as the “rule of 500.” It’s a classic photographic rule of thumb that most experienced photographers will commit to memory for when they are out shooting at night and want to capture one of those beautiful images of the Milky Way that tend to blow audiences off their feet and keeps the stars nice and sharp.

Updated: 22, September 2018 to include great forum discussion on the 500 rule.

500 rule for night sky photography

So What is the 500 Rule?

The 500 Rule refers to camera settings to get a good exposure of the stars and Milky Way that helps you avoid “star trails.”

If you set the shutter speed for any longer than dictated by the 500 rule, then the stars in your image will show up as star trails (rather than dots).





Well, that is the theory, anyway.

The 500 Rule for Full Frame Camera

The 500 rule for a full frame camera requires you to set your camera to ISO 3200 or 6400, Aperture to f/2.8 (or as wide as possible) and your shutter speed to 500 divided by the focal length of your camera.

For example, if you are shooting with a 50mm lens, your shutter speed would be 10 seconds (500 / 50 = 10).

If you are shooting with a 24mm lens, your shutter speed would be 21 seconds (500 / 24 = 21 approximately).

The 500 Rule for a Crop Sensor Canon Camera

The crop factor of a Canon crop sensor camera is 1.6 so you need to account for that in your equation. Then it becomes this:

500 / focal length / 1.6

For example, with a 50mm lens it is 500 / 50 / 1.6 = 6 seconds (approximately).

The 500 Rule for a Crop Sensor Nikon Camera

The crop factor for a Nikon crop sensor camera is 1.5 so you account for that like this:

500 / focal length / 1.5

For example, with a 50mm lens, it is 500 / 50 / 1.5 = 7 seconds (approximately).

Shutter Speed Settings for the 500 Rule

Here are the settings you would use, according to your camera and lens. Just remember that the 500 rule is not perfect – you are probably going to have to adjust slightly for your particular circumstances such as light pollution, the angle of the stars or even atmospheric haze.

Lens Focal LengthFull Frame Camera1.5 Crop (Nikon)1.6 Crop (Canon)
14 mm36 sec24 sec22 sec
16 mm31 sec21 sec20 sec
20 mm25 sec17 sec16 sec
24 mm21 sec14 sec13 sec
35 mm14 sec10 sec9 sec
50 mm10 sec7 sec6 sec
70 mm7 sec5 sec4 sec
85 mm6 sec4 sec4 sec
135 mm4 sec2 sec2 sec
200 mm3 sec2 sec2 sec
500 rule example

Snapwire at Pexels

How to Go Beyond the 500 Rule

Learning the 500 rule is pretty much the basic end of coming to grips with night sky photography. There are a lot of other things to think about from composition through to gear setup and post-production. These articles on Light Stalking should get you started with the full story of shooting at night:

How to Photograph the Milky Way – We wrote up a pretty solid guide to getting those shots of the night sky that really wow an audience. It covers the 500 rule but goes a lot deeper.

How to Photograph the Moon  – If you’re getting into night sky photography, then at some point, you’re going to want to photograph the moon, so this is a detailed post going into all of the ins and outs of getting a good shot.

Where Else Can I Read About the 500 Rule?

Here are some pretty cool resources and websites that you might want to take a look at written by photographers who are experienced with night sky photography. You also might like to subscribe to them, cos we think they are great. Some of the examples are amazing!

There is also a great discussion abou the 500 rule in astrophography going on in our forums here at Light Stalking. Take a look at it here.

Useful Tools for Calculating the 500 Rule

There are a couple of great online tools for calculating exposures with the 500 rule. All do more-or-less the same thing:

The Best 500 Rule iPhone Apps

  1. The 500 Rule Calculator
  2. Dark Skies

The Best 500 Rule Android Apps

  1. Pin Point Stars
  2. Sharp Stars
  3. Star Trail Calculator

What About the 600 Rule?

Whoah there, cowboy! Well, if you look at your night sky image and things are not looking good (ie. you have underexposed images) then you might want to look at the 600 rule which is basically the same except the calculation allows for a slightly longer shutter speed. (ie. ISO 3200 and 600 / focal length). Remember what we said about the rule not being an exact science?

What Next?

Well, once you have the 500 rule squared away in your memory, then you are going to want to get out a start shooting! There is a more comprehensive article on milky way photography here that you might like to read.

If you really want to go next level with this stuff, then you’re going to want to get your hands on the Expert Photography guide to milky way photography. An incredibly comprehensive resources that you should take a look at.


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About the author

Rob Wood (Admin)

I'm Rob, the editor of Light Stalking. I try to keep this ship on course.

  • Dusty Sky says:

    Can I mount my camera onto a celestial tracking mount, like that of a telescope, and take longer exposures without blurring? May be adapter available?

    • Eugene says:

      Yes, you can. Trackers like a Vixen Polarie allow you to take much longer exposures because they compensate for the rotation of the earth.

  • Great post, great topic. I haven’t done much night sky shooting – mostly star trails to this point. Looking to find a good place nearby to shoot when the nights get colder and the sky clears up.

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  • Nice post.. Nicely explained about 500 rule in Photography.

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