THE 500 RULE
A HOW TO IN ASTROPHOTOGRAPHY
Hi guys! If you follow me on INSTAGRAM and FACEBOOK you’ll find no shortage of images captured of the night sky. It’s TRUE! Photographing that beauty of the night has to be one of my favorite forms of photography. Little known fact, my Mother was the one that got me so into star gazing back in 1986 when Halley’s comet came back around in our suns orbit. Crazy to know that the next time Halley’s comet will make its return will be 2062. I hope I’m still around for that! Before we get started, if you’r interested in learning more about astrophotography I hold in the field workshops monthly and do one on classes as well explaining the basic process of night photography including the 500 rule and much more. Click HERE to check out my astrophotography workshop page.
So let me begin first by explaining what probably is the most important subject and easy to remember formula in astrophotography that you need to wrap your head around first before packing that backpack and moving forward onto your next big adventure to capture the big and beautiful Milky Way. The ever so popular and misunderstood "RULE OF 500."
WHAT IS THE RULE OF 500
So with out getting to crazy and technical which sometimes I find to even add more confusion to the matter, I'm going to break it down as easy as I can explaining it to you as I would to anyone else that would come out with me on any of my astro workshops etc.
THE 500 RULE is a simple formula to calculate proper exposure time / shutter speed with a particular lens, full frame and or crop sensor camera. This formula, if done correctly will produced those pin-point, razor sharp stars with out no trailing in your Milky Way photos or images of the night sky.
HOW TO USE THE 500 RULE
It's fairly a very easy thing to remember and pull off. You take the number 500 and then divided by the focal length of your lens = the longest exposure before stars start to trail or blur. For example; let's say your taking a shot with a 16mm lens on a full frame camera. 500 / 16 = 31.25 seconds, which you can round to 30 seconds. I'll always run down to the nearest zero.
(NOTE WHEN USING A CROP SENSOR CAMERA YOU HAVE TO MULTIPLY THE CROP FACTOR FIRST BY THE FOCAL LENGTH OF THE LENS BEFORE DIVIDING THAT NUMBER BY 500.)
So obviously if you caught on to the trick by now every lens will have a different length of time you can shoot before you get that unwanted star trailing in your photos. BELOW listed are the crop factor values for a few popular camera brands.
CAMERA CROP FACTORS
Sony & Nikon = 1.5 crop factor (EXAMPLE) 1.5 X 16 = 24 | 500/24 = 20 SECONDS
Canon = 1.6 crop factor (EXAMPLE) 1.6 x 16 = 25 | 500/25 = 20 SECONDS
USING THE RULE OF 500, THE CALCULATION CAME AS 500 / 24 = 20.8333
ROUNDING DOWN TO THE NEAREST ZERO THAT WOULD BE 20 SECONDS. IF THERE WAS NO SHUTTER OF 20 SECONDS FOR EXAMPLE ON THE SHUTTER DIAL, I WOULD SET IT DOWN A STEP TO 15 SECONDS.
NOTICE NO TRAILING! THE STARS RESEMBLE PIN POINTS. IF I WAS TO SHOOT THIS SAME IMAGE AT EVEN A FEW MORE SECONDS DISREGARDING THE RULE OF 500 I WOULD BE SURE TO SEE SOME TYPE OF TRAILING ESPECIALLY COMING FROM A 42MEGA PIXLE CAMERA.
Due note that the more mega pixels you have the more detail you will see if you zoom into a 1 to 1 ratio. If you do notice some minor trailing and this is a concern to you decrease your shutter speed slightly until you achieve satisfying results.
A CALCULATION CHART FOR POPULAR FOCAL LENGTHS FOR FULL FRAME CAMERAS
(all calculations was rounded down to the nearest zero)
12MM = 41 SECONDS
14MM = 35 SECONDS
16MM = 30 SECONDS
20MM = 25 SECONDS
24MM = 20 SECONDS
28MM = 17 SECONDS
35MM = 14 SECONDS
50MM = 10 SECONDS
So there you have it! That wasn't so bad was it? A very easy technique to live by to achieve those awesome sharp stars in your Milky Way and nighscape photos. I will cover star trailing in another write up which does and doesn't involve a longer exposure time depending how you go about it. I personally choose a one long fourty minute exposure as seen in the photo below other than stacking a number of images in Adobe Photoshop. But hey let's save that for the a next time.
I hope you enjoyed this tutorial and can take away something to lift your night photography to the next level. As always, if you have any further questions please don't hesitate to drop me a email. Also, visit my workshops page for my astrophotography workshop schedule and dates. Like mentioned earlier I provide ONE on ONE or group workshop by contacting me HERE for pricing and availability.
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Till next time. EXPLORE - CREATE - INSPIRE