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Star trails with trees

Star trails with trees

Introduction to Shooting Stars - Beginners' Guide Part II

By: Robert Schall

January 17, 2017

Welcome back to our “Introduction to Shooting Stars.”  In Part I we covered the essentials of getting you ready to shoot.  In the second part we are going to cover what to do when you are on location and ready to shoot.

Since we are talking about shooting at night, pulling focus is a little harder than during the day, so this will take a little more time and explanation to cover.

Night Sky

How to Focus for Night Photography:

Didn’t think that focusing was going to be a tough subject with modern day cameras and their amazing autofocus systems?  Well, at night, focusing will be all on you.  So you’d better prepare yourself with a few tricks of the trade.

• Turn Off AutoFocus

There is no need to let your camera try and attempt to focus.  After all it is dark, and your camera will need light and contrast to achieve accurate focus.  Simply switch your lens to manual focus and take care of it yourself. 

Now there are 2 main schools of thought here as to how to focus properly at night:

• Focus to infinity

If you are just interested in the stars and not the foreground, you can focus at infinity.  You can do this two ways: 

- Option one is to use live view.  Start off by making sure exposure simulation is turned on in your camera (check your camera manual for instructions), turn on live view, set your aperture to its widest (lowest number in order to let the most light in) and if the image in live view is still too dark, increase your ISO until you can make out the stars properly.  Using your screen, zoom in, using the magnification function, on one or a group of stars and then manually turn your focus ring back from infinity until the stars become sharp points of light.  Just remember to return your camera to the correct settings to capture the image you want after focusing.

- Option two is to set the lens to infinity and to adjust from there with trial images.   If you do not have a Focus index window, focus your lens to infinity and back off from there a tiny bit at a time.  Take a picture and then in review, zoom in and check the sharpness. Adjust a tiny bit if needed.  If you have a focus index window on your lens, set your focus to the infinity index mark as shown:

Camera focus

Remember to take a test image to make sure.

• Hyperfocal focusing

If the foreground as well as the stars are important for your image you will need to get familiar with the technique of “hyperfocal focusing.”  Whereby you will be looking to find the focus point that will give you the maximum depth of field (DOF) with the lens you are using.  Basically this technique will give you a DOF wherein everything from half the distance to your focus point to infinity will be sharp.  Sounds simple, right?  And by the way this is also a great technique for daytime landscape photography, but that is a whole different topic.

Now, how do you figure out what the maximum DOF for your chosen lens is?  First there is a formula that is used to calculate hyperfocal distance:

Hyperfocal distance formula

*Circle of confusion – All you need to know here is that this differs depending on your type of camera and is based on what is considered to be acceptable sharpness in an 8” x 10” print seen at normal viewing distance. The most popular values are as follows:

Digital SLR APS-C sensor  = 0.0235mm format and Digital SLR full-frame = 0.03

As you can see, although this might not be rocket science, this might be a little more work than necessary while you are out in the field, plus tough to see on a calculator in the dark.  You could pre-calculate and commit it all to memory.  Or just use a chart such as the one below that Canon’s Explorer of Light Jennifer Wu made:

Full frame sensor cameras

Focal distance in feet

Chart courtesy of Canon EOL Jennifer Wu.

After a while, especially if you are shooting with prime lenses and using the same lenses and focal lengths again and again you will soon remember the different hyperfocal distances.

Please Note: When using the Hyperfocal Method, background and distant subjects will tend to look out of focus when peering through the viewfinder.  Use the ‘depth of field’ preview button on your camera to check what is in focus.

• Double Check Your Focus

There is nothing worse than finding out later that you missed focus on a whole set of images, so check your focus.  After your first shot, look at the image in your display and use the zoom function to make sure that your image is sharp.  The stars should look like tiny pins and not big blurs of light.

I cannot stress the importance of double checking your focus!!!! Check it! Check it! And check it again.

What Your Exposure Settings Should Be:

How long your exposure should be and how to avoid or create star trails is a huge question.  For a while I always operated with the rule of thumb that your max exposure length to avoid star trails is 13-15 seconds.  It had something to do with how fast the earth spins and so forth.  However, there is a much better and more accurate way to determine your exposure time.

• The 500 or 600 Rule:

Getting sick of all those rules and calculations to keep a track of?  This one is simple.  Some people swear by the 600 Rule and others by the 500 Rule.  Personally I feel the 500 Rule is a little safer as it is a little more conservative.

This rule will help you obtain the maximum exposure time that will avoid producing “star trails.”

Please note: The calculated exposure times are meant as a baseline, so feel free to experiment up or down depending on how your pictures are turning out and what you are looking for as image.

Exposure Length = 500 / focal length

So let’s say you are shooting with a 24mm lens on a full frame camera.  This would mean the suggested maximum exposure time would be 21 seconds (= 500 / 24).If you are looking to shoot star trails then add extra time to this exposure time.  

Please note: For star trails, the best practice is to take multiple images, one after each other, and then stitch them together in Photoshop®.  This will result in cleaner, less noisy images than shooting a single very long exposure.

Night Sky

If you are shooting with a cropped sensor camera you need to take this into account.  Your 24mm lens would be the equivalent of 38mm (= 24 x 1.6 (APC sensor)).  Thus making your maximum exposure time 13 seconds (= 500 / 38).

Here are a few parting thoughts and tips I would like leave you with:

• FIRST AND FOREMOST: Take in your location, the scenery and stars!  While you might have travelled to the ideal location to shoot some amazing images, do not forget to simply enjoy the whole experience yourself without the viewfinder.  Take a seat, relax and just take it all in.  Trust me, it is worth it.

Man sitting under the night sky

• After a while of letting the whole experience soak in, look for that perfect composition, for that awesome shot.  It is absolutely worth taking the time to find that special shot and composition.

• Play around with your settings.  None of what I wrote above is set in stone.  Aperture, shutter speed and ISO directly reflect on each other and the amount of light that hits your sensor.  Gingerly playing around with these settings can result in quite some different images, as different stars will appear in your photos.

Man sitting under the night sky

• Most importantly, have fun and enjoy the experience.  Experiment and learn for yourself what works best for you and your locations.