Friday, August 24, 2012

Star Trails Photo/Tutorial

Hello guys, so today, this photo is so special to me, I wanted to make it into a blog post all by itself! This is the result of the first start trails I tried. So a while back, my church hosted a rafting trip with American Whitewater Expeditions in Placerville, CA. Since we camped out for one night, I thought I'd go ahead and do a star trail photo. It was a very clear night anyways... The rest of the photos I took during that trip will come up in the next post. So I hope you enjoy viewing this star trails I did! I would also like to take this opportunity to teach you how to take star trails photography if you are interested. Those will be under the photo. Remember, you can click the photo to view it larger.

If you want to see the rest of the photos I took on this trip, you can view them here.

Full Resolution Photos and Prints: If you want to see full resolution photos or buy prints of any of the photos you see, they are up on my portfolio for viewing. See my best photos from that trip here. See all of my photos from that trip here.

Photo Data:
Exposure: 20 photos X 5 minutes (5 second delay between each)
Focal Length: 17 mm
Aperture: f/5.6
ISO: 100
Artificial Lighting: Very strong LED flashlight to light paint the trees in the foreground.

So how do you do star trails? First off let me tell you some stuff you need to do before you start. The following are required materials for these types of photos:
  • Your camera (obviously)
  • Full battery
  • Tripod (Has to be very sturdy, won't shake in the wind)
  • Powerful flashlight (Optional, depends on if you want to light your foreground)
  • A red flashlight (So you can see the camera controls with out damaging your night vision)
  • Intervalometer with full battery (Sometimes this feature is built-in. Check to make sure. If not, buy one.)
  • Fold up chair, or tent (Somewhere you can stay for the duration of the exposure.)
  • A friend (Optional, but you will be sitting for a few hours at night, all alone with nothing to do)

Next consider the following in the area you are taking the photo at:
  • Are you close to a big city? If you are, you will get light pollution in the photo and it won't look good. You can counteract this later with shorter exposures.
  • Is the full moon out? If it is, it might wash out your photo. Can be compensated with shorter exposures and the camera facing away from the moon.
  • Is the sky clear of clouds? If it isn't, your photo might not turn out that good.
  • Is the North Star in your photo? Depending on what effect you are trying to achieve, take this into consideration. If you have trouble finding the North Star, go get the Google Sky Map app for you Android device.
  • Is there any good foreground in the photo? You will need some foreground for a good star trails photo or it will be boring. 
  • Is it hot outside? If it's hot outside, your camera sensor heats up more quickly which in turn causes image noise.
  • Is there any bright light sources around the area you are taking the photo at? Like me, I was at a camp site, so there was people walking around with flashlights. A little bit of light shouldn't be a problem, but if a person uses a light in the same place for too long, just go ahead and tell them what you are doing, and nicely ask them to turn it off. 
  • Is it likely someone will bump the tripod during the exposure? If it's very likely, find a new place. By bumping the tripod, I also mean yourself! Make sure you place your chair or what ever you will be resting on while you take the photo far enough away from the camera and tripod that you won't accidentally bump into it during the exposure. 
  • Is my battery full? Check that before you start, and make sure it's full! Not half full or 75%, but completely full! Your camera will be locking up the mirror for the entire exposure which will take more power than normal shooting! 
Now that you have checked those things, you have to think of this:
  • How long do I have? It is generally recommended you go at least an hour. If you can't stay awake, you might want to reconsider. Stars move about 15 degrees in one hour, so how long you do the exposure for really depends on your lens's field of view. 
  • When can I start? Around 30 minutes after sunset. Just make sure you can't see the sun's light in the sky anymore. (Technically moon light is really sunlight, but I'm pretty sure you are smart enough to figure out what I mean.) If you are going hours during the night for these photos, it's recommended you check the time of sunrise for the next day. 
  • Should I go for one long exposure or multiple short exposures? (I will go into more detail later in this article.)
Now that you have thought about all that, let's talk about which you should do, one long exposure or multiple short exposures? 

Many beginners may want to try one long exposure but I highly don't recommend you doing this. If you accidently bumped the tripod, it will be very hard to correct if you just have one photo, also your camera is very prone to noise if you have it just take a long one hour exposure. The camera sensor is an electronic component! It will heat up and cause noise! Another reason you should not use one long exposure is if you don't want any airplane trails to show up on your photo, it will be harder to take it out of the final image than if you had multiple shots. 

So what are the pros and cons about using multiple exposures? Well one thing is, your camera will take a few seconds to record the photo down once it finishes a photo, and you have to wait before the next photo can start. This leads to the final product looking like the star trails being dotted lines because the camera missed a little bit of it's rotation during the image recording! If you shrink the photo a bit, or use some other software to fix those, it will be barely noticeable, so don't worry. That is the only con to the multiple shot method, well other than it will also use up more memory card space. That's about it, let's move on to the pros. Don't like airplane trails in your final image? Just take out the exposure with that in there before you combine! Bumped your tripod during your exposure? Take out the bad images before you combine! Taking multiple exposures will also help lower image noise which is great! If you do use this method, I recommend you let each exposure run about 5-20 minutes. I can't tell you exactly how long to take the photo for, but one easy to to try is to use a higher ISO for a few test shots, then work your way down. Every time you cut your ISO in half, you multiply the exposure you used by 2 (More details below). Then do the math on how many exposures you want to do! Program your Intervalometer to take the photos. Don't touch the tripod during the shots! Always make sure you set some delays between your photos so your camera has enough time to write to the memory card before beginning the next photo.

More on the high ISO testing. So here is the bottom line:
If your shot took 30 seconds at ISO 1600, it will take 60 seconds at ISO 800, or 120 seconds at ISO 400 for you to reach the same effect. Notice how whenever I halved the ISO, I doubled the exposure.

Now that you understand all that, let's teach you how to set up the camera settings for this.
  • Long exposure noise reduction should be turned off. Just do this in post processing.
  • Set your camera on RAW. There is more work room for Photoshop later on.
  • Either first auto focus, than turn the lens to manual focus, or just activate manual focus and do it manually.
  • Use a wide aperture. Something between f/5.4 - f/10 is good. If your lens can go wider, do that. Normally in night photography, people tell you to close down the aperture, but with star trails, you open it up wide! Don't forget that. 
  • Use the lowest ISO setting available. Remember, this is a long exposure, you don't want to get any more noise! 
Once you got that all done, start the photos and wait. :) Talk to your buddy during the photos. As much as you want to play with your phone or laptop during the photos, please refrain from doing so. It will cause unwanted light in your final product! If you want to light paint the background, make sure you do it in a few of the exposures and not just one. Just incase one doesn't turn out that well.

After the photos are on your computer, open them up in Photoshop via File >> Scripts >> Load Files into Stacks. Then set the layer mode to lighten for all the layers and you are done! Sadly, I don't know how to do noise removal or filling in the gaps in post processing. If you need to do that, I recommend you go Google for a method. If you know how to do it, please tell me in the comments below.

This is it for this tutorial! If I missed anything, just tell me in the comments below. :) Thank you for reading! Please don't forget to share my blog posts with your friends! If you would like to get notifications next time I post, you can "Like" me on Facebook or follow me on Twitter and Google+. These links can also be found on the top of the right sidebar.