Long Exposures: Part V

I’ve done many posts on things you can do with long exposures (see Disappearing Act and Long Exposures, DSLRs: Photographing Fireworks, Lightening and Long Exposure, and Long Exposures), but here in another one: Star Trails.

First, what is “a long exposure”?

When we talk about the length of exposure, we’re talking about how long the shutter is open in your camera to allow light in. Now, you may already know that how “bright” the image ends up being (or the exposure value) is dependent on the combination of shutter, aperture, and ISO settings. These 3 settings in combination control how much light reaches the sensor as well as how much light is required to get a given exposure value.

So, why would we talk about the length of the exposure separately?

How long you open the shutter determines whether you freeze motion or show motion blur and how much. So, when we talk about a long exposure, we’re really talking about showing motion in our images. Getting good exposure still requires a combination of setting the shutter, aperture, and ISO appropriately.

So, now that we’ve reviewed the basics, let’s get into a couple of examples of what you can do with long exposures (slow shutter speeds).

Star Trails

When we look at the stars, if we look at them long enough, then appear to move in the sky. This is because the earth is rotating so the stars rise and set just like our closest star, the sun. They actually move fast enough that we can record their path as a “star trail” if we leave our shutter open long enough. You can also take a series of photos and use software to combine them.

For the purpose of this blog, I’ll just tell you what I did to get this image:

Star Trails

  1. Find a location where it’s very dark and you are far from the city so you can see lots of brilliant stars in the sky.
  2. Attach remote control to camera (a remote is an absolute requirement for star trails).
  3. Place the camera on a tripod and frame what you want in the image and determine how/where you will need to focus (see next step).
  4. If you have something in the foreground on earth (like the trees in my image above), you might want to check a depth of field calculator to determine whether you need to find focus on the trees of whether you can simply focus at infinity. If you are focusing on something fairly close, you may need to use a flashlight or focus assist on your flash to find focus in the dark if you cannot see well enough to focus manually and your camera can’t see well enough with the available light to focus automatically. Just shine the flashlight on the thing you want to focus on, point your camera at that thing and lock focus (hint: this is easiest if you’re using back-button focusing, but that’s a subject for another blog post). In most cases, you will be shooting wide enough and at objects far enough away that you can simply manually set the focus at infinity and everything will look sharp. In my case, I was using a full-frame camera with a zoom lens at 27mm and my aperture at f/11. Worst case, focusing at infinity would keep everything 8 feet and further sharp. Since the trees were more than 8 ft above my head, I just set my focus at infinity.
  5. Now that you’ve found focus and locked focus, you can get your camera set on your tripod and framed the way you want again.
  6. Make sure your camera is set to “Bulb.” For some cameras, this is a setting on the shooting mode dial (where you pick Auto or Manual). For other cameras, this is an option in the shutter speed selection.
  7. Make sure your remote is set to “Bulb” as well. Bulb allows you to manually open the shutter and then manually close it.
  8. I personally like to just take a shot based on feel and then adjust from there. I started by trying to get a shot that just looked realistic. I left the shutter open about 70 seconds and this is what I got:

How the Sky Looked

  1. Because there was so little light in the area I was shooting in, I wasn’t worried about over exposing the trees with a very long exposure. If you have more ambient light, you might want to stop down more or turn down the ISO. In my case, I did f/11 for aperture and 1600 ISO. I used a higher ISO than usual because I wanted to ensure the sky registered enough light to clearly show the silhouette of the trees. Had I not been so sleepy by the time this shot completed and keeping my husband awake getting in and out of the tent to tend to the camera, I probably would have tried another shot with a lower ISO and longer exposure time to see how long I could get the star trails and if I could reduce the noise.
  2. Make sure you have a comfortable and warm place to sit where you can keep an eye on your camera. I was more worried about curious bears than people at our campsite since there wasn’t anyone else around. Also, set an alarm on your phone so you don’t forget when it’s time to close the shutter. For my example, I opened the shutter (by pressing the button on the remote 1x) and then set the timer for 30 minutes. However, I must have bumped the shutter button early because my metadata says the total exposure time was actually 1275.9 sec (21.26 minutes). The longer you leave the shutter open, the longer your star trails will be. However, be aware that extremely long exposures create more noise in the image and can build enough heat in the camera that it will shut itself off (hopefully) to avoid damage. At one time I recall reading a warning that there is a maximum limit to how long you can safely leave your shutter open on a digital camera, but I have not seen anything like that in years so this may be something only relevant for older DSLRs (or perhaps it was just a rumor).
  3. When your timer goes off, click the button again to close the shutter and go see what you got!

Trivia question: why do the star trails appear in a semi-circular pattern?

 

 

 

FAQ: How Do I Copyright and/or Watermark My Photos?

I have been asked how to copyright photos about a dozen times now, so I thought it might be a good topic for a blog post.

Note: I am in the United States. If you are not, info about copyright laws may not apply. Also, I am not an attorney and this information is not meant to substitute for the advice of an attorney. I am telling you what I have learned, which may or may not be accurate. If you are curious about the law, please see a reputable attorney in copyright law who can advise you far more reliably.

Let’s tease the question apart a bit.

What is a Copyright?

Copyright is, literally, the right to copy something–in this case a photo. As it true for all written work (including this post), all photos are automatically and immediately subject to copyright protection the moment they are published. This is true whether you take any action to copyright your work or not.

This means any time you grab someone else’s photo off a website and share it on Facebook or print it or use it for wallpaper on your iPhone, or whatever, you are guilty of copyright infringement and you could be taken to court and sued.

If you are a photographer who cares about getting paid for your work, this works in your favor.

That said, you are not likely to get enough money if someone infringes on your copyright to make it worth taking them to court unless you have registered your images with the U.S. Copyright office.

As such, if you care or think you might someday care whether people are using your images without your permission, you might want to take a little time to learn about registering your images with the US copyright office. Here is another link that will take you directly to a tutorial on how to submit your images for copyright registration online:  http://copyright.gov/eco/eco-tutorial.pdf

What is a Watermark?

Sometimes people confuse a written copyright statement superimposed over an image with the copyright itself. This is called a “watermark” and looks like this:

Screen Shot 2014-10-16 at 9.58.02 AM

An image is copyright protected whether it has a watermark or not. The watermark serves only as a reminder to others that this work belongs to someone and they should not use it without permission from the copyright owner.

The Professional Photographers Association recommends including the copyright symbol, year the photo was taken, name of the photographer, and how to contact the photographer in a watermark along with a message such as “all rights reserved.”

While the idea of including contact information sounds good, there are two issues with this.

First, watermarks rapidly start to detract from the image. Some people make them huge and centered on the image, which I find ruins the image to the point I don’t even want to waste my time looking at it. There is a delicate balance between protecting your work and having annoying images no one can see through your watermark.

Second, choosing a way to contact you that will neither make you subject to stalkers nor change in your lifetime (your copyright lasts your lifetime plus 70 years after your death) could be quite tricky. Including a website where your images can be ordered might be a way to keep the watermark smaller but still make it possible for people to obtain the right to use the image.

How to Add a Watermark

If you are going to process a bunch of photos at once, you will want to use software that allows you to add a watermark as part of your normal workflow. I use Aperture, but Lightroom will also allow you to do this.

The first thing you have to do is create an image file to apply as your watermark. The good news is that you only create the image file when you need to change the information it contains (e.g., ©2014 Dianne Blankenbaker would need to be updated each year).

Once you create your watermark image, you then apply the watermark at the time you export your images out of the Aperture library.

The following video demonstrates how to create the watermark in Photoshop CC 2014 and how to Apply it in Aperture 3.4:

Another alternative is to use an app that allows you to add watermarks to images. Some of these work such that you open the image file in the app and then create the watermark for just that one image. Each time you want to watermark an image, you have to repeat the process. This is quite tedious if you are processing large numbers of files and really only works if you watermark images only rarely.

Image Resolution

Additionally, posting low-resolution images can help limit what others do with you work. It’s hard to use a <100KB image, for example, for the wallpaper on a 27” screen–unless you find pixellation appealing. But, it might look OK on the much smaller screen of a smart phone.

As a general rule, the images I post on my website and Facebook are between 100-200 KB. These images full size are 24+ MB–that’s 120-240X bigger than what I’m posting. I sometimes break this rule when I really don’t want an image to start pixellating on a big screen–pixellation looks like this:Screen Shot 2014-10-16 at 9.57.51 AM

It’s as annoying as a giant watermark over the center of the image to me–even worse because a low-resolution image can also appear out of focus.