Photographing Solar Eclipses - Camera Control
Author: Bill Kramer
Last update: Saturday, 18-Apr-2015 18:52:08 EDT
Set your Camera to Manual
Some cameras allow for manual control of exposure times and focus. These work best when photographing the eclipse. Automatic focus and light meter systems were never intended to compensate for the type of light changes and the diffuse target of the solar corona.
Cameras that feature interchangeable lenses typically offer manual control of the exposure, focus, and f/stop. You will want to use the manual settings when preparing for the total phase of the eclipse. Detailed exposure settings can be determined using the Exposure Estimate information.
|Manual focusing is a must. Automatic focusing systems have a hard time finding a good sharp edge and waste time getting the image into focus. Set the camera to manual focus mode before totality, use your solar filter to focus (or use a far distant object away from the sun). You may have to refocus slightly as totality starts and you remove your filter. Many skip photographing 2nd contact for this reason.||
Automatic focus just can't deal with the image!
Many consumer digital cameras only allow for changes between icons for scenery or portraits. In most cases the scenery settings will work best since the object being photographed is distant. Experiment by taking pictures of the moon and sunsets to learn how well your camera works under eclipse like conditions. The picture will be mostly dark and some automatic cameras may be difficult to use. If you can't get a decent picture of the moon then set your camera aside and enjoy totality as an observer.
Be sure to disable the flash before totality!
You will hear the above request more than once before the eclipse. The flash is a distraction for anyone near you. As a precaution, you might consider covering the flash unit with black electrical tape just in case something is not set right. Virtually every eclipse group will have one or more members with black electrical tape available on the day of the eclipse - just ask around.
Brightness of the Corona
The corona brightness drops quickly as it gets further from the photosphere. The detail in the corona is a low contrast difference with its background meaning that a camera cannot capture the entire thing in a single shot (neither does your eye for that matter). As such, cameras allowing for variable exposure times can capture more detail in the corona.
Shorter exposures will show the inner corona, chromosphere, and prominences. Longer exposures will wash out the details closest to the lunar disk but will show more of the coronal streamers and structure. Compare the two images from the 1991 eclipse above. The image on the left is a longer exposure with the same camera. It shows much more corona compared to the image on the right. You can detect the prominences in the left image - they are over exposed and more pink-white than red. This is why you cannot really capture a solar eclipse image that matches what the eye sees - not yet at least.
Practice by taking pictures of the moon. The inner corona is as bright as the full moon and the prominences are even brighter. Just one lunar diameter away from the disk the brightness is a quarter the intensity and at two or three diameters it is dim as the background sky. Streamers can be seen up to six diameters away with binoculars or a well trained (and dark adapted) eye. Remember, each lunar diameter is only half a degree.
To obtain a good image of the corona you will need to take multiple images with variable exposure lengths. These images are then stacked and processed later in the computer using a tool like Photoshop.
My recommendation is to start with a shorter exposure and then increase by one setting for another on up to the maximum exposure for the session. Time allowing, repeat the progression in reverse and then wait for third contact before attempting to get a picture of the diamond ring.
The ultimate dream of many eclipse chaser/Photographers is to have a reliable system control the camera while sitting back and enjoying the eclipse view. Many modern cameras support repeated exposures, bursts, and other features that are quite useful when photographing an eclipse. So how can one take advantage of such tools?
Does your camera support burst mode? If so, then you can make use of it. Burst mode takes more than one picture, at different f/stops or exposures, to bracket an image. This is exactly what one should do during a total solar eclipse. A longer exposure brings in more corona while a shorter one reveals prominences. Cameras I've worked with allow for 1 or 2 f/stops worth of exposure changes.
An Intervalometer can be used to automate the clicks further. An intervalometer is a device that can be programmed to repeat clicking at regular intervals. That relieves the operator of having to keep pushing the exposure button. If you are happy with the range of the burst and have an intervalometer then you are there! Set the intervalometer to run exposures every couple of seconds for the duration of totality (add about 10 seconds at the start and end) and you will have a nice set of images when it is all done (assuming the camera remained pointed at the eclipse, was in focus, and the exposures reveal the details you are after).
An example is the Canon TC80N3 controller which features a variety of timing options - perfect for the eclipse photographer that does not want to mess with a camera during totality. I used the TC80N3 during the eclipse of 2008, on a moving ship, in conjunction with a 400mm lens on a tripod. Although a large number of the images are not centered, most came out quite good. During totality I adjusted the base exposure and used a three shot burst +/- 1 f/stop.
Most modern digital cameras for professions offer timers and intervalometer interfaces.
Computer Driven Eclipse Photography
Computers can be used to run the camera. This means you are carrying along a computer of some sort, most likely a lap top. To connect the computer and camera, use the same cable used to move pictures from the camera to the computer. This is normally a USB cable.
Instructions are sent from the computer to the camera. Modern cameras support remote control with instructions such as setting the ISO, aperture f/stop, exposure, and file format details. Under the control of a computer program design for solar eclipse photography an entire range of images can be created.
Several programs can be downloaded directly from the web (listed below) and installed on your computer. I cannot stress strongly enough that practice and preparation time is needed. Not only do you need to adjust the programs to your own camera specifics (normally by changing parameter or script files) but you will also want to be as comfortable as possible when running the assembly during totality. Otherwise you could miss the eclipse fiddling with things at the last second.
Personal Experience: I've always run the camera manually during a total solar eclipse. The reasons are to reduce the amount of equipment to carry along as well as the general rule of thumb - keep it simple. During the Total Solar Eclipse of 2006 I handed control of the camera and telescope to another (our daughter). This allowed me to experience the eclipse like I've never seen it before (and this was my 11th total solar eclipse experience). Also, by bringing her along I could bring additional equipment. A Coranado hydrogen alpha telescope in this case.
2009 was my 13th total solar eclipse. Our daughter did not come along this time. Thus I introduced a lightweight piece of equipment to the process - an intervalometer. This tool performed wonderfully. It allowed me to watch the eclipse while the camera clicked away. Using the three shot burst I obtained a good range of images using a tripod mounted 400mm lens on board a moving ship.
For 2010 I used a small lap top computer to increase the ability of the remote control. The key to success, even with automated solutions, is to practice and make sure you fully understand every step involved (plus counter steps in case of problems). The software I was using did not synch properly with the GPS and the timings of the 2nd and 3rd contacts were off as a result. The rest of the program worked great - the ship moved a lot and I was forced to reposition the camera constantly but I could see that from a stationary position, this solution was optimal.