How To Photograph A Solar Eclipse

How to safely and successfuly capture photos of the Sun

By bdery in Articles and Tips on Mar 11, 2024
How To Photograph A Solar Eclipse

Solar eclipses are among the most beautiful celestial events visible to the naked eye. Such eclipses are rare, occurring much less frequently than lunar eclipses. Given their frequency and geographical localization, seeing a total solar eclipse is often a once-in-a-lifetime event. This makes the upcoming total solar eclipse, which will be visible in North America on April 8th, all the more interesting, as the total eclipse will be visible in Mexico, central and northeastern USA, and eastern Canada.

For photographers, a total solar eclipse presents an exciting opportunity. As with most unique phenomena, photographers will want to capture the various stages of the eclipse.

However, as with everything related to the Sun, photographing a solar eclipse can be dangerous both for the eyes of the photographer and for the equipment being used.

In this article, I discuss the key elements to know to properly enjoy and photograph a total solar eclipse.

Total solar eclipse showing the corona. Image courtesy of Wikipedia

What Is An Eclipse

An eclipse occurs when a celestial body gets in the way of another and hides it from view. On Earth, there are two types: lunar and solar eclipses.

Lunar eclipse. Image courtesy of Wikipedia

A lunar eclipse occurs when the Sun, Moon, and Earth are aligned and on the same plane, with the Earth between the two other bodies. The Moon ends up in the Earth’s shadow and cannot be illuminated by the Sun anymore (the Moon does not produce light, it only reflects light from the Sun).

Solar eclipse. Image courtesy of Wikipedia

During a solar eclipse, the Earth, Moon, and Sun are again aligned and on the same plane, but it is the Moon that ends up between the Sun and the Earth. It thus blocks the light from the Sun, just like placing your hand in front of you will do. However, it does so on a much bigger scale, casting whole regions in shadows.

Even though it is much farther away, the Sun is also many times larger than the Moon, which is why an eclipse does not occur everywhere at once. Only geographic regions where the alignment is perfect will experience a total eclipse. Regions where the alignment isn’t perfect will see a partial eclipse, where a smaller or larger crescent of the Sun remains visible. Lastly, some eclipses are called annular. These eclipses are similar to a total eclipse but with the Moon farther away from the Earth (the distance between the Moon and the Earth isn’t constant). The Moon being farther away, appears smaller and does not completely cover the Sun. It leaves a ring of sunlight visible around the Moon.

The April 8th eclipse will be a total eclipse on a band covering many parts of North America, and at least a partial for all of North and Central America. A good part of the Pacific and Atlantic oceans will also see the eclipse, and even part of the UK and Ireland will see a partial eclipse.

Eclipse Phases

As can be expected, there are several phases to a total solar eclipse.

The first phase occurs when the Moon starts to cover the Sun, creating a partial eclipse with an increasingly smaller area of the Sun being visible. Viewers are in the shadow area called the penumbra. The Sun’s surface brightness remains constant even while its visible area decreases.

For a few seconds before the Moon entirely covers the Sun, a small incomplete ring of light remains visible, with a brighter spot at the center of the ring. This short-lived event is informally called the Diamond Ring.

The key moment of the eclipse is of course totality. Its duration can be a few seconds to several minutes depending on location. During that period, the viewer is in the Moon’s full shadow, called the umbra. Light levels drop almost to the level of twilight. The Sun’s inner corona can become visible; its brightness is comparable to that of a full Moon.

After totality, the reverse steps occur as the Moon covers less and less of the Sun.

People often refer to four “contacts” instead of phases:

  • First contact: the moon starts to cover the Sun
  • Second contact: totality starts
  • Third contact: totality ends
  • Fourth contact: the eclipse ends

Safety

An eclipse presents a safety risk both for humans and for photographic equipment.

The main danger for humans concerns sight. As the Moon passes in front of the Sun, the total brightness of the Sun decreases because it is partially hidden. As such, it becomes easier to look at the Sun with the naked eye. But the part of the Sun that isn’t hidden is just as dangerous as when there is no eclipse. There is still enough light available to burn someone’s retina. Moreover, the diminishing brightness means the eyes’ iris will be opened wider, letting more light in, increasing even more the risks of injuries.

The only moment when looking directly at the eclipse isn’t dangerous is when it is total. At this moment, it looks almost like nighttime, and the Sun is completely blocked. At all other times, no one should look at the eclipse with the naked eye. There are inexpensive protection glasses sold in many stores, and solutions like piercing holes in a shoebox are easily available to protect your eyes.

Photo equipment can also be damaged by photographing the Sun. This is because when the Sun is in focus, it directs its rays on the smallest possible spot on the sensor, which can burn it. Even the shutter can be damaged by continuous exposure to focalized sunlight.

To prevent this, it is mandatory to use a solar filter or an ND filter with an extremely high attenuation. For instance, K&F CONCEPT (a manufacturer often discussed in our forums) makes two filters, one with a 16.6 stops attenuation (ND100,000) and another with 20 stops (ND1,000,000). These are the filters I will personally be using to photograph the eclipse.

Even when using solar filters, I cannot stress enough that looking at the focalized light of the Sun can be dangerous. Modern cameras offer live view, take advantage of it! Do not look through the viewfinder.

Testing the Filters

In the past, I have often tested filters from K&F CONCEPT and other manufacturers. I have been happily surprised by the quality of their filters, and they have become my go-to brand as they have a fair price while achieving accurate attenuation, no discernible decrease in resolution and no color casts even with polarizers and high-attenuation ND filters. Products from other highly-regarded brands do not always achieve this quality level, often at a higher price.

The two filters come with nice packaging. They are both made of metal, with a good grip on the edges to easily mount them.

Testing filters with such a high attenuation presents a challenge, because the longer the exposure, the more likely it is that camera vibrations impact the perceived sharpness. Still, side-by-side comparisons remain the best way to test the quality of a filter.

The ND1,000,000 filter does not yield itself to a side-by-side test using a test chart, because its attenuation is simply too high. The ND100,000 easily allows it, however. The following images show the effect of the filter on color and resolution.

No filter
ND100000

The filter has no visible impact on resolution and does not create a color cast. This is, frankly, beyond expectations.

As a second step to test the filters, I took them out and photographed the Sun directly. I used the K-1 II with the DA* 60-250mm coupled with a Pentax-F AF 1.7X teleconverter, offering a 425mm effective focal length. The setup was mounted on a tripod and the 12-second self-timer was used. Focus was achieved by the teleconverter (it does not directly support manual focus) but it was manually tweaked on the lens afterward to confirm that its lock was accurate, as it can be difficult for the camera to properly lock focus on a subject such as the Sun, especially using live view AF.

The following table shows the exposure settings which gave the best results with each filter. Remember that the teleconverter limits the maximum aperture available and offsets the aperture value of the lens (for instance, F4 on the lens results in F6.7 for the system).

Filter Aperture Shutter speed ISO
ND100000 F10 1/400s 400
ND1000000 F7.1 1/200s 1250

Both of these exposure parameters are adequate to protect the camera and sensor. Even with the lower attenuation filter, these values are similar to what can be obtained by looking at an unfiltered daylit scene.

I started with the ND1,000,000 filter because, as a first-timer shooting the Sun, I preferred to start with more attenuation. The following cropped image shows the result (click on images for a larger view).

ND1,000,000

With the exposure parameters that I used, the Sun is a bit underexposed but still well-detailed. Sunspots are easily visible and the edges are sharp. There is an obvious purple cast.

The second test is with the ND100,000 filter.

ND100,000

This filter allowed for a faster exposure time, a smaller aperture (increasing DOF and making focus easier) as well as better sharpness thanks to the lower ISO value. These benefits are obvious when looking at the image above.

My prior test with the test chart showed that this lower attenuation filter didn't create any color cast. This is apparent from the image of the Sun. despite often being represented as "yellow", the Sun is a reasonably neutral white, with its emission peak actually closer to blue. The filter thus creates an accurate representation of what the Sun looks like. This shows that the higher attenuation filter does create a color cast.

The image created by the ND100,000 filter yields itself well to some post-processing to bring the color cast closer to what most people expect.

ND100,000 with modified colors

In short, while both filters perform well and, more importantly, protect adequately the camera and sensor, during the eclipse I will be using the lower-attenuation (ND100,000) filter since it has no effect on resolution, no color cast, and provides more useful exposure settings.

How To Photograph The Eclipse

There are many aspects involved in actually taking pictures of the eclipse. My main advice is: enjoy the moment! Do not spend the (often short) duration of the totality fiddling with your camera at the cost of missing this once-in-a-lifetime event.

Recommended Gear

There are two main approaches to photographing an eclipse. The most obvious one is to zoom in as much as possible and capture the Sun itself. The second is to shoot a wider-view landscape which includes the eclipse in the field of view.

In both cases, using a proper solar filter is highly recommended. When shooting a landscape, the focus isn’t on the Sun, so its light isn’t as highly focalized on the sensor, and risks of damage are lower, but not absent.

For landscape settings, a wide-angle lens is of course desirable. A tripod isn’t needed during the partial phase. It becomes almost mandatory during totality, but the wider the lens the more difficult it will become to highlight interesting elements of the eclipse itself.

The other approach is to zoom in on the Sun to capture as much of it as possible. The focal length will be the key driver here, remembering that during totality, the Sun’s corona will be visible and extend to roughly three times the diameter of the Sun itself.

Using a 200mm lens with a full-frame sensor, the corona will cover about 1/7th of the horizontal width of the frame. With APS-C, it will be about 1/4. A 400mm lens will have the corona take up maybe half the frame with APS-C (a good ratio to allow for some cropping afterward) and a little more than 1/4 on full frame. 500mm will have the corona almost fill the frame with APS-C, and cover about 1/3 of full frame, again a good ratio.

Using telephoto focal lengths, a tripod will be all but mandatory. Tracking the eclipse will be a challenge; using a slightly wider focal length will offer some leeway for cropping afterward. Focusing can also be a challenge. Make sure to lock focus before the eclipse starts and switch to manual focus to avoid changing your focus distance unexpectedly.

Camera Settings

Exposure during the partial phases will not change much, as the Sun’s surface retains the same brightness even when part of it is obscured. Proper exposure of the partially eclipsed Sun will be the same as on a regular day. Using the proper filter, it is possible to plan in advance and save the correct exposure settings in a User Mode. I recommend setting ISO between 100 to 200, an aperture between F8 and F10, and working with shutter speed only. Determine the proper exposure and record it. It will remain the correct value until totality.

Totality is orders of magnitude darker than a partial eclipse. What’s more, the corona’s brightness isn’t constant: it is brighter closer to the Sun. And by nature, totality isn’t something you can practice in advance. Because of this, preparation is key. There are many tables available to estimate the correct exposure. Use these as starting points, understanding that seasons, geographical locations, and atmospheric conditions will influence the actual results. The best approach is to bracket each picture during totality. This will increase the likelihood of obtaining well-exposed pictures. Composite images obtained via post-processing will probably be needed to show the whole corona in a single image. Of course, shooting RAW will increase dynamic range and give more headroom for post-processing. Totality is also the only period when it is safe to remove protection glasses and solar filters.

Conclusion

Witnessing and photographic a total solar eclipse can be, for many, a once-in-a-lifetime event. With proper preparation and the proper gear, it can be a rewarding experience.

SAFETY FIRST: always remember to take care of your equipment, but much more importantly to protect your eyes!

Using a high-quality and high-attenuation filter such as those by K&F CONCEPT is mandatory. It is much better to use a single filter, specifically designed for this event than to try to stack multiple filters (the math could be wrong, and stacking always ends up decreasing optical quality, increasing reflections, etc).

By following those steps, I hope the upcoming total solar eclipse will be a rewarding experience for you. Let’s wish for clear skies!

Comments

 

 


facebook.com/PentaxForums PentaxForums @PentaxForums News | Reviews | Forum

Support Pentax Forums Donate to Pentax Forums Support Pentax Forums