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Choosing Lenses for Eclipse Photography

April 17, 2017

Written by Dave Henry and Ken Sklute

Choosing a lens to photograph the upcoming total solar eclipse in August takes a lot more consideration than the camera body to be used because the camera is simply a light-tight box that records the image produced by the lens.

Safety

The foremost concern in photographing a solar eclipse is the protection of your eyes and camera’s lens and sensor. This is achieved by using solar viewing lenses over your eyes and an approved solar filter for your camera and using.

Never look at the sun without accredited and approved solar filtration over your eyes. There are special solar viewing frames that can be used over your eyeglasses or solar viewing glasses for those that don’t wear glasses. Permanent, irreversible eye damage and/or blindness can result in seconds.

Never point your camera into the sun without this special solar filter. All camera lenses need an accredited and approved solar filter. Not using a solar filter at eclipse magnifications will ruin your camera in seconds.

Never improvise, modify or use general neutral density (ND) photography filters. They are totally insufficient to provide the protection your eyes, and your equipment, need. There are reasons for this that we’ll address in an upcoming article. Buy an approved solar filter. They’re inexpensive and are designed for the task.

Choosing Your Lens

Choosing a lens to photograph the sun or moon depends on how large of a sun or moon disk you want. The size of the disk is controlled by two things: your DSLR’s sensor size and the focal length of your lens.

Before you do anything, consider any lenses you may already own. Then, check the accompanying sun disk images for a focal length/disk size comparison. If you want a larger image than your existing lens will produce, you can achieve that by buying or renting a longer focal length lens or in some cases, using a telephoto extender. But, be careful you don’t use a focal length that’s too long, because that will create a sun disk that’s too large to see the sun’s corona during the totality phase of the eclipse.

The corona is very faint and can be up to five radii of the sun depending on the exposure. This will be covered in more detail in an upcoming article on exposure.  

Digital Single Lens Reflex cameras

The Canon EF 400mm 5.6L or the new EF 100-400mm f/4.5-5.6L IS II zoom are affordable, high quality, long focal length lenses that will be ideal on an APS-C sensor camera body. You should be looking for a sun disk 1/3 to 1/4 the height of your sensor.

A 400mm lens on an APS-C sensor produces a 1/4 size sun disk. A 400mm lens with a 1.4x extender will produce a 1/3 sensor size sun disk and has an equivalent focal length of 560mm.

When considering buying a new lens, look into what other subjects you will want to shoot after the eclipse. Many bird photographers love the EF 400mm f/5.6L or the new EF 100-400mm f/4.5-5.6L IS II zoom because they are relatively affordable, have L series pro quality, and are easily hand-held and very portable for long walks. Make sure your new purchase has an afterlife.

If you’re using a full-frame DSLR, you should be looking for a sun disk ratio-to-sensor size the same as with APS-C sensors. A good sun disk size will be created with 800mm focal length. This can be achieved by using an 800mm lens or a 400mm lens paired up with a 2x extender to produce the 800mm size.

Using a 1.4x extender on an 800mm lens (1,120mm equivalent) on a full-frame sensor will produce a large sun disk but, during totality, you will cut off most of the corona.

Canon-brand lens extenders are designed for specific L-series prime and zoom lenses. Check the bottom of the Canon USA product page for the various lenses that extenders work with. Just because you can mount them on other lenses doesn’t mean that they will produce the results you’re expecting. These are high quality precision lenses that match the optical quality of the lenses they are designed to fit.

Check all the disk sizes at the end of this article to determine what your existing lenses will produce.

Solar or lunar eclipse photography doesn’t always mean large sun or moon disk sizes. If your plan includes shooting a time-lapse sequence of the entire 2.5-hour solar eclipse with a notable horizon or other foreground feature, you will be using some very wide angle lenses.

On APS-C sensors you would consider the EF-S 10-22mm f/3.5-4.5 or the new EF-S 10-18mm f/4.5-5.6 IS. Both lenses produce an extremely broad 107º maximum diagonal angle of view, at the 10mm zoom setting.

On full-frame sensors you should consider several ultra-wide angle lenses. The new EF 11-24mm f/4L zoom produces a whopping maximum 126º maximum diagonal angle of view (without fisheye-type linear distortion) while the EF 14mm f/2.8L II lens produces a 114º maximum diagonal angle of view. The EF 16-35mm f/2.8L III and the new EF 16-35mm f/4L produce a maximum diagonal angle of view of 108º. All these lenses will produce a wonderful eclipse time-lapse composite image.

PowerShot cameras

In the previous article Choosing a Camera for Eclipse Photography, we discussed two PowerShot cameras that will work nicely in creating large sun disks. The PowerShot G3 X produces a nice size disk when the zoom is fully extended. It’s equivalent to what you’d see with a 600mm lens, on a full-frame DSLR camera. The SX60 HS, with its smaller imaging sensor and 65x optical zoom lens, can effectively zoom in to the equivalent of a 1,365mm lens (again, what you’d see with that lens on a full-frame DSLR camera). Both cameras have two zoom ranges: optical zoom and digital zoom.

Optical zoom uses the optics in the lens to produce a nice clear image. The equivalent focal lengths mentioned above refer strictly to what, optically, the lens alone can deliver.

Digital zoom allows you to zoom in closer to distant objects but magnifies pixels to achieve that higher focal length and the image may appear grainy, and effective final resolution is reduced. The PowerShot SX60 HS digital zoom has the ability to zoom in on the sun too much and more than fill the frame. It produces a sun disk larger than your sensor. Try to avoid using digital zoom when sharper images are required.

Lens handling tips

Most longer focal length lenses have an image stabilizing feature. This is a great feature to have if you’re hand-holding a lens. If you are using the lens on a solid tripod, however, please remember to turn this feature off.

Canon telephoto lens extenders are an affordable, high quality way to magnify the image from a lens and are used on several long focal length lenses. There are two Canon extenders:

  • The Extender EF 1.4x III magnifies the focal length of a lens by a factor of 1.4x. Used on a 400mm lens, the effective focal length magnification equals 560mm. This extender loses one stop of light. This means if you’re using a 1.4x extender on an f/5.6 lens, the new wide open aperture effectively becomes f/8.
  • The Extender EF 2x III magnifies the focal length of a lens by a factor of 2x. Used on a 400mm lens, the effective focal length now becomes 800mm. This extender loses two stops of light. This means if you’re using a 2x extender on an f/5.6 lens, the new wide open aperture, in effect, becomes f/11.

For autofocus through the viewfinder with a DSLR, the widest aperture of a lens (or lens plus extender) becomes an important factor. Many Canon EOS cameras require an effective maximum aperture of f/5.6 or faster (lower f-number) to perform AF. Recent mid-range and advanced EOS cameras can often AF through the viewfinder at effective max apertures down to f/8, at least around the center AF point. With an effective aperture smaller than f/8, such as the 400mm 5.6 lens with a 2x extender (equivalent to f/11), the camera’s autofocus system won’t work with viewfinder autofocusing. The good news is that it will focus using the Live View feature on your LCD monitor, even at these small effective max lens apertures.

Focusing and viewing the sun’s disk on your LCD monitor — again, using appropriate solar filters on your lens — is the safest way to photograph the sun. If you have a variable angle LCD monitor, you can adjust the angle of the monitor that will provide you a comfortable way to track the approximately 2.5-hour eclipse.

When shooting a rare event such as an eclipse, you don’t want to leave anything to chance. Across most of the country, the eclipse will happen almost directly overhead. It will vary from about 55° to about 75° above the horizon, depending where you will be viewing it from. Larger zoom lenses, with heavy glass elements when pointed overhead, may have a tendency to “zoom creep” with time. To prevent this, you can constantly monitor your zoom ring or simply tape it down.  

Taping down the focus and zoom rings on your lenses is also a great way to avoid inadvertent movement in the course of handling your gear while photographing the eclipse.  If you do use tape, please don’t use conventional “duct tape” that you find at hardware stores or home centers. Blue “painter’s tape” leaves no residue and is a good alternative to “duct tape.” Gaffers tape, available at well-stocked photo and cinema dealers, is stronger, and most importantly leaves little or no sticky residue when you remove it. Trust us: gaffers tape is worth the investment.

Some zoom lenses, like the new Canon EF 100-400mm f/4.5-5.6L IS II, have a nifty zoom ring tightening feature to prevent “zoom creep.” Please be aware: some other Canon-brand zoom lenses have a sliding switch to “lock” the lens, but this only locks it in its shortest zoom position, to keep it from moving when you’re transporting or storing the lens. This lock switch won’t allow the lens to be held in place at longer zoom settings so it’s not the same as taping the focus and zoom rings into position.

Whether you already own a long focal length lens or are considering buying one, we hope this overview helps you in the decision-making process. If you are on the fence about buying a new lens, the eclipse is one more reason to go ahead and do it.

For most, the total eclipse of the sun in August will be a once-in-a-lifetime event so don’t put off planning your camera equipment until the last minute.

If you have questions, you can email Dave and Ken at: info@theeclipseguys.com.

 

Sun Disk Size at Various Focal Lengths

200mm Focal Length on an APS-C Sensor, 320mm Effective Focal Length
 
300mm Focal Length on an APS-C Sensor, 480mm Effective Focal Length
 
400mm Focal Length on an APS-C Sensor, 640mm Effective Focal Length
 
600mm Focal Length on an APS-C Sensor, 960mm Effective Focal Length
 
800mm Focal Length on an APS-C Sensor, 1280mm Effective Focal Length
 
400mm Focal Length on an APS-C Sensor + 1.4x Tele-extender, 896mm Effective Focal Length
 
800mm Focal Length on an APS-C Sensor + 1.4x Tele-extender, 1792mm Effective Focal Length
 
800mm Focal Length on an APS-C Sensor + 2x Tele-extender, 2560mm Effective Focal Length
 
200mm Focal Length on a Full Frame Sensor
 
300mm Focal Length on a Full Frame Sensor
 
400mm Focal Length on a Full Frame Sensor
 
600mm Focal Length on a Full Frame Sensor
 
800mm Focal Length on a Full Frame Sensor
 
400mm Focal Length on a Full Frame Sensor + 1.4x Tele-extender, 560mm Effective Focal Length
 
800mm Focal Length on a Full Frame Sensor + 1.4x Tele-extender, 1120mm Effective Focal Length
 
800mm Focal Length on a Full Frame Sensor + 2x Tele-extender, 1600mm Effective Focal Length
 
Canon PowerShot G3 X Maximum Zoom
 
Canon PowerShot SX60 Maximum Zoom
 

Click here for more information on photographing the solar eclipse!

For Eclipse Workshops presented by Canon Live Learning, click here!

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