Keeping It All In Focus

July 25, 2017

Written by Dave Henry and Ken Sklute

The last thing you need after the eclipse has ended is to discover that all your images are just a smidge out of focus. It’s the worst feeling you can have knowing that there’s no “re-do.” The next eclipse here in the United States is 2024. That’s a long time to wait.

You can mitigate this issue by vigilance — continually checking your set-up before, during and through the last moments of the eclipse.

Most problems occur without our knowing it. Usually by an inadvertent brushing up against the lens that you don’t even remember doing. Or, the lens’ zoom ring slipped on its own during the course of the eclipse, known as “focus creep” or “zoom creep.”

Sometimes lenses go out of focus on their own due to heat expansion of the glass elements inside the lens.

Tape it Down

Having learned the hard way, most pros, at major events such as auto racing or large sporting events, make a habit of taping down anything that can move. Usually they use gaffer’s tape (available at professional camera and video dealers), but in a pinch, any tape will do. Unlike traditional duct tape, the benefit of gaffer’s tape is that it won’t leave a sticky adhesive residue. Blue painter’s tape will work as well and also won’t leave any residue.

How does this apply to cameras?

Lens focus rings and zoom rings can be accidently bumped without you even realizing what has happened. Once you have the zoom setting you want and have set the correct focus, tape the rings down.

Zoom lenses are especially prone to what is called “zoom creep” and is usually more noticeable in bigger, heavier zoom lenses. With big, heavy zoom lenses pointed upward to shoot the eclipse, the weight of the big glass elements inside the lens causes them to simply succumb to the forces of gravity. The same lens probably wouldn’t have the same issue if you were photographing horizontal scenes such as a landscape or an auto race.   

You don’t have to accidently bump a focus ring to have the focus change. Glass expands and contracts depending on the ambient temperature and humidity.

First thing in the morning, before the eclipse begins, you might make your set-ups, and with a proper solar filter in place,  manually focus on the sun using your magnifying loupe (Hoodman™ is one popular brand) with live view magnification to obtain a crisp focus. Hours later, just before the eclipse begins, you re-check your focus only to discover your sun disk is slightly soft. That’s called focus drift.

What happened is the temperature in the morning was a lot cooler than the midday sun and your trusty lens has been baking in the sun all that time. The glass inside the lens expanded and moved the focus slightly. Years ago, most lenses had a vertical line where infinity should be. Over time, camera companies acknowledged this phenomenon and turned the vertical infinity line to a “lazy” inverted “L” line. This signifies that infinity can be anywhere along that line, depending on ambient temperature and humidity.

Live View

The introduction of Live View years ago was one of the best inventions in digital photography. Using Live View during an eclipse is the safest way to view the eclipse and also allows you to periodically recheck focus.

To get a sharp image, use the magnification feature. On most EOS cameras the maximum magnification is 10x. The EOS 5DS and 5DS R have 16x magnification. Take advantage of this feature and use your magnifying loupe on the LCD screen to magnify the LCD screen image and also eliminate all the ambient light.

Autofocus vs. Manual Focus

Autofocus is a great feature in a camera especially when your subjects are constantly moving around at different distances. An eclipse is different. Nothing is coming closer or farther away. Therefore, the distances aren’t changing. You can minimize potential problems by setting focus manually. It’s just one less variable to deal with and keep track of.

Manual focus is probably the best way to insure sharp focus throughout the eclipse, especially with less expensive cameras such as PowerShots and EOS Rebels. There’s no detail in the surface of the sun for autofocus to grab onto. Once the eclipse begins there’s the line between the sun and moon to focus on, but you’ll have to move the focus points around to do that and you are losing valuable images during that time. Having one less thing to worry about is the key to a successful project.

Image Stabilization

If your lens has image stabilization built into to it and you’re using it on a tripod, make sure you turn it off. If you’re using it hand-held, leave it on.

Zoom Setting and Focus

Be aware that with many modern AF zoom lenses, if you change focal length, you can shift focus as well — even when you’re set to completely manual focus operation. If you’re considering changing zoom settings during the eclipse, for example to include more foreground area in some shots or change the size of the sun disk (to possibly include more of the sun’s corona during totality), be sure to test this with your camera before eclipse day. You can do this by focusing on a distant on-land subject or scene; you don’t have to put on a solar filter and shoot the sun.  If you zoom to your longest telephoto setting, manually focus on a distinct subject, and then back the zoom off and shoot the same subject, don’t be surprised if focus is no longer tack-sharp. Stopping the lens down to small apertures and relying on depth-of-field can sometimes help, but the most important thing is an awareness of this possibility in the first place. It’s not a sign of a defective lens; many modern AF lenses operate this way.

Recheck Everything

Just before the eclipse begins double check all your camera settings, zoom rings and focus rings. Make sure everything is taped down. Do this periodically up to just before totality begins. Once totality begins, you’ll have more than enough to keep you busy.

If you have questions you'd like Dave and Ken to address in an upcoming article, email them at: info@theeclipseguys.com.


Click here for more information on photographing the solar eclipse!

SAFETY FIRST: Never look at the sun without accredited and approved solar filtration over your eyes. Permanent, irreversible eye damage and/or blindness can result in seconds. Never point your camera into the sun without an approved solar filter over your camera lens(es). Not using a solar filter at eclipse magnifications will ruin your camera in seconds. Never improvise, modify or use general photography neutral density filters.

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

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