Choosing a lens to photograph the upcoming total solar eclipse in April takes a lot more consideration than the camera body to be used because the camera in its simplest terms records the image produced by the 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 camera's sensor size and the focal length of your lens. 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.

If you’re using a full-frame camera, 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.

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.

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. Depending on where you will be viewing it from across the country, the eclipse will happen almost directly overhead. 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.