The Latency Test

Are you trying to determine which document camera is right for your classroom? Then I suggest you try the latency test on several competing document cameras the next time you are in a conference exhibit hall. 

To conduct a latency test, just place your hand on the left side of the document camera’s display area. Your hand should now be clearly visible on either the demonstration projector or monitor screen. Next, pick up your hand about ¼ inch from the surface and quickly move your hand to the right side of the document camera’s display zone. Repeat this action several times. How blurry is the resulting display? Can the capture or frame rate of the document camera keep up? Is the resulting visual experience an unseemly blur? Or does the image abruptly and uncomfortably time shift into focus, a split second or two after your hand stops moving?

A document with low latency is important in classrooms. Here’s why. Blurred images and refocusing waste instructional time. Instructional demonstrations of brush strokes, cutting and folding techniques, micro-images, or food preparation require sharp clarity, so blurring is quite counter-productive. Abrupt images can cause visual upset. Constant rapid movement of hands or materials in a high latency environment can create visually induced motion sickness (just like grandpa’s old home videos). You see, latency matters. And you want low latency. It’s sometimes easy to get bamboozled by a cute low-cost document camera, only to pay the piper when it won’t perform quite the way you want it to in the classroom setting. So before you buy, conduct the latency test.

Warning: wireless document cameras provide a slower frame rate than cable-connected document cameras, which is expected. What you lose in frame rate, you gain in flexibility for positioning—so don’t be overly alarmed. A wireless document camera is still a great tool for your class.