Thursday, February 24, 2011
Is it bigger than a breadbox? Can I hold it in my hand?
Back when I was a child there was a panel game show on television called What’s My Line? Panelists asked the guest a series of questions, like the two above, to determine his or her occupation.
When you use an image in a presentation, the audience also is asking those questions about scale. One way to answer them is to place a calibrated scale (or ruler) in the image. You also could print out a page of graph paper with a 0.1-inch or a 1.0-mm grid to use as a background for showing a small object. Or, if you know a quilter, you might borrow a 14" square Cut for the Cure ruler or a 15" square Omnigrid ruler from them.
The set of six-inch (150 mm) vinyl rulers shown above are a simple way to show scale. One can be selected and placed next to an object. A pattern of alternating dark and light rectangles makes it easy to read the inch or centimeter markings even if the image accidentally was very over or under exposed.
This little gray two-inch (50 mm) scale is for close-up photography. The backing has an adhesive like a Post-It note so it can stick on most surfaces. They also come with white or black backgrounds. Another type has orange print on a white background, but the printing is fluorescent so it glows brightly under an ultraviolet lamp.
These L-shaped mm and inch scales for field or lab use are even more clever. They include gray patches with 18% reflectance for exposure control. The left mm one is the infamous ABFO No. 2 scale developed for taking images of bite marks by the American Board of Forensic Odontology. If you watch the CSI television shows about crime labs, you will see this kind of scale appear frequently.
An oblique view of the dovetail edges on a foam puzzle mat is shown with an L-shaped inch scale. You could easily measure the edges in either direction.
I’m a metallurgist, so I often take images of steel products and components. These scales backed with flexible magnetic material that stick to steel are very useful to me.