Image Distortion
by Hayden B. Baldwin

Image distortion occurs when taking a photograph without a "normal" lens. The switch from film to digital has created a problem with DX, APS-C and full frame imagery (FX). In years gone by we photographed the indoor scenes with 28mm (wide angel) lens and for outdoor scenes and shoeprints we used 50mm (normal) lens. That was the standard. Now that we have DX size sensors and zoom lenses that many police agencies use some are experiencing difficulty in understanding some simple concepts. Just putting a scale in an image does not mean the image is factual at 1:1.   I have seen many CSI's using a zoom lens to capture images for comparison taken at the wide angle setting.  This causes distortion of the image that may create problems in comparison and later in court.  Here is an example of this.  The following animated GIF is two images being flipped back and forth. One is taken with a Nikon D300 (DX) 18-70 zoom lens setting at 18mm and the other at 35mm. 18mm on a DX sensor is equivalent to a 28 mm on a 35mm camera and the 35mm setting is equivalent to a 52mm on a 35mm camera (full frame).

So when photographing an object to show proper size please use a "normal" lens setting for your particular camera rather than a wide angle setting.