Forensic Rulers

Dec 23rd, 2014 - Filed under: Blog

I was looking at the website of a forensic vendor last week and browsing through their selection of rulers, and it prompted me to write to the vendor and make some suggestions. But, it also caused me to remember when I first met Larry Stevens, who, at the time, sold rulers for the Oregon Rule Company. Larry had a booth at an EPIC (Evidence Photographer’s International Council) conference and demonstrated his rulers with an enthusiasm that was contagious! You would think that he was the Ginzu Knife sales person on the old television commercials. Oregon Rule had some innovative designs, and they can still be found on their website. But, almost all the forensic vendors continue to sell the same old products that have been around since the 1980’s and before.

So, what do I think is wrong with today’s choices of forensic rulers?

1) The first problem is that most have metric scales. If I lived in Europe, that would be perfect; but since I live in the United States, it makes no sense. If I photograph a knife blade that is 16 cm in length – what juror knows how long that is? But, if my ruler shows that it is 6 1/4 inches, every juror knows that size. There is nothing more accurate or precise in one system or the other, but there is something much more recognizable in one over the other, depending on where you live and who your audience is. My audience is in the US, and eventually is a group of jurors.

2) The color of the rulers. Most of them have either a white background with black writing; or a black background with white writing. These provide good contrast and don’t reflect stray color into the image, but there aren’t the best color choice either. The white ones can become overexposed, bloom, and become difficult to read. The opposite can happen with the black. And, even worse are the rulers with bright color backgrounds like the highly saturated blue or the fluorescent yellow. These are difficult to look at, much less read – and take away attention from the subject. But, even worse, they may reflect their own color into your scene! The best color choice is a light, neutral, gray background. This won’t be likely to bloom, it won’t contaminate the image with it’s own color, and it can be used to white balance your photograph. I’d suggest something like the neutrality and lightness of the WhiBal card – these are spectrally neutral, and light enough to be able to easily read the printed information.

3) Replace the ABFO markings. I don’t know when ruler manufacturers first started using the circle with the plus sign in their designs – but I don’t know anyone who actually uses it! The concept behind it is great – use the circle to correct any perspective distortion in the image. But, in practice, it really isn’t done, and it really isn’t easy. But, what could be easy is if a manufacturer designed a symbol that could be used to easily correct perspective distortion through software. Imagine a Photoshop Plug-In that would detect the symbol and apply the correction, and perhaps also calibrate the image size. Chris Russ of Reindeer Graphics and I have discussed this in the past. I don’t know if he’s put any time into such a project – but someone should.

4) Add a place for erasable information. I’d love to write my name (as the photographer), the date, the case name, and the location onto the ruler. I’d love to use a fine point marking pen, and then be able to wipe that info off the ruler to write new information for my next case.

5) Accessorize the rulers! There are two ideas that I have – but I’m sure there are other ideas. First would be a snap-on arrow. This would be used when I want to include an arrow to point to north for orientation in my images. It would be removable because I certainly don’t always need it. The second is to create Tee and Ell Connectors. These could be used to attach straight rulers together to get T- and L- shaped rulers. No more carrying multiple L shaped rulers – just carry a few straight rulers, and use the connectors to assemble them how you want. You could even make a rectangle fairly easily.

Of course – all of this would only be any good if the manufactures would take excellent care in choosing the quality of their materials, the precision of the manufacture, and the quality control. I’ve thrown away rulers because they have been inaccurate or have obvious inconsistencies in their line thicknesses.

So, those are my ideas for the simplest of rulers. I’d love to see a manufacturer take these ideas and give us something better than what is currently on the market. I’d like to see forensic vendors insist upon something better. And, I’d love to see the end users think about these issues when making their purchases and placing their ruler in their photograph.

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