I have been spending a bit of time with macro photography of late. I have a penchant for crawly critters [ link fixed ], which I have indulged for over a year now.

I’ve always had issues trying to take these photos indoors, or in dark places. Because the subject matter is so close to the lens, the built-in flash will frequently cast the shadow of the lens into the picture.

So, armed with a high-output halogen flashlight, a few bucks worth of supplies, and some junk I had lying about the house, I built a hands-free rig for lighting these tricky macro photographs*.

I documented the project over in the Chrome Cow Labs section. Stop by and take a look, then build your own!

*In the spirit of full disclosure, the wolf spider photo above was taken before I built the rig. I just like that photo…};^)

I’ve dabbled in macro photography for a number of years, most recently I’ve taken to spiders, insects and other tiny creatures as my main focus. It’s a great way to take yourself out of the world for a moment, and visit someplace completely alien. With the advent of really nice digital cameras, it’s also cheap entertainment..};^)

(After the the camera itself has been depreciated over a few thousand photos).

Many insects have the decency to pose for photos in the great (and generally well-lit) outdoors, like the fellow pictured above.

This is not always the case, however. Every so often a photogenic creature wanders into the house, in the shade, at night. Using the built in flash (I’m using a Nikon Coolpix 5700) gives acceptable results, but often, as pictured below, the really small critters get lost in the shadow cast by the camera’s own lens. See the picture below.

I recently received a small, high-output flashlight [G2 Nitrolon] as a gift. It has a halogen bulb, runs on a pair of Lithium batteries, and is very, very bright. I have tried using this as a lighting instrument for macro photography, but it is extremely awkward to hold the flashlight in one hand, the camera in the other and coordinate their movements.

The only successful test was made with an extra set of hands. But it is tough (not to mention socially unacceptable) to pack an extra set of hands in your camera bag …or is it?

This can mean only one thing: Project!

The goal is to build a small rig that screws into the tripod mount on the bottom of the camera. It has a flexible armature that can be bent into position to point a mounted flashlight where needed to light a macro photo.

Gathering the Materials

I had almost everything I needed lying around the house. Your mileage and actual materials may vary, as the content our junk boxes may differ. I suggest reading the project description all the way through, and then substituting parts as fits your situation.

• Tripod with broken leg, check.
• Old pill bottle, check.
• Hose from useless exercise-ball foot-pump, check
• Fairly stiff but bendable wire…hmmm.

The wire was a lucky find. I was at the craft store stocking up for another project, and I stumbled across "armature wire." This is thick wire made of soft aluminum. It’s used to make a skeleton for sculptural projects, but it is the perfect material for the boom arm, stiff, but easily bent into position. As an added bonus, it is actually designed to be frequently bent and rebent, so it should last for a while without breaking. It is approximately 1/8th inch in diameter.

Again: read through the project first. I had to make some mid-course corrections, so don’t follow this step by step.

Let’s get to it!

Understanding (not to mention actually using) Photoshop’s Difference Layer

Over the years, I’ve accumulated a few different uses for Photoshop’s Difference Layer functionality, in much the same way I’ve accumulated old computer parts. I didn’t really go looking, it just sort of happened. My impression is that there are three kinds of Photoshop users: those who’ve never stumbled across Difference, those who have played with Difference and a few who actually use Difference. This how-to should appeal to all three.

What is this Difference You Humans Speak of?

A little bit of simple math up front, then on to the good stuff…I promise. There are a couple of different spots in Photoshop where difference shows up. For the following fooling around, assume that we’re talking about the Difference option that appears in the Layers blending menu.

What does it do? In simplest terms, it compares a layer to the layer just below it. Where the pixels have the same RGB value, it displays black (0-0-0).

Those zeros mean there is no difference between the two layers.

Original Image

Comparison Image

Let’s start with these two images. The original image on the top contains three swatches; 255 red / 255 blue / 255 green. The comparison image adds a stripe of white 255 / 255 / 255 on top, and black 0 / 0 / 0 on the bottom. If we place the comparison image in a layer above the original image and set that layer to Difference, we get this:

So what does that image tell us? Well, let’s start from the bottom. Where the comparison image was black, we see the original colors. What it means is the difference between black, where all the RGB values equal 0, and any other color is the the value of the original color:

In the middle stripe, where the colors are the same, which is to say, no difference, the result is a black strip. The difference between a red pixel and a red pixel is 0, green and green, 0, and so on.

Etc.

The top looks a little funky. What’s the deal? Well, now we have a white stripe, where all the RGB values equal 255. So now we get this:

The astute reader will notice that I’m not being consistent about what layer’s RGB values I’m subtracting, sometimes one, sometimes the other. All we are really interested in is the magnitude of the difference. The equation would actually look something like this:

• Absolute Value of (Layer_1 Red - Layer_0 Red)
• Absolute Value of (Layer_1 Green - Layer_0 Green)
• Absolute Value of (Layer_1 Blue - Layer_0 Blue)

The bottom line: Where the images are the same, you get black. Where they are different, you get something else.