Beyond Life Size: What Not to Do With a $20 Bill
Macro photography opens up new realm of possible subjects and possible problems. It can be helpful to have a standard of comparison as to how far you have progressed into this new realm, and hence the concept of "life size," and beyond.
Everyone would agree that a "life size" image of Mt. Rainier would be quite large indeed. But when photographing more conventionally sized subjects things may seem less clear cut. People often talk about full frame images as being "close ups" even when the exact magnification of various such images isn't at all the same. But there is a standard nomenclature for close-up magnification and it all starts with a term known as "life size."
First off, it doesn't matter how big you print or view the resulting image. When giving presentations I've often projected images to fill a wall-sized screen, but that doesn't mean I accomplished anything special when shooting it. What matters is how big the actual image I captured was, in the field, when I shot it, not what I did with it after that point. You only get one shot at magnification — when you press the shutter release button.
If you shoot something such that its representation on your camera's sensor is the same size as that object in real life, the resulting image is said to be shot at "life size" or 1:1. Capture something such that the image projected by your lens on the face of the sensor is bigger than that object actually is and you have gone beyond life size. Most images are thus significantly less than life size. Shoot an image of a rose bush such that it fills the frame and you are still far away from life size no matter how close up you think you may be. A life sized image of a rose bush would encompass just a portion of a single bloom.
Back in the days of film when everyone shot with sensors (the film frames) that were all sized at 24x36mm (roughly an inch by an inch and a half) we all shared a common reference for image size. In a digital world when everyone's shooting with different cameras and different sized sensors, the same concept holds true even if the standard of comparison differs somewhat. Regardless of the size of your sensor, a life sized image fills the frame with something that is that same size in real life. Those of you shooting with bigger sensors merely capture a larger surface area at life size than those with smaller sensors.
Capturing an image at life size can be difficult. Going beyond life size gets increasingly difficult.
Some while back, I wanted to demonstrate just what "larger than life size" actually looked like. I decided to start with something everyone would be familiar with, a United States twenty dollar bill. My plan was to shoot a series of images of the same $20 bill at increasing magnification. This turned out not be as easy as I thought. Not because of the difficulty of shooting the increasingly closer shots, but from what I thought would be the easy shot, the very first one: the full frame image of the bill.
You may have heard that the US Treasury frowns on counterfeiting. You may also have heard that, to this end, they worked with the makers of modern color copiers to foil attempts to duplicate money by embedding software to defeat would-be counterfeiters. The same thing holds true for Adobe Photoshop apparently. Not that I thought I was doing anything suspicious — my intentions were honorable — but when I opened an image I shot of a full frame $20 bill in Photoshop I was greeted by a warning not to counterfeit. Thankfully, I didn't encounter the same problem with more close-up images that captured ever smaller portions of the bill, but that first one was tricky in an unexpected way. Apparently, I was busted.
You can see some of the results of my efforts here. How I shot these started with taping the $20 bill to a board I had carefully made sure was perfectly vertical. This then allowed me to use a camera mounted level to verify that my subject and camera sensor plane were in alignment and perfectly parallel. There's plenty of depth-of-field when shooting a full-frame dollar bill, but it gets extremely shallow as magnification increases. The final image here showing just Andrew Jackson's eyeball would have been out of focus on one side had the camera not been aligned.
The other problem was lighting. Long exposure was no problem since the $20 wasn't going anywhere until after I was done shooting and felt compelled to go spend it, but even seeing it at all became increasingly difficult at higher magnification. I ended up setting up a couple of high intensity halogen shop lights to make it bright enough to focus. In addition to the light, they did generate a ludicrous amount of heat, but I could take breaks between shots so I lived to write about it here. On the plus side, digital white balance made correcting for the ugly halogen color cast easy.
If I try this experiment again, next time maybe I'll start with a postage stamp instead of a dollar bill. Perhaps the US Postal Service is more forgiving of photographers trying to teach about macro than the Treasury Department is. Of course postage stamps themselves are getting less common as the years go by so my search for a good example subject may run into different complications by going that route too.