What Are Macro Lenses?
You may have an idea of the basics, but what are macro lenses really? And more importantly, how do you use them?
What a Macro Is and Isn’t
There are a lot of misconceptions about what a macro lens is, chief among them that a macro is simply a lens with a very close minimum focus distance. This is half-true, in that, macros typically have a very short close focus relative to many “standard” lenses, but there are also plenty of “standard” lenses with comparable close focus specs to macros. So, what makes one a macro and one a “standard”? As opposed to a “standard” lens, a true macro is capable of a 1:1 magnification ratio. If you’re confused by this explanation, don’t worry, we’ll break down what this means piece by piece.
Put simply, what is meant by “1:1 magnification ratio” is that the image projected onto your sensor by the lens is the same size as the real life size of your subject. For example, let’s say you’re photographing an extreme closeup of someone’s eye, and their eyeball measures 24mm tall. What happens when you shoot with a macro at 1:1 magnification is that the image enters through the front of the lens and then is projected out the back, and when measured at the sensor plane, the image of the eyeball remains 24mm tall.
Working Distance & Selecting a Focal Length
Typically in photography/cinematography, we are not necessarily concerned with the physical size of our subject’s image on our sensor as much as we are with perspective and field of view, and our choice of focal length for each shot reflects that. With macro photography, it’s sometimes somewhat the opposite, because the lens magnifies the image to that 1:1 ratio mentioned above. This means that, for example, if a 50mm lens has a 1:1 magnification at 6” and a 100mm has a 1:1 at 12”, the images captured at those distances would look nearly identical.
So while field of view and perspective remain a factor, what often becomes the primary consideration instead is working distance, or the amount of space between the front of your lens and your subject. This is especially important in nature photography in situations where being too close to your subject can be either physically dangerous or otherwise disturb your intended subject, but it also comes into play in portraiture or documentary, where being closer or farther can have a subtle psychological effect on the person you’re photographing and affect the way they behave. For product photography, you might need to move to a longer focal length and move away in order to make room to properly light your product.