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Today’s post will not directly answer the above posed question for you. Previously I had written about how useful a simple close-up lens, which screws onto the end of a normal lens, can be when traveling. They are light, take up little space, cost less than a whole new lens, can be used at different focal lengths and are generally easy to use. Today I want to make a direct comparison with a lens lent to me by the folks at BorrowLenses.com, one of DPS’ sponsors.
A major misconception with camera lenses is that 100mm (or any focal length) is 100mm is 100mm. They are all the same, thus the same number! It must be true, otherwise they’d have different numbers. While the idea of different sized camera sensors create a cropping factor from 1.3x to 1.6 times, focal length seems like such an easier field.
Yet it’s not that simple. I have been asked a number of times, “But, if we both have 100mm lenses, why does your Macro lens make things bigger?” To put it simply, because it can focus closer. All lenses have a minimum focus distance. Check your lens’ manual or, if you are lucky enough to have a lens with a distance meter on it, pull the focus all the way in and read the number in meters or feet. This is as close as an object can be to the sensor plane of your camera and still be in focus. Anything closer and it will blur.
This is where Macro lenses shine. Macro lenses are almost exclusively prime lenses; the type of lens that doesn’t zoom. Giving up the mechanisms needed to zoom and the associated elements that go with the technology allows for a lens specialize in getting closer. Remember, a lens is not just a couple of elements like a simple microscope or telescope may be. They contain up to 25 different elements to help focus light. Just how much closer matters? That’s the part that’s up to you.
As a lens gets closer, the apparent size of the object will get larger. Most Macro lenses can achieve a 1:1 ratio, meaning the image will take up the same amount of space on the sensor as it does in real life. Looking through a viewfinder at an object zoomed this close will seem HUGE. But you have to remember, in the sense of your camera’s sensor, you’re looking at a space of only 36mm x 24mm (full frame) or generally 22mm x 15mm (various APS-C sizes). In other words, postage stamp size, more or less. What you see through the eyepiece is what will fill the space of your sensor and that’s why it seems so big. Hold a stamp up 6 inches from your eye; it will look HUGE.
So how does a normal zoom lens stack up against a Macro? Let me show you. First, I’ll start with a Canon 7D and Canon 28-300mm L. It is focused to its closest distance of 12″ or 305mm. 105mm, ISO 100, f/5.0 (minimum), 1/25 second. What did I choose for an image? Bank Of America was kind enough to send me a notice about how they use personal information. It seemed spell binding and exciting (and not directly copyrighted).
The space of the piece of paper covered in real world terms is 4.5″ x 3″, nearly exactly (114mm x 76mm).
Now I will add on the Canon 500D Close-Up lens, touted in my previous post. Focus distance is now almost exactly 7″ (180mm) from the front of the close-up to the subject. 105mm, ISO 100, f/5.0 (minimum), 1/25 second (NOTE: while the settings were kept the same, this second image’s exposure is increased a whole stop in post production as the close-up lens drops the amount of collected light)
This space of the piece of paper covered in real world terms is 2.625″ x 1.75″ (67mm x 45mm). A pretty good increase. Five inches closer does make a difference. Now to see how it compares to a real Macro lens.
Same Canon 7D but now with a Canon Macro 100mm 2.8 L. ISO 100, f/2.8, 1/160 seconds with a focus distance of just 5 inches from the subject to the front of the lens.
This space of the piece of paper covered in real world terms is .9375″ x .625″ (23mm x 15mm). Do those millimeter numbers look familiar? If you’re super geeky on your sensor sizes, you likely notice that number as being freakishly close to the actual size of the 7D APS-C sensor (22.3 x 14.9 mm according to Canon’s website).
Therefor the image is reproduced at a 1:1 ratio, where as the close-up lens was closer to 1:3 and 1:5 without it.
All of this information is to give you an idea of how much more ‘zoom’ you can get from using a Macro lens as compared to a standard 100mm or a close-up lens. I also hope it serves as a handy reference of different levels of magnification and what 1:1 looks like when blown up to screen sizes. A note on the focus distance: I measured the practical focus distance by measuring from the front of the lens to the subject, while the lenses themselves list their focus distances to the plane of the sensor. Both are relative and work. I prefer the distance from the front of the lens for this simple demonstration because it lets me know if the hood on the lens will block ambient light or not.
It’s also important to note that a Macro lens typically is not limited to the closest of photos. That 100mm on a full frame camera will serve well as a faster portrait lens.