The 10 Best Wide Angle Lenses
A Glass Menagerie
Camera lenses have guts. Lots of them, more often than not, and a fair amount of those guts are made of glass. Even in this very generalized diagram you see a good ten glass elements–or individual glass lenses–in three groups.
It may make you wonder: Why so much glass? Well, a lens can be used to direct, magnify, or to focus light, and it takes a combination of magnification, direction, and focus to allow a desired photographic object to appear on a camera sensor as sharply as it does to the naked eye, maybe even more sharply.
This is, of course, one of the reasons that higher end lenses are more expensive. They often start with a wider front element for maximum light collection, which improves the camera's ability to see in low light.
But a larger lens out front will cause more refraction, which must be compensated for by a precise combination of elements between the front glass and the back glass.
Optical glass can cost around $2,000/kilogram, and a good lens can weigh upwards of 5 kg, most of which is plastic and lightweight metal, so you can see how these things get pricey fast.
Want To Go Wide? Know Your Crop Factor
While Crop Factor might sound like the name of a competitive farming reality show (and maybe it should be), it's actually a way of understanding how much of the focal length your lens claims will actually make it into your image.
If you mount any lens built for a 35mm film camera before the digital revolution changed just about everything on a modern full frame DSLR, you don't have to worry about crop factor.
If you mount a modern digital lens on a modern full frame DSLR, well, you have to check to see if that lens was built for a full frame or an APS-C sized sensor.
What's the difference between full frame and APS-C? Well, an APS-C sensor is smaller in area than a full frame sensor, the latter of which was designed to replicate the area of a 35mm piece of film.
As a result, an APS-C sized sensor can only collect a fraction of the light projected onto it through a lens designed for a 35mm sensor. And, conversely, a lens designed specifically for an APS-C sized sensor will project a smaller image onto a full frame sensor.
So, when buying a wide angle lens, make sure you know what size sensor you're shooting with, and be prepared to do a little simple math to know what your actual focal length will be.
For example, let's say you own a Nikon D90, which has an APS-C sized sensor in it, and you buy that Nikkor 50mm f/1.4 lens up there at number 5. Well, that lens is built to project onto a 35mm sensor, so if you put it on your D90 you have to look along the left hand side of the chart there to get the real focal length.
In Nikon, the crop factor from a full frame lens–or FX lens (APS-C lenses are signified as DX, not FX)–is 1.5x. So, a 50mm FX lens gives you a 75mm focal length on an APS-C sized sensor.
If you own a body with an APS-C sized sensor and you're looking to go as wide as you can, shoot for the highest rated lens with the lowest focal length around, or you might end up tighter than you wanted.
A Field Of Constant Innovation
That design was quickly found to be insufficient, as the manner in which a convex lens bends light makes it very difficult to focus an image across a flat plane. It's like trying to make applesauce with a cheese grater (who does that?); you have to keep turning the apple because the grater is a flat surface and the apple is curved.
This is a phenomenon called Petzval Field Curvature, and lens makers for the next 175 years would find new ways of grouping and spacing lens elements to minimize this effect and maximize image clarity while keeping both the cost and the weight of a lens in check.
Recently, however, a new design has been patented by the folks at Sony, made available by the more pliable materials with which manufacturers can make camera sensors.
Essentially, Sony solved the problem of catching curved light waves with a flat surface by curving the surface itself. Sony's curved sensor promises to allow for less expensive lenses that are smaller and lighter, though it's still only a patent without a prototype.