When you buy a Canon camera Lens. Focal length is the first thing you’ll see, then largest aperture, USM, STM, IS…and so on. These parameters are quite familiar with most of photographer. But look down the Canon Lenses Specs you may see some “odd parameters” such as Lens Construction, Diagonal Angle of View, MTF chart…Some people may don’t know what these parameters mean.
This article show the detail meaning of all parameter on Canon Lenses Spec. However some basic definition we won’t explain it again.
Lens Construction – Canon Lenses Specs ↑
In Canon lenses Specs you’ll see lens construction like xx elements in xx groups. It’s mean that lens have xx individual pieces of glass and group means two or more elements are glued together.
Example: The picture below show Lens with 6 elements in 3 groups.
MTF chart – Canon Lenses Specs ↑
MTF or Modulation Transfer Function is a measurement of the Camera lenses performance. It help you to understand the optical quality of a Lens and easy to researching, comparing when purchasing a lens.
MTF chart draw down the resolution and contrast from the center to the adges of a frame which was produced by a lens. The vertical axis (y-axis) of MTF chart show the transmission of light through the lens, maximum value is 1.0 (maximum 100% transmittance of the light). However, lens couldn’t give 100% transmittance of light because optical elements are not 100% transparent. The horizontal axis (x-axis) of MTF chart show the distance from the center to the edges of the image, minimum value “0” in the left is the center of lens and the values along axis are distance from center toward the adge (measurement in millimeters).
Aperture Blades – Canon Lenses Specs ↑
In Canon lenses specs you also can see the the aperture blades. It’s show how many blades in the lens and what type of aperture blades of lens. Lenses with higher number of blades will create more perfectly round circle than Lenses with few blades. So, the higher number of blades the smoother bokeh you can get.
Normally lenses have 2 type of blade: straight aperture and rounded aperture. The shape circle of Rounded aperture are more smoother than Straight. So, most of photographers prefer the rounded aperture which can create smooth and circular bokeh.