Canon EF 70-200 F4 L IS, one of famous telephoto lenses of the photography world today, is comprised of 4 main important parts which are lens construction, a lens body, IS (Image Stabilizer system) and an aperture. I have been using this lens for awhile and I would like to share my review into 4 important parts as listed below.
Firstly, the lens construction is composed of 15 lens groups and 20 lens elements with a filter diameter of 67 mm and it has a focal length range from 70 mm to 200 mm. Moreover, there are 2 UD (Ultra-low Dispersion) lens elements and 1 fluorite lens element which help dramatically light dispersion, color balance, image sharpness and a vignette while minimizing ghosting and flare. It has the closet focusing distance of 1.2 m and the maximum magnification of 0.21 m. It is used for dispersing light reflected from objects into an image sensor in a camera.
Secondly, with a total weight of 760 gram, the lens body has a diameter of 76 mm and a length of 172. It has a strong white magnesium alloy case with black rubber cover at a zoom ring and a focal ring and a red ring showing as the Canon professional lens, called L-series lens, around a front part of the lens. It is used to protect the lens elements, the aperture, dust and moisture from outside.
Thirdly, the aperture is made of 8 circular diaphragm blades. Its maximum aperture (F-Stop number) is 4 and its minimum aperture (F-Stop number) is 32 throughout all focal length. Moreover, there is no an aperture ring at the back of the lens so the aperture must be adjusted by the camera only. Its functions are for controlling the amount of lighting coming into the image sensor and depth of field.
Finally, IS (Image Stabilizer system) contains a special gyro system which shifts lens in the gyro system in the opposite direction of hand shaking both x-axis and y-axis in order to compensate vertical and lateral movement of hands while taking photos. Consequently, the motion of IS will cancel out hand shaking directions and the light coming into the image sensor will be steady. It is very useful when photographers would like to take photographs in low shutter speed condition and it gives an equivalent effect of shutter speed approximately 4 stops. With the IS, it helps considerably photographers get sharp images in low shutter speed condition.
In conclusion, the 4 main important parts of the Canon EF 70-200 F4 L IS lens which are the construction, the lens body, the IS (Image Stabilizer system) and the aperture make this lens as the outstanding professional telephoto lens.
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