Canon EF 300mm f/4.0 L IS USM is very good at the Canon L-series lens. Although the focus has been long enough to feel old, very well built lens remains relatively small and light. The image quality of Canon EF 300mm f/4.0 L IS USM is very good.
Canon EF 300mm f/4.0 L IS USM is relatively small, built 2.6 pounds (1190 grams) and very good. The weight is 300 f / 4 is ranked at slightly less than the Canon EF 70-200mm f/2.8 L IS USM. 300 f / 4 is relatively thin and long – 3.5 “x 8.7″ (90.0mm x 221.0mm) – and to feel that way. The handling is very good and very good to bring. 

Canon EF 300mm f/4.0 L IS USM Lens Specifications

Focal Length Range                                    : 300mm
Angle of View: Diagonal                           : 8°15′
Angle of View: Horizontal                       : 6°50′
Angle of View: Vertical                            : 4°35′
Lenses / Groups                                          : 15/1
Aperture Range – Wide / Long              : f/4.0-32
Number of Aperture Blades                   : 8
Manufacturer Specification Weight    : 42 oz
Actual Weight                                              : 41.7 oz
Tripod Ring Weight                                   : 3.9 oz
In-Use Weight                                             : 45.6 oz

With Canon’s ring USM) (Ultrasonic Motor, about 300 f / 4 IS focuses very fast, precise and quiet. I have the accuracy of the focus will be very good – especially when shooting in AI Servo mode. FTM (Full Time Manual) focusing is enabled.

300 f / 4 is one of the two current Canon lens that has a built-in retractable lens hood (Canon EF 400mm f/5.6 L USM the other). I like the convenience hood rages out / to / storage – use or gain access to the filter to. A 77mm filter to be more precise – the same size as many other Canon lenses, the L-series. Apart from the hood, this lens does not extend to the focus. The filter does not rotate.

Canon EF 300mm f/4.0 L IS USM lens is known as the sharpness. Sharpness wide open at f/4.0 is very good with a slight increase in the f/5.6 looks. Very good sharpness corner, even when used on full body.

Near full-frame look-vignetting corners can be seen at f / 4 at full frame body – this is mainly a non-factor, and disappeared after stopping down slightly. Color and contrast. CA (chromatic aberration) is quite well. Very little cushion distortion – but you probably will not notice. Flare is not a problem.

Disconnect the subject from the background easily opened with this lens because of the long focal length and relative width of f / 4. Also f / 4 lens is available, but it comes at a price much higher. Put a little distance between the Canon EF 300mm f/4.0 L IS USM lens themes and backgrounds, choose a variety of apertures and observe the subject is blurred from the nice, smooth background. Oof quality (out of focus) This area with an 8-blade aperture improved.

One of my favorite features of the Canon EF 300mm f/4.0 L IS USM lens is the image stabilizer (IS). Canon 300 Is it possible at much lower shutter speed than normal – 2 stops lower his handheld. This does not stop a moving object, but it is amazing to stop what the movement of a photographer. Please note that the version of this lens to be switched off when tripod mounted. Otherwise, the image stabilization can act recklessly. Also to be noted that the implementation is not that difficult, but more than some newer implementations heard.