The Rokunar 1.4x is designed to electronically operate the same way as an original manufacturer's converter.
The 1.4x teleconverter (also known as a tele-extender) will multiply the focal length of the existing lens by 1.4x, and will cut back the amount of light by one f/stop. For example, using a 1.4x teleconverter with a 300mm lens will effectively increase the focal length to approximately 420mm. A lens set to f/2.8 will now be f/4.
Please note: full AF operation is only possible with lenses with open aperture of f/4 or brighter. Please be aware that AF will work properly only if there is enough light and contrast on the subject to activate the camera's AF sensors. Manual focusing is recommended when using lenses with smaller open f-stop value than those given above.
Compatible with both digital and film SLR cameras.