VILTROX EF-E II 0.71x Auto Focus Speed Booster Adapter - Canon EF to Sony E-Mount Converter for a9, a7R III, a7R II, a7III, a7S, a6500, a6300 Cameras - Perfect for Low Light Photography & Videography

First things first: This is a focal reducer. It does two things. 1. If you have a full frame lens and a crop sensor camera or are shooting aps-c mode on a full frame camera, it takes the full frame image circle and compresses it so it fits onto a crop sensor. 2. Because of the nature of the light gathering not only does it give you a near full frame FOV on the crop sensor, it increase the light sensitivity by approximately 1 stop. 3. It has a magnification factor of .71 so for instance at a crop factor of 1.5 a 50mm lens gives you (50*1.5)*.71 FOV = 53.25mm equivalent.This is NOT a photography product. Do not by this because you want your full frame 50mm 1.8 STM II on your 7D lens to be 50mm on your 70D. It doesn't provide enough coverage. You will have dark corners most likely. It covers, by design, roughly a 16X9 image circle, very very well. So, consequently if you don't mind making your photos 16X9 instead of 3:2, by all means do so, but focal reducers are not truly meant for photos.This IS a video product designed to make an s35 crop factor look almost like FF.My observations: 1. It does what it's supposed to beautifully. 2. It's sharp from the widest aperture to the lowest (surprisingly so) 3. It gives roughly 2/3 stop increase in brightness as measured using waveforms, not 1 full stop. 3. AF works great, although for video there really isn't much need. 4. for people noting fall off in the corners that can happen with focal reducers in general, not just this one. My experience so far is that some lenses do (primarily optics with light falloff anyway) and some lenses don't (fast primes). There are lenses on which is have 0 light falloff even at widest aperture and others with 1.5-2 stops difference in the corners, for example. 5. It doesn't support all lenses equally. My Canon 85mm 1.2L works, but in order to change aperture the lens or adapter must be reseated each time. 6. If you attach a fully manual EF compliant lens with no electronic number 5 will happen. 7. It flares beautifully. 8. pointed directly at light sources nothing 'unpredictable' happens.If you are the finickiest of finicky drop another $500 and get a metabones for marginally better performance. Otherwise, this product is a total hidden gem.