USING 3rd Party LENSES & ADAPTERS ON DSLR BASED VIDEO-BIG ISSUE FOCUS BREATHING

What is focus breathing?
Change in focal length (magnification etc.) as your focal distance changes... that change is called focus breathing. 

Simply stated it is a phenomenon seen in video and most common on a rack focus where the image appears to breath as focus is being applied and is exaggerated through the use of Zoom lenses.. In other words the size of the image varies during the focusing from one object to another. This makes for undesireable imaging in your video. Is their a workaround with zoom lenses? Not really and this brings us to the issue of using adapters and 3rd party lenses deployed on another manufacturers camera body.


SCENARIO
The new SONY A9 is a fantastic camera but throw a metabones adapter and Canon EF L Glass ZOOM lenses on it and be prepared to deal with the breathing issue. Place the equivalent SONY zoom on the A9, A7 etc. and the problem is pretty much non-existent. So if you are considering switching from one camera manufacturer to another and are counting on utilizing your expensive existing lens collection through adapters, be prepared as you will need to think twice when it comes to shooting video.

THINK PRIMES, CINE LENSES

The best solution here of course is to use primes but if your existing lens collection for example consists of Telephotos, zooms like 16-35mm, 24-70mm, 70-200mm, etc. lenses then you really need to re-evaluate your decision to switch cameras and again this strictly applies to video on a DSLR, mirrored or mirrorless.

PRIME CINE LENS

CINE WIDE SOOM

WIDE ZOOM (BREATHING ISSUES)

FOCAL LENGTH DEFINITION
The focal length is the distance between a hypothetical single-element lens and a sensor required to reproduce a given magnification of image. This is unrelated to the distance from the sensor to the flange.