I have a two part question. I recently bought a BMPCC 4K and I’m looking for the perfect combination of Metabones Speedbooster for the Rokinon 35mm Cine Ds lens I’m going to purchase. What would be the best fit for a cinematic feel? Also, I’ve noticed that Rokinon not only has a 35mm lens micro four thirds but a Canon EF option. Which would be the best option of the Rokinon 35mm for me to buy to work with the best Metabones Speedbooster?
The blackmagic pocket 4k uses a smaller, cropped Micro 4/3 sensor, which has a crop factor of about 2x (half) a full frame sensor. That means when you use a full frame lens, like the Rokinon Cine DS (EF mount), the equivalent focal length will double when you put that lens on a Micro 4/3 system. Simply put, a 50mm Rokinon Cine DS EF lens will look like a 100mm lens on the Pocket 4k (if you use a simple adapter from Micro 4/3 to EF) On a super 35mm sensor like the Ursa Mini Pro, that same 50mm EF lens will look like 75mm. On a full frame sensor, like a Canon 5d, that 50mm EF lens will be 50mm. If you use the Metabones Speedbooster at x0.71 with the Rokinon Cine DS EF lens, you gain an entire stop of light. So an f/4 lens become f/2.8 on that Pocket 4k. Or in the case of the Rokinon Cine DS, the 50mm lens goes from T1.5 to, theoretically, T1.07. It also reverses the effect of the crop factor on your focal length. So remember how your 50mm full frame EF lens looks like 100mm on a Micro 4/3 Pocket 4k? The Speed Booster multiplies your light AND your equivalent focal length by 0.71. Which means that your effective focal length on a 50mm Rokinon Cine DS EF mount on a Pocket 4k using the Metabones Speedbooster will be 71mm (instead of 100mm) and have a t-stop of T1.07 (instead of T1.5). To answer your first question, any sensor and lens can give you a "cinematic look", which is determined by your lighting, composition, and subject...and has much less to do with your lens and sensor size. When buying a lens, you should be primarily concerned with the quality of the lens, and the platform you will get the most use out of the lens for. The EF mount is nice if you ever want to use Canon mounts on any camera system. The Speedbooster not only allows you to adapt the Canon EF mounted lens to the Pocket 4k Micro 4/3 mount, but it also gives you a light boost, hence the name, "speed booster". Personally, I love the speedbooster, and I use this same speed booster with Rokinon Cine DS Canon EF mount lenses for my Pocket 4k. But some people may disagree. It's preference.
Date published: 2019-07-10