Newbie Question About Speedboosters

Hello everybody! I'm an amateur videographer, and recently jumped from a Canon GL-1 camcorder to a Blackmagic Cinema Camera - my first interchangeable lens system, and quite a jump! With this jump came the introduction to such attachments as speed boosters, and I was hoping somebody could clarify their use for me. I'm a little confused as to what the benefit is of using one, besides the additional f stop(s). I've read that it widens the field of view, although I don't understand why this is necessary! Can't the same effect just be accomplished by changing the camera placement? If I don't need the extra stops, is there really a reason to use one? Thanks, and please excuse my ignorance on the matter... this is all pretty new to me!

- Cinematography newbie, Mark

When you widen your FOV, it's easier to get shallow depth of field.

So without speedbooster, your 50mm lens turns into ~130mm (too lazy to do the math), but DOF/bokeh stays the same.

With it you get about 85mm (bokeh always stays the same if you don't touch the aperture ring).

Additionaly, it's a really good nikon->mft adapter and has another clickless aperture ring, useful for digital lenses...

Cheers!

The Speed Booster effectively makes the sensor bigger (by reducing the size of the image circle that the lens is producing).

So any lens on a BMCC connected via Speed Booster would perform in a similar way it would perform on an ASP-C or Super35mm camera.

Thanks for the quick replies. Helped a lot, thanks!

I've read that it widens the field of view, although I don't understand why this is necessary! Can't the same effect just be accomplished by changing the camera placement?

No. Changing the focal length is not the same as changing the camera-scene distance, or in other words: zooming in is not the same as stepping closer.

Take a look at these two images:

Image #1:

bw_01.jpg (320.5 KiB) Viewed 1420 times

Image #2:

bw_02.jpg (300.88 KiB) Viewed 1420 times

Imagine the sign post to be an actor you want to frame in a certain way. Image #1 is what you might get from 5 m away with some lens. Now if you add the speedbooster, you can (or have to) get closer to frame the actor (sign post) the same way, but your image background changes dramatically.

Selecting the right focus length and camera position you can either add or subtract depth from a scene, either distancing fore- and background or compressing the scene. And while you do so, you get deeper or shallower depth of field, which you can use to detache the actor from the background.

Speedbooster not only captures more light (to me that's a nice side effect), but it virtually doubles your arsenal of lenses, and more important (at least for Pocket cam owners) it can help getting wider shots which you couldn't otherwise get with the lenses you have. Both features make this addon lens a must-have for interior shots.

Wow, that was EXTREMELY helpful! Thanks!

Nice one Mac. Good simple explanation.