BMCC - Camera A and Camera B

Hi Everyone.

Not sure if this is the right place to ask this. I sort of have been losing some sleep on this question and hopefully more seasoned film persons can answer.

I am going to shoot a short with two BMCC. I want one for a wide shot and one for a mid to close up shot. Now how do I keep consistent light on film between both cameras. In other words, I plan to shoot Camera A at a F 5.6 / 800 ISO and camera B at F 2.8 / 800 ISO (to blur background). From what I understand - lowering the aperture will cause more light to come into the shoot. How do you control this so that there is consistency between footage on both cameras.

Please I hope someone can help with this. Are ND Filters required?

Thanks.

Victor

An ND filter is your best choice. It depends on how close/tight you are with the closeup lens though. You should get a blurred background above F2.8. You don't absolutely need to be wide open on that lens.

The reason I'm so concerned is that I saw a friend's attempt at running a Camera A and B only to see that there was a distinct level of light in the wide shoot and then when the B camera footage was shown, it was way brighter. Needless to say the film looked bad when they edited those scenes together.

Victor

As Forstm says you need to correct the exposure of both cameras with ND.

In your example. If the exposure of cam A (shooting at 2.8) was correct, then the exposure of cam B (shooting at 5.6) would be under exposed by 2 stops. So you would need to increase the light in your scene or increase the ISO.

Lets say you add more light to the scene. Once you have the exposure of cam B (shooting a 5.6) correct you'll now have an issue with cam A (shooting at f2.8) as it'll be over exposed by 2 stops. Adding a 0.6 ND (2 stop ND) will correct this and both camera will have the same exposure.

This is of course if both cameras are the same brand and the lenses are from the same range and have the same transmission properties. The same lens set to 2.8 on different cameras might result in slightly different exposures as can using 2 different lenses set to 2.8 on the same camera. You would only know through testing the lenses and cameras what the difference might be. Tho it's usually very slim.

Once you have your shots in your edit you would then deal with any slight differences by balance the exposure and colour of the 2 shots so that they match better (this is part of the grading process).

When we run 2 or more cameras at a time, we use a monitor (or passive switcher) so we can A/B the cameras. That way we can adjust our exposures so they match. Of course, you can fix this in post during grading, but that adds a lot of time.

Just wondering in terms of depth of field compared to wide or close up or medium shots is it wise to not go to far apart on that. Say shoot at 1.4 close up and 8 wide.. (could be a horrible example)

Just wondering if it could break or make the overal flow / feel of a scène

Sent from my Android Phone

Hi Adam.

Thank you for your explanation. I think I'll sleep a little better tonight!

Victor

PPstudios.

Thank you for your suggestion.

Now a passive switcher? Will this monitor allow me to view what is being shot by both Camera A and B at the same time side by side.

Victor