Calculating light loss

[patssle]

I'm thinking of putting a 35mm adapter on to my HVX200. I have a light kit and know how to light. My main key for sit down interviews is a 500 watt medium sized softbox with a grid.

If I were to go with the Letus35 and it's 1/2 stop loss, plus a Nikon 1.8 50mm lens, would my total loss be 2.3 stops?

I'm trying to figure out if my current light kit (500 softbox key, 250 diffused hair, 500 + 500 + 250 for backgrounds or fill with dimmers) can handle a 35mm adapter for mainly just sit down interviews for now with indie shooting in the near future.

Thanks!

 

[Huy Vu]

If I were to go with the Letus35 and it's 1/2 stop loss, plus a Nikon 1.8 50mm lens, would my total loss be 2.3 stops?

Well...no. F-stops are determined logarithmically so using an f1.8 lens does not mean you lose 1.8 stops. The f-number has a non-linear relationship with the number of stops (for example from f1 to f1.4 is a stop, but from f1.4 to f2 is also a stop). When you put an adapter in front of the camera things tend to get even funkier since the ground glass of the adapter will allow light to pass through differently so stopping down one stop might not cost you the same amount of light. You also have to take into account light loss from having to zoom in through the stock lense. I would say that a single 500w is not gonna be enough under most circumstances to get good exposure.

 

[patssle]

I would say that a single 500w is not gonna be enough under most circumstances to get good exposure.

Hmm. What would you say is necessary to shoot a headshot interview with a softbox with the HVX and a 35mm adapter? 750 watts? 1000?

 

[cowofevil]

I use a mix of 1000W and 500W softboxes to do standard lighting.

 

[patssle]

Hmmm, probably cheaper just to pick up the new Canon EOS 7D and use that for standard interview shots in junction with the HVX. Instead of an adapter, rails, lenses, extended light kit and with more heat. And less of a hassle to carry around and setup. Plus a great still camera!