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How can you minimize exposure "pumping" when going between indoors and outdoors?

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Sean Kendall
How can you minimize exposure "pumping" when going between indoors and outdoors?
on May 2, 2012 at 1:05:55 pm

We've got a shoot coming up that will have a Panasonic Lumix GH2 DSLR camera shooting one continuous video shot using a stedicam and we'll be going from outside to inside, back outside and then inside again.

We have the camera set to auto ISO and iris because we don't want to shake the camera by making adjustments, but the problem we run into is that the camera doesn't smoothly move from one f-stop to another, it is very obvious and gives a "pumping" look as it steps up or down.

Is there a way to reduce or eliminate this problem? We have another camera we could use, a Panasonic HMC150, but if we used that camera we'd have to manually flip between the ND filters on the camera, which would be very noticeable and give the same effect and most likely shake the camera as well.


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Steve Crow
Re: How can you minimize exposure "pumping" when going between indoors and outdoors?
on May 2, 2012 at 2:10:44 pm

Ideally there would be some sort of wireless device (like a wireless follow focus) that could adjust your aperture but lenses with aperture rings are not the norm...in any case this kind of system is expensive.

The only other solution I can think of (besides redesigning the shot!) is to set a fixed aperture and ISO in the camera before filming and try and adjust the overall brightness in editing to match as closely as possible. Neither indoors nor outdoors are going to be perfectly exposed in camera. Keeping the inside area as well lit as possible (assuming a bright sunny day outside) should help minimize the issue.

Keep a second camera running too that isn't on a steadicam and which can be quickly set up and moved to get better exposed shots - that way you will have footage to cut to at the critical transition points (outside to indoors and vice versa)

Bottom line, some shots are just not very feasible with current DSLR technology and the best you can do is a workaround.

Steve Crow
Crow Digital Media
http://www.CrowDigitalMedia.com


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Peter J. DeCrescenzo
Re: How can you minimize exposure "pumping" when going between indoors and outdoors?
on May 2, 2012 at 6:08:24 pm

ISO setting changes typically result in relatively large exposure jumps compared to lens aperture setting changes. A lens iris can adjust in fractional steps (e.g.: f4.0 to f4.1 to f4.2, etc.) depending on the lens.

I'd recommend doing some tests first. You might get smoother exposure transitions if you lock your camera's ISO at the highest value required for the scene (don't use auto ISO).

Lock the GH2's shutter speed, too, typically at approx. x2 the frame rate (if shooting 24p use 1/50th, or if 30p use 1/60th).

Together with the above settings, use auto aperture (shutter priority) to adjust exposure.

Of course, some shots are challenging and some are "impossible". The GH2 has about 6-7 stops of dynamic range to work with. For example, compare that to the much more expensive Nikon D800 which has >11 stops of DR in video mode, or the new Blackmagic Cinema Camera which BmD says will have 13 stops of DR.

But no matter what camera is used, some scenes will be beyond its capabilities, and compromises -- or a different approach -- may be unavoidable.

---

http://www.peterdv.com


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Tim Crowe
Re: How can you minimize exposure "pumping" when going between indoors and outdoors?
on May 12, 2012 at 10:43:00 pm

Hi Shaun,

We had a similar problem on a shot we did going from the bright and sunny outdoors to a heavily shaded front porch, then into the lower light of the entry way and house. You can see it here:



. It's the first sequence and what ended up doing to get around it was a series of cut shots to allow the transition of camera settings. For us, it was the only option. DSLRs and cameras with similar sensors just don't have the dynamic range necessary to handle lighting transitions like this.

Until we can afford a better dynamic range camera like the RED Scarlet or a Canon C300, we'll have to make due.

Tim


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