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Filed under: DSLR • Lenses • Lighting • Technique • Training •

5D Mark II Video, Part Two

Bruce Dorn | 12/23- 08:50 AM

Let’s recap with another example, this time regressing to the film era.  If I load my camera with a slide film that is rated at ISO 125 and walk outside to shoot some sunny day transparencies, I could preset my camera at 1/125th at f16 and be assured of good front-lit exposures.  I might not want all the depth-of field that an f16 would deliver but that’s okay; any equivalent exposure value would return identical results so I can adjust my f-stop and shutter-speed to taste. 

I understand that some of this baseline knowledge is in danger of being lost in this era of highly-automatic cameras but that does not diminish its inherent value.  In that spirit, I’ll expand this explanation just a bit further. 

Equivalent Exposure Value refers to any combination of f-stops and shutter-speed that will result in the same exposure on the film or digital sensor.  In the aforementioned example, an ISO 125 film set for the Sunny 16 rule will give me a good front-lit exposure. So to will many other combinations. Let’s explore this a little further to make sure we fully understand the principles involved and then we’ll get back to how it relates to HDSLR movie making. 

If our opinions about depth of field say that f16 is a bit much and isn’t appropriate for this particular shot, we might want to open the iris to f11. In so doing we will effectively double the light that passes through the aperture.  To maintain the equivalent exposure value we must now drop the shutter speed to 1/250th to reduce by half the time that it is open.  Continuing with this example, an f8 would demand a shutter speed of 1/500th and an aperture of f5.6 would require a shutter speed of 1/1000th.  And so it goes; as the aperture opens, the shutter speeds must rise…

Okay, enough background on Equivalent Exposure Values.  Sorry if this recap strikes you as inanely fundamental but for some new arrivals, this may be a minor revelation.  Now that we’re all on the same page, lets see what the implications are for recording video with the Canon 5D Mark II. 

In digital, the lowest normally-accessible ISO setting is the sensor’s native ISO rating.  All other higher settings are simply electronic gain increases and not relevant to the immediate point. The Canon 5D Mark II’s sensor is natively ISO 100 and can be expanded to as high as ISO 12,800.  This means its nighttime or low-light work is exemplary; especially when one couples the nose-bleed-high ISO ratings with a see-in-the-dark optic such as the Canon 50mm f1.2.  Bright daylight, on the other hand, offers a real challenge. 

As I mentioned in my last posting, video capture in the 5D mark II has a limited number of shutter-speeds available.  To refresh your memory, these speeds range from 1/30th to 1/125th of a second.  This is a fairly reasonable spread of choices as speeds lower than 1/30th could introduce excessive subject blur and speeds above 1/125th might result in a distracting staccato effect on objects moving laterally across the frame. Regardless of the technical and aesthetic rationale, this limited range of shutter speeds has an unfortunate effect on bright daylight filmmaking. 

Let’s apply the classic “Sunny 16 Rule” to find out why…

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Bruce Dorn | 12/05- 11:20 AM

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