One of the things we love about shooting video with a DSLR is the low light capabilities. I’ve shot at night with hardly any light using my Nikon D90 and ended up with amazing footage.
But shooting in the full sun shifts things around. If you want to keep that wonderful shallow focus and sweet look of your DSLR in daylight you need to know about ND filters.
What happens is this. In low light you have to open up the iris to expose the sensor to as much light as possible. This reduces the depth of focus and produces lots of other artifacts that we like.
In bright light you have to close the iris down, increase the f-stop, or you’ll blow out all the highlights in the shot. You’ll get nothing but a white blur that can’t be fixed in post production.
The problem is that closing down the iris increases the DOF so much that everything is in focus. That’s nice when you want it but it’s not “filmic”. And it may be just too crisp and clean for the effect you’re trying to create.
Adding neutral density (ND) filters in front of the lens lets you drop the exposure back down to wide open. All of that wonderful film-look DOF comes back into your footage, also bringing lots of soft gradations in the light values that make it easier to work with in color grading for the final look.
The problem is matching the amount of ND to get the right effect.
The cheapest solution is to buy a pack of three filters – a 3, a 6 and a 9 – and use them alone or in combinations to get the light cut back to where you want.
Another solution is to use a variable ND filter.
These vary the amount of density by rotating one linear polarized filter in front of another linear polarized filter. When they are aligned most of the light gets through. When they are at 90 degrees to each other they cut out most of the light.
Here’s a link to two variable ND filters – the first one cost less but should do a good job.
LightCraft Workshop – Fader ND
Which ever way you go – a stack of fixed ND filters or a variable one – make sure you buy a filter size larger than your current lenses. You can always use a step-down adapter to fit smaller lenses but you can’t go up. And a larger filter will make sure you don’t get any vignetting along the edges of your image.
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