Why I Use a Matte Box

Inserting ND Filter into matte box

There are at least two reasons for a matte box; to control stray light from entering the lens and fogging up the image and to facilitate the use of filters. Most important for me are the ND filters.

Neutral Density filters are the equivalent of sunglasses for your lenses, they decrease the amount of light entering the lens without changing the color or quality of light.

Effect also known as "selective focus"
We use them when we want to open the aperture to decrease depth of field. The still capture on the left is an example of narrow depth of field. Click on it to enlarge.

The bottle in the foreground is barely in focus and everything else is a soft blur. Only fast lenses can accomplish this degree of blur at such a short distance. The lens, in this case, is wide open.

Imagine you are outside on a very bright day and you want to create this effect; to blur the background behind your subject. The problem is that you want to keep your shutter speed at 1/60 for 30fps video, which means that you would have to close the iris to get the proper exposure, remember it's very bright outside.

By closing the iris you increase the depth of field and more area behind your subject will be in focus. This is not what you want. You want to open the iris as much as possible to narrow the focus area. Here's where the ND filters come in. Like putting on sunglasses. With the ND filter installed you will have to open the iris to expose properly, therefore achieving selective focus or narrow depth of field.

Below is another example where the woman's ears are already starting to soften to a nice blur. For more on this subject see my other post on Depth of Field.

Audio Set-up: ATOMOS Shogun 4K & Sony Alpha a7s

I decided to test the Sony a7s and Shogun 4K recorder's audio capabilities for an upcoming project. Wouldn't it be great if I could use two wireless microphones plus camera audio through HDMI? It should be possible with the a7s and the shogun 4K recorder.

Sony a7s with ATOMOS Shogun and 2x wireless Lectrosonic mics
The Sony a7s works flawlessly with the Shogun 4K recorder/monitor for video; let's see what we can do with audio. I hooked up two Lectrosonics wireless microphones with the Lemo/XLR cable to the Shogun recorder turned everything on and made sure that the microphones were working.

Nothing on the Shogun. No levels, no audio. Nada!

You won't get anything from the wireless mics until you enter the menu in the Shogun and adjust various audio settings.

ATOMOS Shogun audio settings

Above is the Audio menu on the Shogun. I have selected to record only the first two channels (a7s Camera) and the last two (Lemo/XLR) You cannot adjust the camera audio from here, it's coming into the Shogun from the HDMI. The only way to adjust the camera audio is through the camera menu or by adjusting the microphone that is connected to the a7s.

Audio Options

Here are my settings for the Lectrosonic wireless microphones. ATOMOS refers to these two inputs as Analog inputs. (You can click on the picture above to see it more clearly) Analog Gain on both L & R: 20.0 dB. Audio In: Mic Level (-40 dBu). I have also set the Audio Delay to 2 frames.

To get adequate audio through the camera's HDMI I will be using an Aputure V-Mic D2 microphone. It's an on camera shotgun that has an adjustable 40db sensitivity range, according to the manufacturer. (We'll see how it performs as soon as I get mine)

For the moment I have the reference audio from the built-in camera mic and the two wireless microphones. After shooting some test footage I loaded everything into my NLE software and I was happily impressed at the great audio quality.