Simple Steadicam for DSLR

For a shoot (where I was running backwards through the woods) I made a simple steadicam which works very well.
A steadicam is basically a pendulum which adds inertia to the camera movement. It's suspended directly underneath the camera, here just with my hand and arm. The two exercise weights at the bottom add the inertia. The longer the boom and the heavier the weights the smoother is the movement. Because the DSLR is pretty light the weights at the bottom need not to be that heavy to pull the camera in a vertical position. What is trickier is the rotational movement of the camera which is prevented by having two weights sideways on a metal bar. Ideally, the rotation could be even more dampened by a soft suspension. It's not that optimal to hold the pendulum directly with your hands. It would have been better to have a handle sideways but I never managed to build that. As long as the camera is held pretty loose in your hand also the rotational movement is pretty smooth.
I use 1kg of exercise weights but could add a second set (after more time in the gym!). These are from a set of exercise weights I got from Argos. The aluminium sheet at the bottom and the screws are from B&Q. The tripod was just a cheap still camera tripod which conveniently had this quick release mechanism attached to it which lies quite nicely on my hand and acts as a bearing:

How to merge MPEG4 with AC3 audio

Sony Vegas 11 has an annoying bug, namely that the Sony AVC encoder won't export audio. Solution: render out AVC without audio and then render out a separate AC3 audio file and merge them using MP4Box.

1. Download GPAC and install it on your computer.
2. Extract the H264 from the MPEG4 file:
   MP4Box -raw 1 attr_2_resiliance03_sonyavc.mp4
   assuming that stream 1 contains your H264.
3. Merge with AC3 audio:
   MP4Box -add attr_2_resiliance03_sonyavc_track1.h264 -add attr_2_resiliance03.ac3 merged.mp4

That's it. And it's even streamable for flash.
Update: this bug only shows up if the audio rate is higher than 192kbit/sec.

Colour rendering index

The colour rendering index is a percentage measure of the quality of a light source in terms of colour reproduction. For example, a sodium lamp has a colour rendering index of 0 because when you shine it onto an object you cannot reproduce its colours. It's just yellow, isn't it? Tungsten bulbs or daylight have a colour rendering index of 100 and serve as a reference to other light sources. More strictly the black body radiation is the reference but tungsten light is a good approximation (a more nerdy definition is here). Note that the colour rendering index is not identical to the colour temperature! The colour temperature defines the temperature of the radiator. So, roughly a light bulb with 3200K colour temperature has that temperature!
So, why don't we just use tungsten light? Because it's terribly inefficient. Most of it's output is in the invisible range which is basically heat (think of the 3200K). Anybody who has blown up fuses with red-heads or burnt him/herself knows what I mean.

What are the alternatives? There are quite lot. The only problem is that most other sources have CRI of <100%. For filming a CRI of 90% or higher is required.
The oldest alternative are the so called HMI lights which have roughly 90% CRI. These are gas discharge lights. In the old days these were really just the HMI lights but now you have a large range of discharge lamps with a CRI of well over 90%. They are often called metal halide lamps, for example, the Osram Powerstar D. See my post about HMI style lights. Lights of this type are often used in fashion shops because they need to reproduce colour faithfully.
Three phosphor fluorescent striplights also have a colour rendering index of over 90%. People associate them usually with Kino flos. However, many companies make them now -- and much cheaper. For example, Fotowerkstatt Mainz or Walimex. All fluorescent lights use basically the Osram Dulux 954 55W tube. The rest is just a box with barn doors.
On the left there are fluorescent lights from the Fotowerkstatt with the Osram Dulux tubes in it, mixed with HMIs to create a sunny daytime atmosphere. Here for the film BIG BOOTS. When you watch the film, the lights are on the right of the window which was covered with ND filters to reduce the incoming light by 2 stops. The room was basically lit by the fluorescent lights and the HMI while the ND reduced the incoming light so that the windows won't burn out.
The colour rendering index of both light sources is above 90%. The colour temperatures are actually slightly different but add a bit of texture to it.

Much worse are LED lights. They have often a colour rendering of less than 80%. This is because they have strong blue component which is not very flattering on faces. I've used LED lights in documentary making but I wouldn't use it in fiction, certainly not on faces. It is well known from theatre that blue light brings out blood vessles and makes faces look ugly. Actors will hate them.

cheap ND filters off ebay

For my GH-1 I bought recently cheap ND filters off ebay.

Then the shoot. It was a typical Scottish day: some times it was really overcast and sometimes pretty sunny so that I had to use sometimes the ND4, ND8 or even both on top of each other. These filters I've used have a lilac kind of colour tint. In order to correct in post I shot a white sheet of paper and then put the different filters on. Below is the result.

The ND4 filter adds especially more blue to the image whereas the ND8 adds both blue and red to the image but in slightly different proportions. Pretty annoying. The other option would have been to have 4 different custon WB settings in the camera which the GH-1 won't allow. Bottomline is that I'll tape a greycard to my clapperboard! Taking every time a white balance just takes too much time.

"HD" monitors for HDSLRs

There are loads of monitors out there for HDSLRs which claim to be high def. What turns out is that most of them take an HD signal but then down convert it to standard definition.
For example,

• 5 inch RUIGE

• 7 Inch On-Camera HD

They both offer so called HD. But if you look at the actual resolution, you get just 800x400. This is not even standard PAL resolution.

In addition many Canon cameras scale down to standard resolution while filming. As far as I know it's only the 7D which provides full HD all the time.

My personal bottomline is: I rather buy a camera with a proper viewfinder than trying to find an external monitor which is sharp.

HMI style lights

 

This is a film light which has about the same light output as a red-head but at only 150W power consumption. It uses a bulb which is used in HMI lights. The parts are:

- Lanzini, Alaska display light. They are the lightest and available from many places but any other for 150W MH bulbs will do.

- 150W metal halide bulb with a CRI>90%. Recommended: Osram Powerstar, daylight balanced.

- par 56 barn doors. They fit exactly around the light

- aluminium U shaped bar & self tapping screws (see picture below):

 

- Calumet rapid adapter which allows mounting the lamp on a standard tripod

Important is that the bulb has a colour rendering index (CRI) of more than 90%. The Osram Powerstar bulbs are generally best and are indistinguishable from daylight on camera. They have a colour temperature of 5200K which is the same as daylight. They work nicely as a fill against the ceiling in a INT/DAY scenario and also as a source of sunlight. If used in interior shots it is recommended to balance the camera also to daylight and wrap half C.T. blue around practical lights which are usually too bright anyway.

How to capture audio under Linux?

I needed to capture audio from a video running in a flash player. Here's what I did:
Created .asoundrc in my home directory:
pcm.fileout {
   type empty
   slave.pcm "tee:default,'/tmp/out.raw',raw"
   # 48000 S16_LE 2ch (aplay -t raw -f dat)
}
Started firefox from the command line:

FLASH_ALSA_DEVICE=fileout firefox

Converted the raw file it to a wav file:

sox -r 48k -s -b 16 -c 2 out.raw out.wav

...assuming that it's 48kHz sampling rate, 16bits and two channels stereo.