The DIT Cart – Things to Think About in Planning a Cart

If you plan to own and operate a DIT cart, there are many things to take into account as you plan the rig. Remember that it will be more than just an equipment holder. It will also be your workspace, your office and your refuge for those inevitable long days on the set. It will also need to be adaptable for different jobs and new technology as it comes along. Some things to think about:

1. What are your transportation conditions? A van?, SUV?, car?, camera truck?

2. Need to travel by air sometimes?

3. What types of productions are you going to be working on? Features? Commercials? 3D? High speed? Multi-camera?

4. Will you be working on the set? Near the set? Off the set?

5. Will you be fairly static (as in long studio shoots) or moving many times a day?

6. Need to go upstairs or hills? Small elevators?

7. Studio conditions (level floors and loading docks) or locations (outdoors, hills, sand, gravel, etc.)

8. Will you be doing dailies? Transcoding? Monitoring the camera with a waveform monitor?

9. What happens when it rains on location? High winds?

10. Will you need a black-out tent or similar setup to give you good viewing conditions on daytime locations?

11. Will there always be AC power available or will you sometimes need battery power or your own putt-putt generator?

12. Real estate. Will you need a work area for a control surface, laptop or card readers? Will a digital loader be working alongside you?

Other considerations

Do you want to set up a “mega-cart” that can handle anything you may encounter, or do you want to be able to change out equipment to suit the job? How often will you need to get inside the computer to make changes? Of course another factor is that equipment changes, is upgraded, needs repair or is replaced, so having the inner workings of your cart accessible is a key factor.

Some DITs reconfigure their setup for nearly every job; changing out PCI cards (such as a Red Rocket, for example), hard drives, connectors (such as fiber optic) and RAIDs depending on the type of cameras the job will use, whether the project is 3D, high speed, multi-camera, etc.

Cooling has always been an important factor for computer gear (including digital cameras) and the other side of that coin is that cooling generally creates noise. In some circumstances such as working at a desert location in mid-summer, some DITs even find it necessary to run small air conditioners to keep their computers and hard drives within a reasonable temperature range. Obviously, a rig like this is not going to be welcome near the set if they’re recording sound — the audio people would forbid it. While a good deal of cooling capability and access can be accomplished with careful design of the layout and exterior of the cart (such as the removable sides on some carts), there are limits to what can be done.

Figure 9.24. Two carts working inside a van on a 3D shoot. Note how everything is color coded for left and right sides of the stereo cameras for 3D. These carts have slide out shelves on the side for access to the computers(Courtesy of New Media Hollywood).


Obviously, the equipment is always going to need to travel to the set in some sort of van or truck and this is likely to be different for every job. Some DITs just require that the production company rent a truck to transport the gear; some own their own vans and some use space on the camera truck — something the audio folks have been doing for years with their sound carts. All this means that there has to be a way to get the gear on and off the vehicle — in many cases, especially with a van, this involves portable ramps, which are widely available. They come in types that include rigid, extra light weight and collapsible to make them easier to store. Large cube vans and trucks (such as a typical camera truck) will usually have a lift gate, which greatly simplifies loading and unloading. The size of the wheels is a big factor to consider: larger wheels make it easier to move on rough ground such as on location but might be difficult in a tight location.

Another consideration is whether or not air travel is going to be necessary. In this case, a cart that is designed to close up completely and ruggedly will be necessary, see Figure 9.15 for an example of an air shippable configuration.

Figure 9.15. A clamshell design and detachable wheels make this cart air shippable for remote locations.


With the possible exception of downloading a few digital mags on a laptop during a less than full day shoot, you’re always going to need a power supply of some sort to run your rig. While computers, hard drives and monitors don’t use an enormous amount of power, they do consume their share of current. For years, sound recordists have used heavy duty batteries and DC to AC inverters to power their equipment when other power sources are not available. They often build their own by putting motorcycle batteries in small cases such as those from Pelican and others. One advantage is that DC tends to be “cleaner” than AC power, especially that from a generator.

AC Power

The simplest way to get power is, of course, plugging into an AC power supply. Most film sets will have some kind of power: either in a studio, on location with a big generator for the lighting, a small putt-putt for just essentials; in extreme cases, a vehicle battery can run an inverter to convert DC to AC. Some trucks are equipped with an extra battery for just this purpose; obviously the danger of using your main vehicle battery to power your rig through an inverter is that you may not be able to start the vehicle later on.

Another potential source of power is the RV that is sometimes used for makeup, hair and wardrobe or as a mobile production office. They usually have a small AC generator built in. If noise is a concern, which it is anytime audio is being recorded, the RV will be parked far away from the set, so you’ll need plenty of stingers (extension cords) to reach your cart position. Don’t count on the RV generator running unless you check with the AD to be sure. Most of the time, it will be running to power the air conditioning and hair dressers dryers and curling irons, but occasionally it will be turned off if the audio department complains. Never assume!

Small Genni

Some DITs carry a small putt-putt generator to provide power for their equipment without relying on other sources ; sometimes just as a backup. It is important to remember that the lighting crew often shuts down the main generator very soon after wrap is called or at the very least, an electrician anxious to get home might go around pulling out plugs without worrying too much about where they are going. The drawback of a generator is, of course, noise. Big movie generators are enclosed in heavy duty sound proof blimped housings and even then they are parked as far away from the set as is practical. Small unblimped putt-putt generators are going to make you very unpopular with the sound department so they are really only useful if you are working off the set or if audio isn’t being recorded at all; such as on a high-speed or product shot job. Don’t think that a couple of sound blankets (as they are called on the East Coast) or furny pads (as they are called on the West Coast) are going to muffle the sound enough to keep the audio people from coming after you — they won’t.

AC Cables

In most cases, you’re going to need to have plenty of AC stingers available for you own use. It’s not wise to depend on the lighting department to supply you with them; as previously mentioned they may be pulling up stakes and driving away long before you’ve finished your work. AC stingers on the set are universally black and heavy gauge (#12 wire with double jacketing), so if you use ordinary #14 or #16 orange extensions, they will stand out as being separate from the equipment used by the lighting crew which makes them less likely to get yanked by an overenthusiastic electrician and also less likely to accidently get loaded back onto the lighting truck at the end of the day.

Backup Power

Even if you supply your own power and cables, something can always go wrong. An inattentive PA tripping over a cable could potentially result in the loss of all or most of the days footage! For this reason, every DIT cart always has a backup power supply which switches online instantaneously. Called uninterruptable power supplies (UPS), they are battery based and switch online instantly in the event of loss of the main power supply. Most units also include surge protection which is obviously of critical importance when dealing with equipment and precious data.

They are heavy and take up a good deal of space on the cart but they are an absolute requirement for any rig that deals with video data. They last long enough to save your data and shut down safely to avoid disaster. Computers that are processing files, card readers that are downloading and other similar gear will often experience fatal and unrepairable errors if there is a sudden unexpected loss of power or a surge. In some cases, entire video files can be lost; this can be disastrous when you’re dealing with footage that took hours of hard work and large amounts of money to shoot.

Video and Data Cables

Besides power, you will need a variety of video and data cables. Especially if you are tethered to the camera for instantaneous viewing of the recording signal on the waveform and vectorscope, you will need video cables (Figure 9.12). These are almost always BNC connectors with coax cables and are sometimes provided by the camera crew but you should never depend on that — have backups — and it is certainly something to bring up at the Meeting, which should happen in preproduction and involve the DP, line producer or production manager, the DIT, first AC and editor or post production supervisor. These meetings have been known to save the production thousands of dollars and the lack of them has sometimes led to mistakes, confusion and large unnecessary expenditures to make corrections in post that you could have easily avoided with some preproduction coordination and planning. On commercials and smaller projects, an exchange of emails or phone calls may take the place of a sit-down meeting.

Figure 9.12. It’s important to have plenty of cables, not only to reach remote places but also as backups; faulty cables are a frequent source of failure.

BNC video cables are important and as they are frequently a problem, backups are necessary. They might be provided by the camera department but most likely the camera crew is only going to have the length of cables to serve their own needs.

You may also need USB (2 or 3), eSATA, Firewire (400 or 800), Ethernet, Thunderbolt or fibre optic cables depending on your equipment. One rule of thumb in video — if something stops working or gets glitchy, the cable and connections are the first things to check. Wiggling the switch may work with electrical cables, but with video and audio connectors, making sure it is securely plugged in is a better idea. Unplugging and replugging will at least assure you that the connector is solidly seated, especially if the cart has been subjected to vibration from being transported or moved from set to set. The same applies to PCI cards as well, even though inside a computer or extension chassis. Backups, backups, backups when it comes to cables and connectors!

Moving Around On The Set

Beyond just getting to the location as we previously discussed, you need to think about moving around once there. It might be a single location (warehouse, hospital, office building, house) but there might be many different sets within that building. Are there elevators or stairs? Is the second set up a hill, maybe over a gravel drive-way? These are things to think about particularly as you select the type of wheels for your cart. It also includes a bicycle type locking hand brake on the handle for better control. For many years, the sound department has made arrangements to park their audio cart on the camera truck, but don’t assume that there will be room or that they can accommodate you; however it never hurts to ask.

One thing is universal on sets — everything needs to move fast. If your rig is difficult and slow to move, it’s going to be a problem. This is also something to keep in mind when you consider if you need to ask for a digital utility or video utility person on your team; they will be able to help you get around more efficiently, especially when it comes to wrangling all your power and video cable.


Failover is just another form of backup. For example, many DITs have two computers on their cart; the second one might be used for separate tasks such as transcoding but it also is ready to perform as a failover backup — it can be used as the main computer if the first one fails in some way.

Rack Mount

Many self-contained carts incorporate standard rack mount rails. This is a standardized system that has been around for quite some time, as shown by the original name for them, relay racks. They were first developed by AT&T to house banks of relays, before the phone system became largely digital. They are also called 19” racks based on the spacing of the mounting rails and thus the horizontal size of equipment or shelve that can be mounted in them; 19” translates to 48.26 centimeters. Equipment that fits the specifications (including the size and spacing of mounting holes at the sides) is called rack mountable. The racks, have side rails with predrilled and tapped mounting holes (10-24 screws) are specified in terms of height, with the unit being “U.” A 1U piece of gear is nominally 1.75 inches high but in practice is usually slightly less to allow some wiggle room. A 2U unit would be nominally 3.5” (88.9 mm). There also rails that have square holes for mounting without screws or bolts (Figure 9.18).

The standardization makes it easy to buy and install a great variety of commonly needed equipment such as power bars, shelves, power backup units and so on.

Figure 9.18. A well-organized cart used by Swiss Filmmakers. It has Red camera card readers, a compact flash card reader, RAID, backup power supply and transfer hard drives. At the top of the standard rack mount that holds the shelves is a panel of European style power plugs; on top are a laptop and an iPad. This unit uses square hole rack mount rails. (Courtesy of Swiss Filmmakers).

Excerpt from The Filmmaker’s Guide to Digital Imaging for Cinematographers, Digital Imaging Technicians, and Camera Assistants by Blain Brown © 2015 Taylor and Francis Group. All Rights Reserved.

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