Heat, Power and Recording Limits

The recital starts at seven and runs for two hours. The camera rides a DJI RS 5 gimbal down the side aisle, following dancers who perform each piece once, with no second take. Three clocks start when the record button goes down. Nikon allows one clip to run 125 minutes (p. 1017). Nikon's own test gets about 100 minutes of video from a charged battery (p. 1016). And inside the body a temperature climbs towards the point where the camera warns, counts down and switches itself off (p. 830).

Two of those clocks can run out before the curtain falls. This chapter traces where the heat and the battery drain come from, which turn out to be the same thing, takes each limit in turn, and ends with the arithmetic for four batteries and one evening.

Page numbers in parentheses point to Nikon's Z6III Reference Guide, edition 09, which matches firmware 2.00.

01.Where the Heat Comes From

A battery is a store of energy, and its label says how much. The EN-EL15c is rated at 7.0 volts and 2,280 milliamp-hours (p. 1010). A milliamp-hour (mAh) measures electric charge: 2,280 mAh, or 2.28 amp-hours, is the charge that flows if the battery supplies 2.28 amps for one hour. Voltage is the energy each unit of that charge carries. Multiply the two and you get energy in watt-hours, one watt-hour being what a one-watt device uses in an hour:

$$E = V \times Q = 7.0\ \text{V} \times 2.28\ \text{Ah} \approx 16\ \text{Wh}$$

Here $E$ is the energy, $V$ the voltage and $Q$ the charge.

Nikon says that energy records about 100 minutes of video (p. 1016). Spread 16 watt-hours over 100 minutes, which is $100/60 \approx 1.67$ hours, and the average power comes out as

$$P = \frac{E}{t} = \frac{16\ \text{Wh}}{1.67\ \text{h}} \approx 9.6\ \text{W}$$

where $P$ is the power in watts and $t$ the time in hours. This is my estimate from two of Nikon's numbers, not a measurement, and it is rough in both directions. The 2,280 mAh on the label is a rating, not a measured amount, and Nikon does not say how much of its test's energy went into recording itself. Call it roughly 10 watts, about what a household LED bulb draws.

Electronics do not use energy up. They convert it, and almost all of it ends as heat in the parts that did the work: the sensor reading out every frame, the processor compressing the stream, the card storing it, the screens lighting the picture. A sliver leaves as light from the screens. The rest warms the camera.

Over a two-hour recital, 7,200 seconds, that is about

$$9.6\ \text{W} \times 7{,}200\ \text{s} \approx 69{,}000\ \text{J}$$

of heat, a joule being one watt for one second. The body weighs about 760 g with battery and card (p. 1008). Take, as a rough figure typical of light metals, 1,000 joules to warm each kilogram by one degree. If none of the heat escaped, the camera would warm by

$$\Delta T = \frac{69{,}000\ \text{J}}{0.76\ \text{kg} \times 1{,}000\ \text{J per kg per}\ ^\circ\text{C}} \approx 90\ ^\circ\text{C}$$

where $\Delta T$ is the rise in temperature. No camera would survive that, so the heat must leave, through the surface into the air around it.

How fast it leaves depends on how much warmer the body is than the air. A recording camera therefore warms until the heat leaving each second matches the heat made each second, and then it holds steady. In a simple model,

$$T_{\text{body}} = T_{\text{air}} + \frac{P}{k}$$

where $T_{\text{body}}$ is the temperature the body settles at, $T_{\text{air}}$ the room temperature, $P$ the power turned into heat, and $k$ the watts the body sheds for each degree it sits above the air. A small body has little surface, so $k$ is small and $P/k$ large. The useful consequence sits in the first term: for the same work, a room 10 °C warmer puts the body about 10 °C closer to its cutout. That is a textbook model, not a Nikon statement, but it explains why a clip that runs happily in an air-conditioned hall can end early on a summer lawn.

Every watt that drains the battery also heats the body, so whatever Nikon lists as shortening battery life (p. 1016) adds heat as well. Battery and temperature are one budget, read from two ends.

02.How Long One Clip Can Run

A single clip can run 125 minutes (pp. 212, 1017), the figure What the Z6III Is also gives. That is a ceiling, not a promise. Nikon lists six ways a recording ends by itself: the clip reaches its maximum length, the battery runs flat, you change shooting mode, you turn the photo/video selector, you remove the lens, or the internal temperature climbs too far (p. 109). Heat or a low battery can end a clip early with room left on the card (pp. 1014, 1017), and so can a card too slow for the frame size and rate (p. 212), which Cards and Data Rates for Video covers.

Nikon's battery figure of about 100 minutes (p. 1016) sits 25 minutes short of the clip limit, but it is not one unbroken take. Nikon calls it "actual" endurance under CIPA's conditions and prints no figure for continuous recording, so it neither promises a 100-minute clip nor rules out a longer one. Nor does it give me any reason to expect one charge to reach 125 minutes, so on battery alone I plan as if the battery runs out first. The 125-minute ceiling becomes the limit to plan around when outside power keeps the camera running.

File Splitting

A clip and a file are not always the same thing. On a card of 32 GB or less, one clip may be saved as up to eight files of 4 GB or less, with the number and length of the pieces depending on frame size and rate (p. 212). With ProRes 422 HQ 10-bit (MOV) on such a card there is no splitting: the clip ends when its file reaches 4 GB (p. 212).

Nikon does not say why the limit is 4 GB, and my reading is that it comes from the card's filing system, the format that organises files on it. Nikon notes that a file of 4 GB or more can only be saved to a card formatted as exFAT, not FAT32, and suggests a card over 64 GB formatted in the camera (p. 928), but never says which a card of 32 GB or less receives. FAT32 stores each file's size as a 32-bit number, and the largest value 32 bits can hold is

$$2^{32} - 1 = 4{,}294{,}967{,}295\ \text{bytes} \approx 4.3\ \text{GB}$$

so no FAT32 file can grow past that. Nikon prints no splitting rule for cards above 32 GB. The author's cards, 512 GB and 128 GB CFexpress and 256 GB SD, are all far above that size, so for this kit splitting is a footnote.

03.Heat Warnings and Auto Temperature Cutout

When the camera gets hot during recording, a high-temperature warning icon may appear in the shooting display (p. 109). While it shows, the body, battery and card may all be hot. Nikon asks you to wait until the warning has gone before taking a card out, because a hot card can burn your fingers or slip from them and be damaged (pp. 39, 109).

This item sets how hot the camera may become before it shuts itself down, with two choices, Standard and High (p. 830). Standard is the default (p. 806). Under Standard the camera shows one warning icon, then a second, which is the high-temperature warning of p. 109, and if the temperature keeps rising it switches to a countdown timer. Under High it works through three icons before the countdown starts. Either way the timer turns red at 30 seconds (p. 933), and at zero the camera turns off and shooting stops (p. 830).

High buys time before the shutdown, and Nikon attaches one caution to it: the body may become hot to hold, so Nikon suggests a tripod or other support to cut the time your hands spend on it. Two more cautions apply to any hot camera, whichever level is set. Image quality may fall while the camera is hot, and the countdown can appear the moment the camera is switched on, even on High (p. 830).

Two messages belong with these. One says the camera is too hot to use, and the remedy is to stop until it cools. Another reports a hot battery, and the remedy is to take it out and let it cool (p. 927). Heat also blocks charging. A battery charging in a hot camera fails, which the charge lamp shows by flashing quickly for about 30 seconds (p. 91), and Nikon asks you to let a hot battery cool before charging it (p. 995).

I leave Standard in place for handheld filming, where my hand is on the grip for the whole take. For the recital I switch to High. My hands hold the gimbal's handle rather than the body, which as I read it is the kind of support Nikon's caution has in mind, and a solo that does not repeat is where a shutdown costs most. The price is Nikon's warning that a hot camera may record lower image quality, and for an event that happens once I accept that trade. If a warning icon appears, I stop at the next pause rather than carry on towards the countdown.

What Nikon Says About Recording in Heat

Nikon rates the camera, and the EN-EL15c in it, to work from −10 to 40 °C (pp. 1009, 1010). It says heat can end a recording early (pp. 1014, 1017), may lower image quality (p. 830) and interrupts wireless links (p. 933). It does not say how many minutes the Z6III records before the first warning, or which frame sizes, rates or file types heat it fastest. I have not measured those either, so this guide prints none.

The rest is my inference from the physics above. A camera in direct sun takes in heat on top of the heat it makes, so shade counts outdoors. Switching off during a long pause stops the heat at its source. And because a setting that drains the battery also heats the body, turning off Wi-Fi and Bluetooth, two drains Nikon names (p. 1016), helps on both counts. Airplane mode in the network menu turns both off (p. 872).

04.How Long a Battery Lasts in Video

Nikon's figure is about 100 minutes of footage per charged EN-EL15c, whether the monitor mode is Viewfinder only or Monitor only (p. 1016), and Viewfinder and Monitor Displays quotes it too. The conditions matter more than the number. Nikon measured it the way CIPA, the Camera and Imaging Products Association, prescribes. CIPA is a Japanese industry body whose shared test rules let different cameras be compared. The camera ran at its default settings, fitted with the 24-70mm f/4 S zoom and Nikon's own 660 GB CFexpress card, the MC-CF660G, in a room held at 23 °C give or take two degrees (p. 1016).

Nikon then lists what shortens battery life. Some of it is handling: half-pressing the shutter-release button for long spells, focusing again and again, and zooming in and out repeatedly. Some is what the camera is doing: shooting NEF (RAW) photographs, using slow shutter speeds, keeping Wi-Fi or Bluetooth on, and running with accessories attached. Cold weighs on it too (p. 1016). The older EN-EL15b and EN-EL15a also fit, though Nikon says they take fewer pictures per charge and gives no video figure for them (p. 1016).

The recital setup departs from that test in at least one way: an HDMI cable feeds the F700 monitor throughout, which I count as an accessory connected. Full-time AF, which I use, is not a departure, because it is the video default (p. 579) and Nikon tested at default settings. The cable points below 100 minutes. Nikon does not say how far and I have not measured it, so the plan below treats 100 minutes as a planning figure, never a forecast.

05.Running the Camera over USB

First-Day Setup covers charging over USB-C, the charge lamp and the minimum output Nikon asks of other makers' chargers. What matters here is what happens while the camera records.

With this item at ON, its default (p. 807), the camera draws power from a connected source while it is switched on, which Nikon describes as limiting the drain on the battery (p. 856). Limiting is not stopping, and Nikon does not say whether the level holds still.

Three of Nikon's conditions shape a recording plan. A battery must be in the camera or no outside power is accepted (p. 856), so a USB supply cannot carry the camera through a battery change. The battery does not charge while outside power runs the camera (p. 92), and Nikon counts a lit card access lamp, which a recording keeps lit (p. 108), as the camera being on (p. 857). A cable plugged in at the start of a clip will not refill the battery by its end.

Nikon also names the sources allowed to run the camera: its own EH-8P AC adapter or a computer's Type-C port, each through the supplied C-to-C cable, and a third-party portable charger, usually called a power bank (p. 856). For a power bank Nikon sets three conditions. It must speak USB Power Delivery (USB PD), a standard by which the source and the camera agree a voltage and current. It must supply at least 27 W, given as 9 V at 3 A. And its cable must carry Type-C plugs at both ends. Even then Nikon guarantees nothing (p. 92). The quickest way to confirm a source works is the USB power delivery icon, which shows on the shooting screen and the control panel while outside power is in charge (p. 856).

One setting elsewhere switches all of this off. Setting USB in the network menu to iPhone or USB-LAN disables both powering and charging over USB (p. 900). Leave it at MTP/PTP, its default (p. 871), unless you need one of those links.

Mains Power Through the Battery Chamber

For a reader who owns them, Nikon offers a second mains route: the EP-5B power connector, which sits in the battery chamber in place of the battery, with an EH-5d AC adapter or the older EH-5c or EH-5b (pp. 969, 984). Nikon presents the pairing as the way to power the camera for extended periods (p. 969). With no battery behind the connector, a pulled plug leaves the camera nothing to fall back on. That suits a camera locked off on a tripod beside a socket, not a gimbal. Nikon's MB-N14 power battery pack holds two EN-EL15c batteries (p. 969), but Nikon prints no video runtime for it.

06.Planning the Recital

The recital runs 120 minutes and one battery under Nikon's test gives about 100, so measured in Nikon's batteries the show comes to

$$\frac{120\ \text{min}}{100\ \text{min per battery}} = 1.2$$

and at least one swap belongs in the plan before any real-world losses. The author carries four EN-EL15c batteries, which under Nikon's test conditions add up to

$$4 \times 100\ \text{min} = 400\ \text{min}$$

or $400/120 \approx 3.3$ times the length of the show. These are estimates built on Nikon's laboratory figure, not anything measured on this kit. Four batteries are plenty, and the only real question is when to swap.

Swap early, and at a pause. A swap means stopping the recording, switching the camera off, as Nikon asks before any battery change (p. 995), changing the battery, switching back on and starting a new clip, and none of that can happen during a piece. I change the battery at the first natural break after about an hour, the interval if the programme has one, whatever the battery icon says. That leaves the second battery the remaining hour with about $100 - 60 = 40$ minutes in hand against Nikon's figure. If a warning icon is showing when the break comes, I let the camera cool before opening the battery door, as Nikon asks (p. 830), and the swap waits.

Clips follow the same logic. One 120-minute clip fits under the 125-minute ceiling on paper, but it would ask one battery to last 120 minutes, which Nikon's figure gives me no reason to count on, and any of the six stops on p. 109 would cost whatever was being danced. I stop and restart between pieces. Each restart costs a few seconds of applause and gives a chance to check the battery and look for a warning icon.

The Wall Adapter and the Night Before

The 100 W adapter earns its place the night before, not during the show. Nikon's figure is about two and a half hours to charge an exhausted battery in the camera on its EH-8P adapter (p. 91), so four batteries charged one after another in the camera take about

$$4 \times 2.5\ \text{h} = 10\ \text{h}$$

Nikon gives no charging time for third-party adapters, so the author's may be quicker or slower. A separate charger shortens the job, and the batteries and power part of this guide covers chargers and battery care.

On the night, a cable to the wall suits only a camera that stays near a socket, such as a tripod at the back of the hall, covered after the settings table. On a gimbal following dancers, a cable is a tether and a trip hazard, and I would not use one.

The Monitor and the Gimbal

The monitor and the gimbal run on their own batteries. NEEWER's product page rates the F700 at about 2.4 hours on each of the two 4400 mAh NP-F750 batteries in its two-battery bundle, the bundle I bought. That is $2.4 \times 60 = 144$ minutes, so on NEEWER's figure one battery covers the 120-minute show with about 24 minutes spare. NEEWER states no test conditions for that figure. NEEWER also advertises a DC output for powering a camera through a dummy battery, a route Nikon does not name for the Z6III (p. 969), so this guide does not use it. I carry four monitor packs in all.

DJI's specifications page gives the RS 5 a maximum standby time of about 14 hours with its BG33 battery grip, with the gimbal balanced, level and stationary, and says operating time is shorter when the gimbal moves. DJI does not say by how much. DJI's RS 5 page also says the gimbal's Bluetooth shutter works with Nikon cameras, among other makes, with no cable, and points to its compatibility list for models. My inference is that Airplane mode, which turns the camera's Bluetooth off (p. 872), would cut that wireless link too. If you start and stop recording from the gimbal that way, test it at home with Airplane mode at ON before the night. HDMI and External Monitors covers cabling the monitor.

07.Recommended Settings

For stage dance indoors I expect batteries rather than heat to set the rhythm, though Nikon does not say when the first warning comes, so the plan above stands and the warning icon still gets a glance at every pause.

For outdoor dance on a summer afternoon the balance shifts towards heat. Keep the camera in shade between takes, switch it off during long waits, and watch for the first warning icon from the start. Nikon's upper working limit is 40 °C (p. 1009).

For a long talk filmed from a tripod near a socket, outside power is where it pays. With an EH-8P, or a power bank that meets Nikon's conditions, and a battery inside as a reserve, the 125-minute ceiling becomes the limit to plan around.

08.Beginner Mistakes

Treating 125 minutes as the plan. The clip ceiling is the most a clip can run, not what it will run. On battery alone nothing Nikon prints says one charge reaches 125 minutes, and heat, a slow card or a nudged selector can end a clip sooner (p. 109).

Expecting the cable to refill the battery during a take. While the camera records it counts as on, and outside power runs it rather than charging the battery (pp. 92, 857).

Reading 100 minutes as a forecast. It is Nikon's "actual" endurance result at 23 °C with default settings and a particular lens and card (p. 1016), not one unbroken take. A connected monitor and wireless left switched on both pull it down, so plan the swap well inside it.

09.Related Chapters

• What the Z6III Is: the headline video specifications, including the 125-minute clip.
• First-Day Setup: charging over USB-C and the 27 W rule.
• Viewfinder and Monitor Displays: monitor modes and their battery figures.
• Video from First Principles: starting and stopping a recording.
• Cards and Data Rates for Video: card speed and minutes per card.
• HDMI and External Monitors: feeding the F700 over HDMI.
• Video Autofocus and Stabilisation: Full-time AF and the camera on the gimbal.