Pre-Release Capture

A kingfisher sits on a dead branch twenty metres away at 600 mm. You have watched it for four minutes with the camera at your eye. It leans forward, opens its wings, and by the time your finger has pushed the shutter-release button down, the frame holds an empty branch. The picture you wanted happened in the fifth of a second between your eye seeing the movement and your finger answering it.

Pre-Release Capture moves the start of picture-taking to before you decide. While you hold the button halfway down, the Z6III shoots into its memory and saves nothing. Press fully and it saves the most recent part, up to about one second by Nikon's figures, then keeps shooting for as long as you allow. The take-off you were too slow for is already inside the camera.

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

01.Why the Finger Is Always Late

Reaction Time in Numbers

Reaction time is the delay between something happening and your body responding. The simplest kind times a finger, already on a button, answering a flash of light. For young adults the average usually quoted is about 190 milliseconds, or 0.19 s. Wikipedia's article on mental chronometry gives that figure, and a 2019 study in Clinical Optometry reports earlier findings of about 190 ms or more for students and measured 208 to 224 ms itself. Treat it as an approximate floor. Deciding that a movement is a take-off adds more time in the field.

Suppose the bird leaves the branch at an illustrative 5 metres per second. Distance is speed multiplied by time, so with $d$ for the distance, $v$ for the speed and $t$ for the delay:

$$d = v\,t = 5\ \text{m/s} \times 0.19\ \text{s} = 0.95\ \text{m}$$

How much of the picture is that? A lens of focal length $f$ shows a distant scene at distance $D$ shrunk by roughly $D/f$. The sensor is 35.9 mm wide (p. 997), so with $s$ for that width, the frame at 20 m and 600 mm covers a width $W$ of about

$$W \approx s\,\frac{D}{f} = 35.9\ \text{mm} \times \frac{20{,}000\ \text{mm}}{600\ \text{mm}} \approx 1{,}197\ \text{mm}$$

which is about 1.2 m. The bird crosses $0.95 / 1.197 \approx 0.79$ of the frame before the camera starts its picture.

A dancer's leap shows the same problem on a different clock. Take a leap that lifts the dancer's centre 0.5 m, again an illustrative height. With $h$ for that height and $g \approx 9.81\ \text{m/s}^2$ for the acceleration of gravity, the time to reach the top is

$$t_{\text{up}} = \sqrt{\frac{2h}{g}} = \sqrt{\frac{2 \times 0.5}{9.81}} \approx 0.32\ \text{s}$$

so the whole leap lasts about 0.64 s, and 0.19 s is nearly a third of it. React to the top and the frame catches the dancer already falling, by $\tfrac{1}{2} g t^2 = \tfrac{1}{2} \times 9.81 \times 0.19^2 \approx 0.18$ m.

Why a Faster Burst Does Not Fix It

Frame rate, in frames per second (fps), is how many pictures a burst takes each second. The Z6III's fastest ordinary burst, Continuous H (extended) with the electronic shutter, runs at about 20 fps (pp. 154, 1000). A faster burst fills the gaps between frames, but every frame still comes after the press: at 20 fps the 0.19 s delay costs $20 \times 0.19 \approx 4$ frames, and at 60 fps about 11. Only a camera that was already shooting when the bird moved can reach back.

02.How Pre-Release Capture Works

A Memory That Keeps Only the Recent Past

The camera has a buffer, fast temporary memory that holds pictures until they are written to the memory card (p. 155). With Pre-Release Capture on, a half-press sets the camera shooting into the buffer while the card receives nothing. A full press writes only the frames from the final $n$ seconds of the half-press, where $n$ is a length you choose, and shooting continues while the button stays down, up to a second limit you also choose (pp. 156, 664-665).

A car's dashboard camera works the same way, recording over a short loop and keeping a stretch only when something happens. If the full press comes before you have half-pressed for $n$ seconds, the camera can save only what it gathered so far (p. 665), so stabbing the button straight down yields almost nothing from before the press.

Which Release Modes Offer It

A release mode decides what a press does: one picture, a burst, or a delayed picture. Pre-Release Capture belongs to the family Nikon calls high-speed frame capture +, shortened to HSFC in some menu names. Its members, C15, C30, C60 and C120, shoot at about 15, 30, 60 and 120 fps (pp. 154, 1000). Choose one by holding the release mode button and turning the main command dial, or from Release mode in the photo shooting menu (pp. 156, 493).

Nikon states that Custom Setting d3 applies when C15, C30, C60 or C120 is the release mode (pp. 569, 664), so Continuous L, Continuous H and Continuous H (extended) offer nothing like it, and all four C modes are for still pictures. It also works in auto capture, covered in a later part of this guide, where the camera fires by itself when a subject appears, if the release mode chosen there is a C mode (pp. 562, 569). Release Modes, Frame Rates and the Buffer covers the other modes.

What the Camera Shows You

Whenever Pre-release burst is set to anything but None, a Pre-Release Capture icon appears in the monitor and viewfinder displays (pp. 931, 939), with a green dot that lights while a half-press is filling the buffer. After about 90 seconds of half-press the icon changes, meaning the feature has been cancelled, and a full press then saves no pre-release frames. The icon flashes for the 30 seconds before that, and lifting your finger and half-pressing again starts a fresh buffer (p. 665).

During a half-press the frame count shows roughly how many more pictures the buffer can take, and r000 means it is full (p. 155). The top control panel has its own buffer readout for these modes (pp. 942-943). The display does not black out between frames, and Custom Setting d15 sets what marks each release instead (p. 679).

03.Custom Setting d3 Pre-Release Capture Options

This item holds two settings, one for each side of the full press, and both act only in high-speed frame capture + (p. 664). It can also go in the i menu, the quick menu behind the i button, because Custom Setting f1 Customize i menu lists Pre-Release Capture options among its choices (pp. 699, 701). Menus and Controls shows how to add it to My Menu instead.

Pre-Release Burst

Pre-release burst sets $n$, the length of half-press history saved at the full press. The default is None (p. 624), and with None the C modes behave like any other burst, starting only when the button reaches the bottom.

The Reference Guide prints only the label None and calls every other value "n seconds" (p. 665), so I name no labels I cannot check. Nikon's launch announcement, its product page and the firmware 2.00 announcement all put the longest window at up to one second before the full press. Pick the longest value offered, which covers the 0.19 s reaction with about 0.8 s to spare for slower decisions.

Post-Release Burst

Post-release burst sets the longest time the camera keeps shooting while you hold the button fully down. The choices are 1 s, 2 s and 3 s, plus Max., which is the default (pp. 624, 665). Lifting your finger sooner ends the burst sooner. At Max. the camera keeps going until the buffer is full, a length that depends on frame rate and other settings (pp. 156, 665). The Reference Guide gives no buffer depth for the C modes.

I think Max. is the wrong default. A bird that takes off leaves a 600 mm frame within a fraction of a second, and a burst that runs until the buffer fills mostly records sky. I set 1 s for birds and 2 s for dance.

04.The Arithmetic of a Burst

Counting Frames

At C60, one second of history holds 60 frames, and one more second after the full press adds 60, for 120 frames in a burst. In general, with $r$ for the frame rate in fps, $t_{\text{pre}}$ for the pre-release window and $t_{\text{post}}$ for the time the camera keeps shooting after the full press, both in seconds, the number of frames $N$ is

$$N = r\,(t_{\text{pre}} + t_{\text{post}})$$

Both times are ceilings and the frame rates are approximate (p. 1000), so treat each $N$ as an upper estimate.

Turning Frames Into Megabytes

Every picture in the C modes is a JPEG at Large size (p. 157). JPEG is the compressed format the camera finishes itself, and NEF, Nikon's raw format that keeps the sensor's data for later processing, is not offered. A Large picture is $6048 \times 4032$ pixels, or 24.4 million, with the full-frame FX area, and $3984 \times 2656$ pixels, or 10.6 million, with the smaller DX crop (p. 998).

Nikon's card table lists a Large JPEG fine file at about 10.3 MB and a Large JPEG normal file at about 6.3 MB (p. 1012), where a megabyte (MB) is a million bytes. Those sizes were measured in Continuous H (extended) and vary with the scene (pp. 1012-1013). Nikon publishes none for the C modes, so I borrow them and treat every result as illustrative. For DX I scale by pixel count, $10.3 \times 10.6 / 24.4 \approx 4.5$ MB for fine and about 2.7 MB for normal, my estimates, since compression also depends on detail. With $s$ for the size of one file, a burst occupies $B = N s$ megabytes, so the 120-frame C60 fine burst takes $120 \times 10.3 = 1{,}236$ MB.

C120 in DX makes the most frames yet one of the smaller bursts, because each picture has fewer than half the pixels. Custom Setting d2 Maximum shots per burst stops bursts in continuous release modes at 200 frames by default, and removing that cap works only with the electronic shutter (pp. 624, 663). The Reference Guide does not say whether d2 governs the C modes, so a 240-frame C120 burst may stop at 200.

What It Means for the Card

My first slot holds a 512 gigabyte (GB) CFexpress card. Counting a GB as a thousand megabytes, as card makers do, that is about 512,000 MB, or $512{,}000 / 1{,}236 \approx 414$ bursts of the C60 fine example. Read that as an upper figure, since Nikon's capacity table credits a card with fewer pictures than plain division gives (p. 1012). Space is rarely the limit: fifty take-offs come to $50 \times 1{,}236 = 61{,}800$ MB, about 62 GB, an eighth of the card.

Speed matters more. A C60 fine burst produces $60 \times 10.3 = 618$ MB every second, while Nikon recommends CFexpress or XQD cards rated at 250 MB/s or more for these modes (p. 1011), so a card at that minimum could not keep pace. The buffer absorbs the difference. At exactly 250 MB/s, writing all 1,236 MB takes $1{,}236 / 250 \approx 4.9$ s from the full press, and the one second of shooting after the press falls inside that time, so the buffer clears about $4.9 - 1 = 3.9$ s after the burst ends. Both figures are illustrative, since Nikon does not publish the camera's write rate. Meanwhile the access lamp can stay lit for up to about a minute, and the card must stay in (p. 155).

My second slot holds a Secure Digital (SD) card, which is neither CFexpress nor XQD. With Secondary slot function at its default, Overflow, the SD card is used only once the first card is full (pp. 446, 457). With Backup, every picture goes to both cards (p. 457), so the SD card must take all 1,236 MB: $1{,}236 / 90 \approx 13.7$ s at the 90 MB/s floor of the V90 speed class, and $1{,}236 / 260 \approx 4.8$ s at the 260 MB/s write ceiling Lexar quotes for my card. RAW primary - JPEG secondary writes any quality other than raw plus JPEG to both cards (p. 457), so with JPEG-only C modes I expect it to double every burst too. JPEG primary - JPEG secondary also sends every frame to the SD card, as a smaller JPEG/HEIF basic copy (p. 457), which doubles the files each burst writes. I keep Overflow. Card Slots and File Handling explains speed classes and write times.

05.Restrictions and Trade-Offs

What the C Modes Give Up

Pictures are JPEG at Large size, with quality set by Image quality (HSFC) under Image quality settings in the photo shooting menu, which offers JPEG fine or JPEG normal, with JPEG normal as the default (pp. 157, 446, 464). Changing quality from the i menu, or with a button assigned Image quality/size in Custom Setting f2, while a C mode is active changes this HSFC setting (p. 464). Nikon's firmware 2.00 announcement lists JPEG fine at 60 fps in full frame with Pre-Release Capture as new. Without a raw file, white balance and exposure must be right in the camera, and RAW, JPEG, HEIF and Tone Mode explains why.

C15, C30 and C60 offer FX (36×24) or DX (24×16), and C120 offers only DX (24×16) (p. 157), a central crop about two thirds the width of FX. Image Area and Crop covers it.

Shutter speeds run from 1/16000 s to 1/60 s at C15, C30 and C60, and to 1/125 s at C120 (p. 157). The mechanical shutter stops at 1/8000 s and only the electronic shutter reaches 1/16000 s (p. 1000), which suggests the C modes read the sensor electronically, although the Reference Guide never says so and its Shutter type page does not mention them (p. 668). An electronic shutter reads the sensor row by row, so a fast wing can be drawn bent and flickering lights can leave bands. Shutter Types, Rolling Shutter and Flicker explains both, and What a Partially Stacked Sensor Changes explains the fast readout behind these modes.

Exposure compensation works only between $-3$ and $+3$ EV, though you can dial up to $\pm 5$ (p. 157). EV, exposure value, is the unit of exposure change, and one EV doubles or halves the light. ISO, the sensitivity setting, stops at ISO 64000 even with Hi 0.3 to Hi 1.7 chosen, and Auto ISO ignores your Minimum shutter speed (p. 157), the setting that normally keeps it away from slow speeds. ISO and Auto ISO describes it.

The C modes cannot run alongside flexible program, the HLG (hybrid log-gamma) tone mode, photo flicker reduction, flash, bracketing, multiple exposures, HDR (high dynamic range) overlay, the interval timer, time-lapse video, focus shift or pixel shift (p. 157). HLG is the tone mode for high dynamic range screens, as opposed to SDR, standard dynamic range. With tone mode at HLG you cannot select a C mode and d3 is greyed out (p. 462). Skin softening is unavailable (p. 480), and photo flicker reduction does not act during these bursts (p. 484).

Subject detection, the autofocus system's recognition of people, animals and vehicles, may work less well (p. 130). Preset manual white balance cannot be measured in a C mode, so measure first and then switch (p. 178). And the touch shutter takes a single picture, so only the shutter-release button fires a burst (p. 156).

What Ends the Buffering

Two things cut the history short: the 90-second cancellation and a half-press shorter than $n$ seconds (p. 665). Two others end the burst after the press, the post-release ceiling or a full buffer, whichever comes first (p. 665), and letting go ends it sooner. The Reference Guide describes saving only at the full press, so a half-press released without one should leave nothing on the card.

On power and heat the Reference Guide says only that a flat battery locks the release while buffered pictures are still saved (p. 155). It gives no figure for the charge a long half-press uses, and on heat nothing specific to these modes, only the general Auto temperature cutout in the setup menu, which switches the camera off as it heats (p. 830).

06.Using It in the Field

Birds Taking Off

Frame the perched bird with space on the side it is likely to fly towards, then half-press and hold. When the icon flashes, lift and re-press while the bird is plainly still settled, because a new half-press needs $n$ seconds to hold a full window. When the bird moves, press fully at once and let the 1 s post-release limit end the burst.

I set C60 with FX and JPEG fine. At the illustrative 5 m/s the bird moves $5 / 60 \approx 0.083$ m, about 8 cm, between frames at C60, and about 4 cm at C120. Eight centimetres already gives a choice of wing positions, and C120 forces DX and 10.6 million pixels, so I keep it for a small bird far away that I would crop anyway.

For exposure I would choose manual mode, M, with Auto ISO and 1/2000 s or faster, during which the bird moves $5 / 2000 = 0.0025$ m, or 2.5 mm. Because the camera ignores Minimum shutter speed with Auto ISO here (p. 157), I would rather fix the speed myself than let aperture-priority choose it.

Outdoor Dance

I set C30 with FX and JPEG fine, the longest pre-release window, and 2 s after the press so the landing is included. The 0.64 s leap from the worked example spans $30 \times 0.64 \approx 19$ frames, enough to find the top, and C60 would only double the sorting. At 1/1000 s a limb moving at an illustrative 5 m/s blurs by 5 mm. Half-press as the run-up begins, press fully at the top, and let the buffer cover your lateness.

The word outdoor matters. Daylight does not flicker, but many stage lights do, flicker reduction cannot help in the C modes (pp. 157, 484), and an electronic readout is where flicker shows as bands. On an indoor stage lit by LEDs, light-emitting diodes, I would not use the C modes.

Culling a Burst

A C60 take-off at these settings leaves 120 near-identical frames, so sorting is the real cost of the feature. Series playback in the playback menu treats each burst as a group (pp. 155, 792). Set List series as single thumbnails to ON, which is not the default (p. 784), and each burst shows as one thumbnail with a frame count (p. 793). That also adds Manage series to the playback i menu, which deletes, protects or marks for upload a whole burst at once (pp. 236, 793). With Sub-selector displays first shot at its default of ON (p. 784), the sub-selector jumps between bursts when tilted left or right and steps through one burst when tilted up or down (p. 792).

Auto series playback, off by default (p. 784), plays a burst by itself once switched on, after the first frame has shown for a few seconds (p. 792). At the default playback speed of 30 fps (p. 784) a 120-frame burst plays in $120 / 30 = 4$ s. At current release mode speed follows the release mode set when you play back, not necessarily the one the burst was shot in (p. 793). Rating in the playback i menu gives a picture zero to five stars or a candidate-for-deletion mark that Nikon's NX Studio software reads (p. 246).

In the field I would delete with Manage series every burst where the bird left the frame or focus missed, and rate the best two or three frames of each survivor. The playback part of this guide covers these tools in full.

07.Recommended Settings

08.Beginner Mistakes

Pressing straight through. A full press with no half-press before it saves almost no history (p. 665). Half-press early and hold it for at least the window you set.

Holding the half-press until it lapses. After about 90 seconds the feature cancels itself (p. 665). Watch for the flashing icon, and re-press while nothing is happening.

Leaving Post-release burst at Max. The default (p. 624) lets every burst run until the buffer fills. Set 1 s or 2 s and the card load and the culling both shrink.

Expecting raw files. The C modes record JPEG only (p. 157), and Image quality (HSFC) starts at JPEG normal (p. 446). Switch it to JPEG fine.

Writing every burst to both cards. Backup and JPEG primary - JPEG secondary send each picture to the SD card too (p. 457). Keep Overflow on days you use the C modes.

Looking for it in Continuous H. Pre-Release Capture lives only in C15 to C120 (pp. 156, 664). If d3 seems to do nothing, check the release mode and check that tone mode is not HLG (p. 462).

09.Related Chapters

• Release Modes, Frame Rates and the Buffer: every release mode and the buffer.
• Shutter Types, Rolling Shutter and Flicker: bent wings and banded LED light.
• What a Partially Stacked Sensor Changes: the readout behind 120 fps.
• Card Slots and File Handling: card speeds, write times and slot roles.
• RAW, JPEG, HEIF and Tone Mode: what a JPEG gives up, and HLG.
• Image Area and Crop: FX, DX and the crop C120 forces.
• ISO and Auto ISO: the minimum shutter speed these modes ignore.
• Glossary: buffer, release mode and rolling shutter defined.