Cards and batteries

How much card, and how many batteries?

How much to spend insists a working kit is a body, two lenses, two cards, a spare battery and something to carry it in — and then leaves you to guess how big the cards should be. This is that missing paragraph: the file size comes out of the sensor's bit depth, and the arithmetic is on the page.

The day

Camera 33 megapixels · rated 580 shots a charge

File format

Raw, uncompressed 58 MB14 bits a pixel, written straight out. The largest file a camera makes and the one some bodies still default to.Raw, lossless compressed 40 MBIdentical data, packed. Nothing is discarded, so there is no reason to shoot uncompressed if the body offers this.Raw, lossy compressed 20 MBSony’s compressed raw, Canon’s C-RAW, Nikon’s High Efficiency. Discards what the sensor could not resolve anyway; survives normal editing.JPEG, finest quality 12 MBEight bits, already developed. Fine for delivery, much less forgiving of a big exposure or white-balance correction later.HEIF, 10-bit 6.6 MBAbout half a JPEG for better quality, and ten bits rather than eight. Support outside the camera is still patchy.

Framesstills over the day

Videominutes recorded

Card size

How you shoot

The rated figure ×1CIPA’s own cycle: wake, shoot, review, sleep, every thirty seconds. Harsh on purpose, and the only figure that compares two bodies fairly.A normal day out ×2Camera awake in bursts, viewfinder rather than screen, images reviewed occasionally. Most mirrorless bodies roughly double their rating here.Continuous shooting ×3Sport or wildlife: long bursts with the camera already awake. The per-frame cost collapses, and the limit becomes the card and the buffer.

What to pack

1 × 128 GB · 1 battery

Counting the battery already in the camera. Two smaller cards beat one large one — camera care and travel makes the case: a card failure then costs part of the trip rather than all of it.

One frame: 40 MB
600 frames: 24 GB
The day: 24 GB
Frames on one 128 GB card: 3,166
Frames a charge, as you shoot: 1,160

33 MP × 1.75 MB × 0.7 = 40 MB

How the sum works

A raw file is one number per photosite. At the usual 14 bits that is 1.75 bytes a pixel, so an uncompressed raw is 1.75 MB per megapixel — exactly, before any compression. Every other format on the page is a fraction of that figure, and the fraction is shown next to it.
Compression is an estimate, not a specification. A frame of dense foliage packs worse than a frame of sky, and the same camera will write files a third apart across a day. Treat the answer as the size of the card to buy, not as a measurement.
Video is simply the bitrate. Megabits a second ÷ 8 gives megabytes a second; times 3,600 gives the hour. 100 Mbps is 45 GB an hour, whatever the resolution label on the mode. The presets are typical rungs — use the figure in your manual if you have it.
CIPA is a harsh cycle, not a prediction. The rated figure comes from waking the camera, shooting, reviewing the frame and powering down every thirty seconds. Nobody shoots that way, which is why a normal day usually doubles it — and why the rated number is still the fair way to compare two bodies.

Gigabytes are decimal here, the way card makers and bitrates count them, so a 128 GB card is 128,000 MB. The camera will format a little of it away and report slightly less.

Find a body that lasts the day Build the kit around it

The day

How the sum works

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