Reading Byte Counts Off the Card After a Shoot
Cameras and card readers are stubbornly literal. Mount the card, list the folder in a terminal, open the file properties, or read the length field that a metadata tool pulls out of a frame, and you get a bare byte count: 32500000. Nothing in that string tells you whether the frame is a heavy 14-bit RAW or a modest JPEG, or whether tonight's shoot will fit on the travel drive. Divide it into megabytes and the answer becomes obvious at a glance.
The habit matters most during a cull. You are comparing frames, working out which format the camera actually wrote, spotting the shot that came out twice the size of its neighbours because the scene was full of fine detail. Megabytes let you hold a whole shoot in your head; raw byte counts do not.
MB = bytes ÷ 1000000. A 24 MP 14-bit lossless-compressed RAW reported as 32500000 bytes is 32500000 ÷ 1000000 = 32.5 MB.Every Frame Is a Different Size
Megapixels Are Not Megabytes
Cards Are Labelled in Decimal Megabytes
Sizing a Shoot Folder Step by Step
Take the byte figure from the file listing
A directory listing, a properties panel or a metadata readout all give you exact bytes. Paste it in as it comes: separators and spaces are ignored, and a decimal comma is accepted alongside a dot.
Read the megabyte figure as you type
The second field keeps pace with every keystroke, so checking a run of frames is a matter of retyping the number rather than restarting the conversion.
Copy the number into your shoot notes
Each field has its own copy button and hands over the bare number with no unit attached, which drops cleanly into a spreadsheet column where you are totalling a day's cards.
Work backwards from a delivery ceiling
The swap button reverses the two units, so you can start from a megabyte figure and get the byte count instead — handy when a client specifies a maximum size in MB and an export or upload dialogue wants bytes.
Both fields stay editable and both unit menus are searchable, so if you would rather see a card total in gigabytes, or check a tiny metadata file in kilobytes, you can pick those units in the same two boxes.
RAW and JPEG Byte Sizes by Camera Class
Representative single-frame sizes for common sensor classes and capture formats. Treat them as a planning baseline; your own bodies and scenes will land in a band around these figures rather than exactly on them.
| Frame | File size (bytes) | Megabytes |
|---|---|---|
| 20 MP APS-C, lossless RAW | 25 600 000 | 25.6 MB |
| 24 MP full-frame, 14-bit lossless RAW | 32 500 000 | 32.5 MB |
| 24 MP full-frame, lossy compressed RAW | 12 500 000 | 12.5 MB |
| 24 MP fine JPEG, straight out of camera | 11 500 000 | 11.5 MB |
| 45 MP full-frame, lossless RAW | 55 000 000 | 55 MB |
| Sidecar file written by the catalogue | 8 500 | 0.0085 MB |
The last row is why a file count and a byte total rarely agree in a satisfying way: sidecars and catalogue previews add thousands of tiny files that barely register in megabytes but clutter every listing you look at.
Compare Two Frames Back to Back
Type one frame's bytes, note the megabytes, then overwrite with the next. Nothing is kept between entries, so the comparison is purely what you have in front of you right now.
Jump to Card-Sized Units in the Same Box
The searchable unit menu on either side covers the whole storage ladder, so a shoot total can move from megabytes up to gigabytes without opening another page.
Works Off a Card Reader, Not a Server
The arithmetic runs in your browser once the page has loaded, which suits offloading cards in a hotel room on a connection you would rather not lean on.
Questions From the Culling Bench
Why do two frames from the same camera have different byte counts?
Because lossless RAW compression is content-dependent. Smooth areas — sky, a seamless backdrop, a shallow-depth background — compress hard; fine repeating detail such as foliage, fabric weave or high-ISO noise barely compresses at all. A frame shot at high ISO can be noticeably larger than the same composition at base ISO, which also means a night shoot fills a card faster than a studio day at the same frame count.
Does doubling the megapixels double the megabytes?
Roughly, but not exactly. Pixel count sets the amount of sensor data, so it is the dominant term, yet bit depth and compression mode ride on top of it. Moving from 12-bit to 14-bit capture adds data for the same pixel count, and a body that offers a reduced-resolution RAW mode changes the pixel count itself. Measure a handful of your own frames rather than trusting a single multiplier.
How much does lossless-compressed RAW actually save?
Against fully uncompressed RAW, lossless compression commonly cuts something in the order of 40–50% with no image data discarded. The lossy compressed RAW modes several manufacturers offer go further again, roughly halving the file once more at the cost of a little latitude in extreme edits. Since the first saving costs nothing in quality, most photographers leave it switched on permanently.
Do sidecar files matter when I total up a shoot?
In megabytes, barely — a sidecar carrying your edits and keywords is a few kilobytes, so a thousand of them add up to single-digit megabytes against a shoot of tens of gigabytes. They matter for a different reason: they have to travel with the frames. Copy the images without them and the byte total looks almost unchanged while every rating and adjustment is gone.
How many frames should I expect to fit when I shoot bursts?
Take your body's typical RAW size in megabytes, multiply by the frame rate to get megabytes per second of held shutter, then by a realistic burst length. A 32.5 MB frame at ten frames per second is 325 MB for one second of continuous shooting, so a few dozen short bursts across a day run into tens of gigabytes before a single deliberate frame is counted. Sizing cards from that figure, rather than from an average across the whole day, is what stops a card filling mid-action.
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