2,000 35mm Slides, Scanned: Resolution, File Sizes and What a Real Carousel Tray Becomes
Have 2,000 35mm slides scanned at around 4,000 DPI and the files come to up to about 40 GB as high-quality JPEGs of 10–20 MB each, or about 324 GB as 16-bit TIFFs of around 162 MB each — roughly 20 megapixels of real detail per slide at best. That is what "slide to digital" actually means once the marketing is stripped out. This guide gives you the honest numbers: real resolving power versus the DPI on the box, the file sizes and storage footprint you will need to plan for, and what a full physical Kodak Carousel tray turns into when it becomes a folder of files.
Key takeaways
- A 35mm slide is ~27 megapixels at a nominal 4,500 DPI, but a scanner rarely resolves what the box says: at the ~3,900 DPI that filmscanner.info reports for a Nikon Super Coolscan 9000 ED (4,000 DPI specified), the real detail is about 20 megapixels.
- That 20 MP prints sharply to roughly a 47 cm long edge (a little larger than A3) at 300 ppi — far bigger than most families ever need.
- Per slide, a high-quality JPEG is roughly 10–20 MB, and an uncompressed 16-bit TIFF, the archival master, is about 162 MB. 2,000 slides come to up to about 40 GB of files as JPEGs.
- A full Kodak Carousel tray of 80 slides becomes about 80 files / up to ~1.6 GB; a 140-tray, up to about 2.8 GB.
- EachMoment slide scanning is from £0.40 per slide with the full volume discount (the base price is £0.79), when your box is back at our lab within 4 weeks of dispatch.
The phrase "slide to digital" hides a decision most families do not know they are making. The Google results for it are almost entirely product pages and £19 desktop converters, and none of them tell you what lands in your folder afterwards. This article does. The pixel counts below are plain arithmetic on the geometry of 35mm film; the one measured resolution figure is credited to its source.
What a 35mm slide actually contains
A mounted 35mm slide has an image area of 24 × 36 mm — a piece of film about the size of a postage stamp. The interesting question is how much real detail that film holds, because that is the ceiling on any scan. Kodachrome and fine-grained Ektachrome resolve somewhere around 60 line-pairs per millimetre; a good scan needs to get close to that to be worth doing.
Here is the first honest number. At a nominal 4,500 DPI, a 35mm frame works out to 6,378 × 4,252 pixels — 27.1 megapixels. But measured resolving power is usually lower than the marketing figure. The independent test site filmscanner.info finds that the Nikon Super Coolscan 9000 ED, which Nikon specifies at 4,000 DPI, resolves about 3,900 DPI of genuine detail. At 3,900 DPI a 35mm frame gives 5,528 × 3,685 real pixels, or about 20 megapixels of information you can actually use.
Twenty megapixels is not a disappointment — it is plenty. At the photo-lab standard of 300 ppi, it prints a sharp image with a 47 cm long edge, a little larger than A3. Almost no family slide is ever printed larger than A4. The gap between "27 MP nominal" and "20 MP real" matters not because 20 is too small, but because it tells you which claims to trust: a megapixel figure on a box is not the same thing as resolved detail.
Illustration: simulated with filters, not a recording of a real transfer. Drag the handle across.
Illustration: simulated with filters, not a recording of a real transfer.
File sizes and storage: the numbers nobody quotes
This is the part that surprises people, so plan for it before you order. The size of each scanned slide depends on the file format:
- High-quality JPEG — the everyday file, perfect for screens, prints and sharing: roughly 10–20 MB per slide.
- Uncompressed 16-bit RGB TIFF — the archival master, every bit the scanner captured: ~162 MB per slide (6,378 × 4,252 × 3 channels × 2 bytes).
Multiply that across a real collection and the storage footprint becomes concrete. A full Kodak Carousel Transvue 80 tray holds 80 mounted slides; a Carousel 140 holds 140 (thin card mounts only). As files:
Approximate JPEG storage at 20 MB per slide, the top of the 10–20 MB range. The 16-bit TIFF set is roughly 8× larger. Derived from the file sizes above.
The practical upshot: a 2,000-slide loft box comes to up to about 40 GB of JPEGs — comfortable on a single 64 GB USB stick — while the full archival TIFF set is closer to 324 GB and is worth having only if you are preserving for an institution or plan heavy re-editing. At EachMoment the files arrive in a private Cloud Album; a USB stick or DVD set is a paid extra. If you need a particular file type, such as TIFF, ask us before you order.
Illustration: simulated with filters, not a recording of a real transfer.
Illustration: simulated with filters, not a recording of a real transfer.
What slide scanning costs
Our slide scanning is from £0.40 per slide with the full volume discount (the base price is £0.79 per slide), which applies when your Memory Box is back at our lab within 4 weeks of dispatch. The discount is counted on the value of the slides in your order at the base price, in steps from 10% (from £75) to 50% (from £1,199). A full 2,000-slide loft box comes to £1,580 at the base price and £790 at the 50% step. The Memory Box costs £10, and the tracked courier is free on orders over £50 (£25 below that).
JPEG or TIFF: which is worth having?
For almost everyone, high-quality JPEG at full scan resolution is the right answer: it looks identical to the TIFF on any screen or print you will realistically make, and 2,000 of them fit on a cheap USB stick. A TIFF is worth having if you are donating to an archive, restoring badly faded film, or expect to re-edit heavily — the 16-bit master gives restorers the most latitude. If your slides have shifted colour with age, the deeper mechanics are in our guide on why Kodachrome looks so different once scanned.
Ready to see what your slides really hold?
Order a Memory Box, send your slides to our lab, and get your scans in a private Cloud Album, with a tracked courier both ways. The box costs £10, and the courier is free on orders over £50 (£25 below that).
Start your slide scanning →Frequently asked questions
How many megapixels is a scanned 35mm slide?
About 20 real megapixels at best. At a nominal 4,500 DPI the geometry gives 27 MP (6,378 × 4,252 px), but filmscanner.info finds that a Nikon Super Coolscan 9000 ED, specified at 4,000 DPI, resolves about 3,900 DPI, or roughly 20 MP of genuine detail. That is enough for a sharp print a little larger than A3.
How big is a scanned slide file?
A high-quality JPEG is roughly 10–20 MB per slide. An uncompressed 16-bit archival TIFF is about 162 MB per slide. A collection of 2,000 slides is therefore up to around 40 GB as JPEGs, or about 324 GB as TIFFs.
How much storage do I need for 2,000 slides?
Up to about 40 GB for the JPEGs — a single 64 GB USB stick is plenty. Only go for the full TIFF set (~324 GB) if you are archiving for an institution or plan major restoration work.
What does a full Kodak Carousel tray become when scanned?
A standard Carousel Transvue 80 tray of 80 slides becomes about 80 files, up to roughly 1.6 GB as JPEGs. A 140-slide tray becomes up to about 2.8 GB. The archival TIFF equivalents are around eight times larger.
What resolution should I scan 35mm slides at?
4,000–4,500 DPI is the sensible ceiling for 35mm: it captures everything the film holds without inflating file sizes for no gain. Scanning higher only enlarges the file, not the real detail, because you hit the film's grain and the scanner's true resolving limit first.
