What file format and resolution do museums use?

A museum does not digitize an object once. It creates a master file meant to outlast the scanner, the software, and often the staff who made it, so the format and resolution are chosen for decades of reuse, not for one screen. In practice this means an uncompressed or losslessly compressed TIFF, a resolution high enough to support printing and detailed study, and a documented color space, following public technical guidelines rather than ad hoc habit.

Why TIFF instead of JPEG for the master file?

JPEG compresses an image by discarding information the algorithm judges unnecessary, and it does so again every time the file is re-saved. That loss is invisible on a phone screen and real on a zoomed detail of brushwork or tool marks. TIFF, saved uncompressed or with lossless compression such as ZIP (Deflate), keeps every pixel value a scanner or camera captured. The Federal Agencies Digital Guidelines Initiative (FADGI), the technical reference most US institutions cite, states that master files should be lossless and lists TIFF, uncompressed or ZIP-compressed, among its accepted master formats alongside lossless JPEG 2000 (https://www.digitizationguidelines.gov/guidelines/digitize-technical.html). JPEG remains useful, but only as a derivative generated from the TIFF for web display, never as the file of record.

How much resolution is actually enough?

Resolution for a museum master is set in pixels per inch relative to the object's physical size, not in a flat "megapixel" number. FADGI's four star levels tie resolution to quality: for many types of material, the minimum sampling frequency rises from about 200 ppi at one star to 400 ppi at four stars, the level FADGI describes as the best imaging practical today. FADGI advises against digitizing below three stars when possible, to avoid rescanning later, while cautioning that four stars suits only the most sophisticated imaging programs. The Library of Congress points the same way in its Recommended Formats Statement for still images, which prefers the highest resolution available, not rescaled or interpolated, and the highest bit depth available (https://www.loc.gov/preservation/resources/rfs/). The reasoning is simple: downscaling a high-resolution master costs nothing, while rescanning a fragile object costs time, handling and money.

What does color space have to do with accuracy?

A pixel's numbers mean nothing without a declared color space telling software how to render them. FADGI recommends Adobe RGB (1998), ProPhoto or eciRGB v2 for RGB master files, wider gamuts than the sRGB space usually reserved for web derivatives, whose narrower range can clip saturated reds and greens found in pigments and dyes. Alongside the color space, FADGI technical guidelines call for reference targets, including a gray scale and a color reference, captured in the same session and under the same conditions as the object, so later viewers can verify or correct color years after capture (https://www.digitizationguidelines.gov/guidelines/digitize-technical.html). Without that target, a shift in monitor calibration or a software update can silently change how a color reads, with no way to check against the original.

Why does metadata travel inside the file, not beside it?

A TIFF master embeds technical metadata directly in its header: capture date, resolution, color profile, equipment, and operator. This matters because files get renamed, copied between systems, and separated from the database record that first described them. Embedded metadata survives that drift. It is the same principle behind the move from local card catalogs to shared, portable metadata standards described elsewhere in this archive: information that lives only in one external system is information that gets lost the first time the system changes.

How does this connect to what came before digital capture?

Digitization did not invent the need for a reliable, reusable master. It replaced microfiche and photographic negatives, formats with their own stability and resolution limits, with a different physical object: the file. A master TIFF is handled with the same institutional caution an archive once gave a negative, stored separately from working copies, never edited in place, and migrated forward whenever the next format threatens to become unreadable. The technical choices covered here, format, resolution, color space, metadata, are what let that migration happen without loss, decade after decade.

What should a researcher or licensee ask for?

When requesting a reproduction, ask specifically what was delivered: a cropped, compressed JPEG derivative, or access to specifications of the TIFF master. The two can look identical in a small preview and differ enormously once printed or examined closely. Institutions that follow FADGI or Library of Congress guidance can usually state, on request, the star level and color space of a given digitization project. That answer tells you more about what you can actually do with the image than the file size ever will.

Early photographic surveys set out to document collections comprehensively; today's digitization guidelines extend that ambition with a technical discipline those early campaigns could not have had. Reading a museum's cataloguing history alongside its current digitization standards shows the same goal pursued with better tools: an image that remains trustworthy long after the person who made it has moved on.