Darkroom Enlarger Exposure Timer
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Common uses for a darkroom enlarger exposure timer
- Test strip exposure
- Finding a base exposure
- Dodging and burning increments
- Darkroom printing sessions
A test strip finds a print exposure by giving successive bands of paper increasing amounts of light, then choosing the band that looks right. How those increments are spaced determines how useful the strip is, and this is where linear and f-stop timing differ.
Ten seconds is a typical base exposure for a small print at a moderate aperture. The number itself matters less than the intervals around it: our perception of print density is roughly logarithmic, which is why equal-ratio steps read as evenly spaced and equal-second steps do not.
F-stop timing versus linear timing
Linear timing steps by equal seconds — 4, 8, 12, 16 — which gives large perceptual jumps at the short end and almost imperceptible ones at the long end. F-stop timing steps by equal ratios — 4, 5.7, 8, 11.3, 16 — so every step is the same visual increment.
In practice this means a half-stop strip covers a useful range in five bands where a linear strip wastes several on differences you cannot see. It is the single change that most improves test strips, and it costs nothing.
Strip across something that matters
A test strip laid across an empty corner of the image tells you about the empty corner. Placing it so the bands cross the important tonal area — usually a face, or whatever the print is about — is what makes it informative.
For prints with a wide tonal range, two strips across different areas is more useful than one long one, because a single exposure often cannot serve both and knowing that early saves paper.
Judge dry, under the right light
Prints dry down — they appear slightly darker dry than wet — so a print judged wet under a safelight tends to come out darker than intended. Experienced printers allow for that, and beginners learn it by producing a run of prints that looked right in the tray.
Judging under normal room light rather than the safelight is the other half. A safelight is dim by design, and it flatters a print in ways that vanish when the lights come on.
F-stop stepping from a 4-second base. Each step is the same perceptual increment, unlike equal-second stepping.
| Step | Half stop | Full stop | Linear (for contrast) |
|---|---|---|---|
| 1 | 4.0 s | 4 s | 4 s |
| 2 | 5.7 s | 8 s | 8 s |
| 3 | 8.0 s | 16 s | 12 s |
| 4 | 11.3 s | 32 s | 16 s |
| 5 | 16.0 s | 64 s | 20 s |
| 6 | 22.6 s | — | 24 s |
- Perception of print density is roughly logarithmic — equal-ratio steps read as evenly spaced, equal-second steps do not.
- Lay the strip across the tonal area the print is about, and judge dry under room light rather than wet under the safelight.
Source: F-stop printing and test strip practice are established darkroom convention
Sources
- F-stop printing and test strip practice are established darkroom convention , TheTimerLab — accessed 2026-07-28