Recompute Darkroom Exposure After Filter Stops — Free
Each filter stop doubles the light you must give back. Multiply a metered base exposure by two to the power of the added stops, and see which shots pass the longest time your process tolerates.
The proof surface
Contact sheet tools plan review pages after the shoot. This computes at capture: base seconds times two per added stop, checked against a tolerance you found on your own test strips.
Why the flat version breaks
Doubling once for two stops
Each stop doubles again: two stops is ×4, three is ×8.
Trusting arithmetic over test strips
Reciprocity failure is not in this model.
Metering through the filter
That hides the very loss you are computing.
How to work the exposure bellows scale
Take the reading through the lens or with your meter as you normally would, before any filtration. The first print meters eight seconds.
Two stops quadruple the exposure: eight seconds becomes thirty-two. The tool caps stops at twenty because beyond that the numbers exceed any real tolerance and usually mean a data-entry slip.
The sample tolerance is sixty seconds — the longest exposure your development, film or paper handles before quality or reciprocity problems you have observed. The pushed film at 160 seconds is flagged: over two and a half times the line.
Long exposures suffer reciprocity failure that pure doubling does not model; manufacturer data and your own test strips govern. The summary reports the longest exposure because it is the shot most likely to fail.
What the exposure bellows scale replaces
| Question | Before | Visible working |
|---|---|---|
| Doubling once for two stops | Each stop doubles again: two stops is ×4, three is ×8. | Count whole and fractional stops as your filters state |
| Trusting arithmetic over test strips | Reciprocity failure is not in this model. | Compare with your process tolerance |
| Metering through the filter | That hides the very loss you are computing. | Test-strip anything near the line |
A local arithmetic aid replaces hand calculation, not expert review. No paid AI service is needed.
Run it on the samples, right here
FIRST-LOAD
Input is processed locally and a draft is saved automatically in this browser profile when storage is available. Reset to sample clears that draft; Pro history has its own clear button. A state link encodes your inputs in its URL: share only non-sensitive rows. Browser history, clipboard and anyone receiving the link may retain it. Optional AI use below leaves this device; it is not required.
Exposure arithmetic on your own metered numbers. Reciprocity failure, film and process behaviour are not modelled; confirm with test strips and manufacturer data before committing a shot.
Data note: Everything runs in this browser tab on the exposure bellows scale: your shot | base exposure seconds | added filter stops stays on this device, nothing is uploaded, and the reading is rebuilt only when you press run.
Go deeper: the companion app files the same reading as a clerk's docket sheet
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the exposure bellows scale reading, and holds your drafts on this device — one free run, then $ 4 one-time for the layer that keeps filing.
The exposure bellows scale reading is complete for free. The optional $4 layer adds print, row CSV and the last five local reading summaries; it does not add hidden answers. Checkout is not configured yet; the article demo remains unlimited.
Open the recompute darkroom exposure after filter stops companionBoundary
Exposure arithmetic on your own metered numbers. Reciprocity failure, film and process behaviour are not modelled; confirm with test strips and manufacturer data before committing a shot.
What this is built on
- Method: The sample tolerance is sixty seconds — the longest exposure your development, film or paper handles before quality or reciprocity problems you have observed. The pushed film at 160 seconds is flagged: over two and a half times the line.
- All sample records are invented examples. The app does not fetch measurements, policies, files or personal records.
- Google’s official pricing page, fetched 2026-09-28, lists free-tier access including AI Studio. Optional formatting only; limits and availability can change. Free-tier content may be used to improve products. Never paste private records there.
Before: Each stop doubles again: two stops is ×4, three is ×8. After: the exposure bellows scale shows the working beside each named row so the reader can change the assumption and inspect the consequence.
Optional AI formatting, not calculation
For this exposure bellows scale, use the free AI Studio interface only if available to you, with no paid API key. Manual entry completes the same workflow for free. Supply only fictional or non-sensitive notes. Review its output against the source; never paste unresolved questions into the numeric rows.
Format my non-sensitive notes for a exposure bellows scale. Return plain rows only: shot | base exposure seconds | added filter stops. Preserve supplied quantities exactly. Do not guess missing values; list questions separately. Do not calculate or add advice. I will check every row before pasting into the local tool.
Accepted schema: shot | base exposure seconds | added filter stops. No AI response is executed as code.