The exposure calculator sits below the image in offline mode. It takes the metered midtone EV and solves the exposure equation for the settings you will actually dial in — accounting for exposure compensation, colour and ND filters, bellows extension and reciprocity failure.
EV is read-only
The EV field shows the metered midtone value for the selected ISO — with the calibrated value used if calibration is active. You cannot type over it. This is deliberate: EV here is a measurement, not a setting. To change it, change the measurement — drag the midtone spot somewhere else, or change the ISO.
Stops
The Stops picker switches every value in the panel between full (1), half (½) and third (⅓) increments. Values snap to the nearest available step when you switch, so a shutter speed that has no exact equivalent in the new series moves to the closest one that does.
The parameters
| Picker | Label | Range |
|---|---|---|
| ISO | ISO | 25 – 102400 |
| Aperture | f | f/1 – f/64 |
| Shutter speed | SS | 1/8000 s – 8 min (480 s) |
| Exposure compensation | +/−EV | −5 – +5 |
| Colour filter | Color | None, plus the Wratten series |
| ND filter | ND | None, plus ND2 – ND100000 |
How they move together
Aperture and shutter speed are linked. Change the aperture and only the shutter speed moves; change the shutter speed and only the aperture moves. The exposure stays where the meter put it either way.
Everything else respects your last choice. When ISO, EV, exposure
compensation or a filter changes, something has to give — and the app keeps
whichever of aperture or shutter speed you last set by hand, moving the other.
The status panel names it as the Priority, f or SS. If you have set
neither, shutter speed moves.
At the limits, both move. If holding one parameter would need a shutter faster than 1/8000 or longer than 8 minutes, the app adjusts aperture and shutter to reach the closest valid pair rather than reporting an impossible setting.
Base and effective
The status panel lists each of aperture and shutter speed twice: the base value, and the effective value after every compensation has been applied. The effective EV behind them is:
effective EV = EV − exposure compensation − colour filter − ND filter − bellows compensation
with the EV being the calibrated one if calibration is on. Reading the two rows against each other tells you how many stops your filters and extension are actually costing.
Bellows extension
Turn on Bellows for macro or view-camera work. Pick the lens focal length and the extension (1× to 4× of that focal length) and the app adds the light lost to the extension:
compensation = 2 × log₂(extension ÷ focal length) stops
which is the inverse-square falloff you get when a lens is racked out past its infinity position.
Reciprocity failure
Turn on Reciprocity for long exposures and choose your film from the
built-in preset library, or set the Schwarzschild p-factor by hand with the
slider. Once the metered shutter speed passes one second, the panel shows the
corrected time — t raised to the power p.
Reciprocity does not feed back into the linked aperture/shutter calculation. It reports the time you should actually give the film, alongside the time the meter asked for. The ⓘ button explains the effect if you want the background.
Record and Rolls
The two buttons at the bottom of the panel open the shooting notebook: Record logs this exposure, Rolls browses what you have logged. See Rolls & Memos.