Subject Brightness Range SBR readout
Show the stop difference between brightest and darkest spots.
Where to find it
Viewfinder (appears after multi-spot reading) or Tools Zone System
Summary
After measuring multiple spots, the app calculates and displays the Subject Brightness Range (SBR): the number of stops between the darkest spot you measured and the brightest. Essential for zone system and development planning.
How it works
What SBR is
Subject Brightness Range (SBR) is how many stops of light separate the brightest and darkest important parts of your scene. A flat, overcast portrait might be 4 stops (EV difference of 4). A sunlit street with deep shadow might be 9 stops. The SBR tells you whether your scene will fit on your chosen film.
How it is calculated
Take your brightest multi-spot reading and your darkest. The EV difference is the SBR. If bright = EV 14 and dark = EV 5, then SBR = 9 stops.
Using SBR for exposure
Most negative films have a 6-7 stop latitude. A scene with SBR of 5 will fit comfortably (you can expose for shadows and highlights will still have detail). A scene with SBR of 9 will require compromise: expose for shadows and highlights blow, or expose for highlights and shadows crush.
Development planning
The SBR feeds into the Development Advisor (Section 4.8). You tell the advisor your scene SBR and your desired contrast index, and it recommends N, N+, or N- development to land at the contrast you want.