How Film Stock works
ISO, reciprocity, color balance, and latitude pulled from the film card.
Where to find it
Tools tab Film Stock
Summary
Film stock selection: pin ISO to box speed, set reciprocity behavior for long exposures, set color balance for color stocks, and tell the meter how forgiving the film is.
Detail
How it works
This is where you tell the app which roll of film is in the camera. The choice drives ISO, reciprocity behavior, color or black and white processing, and any film-specific calculations the other modals run.
Box speed
Each film has a manufacturer-rated ISO printed on the box. Picking the stock here pins the ISO wheel to that value. You can still override ISO on the main wheel if you choose to push or pull.
Reciprocity
At very long exposures (typically over one second) film no longer responds linearly to light. Two seconds of light does not give you twice the density of one second. The film card stores each stock's reciprocity factor so the meter can add the extra time you actually need for long exposures.
Color balance
Color stocks are balanced for daylight (around 5500K) or tungsten (around 3200K). The Color Temperature modal uses this to recommend the right corrective filter.
Latitude
How forgiving the film is. Color negative is generous, especially toward overexposure. Slide film is tight in both directions. Black and white is forgiving in the highlights with traditional grain. The Development Advisor uses latitude when recommending push or pull.
If you cannot find your stock
Pick the closest match. The differences between similar-speed films are smaller than most people assume. You can always fine-tune ISO on the main wheel.