Measure, in Japanese Soku (measure, fathom), is one of the various functions that can be equipped on to the Camera Obscura. This function allows the nearest hostile ghost's health to be displayed while they are within the Capture Circle. The ghost's health appears as a small yellow meter that depletes as damage is dealt.
The "measure" function can be acquired early on in the game, at the beginning of Chapter II. After seeing Mayu walk outside of the Osaka House, the function can be picked up close to the fireplace in the Sunken Fireplace Room.
The "Measure" function here, is obtained relatively late and can easily be missed, as it requires optional steps. After Yoshino Takigawa isolates herself in the Partitioned Room in Hour VI, her photo must be taken and developed in Rei's house. Afterwards, on Hour IX, a battle with Stroller Grandma will be triggered in the Foyer. When defeated, she will drop the Notched Arrow Key, which can be used to enter a secret passageway from the Foyer to the barred area in the Partitioned Room. Once there, Yoshino Takigawa will attack, dropping the "measure" function and a photo when dealt with.
- Like many other items, the design of the camera functions were changed in Fatal Frame IV. The new design is essentially the same with a bit more detail and darkened colors.