Page 269 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

258 CHAPTER 10 Video
FIGURE 10.11
Examples of f-stop settings from f/1.4 (low) to f/8 (high).
f/1.4 f/2 f/2.8 f/4 f/5.6 f/8
FIGURE 10.12
Example of two pictures of the same scene—one with low f-stop (a) and the other with high f-stop (b).
(Photos by Pat McCallan.) and f-number) will vary in proportion to achieve the desired image quality. Some rules of thumb
are as follows:
• A small, or high, aperture setting (e.g., f/8) is great for a greater depth of field (i.e., nominal distances from the camera lens whereby all objects within those areas are in focus), but bad for both low lighting situations and/or fast shutter speeds. A higher f-stop setting (smaller aperture) is used for daylight shots with a slower shutter speed for nonmoving objects while night photography requires a lower f-stop (larger aperture—e.g., f/2) with a higher sensitivity
camera (HSC from above) (Figures 10.11 and 10.12).
• A high f-stop (smaller aperture) with a longer focal length (telephoto magnification) requires
either a very slow frame rate or some type of HSC in order to gather enough light for a
meaningful picture rendering.
• Use a low f-stop and HSC for low ambient lighting subsea conditions.
In Figure 10.12(a), the picture was shot with a low f-stop, causing a narrow depth of field (i.e., distance whereby the object is in focus) while Figure 10.12(b) is shot with a higher f-stop, allowing a great depth of field.