What gap range should be used for depth-of-field references?

• A. Standard 0.25 inches
• B. Standard no more than .75, wide .75 to 1.5, super wide 1.5 or more
• C. Wide 2.0 to 3.0 inches
• D. No gap is required

Answer: (B)

Depth of field references rely on practical gap ranges to indicate how much variation in distance you can have while keeping the image acceptably sharp. The best approach uses three levels: standard, wide, and super wide. The standard gap is no more than about 0.75 inch, providing a tight but realistic tolerance for typical surveillance setups where precise focus matters. For a wider field of view, the acceptable gap widens to 0.75 to 1.5 inches, reflecting how a wider lens naturally increases depth of field. For very wide views or shorter focal lengths, a gap of 1.5 inches or more acknowledges that the scene can remain sharp across a broader range of distances. This tiered framework gives installers a clear, consistent way to judge focus across different cameras and lenses. The other options don’t fit because they either propose an unrealistically small fixed gap, a single large gap without tiers, or no gap at all, which doesn’t align with how depth of field varies with lens and distance.