How can I choose one lens and camera setup for top-down product photos in boxes of different sizes?
Asked 9/17/2017
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2 answers
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I photograph items for online sales in four top-down light boxes/chambers with heights of 300, 350, 400, and 450 mm. I’d like to use the same camera sensor and one lens for all four setups.
The products vary a lot in size and height, from a few millimeters tall up to about 200 mm. I’m trying to determine what lens/focus setup will work across all the chambers, including focal length, focus distance, f-number, and depth of field. I’m also unsure how to factor in field of view when the camera is mounted directly above the subject.
Is there a practical way to choose one lens for all of these chambers, and how should I think about depth of field and field of view for this kind of product photography?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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If your objective is images that be mainly viewed on a computer screen by prospective buyers, your depth-of-field calculations can be greatly relaxed. I suggest a circle of confusion diameter computed as 1/1000 of the focal length. Thus if an 80mm lens is mounted, the COF would be 0.08mm etc. For this application you might get away with 1/900 of the focal length or perhaps even courser. Anyway, depth-of-field calculations are based on subjective things that may or may not be applicable. Also, all depth-of-field table, online computers and math formulas are calculated for object distances only on the lens axis. You are on your own if you are worrying about depth-of-field calculations for object placements near the borders of the area being imaged. In other worlds, you are entering into the realm of trial-and-error and tables and charts will only be guesstmates and likely for your application you can loosen them.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
8y ago
0
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Start with field of view, not depth of field. Since the camera is fixed overhead and the box heights differ, the lens must be wide enough to cover the largest required top-down area at the shortest working distance, while still giving acceptable framing in the taller boxes.
For online-sale photos viewed mainly on screens, depth-of-field demands can usually be relaxed. One answer suggests using a circle of confusion around 1/1000 of focal length, and possibly even a bit looser for this application. That means you may not need to chase extremely strict DOF calculations.
Also note that standard DOF formulas assume points on the lens axis; they do not fully describe sharpness toward the edges of the frame, so treat the calculations as approximations.
In practice: pick the focal length based on the widest field of view you need, then stop down enough to cover the expected subject height range as well as your lighting allows. If one setup must handle very tall objects and very wide coverage, a single lens may involve compromises, so testing with your actual chamber dimensions is important.
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