How can I estimate whether my strobes can balance ambient light in a sports hall?
Asked 10/18/2022
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I normally shoot either flash-only or ambient-only, but I need to do a small on-location shoot in a fairly bright sports hall and want to mix ambient with flash. My ambient exposure is about ISO 100, f/5.6, 1/30s. I have a Godox SK400II (minimum 1/16 power) and a Godox 600 (minimum 1/32 power). Is there a way to estimate in advance whether these strobes can be used to balance the ambient, or whether I’ll need lights that can be turned down further?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
3y ago
2 Answers
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There really is no way to accurately calculate flash exposure for the "sports hall" situation you describe. Too many variables will come into play.
The size of the room, size and number of ambient light sources, flash distance to subject, flash angle to the subjects, flash angle to the camera, color and placement of reflective walls and furnishings, etc., will all vary the amount of light reaching the camera.
Are you planning to shoot from a tripod with a fixed location? If not, as you walk around, you will constantly be changing these variables.
I would suggest using a flash meter, or simply relying on trial and error.
Originally by user39427. Source · Licensed CC BY-SA 4.0
user39427
3y ago
0
Generated from our catalog & community — verify before relying on it.
You can estimate it, but not calculate it exactly from the room reading alone. In a sports hall, flash exposure will vary with subject distance, light position, angle, room size, wall reflections, and whether you stay in one spot or move around.
A practical starting point is the strobe’s guide number. For example, if the SK400II has a guide number of 65m at ISO 100, then at full power:
GN ÷ f-number = distance 65 ÷ 5.6 ≈ 11.6m
So at f/5.6, full power would expose a subject at about 11.6m. If your light is closer, reduce power accordingly. Example: at 6m, 65 ÷ 6 ≈ f/11, which is 2 stops brighter than f/5.6, so about 1/4 power would be a starting point. You can also use the inverse square law: doubling distance gives 1/4 the exposure.
If your minimum power is still too bright, increase flash-to-subject distance or add ND to the light. For real-world accuracy, a flash meter or test shots are the best approach.
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