How can I estimate the LED light output needed for close-up photos of indoor plants?
Asked 11/8/2019
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I want to photograph indoor plants at close range (not true macro) and would like to know how to estimate how much LED lighting I need to reach practical exposure settings for ISO, shutter speed, and aperture at a fixed light-to-subject distance. Is there a useful way to calculate this from LED specs, and how do brightness, distance, and beam spread affect the result?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
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If you use a directional light, and we make some assumptions, we can roughly calculate the shutter speed for the ISO and f stop in your comment.
As a sanity check, here is the calculation for my test setup. It is a stop off, so some of the assumptions aren't correct. This is only a ballpark calculation anyway.
More comments on my test setup. A typical household interior has an EV of 5-7. With one 8W LED spotlight at 18 inches away, and a white reflector on the other side, I measured about EV 9 (based on my test exposure). You can get more powerful spotlights or you could use several. A distance of 18 inches is a little close, you probably want to be further away to get more even lighting. So, I am going to use EV 9 for the remainder of the calculations.
ISO Aperture Shutter
800 f8 1/60 With image stabilization, Handheld is OK
400 f8 1/30 With image stabilization, handheld is marginal
400 f11 1/15 Need a tripod
100 f11 1/4 Need a tripod
200 f16 1/4 Need a tripod
You will need to decide if these are reasonable. See the Wikipedia article on Exposure Value for more information. With a larger or several lights, you should be able to get to EV 10 or 11.
I am assuming a simple setup, if you want a pure white background, you will want separate lights pointing at a white background.
Note that the Color Rendering Index (CRI) of household LEDs isn't very good. If color accuracy is important you should use something else.
I shoot a lot of flowers in my house. I use a speedlight and a small softbox on one side, and a white foamcore reflector on the other side (very close). If I want a dramatic image, I often put another speedlite in the back for a rimlight (need to be careful to shield the lens from this light). I use cheap Yongnuo RF flash triggers instead of sync cords.
Originally by user84623. Source · Licensed CC BY-SA 4.0
user84623
6y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—roughly. For photography, what matters at the subject is illuminance (lux), not just the LED’s rated output in lumens. Lumens describe total light output; lux describes how much of that light actually falls on the plant. Beam angle, reflectors, room bounce, and distance all affect lux, so exact calculation is difficult.
A practical guide is to think in exposure values (EV). Bright sunlight is about EV 15 at roughly 100,000 lux. Every doubling/halving of light changes EV by 1 stop. That means about 100 lux is around EV 5. Typical household interiors are often around EV 5–7.
One community test found that a single 8 W LED spotlight placed about 18 inches from the subject, with a white reflector, gave roughly EV 9. That’s enough for workable close-up exposures, and stronger spotlights or multiple lights would increase this further. Distance matters a lot: moving the light farther away reduces intensity, though placing it too close can make lighting uneven.
So the best method is to estimate or measure the lux/EV at the plant, then choose exposure settings from that. If possible, use a directional LED, test at your intended distance, and adjust by adding lights, using a reflector, or raising ISO / slowing shutter speed.
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