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2 Days Ago   #1
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Making the Photo of Colored LEDs

I need an advice. I am preparing tutorial of concurrent programming on Attiny85 chip. As an example I choose pumpkin glitter with colored eyes. There are two 10mm three-colored LEDS. Program changes LED color (There are 7 colors. Three pure colors: red, green, blue and four mixed colors, which are close to white, cyan, magenta and yellow). Before diving into programming details I would like to show the outcome: either a short movie or GIF made from static images. In real life colors look more or less OK but, when I try to photograph or film it, result is disappointing. There is almost no differentiating in colors, everything looks like glowing spots. I have attached iPhone photo as an example, tried DSLRs (Pentax K-5II, K-01 and Q-7) and did not see much difference. Is there any way to get reasonably good photos of colored LEDs?

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IPhone 8  Photo 

Last edited by jumbleview; 2 Days Ago at 10:39 AM.
2 Days Ago - 1 Like   #2
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Haven't tried so I don't have personal experience but...

LEDs will be drastically brighter (severely overexposed) compared to everything else. I'd try:

1. Underexpose as much as possible. Pumpkin will be very dark but the LEDs will look better.

2. Get cheap & dark window tint from an auto parts store (or any dark film). Cut small circles (hole punch?) and cover the LEDs. Might need a couple layers. Basically trying to create a ND filter for the LEDs. Not certain if window tint will affect the color of the LEDs so that may create a different problem. Maybe there's ND film available somewhere?



---------- Post added 09-15-20 at 05:55 PM ----------

Google "neutral density gel sheet" and you'll find stuff. I guess I should have done that before responding.
2 Days Ago - 1 Like   #3
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This is not something I have tried, but my first approach would be to use supplemental light (flash or continuous) to balance against the very bright LEDs. I would also use fixed white balance shooting RAW and adjust both the white balance and color balance in post-processing. Including a gray card in a test shot may be helpful in this regard. You may need to adjust the eyes separate from the rest of the frame.


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2 Days Ago - 2 Likes   #4
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If you have access to the electronic circuit or programmatic control of the light's intensity, you could just dim the LEDs to match the brightness of the pumpkin area.

Or, as others have said you could try to boost the lighting - take the item out into full sunlight or use a flash.

In either case, the spot meter on your camera can be used to check the brightness of the illuminated pumpkin compared to the brightness of the lit LEDs. The LEDs can probably be a stop (or maybe up to 1.5 stops) brighter than the pumpkin and still show as bright color.

2 Days Ago - 1 Like   #5
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QuoteOriginally posted by photoptimist Quote
If you have access to the electronic circuit or programmatic control of the light's intensity, you could just dim the LEDs to match the brightness of the pumpkin area.
From somebody who likes to play with LEDs, this is the best, and perhaps really, the only way it's gonna work.

Note also that the light from the LEDs may be very pure in a wavelength sense - i.e. a red LED really puts out a very narrow wavelength band of red light. The color sensors in your camera sort of don't know what to do with this - there is overlapping sensitivity that varies by wavelength of the 3 color sensors.
2 Days Ago - 2 Likes   #6
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You could try to spot meter the led, undexposing the rest and then shoot an image without the LEDs illuminated and merge them in post.
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QuoteOriginally posted by jspi Quote
Maybe there's ND film available somewhere?
Polarizer film would work (available on Ebay as thin film, or cheap clip-on sunglasses at the drugstore). Very little color effect, and you'll get about a stop per layer; with two layers you could vary the amount of cross-polarization loss - that's how variable density ND filters are made).

LEDs might be polarized, though - I'll take a look at that for my own curiosity!
2 Days Ago - 4 Likes   #8
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0 EV comp and light source bounced off a white mat board




2 Days Ago - 1 Like   #9
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Thanks everybody for advises. I got the main point: strong external light, under-exposure, and post-processing. Not prefect but suites my need.
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2 Days Ago   #10
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QuoteOriginally posted by UncleVanya Quote
You could try to spot meter the led, undexposing the rest and then shoot an image without the LEDs illuminated and merge them in post.
This is what I would do.
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QuoteOriginally posted by tuco Quote
0 EV comp and light source bounced off a white mat board


Hey, I like that!
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