LED photographing? - Page 1
Forum section: electronics / projects

author: FrankBuss
author_rank: Unknown
timestamp: July 09, 2017, 11:23:45 am
content: How can I photograph and record videos of a bright LED when it is lit? This is how it looks like when I tried it with my iPhone:As you can see, most of the time it is overexposed and just white. Then I tried it with my Canon EOS 6D and a ND64 filter:This looks much better for the LED, but now the background is too dark and it is slightly discolored. Maybe I need brighter ambient light? But then it might not look as bright as it appears when I see it with my eyes. I guess I need something like HDR tone mapped imaging, the example at the bottom of this article looks very good:https://en.wikipedia.org/wiki/High-dynamic-range_imagingIt is from this project:https://hackaday.io/project/25689-rgb-led-fading

author: kalel
author_rank: Frequent Contributor
timestamp: July 09, 2017, 11:34:33 am
content: Quote from: FrankBuss on July 09, 2017, 11:23:45 amYou could try HDR. Maybe the camera has an HDR preset already? If not, you could take some bracket images, and then join them with any software designed for the purpose (Gimp's GMIC also has some layer combining features, but latest official GIMP doesn't import raw as far as I know, maybe with some plugins, and even if it did, I'm not sure the GMIC layer merging techniques would work with RAW).

author: BrianHG
author_rank: Super Contributor
timestamp: July 09, 2017, 11:40:12 am
content: You can wrap the led in a single layer of thin white or grey electrical tape. For photographing purposes, it will cut out the really powerful glare.As for solving the problem on the video side, you need a camera without a software iris and a manual iris on the lens, a really non noisy camera in the dark shades. Then in software, you will need to have the ability to perform a manual gamma ramp to balance out the dark background with the peak bright LED in the middle. Though I know how to do this in photoshop with a still image, I am not well versed with modern video editing suite software.

author: BrianHG
author_rank: Super Contributor
timestamp: July 09, 2017, 11:49:46 am
content: Like this: (the effect could have been pushed further if you had a better camera focus and angel, and I was dealing with the source, not a compressed YT video)

author: DrGeoff
author_rank: Frequent Contributor
timestamp: July 09, 2017, 12:39:10 pm
content: Try spot metering on the LED itself. Not the scene.Also manually adjust white balance.

author: cdev
author_rank: Super Contributor
timestamp: July 09, 2017, 02:31:53 pm
content: If you're trying to photograph a light and have it look natural there is no substitute for either a camera with a lot of inherent sensitivity to low light or a fairly long exposure.Make sure to use a tripod (and detached shutter release button too) if you have one unless your tripod is so solid that it completely immobilizes your camera from moving even the tiniest amount when the shutter is pressed..Some of the newest cameras have amazingly high ISO speeds. They would make good cameras for shooting LEDS to their best advantage in their own natural light.If done right, you might be able to achieve a candlelight-like look which could maybe be really nice. If you don't have the high ISO, try an manual extended exposure, with your long shutter and use the aperture to get the exposure right.To take pictures suitable for use with HDR you need to use a tripod and manual exposure and take at least three images with identical framing and different exposure times.HDR refers to a combining of several images taken with different exposure values, exposed to optimize different parts of the image. HDRs merging 3 identical images each optimized for highlights, midtones and shadows is typical. So then take 3 images two or possibly three F-stops or EVs apart. One in the middle, exposed as normally one dark one overexposed, and see what you can get with using those images as the basis for an HDR. That's also a useful technique with a scanner when you are trying to scan real photographs or slides, unless your scanner supports more bits than many do, in that case use them.

author: NorthGuy
author_rank: Super Contributor
timestamp: July 09, 2017, 03:01:23 pm
content: For static photography, you just use a flash. This will brighten the background and won't affect the LED. The trick is to get the correct intensity of the flash. Once you get the background right, you can control the brightness of the LED with shutter. Slowing down the shutter to 1:30 will make LED brighter (relative to background). Using faster shutter, e.g. 1:250 will dim the LED relative to background. I have Nikon, but I suppose Canon EOS should be able to do it.For video, I don't know, but some sort of studio lights could be helpful.