Photographing LEDs...advice wanted

Hi All,

Was wondering if anyone has any tips and techniques for taking photos of LEDs and LED products...suitable for putting in a product spec.

My motley collection of digital cameras (CMOS sensors, one CCD) is pretty low tech, and have trouble taking pictures without washing out the colours.....my bright reds turn out white, my bright greens turn out white....and you guessed it the blues turn out white.

PC Modders take pics of their PC cases by double exposing one pic by daylight, then another with all the lights on in the dark......would something similiar be applicable, only problem is I still get washout. Would an infrared filter help?

phil

I've had great results with HDRI.

The white is the sensor going into saturation or clipping. It will help to illuminate the ambient area to a level that's almost as bright as the LED itself.

I've found this out the hard way with video cameras (which use similar CCD sensors). In my case I've tried to shoot video of LED videowalls in action, and I've found that I have to dim the LEDs in the wall way, way down to around 10% of normal brightness in order to keep the camera from saturating and blooming. I have to photograph them this way because I have no control over the ambient outdoor lighting.

without IRIS control your screwed.
add ambient (like he said) , or fill flash even to stop that oversaturation of the chip.

its possible that "ND" filters , nutreal density, which are just GREY darkening filters can work when you have little CONTROL of the camera.
also a DUAL polarizer makes a great Multi ND filter, allowing ANY setting of darkening by rotating the 2 polarizations.
but
darkening what comes in the lens on a camera with little control will often just get you a grainey pic , when it tries to boost it back up, with cheap gain tricks.

some stuff that doesnt have IRIS control has Shutter control, that can also decrease the chips exposure time electronically.

try and get the camera to ADJUST TO the light its seeing, some cameras you can find a place IN your pic where the camera does adjust the iris automatically. depending on the camera that would be 20% in the center, or 80% of the total picture having the same high levels.

one guy put a piece of paper over them, which spreads out the light to "ambient" and cuts off the led glare.

if you can do a PINHOLE, you can do alaska sunglasses with the camera .

PROJECTION, use a simple magnifying lens, and shoot your led output onto a wall or screen , then you see the same basic thing, but its blown up to 100X size, and it can be photograhed that way too.

or just Blow it out the top, so we know how bright it really is, we can still see the colors coroning around the edges /ubbthreads/images/graemlins/smile.gif

That would require a great deal of control over the setup of the items and the items themselves:
- try to avoid flash (I guess that if you had the equipment and knowledge to use flash in this situation - I don't - you wouldn't have to ask). Otherwise, you need to control the flash just right.
- either dim down the LEDs or push up the ambient light; the problem is the contrast between the ambient light you need for the setup and the light emitted from the LEDs.

Bye
Markus

OK thanks guys...I've only got very cheap digital cameras to play with (ie no control over anything).....but I can easily dim the LEDs as recommended or borrow someone elses more capable and flexible camera..