Challenge: Need help taking christmas tree w/ LED lights photo

victor_vvv · Dec 11, 2009

Hi All,

I'm new to this forum and also relatively new to photography (about 1 year). I'd post this in the begginners forum but I'm afraid my question is more suited for advanced level photographers. . .

I have a Canon 40D with a 18-55 IS lens and need help photographing my Christmas Tree! From what I hear this is a very difficult thing to do properly. I tried for over an hour last night with various WB/aperature/shutter speed settings without much success. Basically I have a 8 foot tree in my living room all decorated up. I've got about 1400 icicle white and blue LED lights (yes it's bright). I can't figure out what settings to use to get the optimal photograph. The main problems i'm having are that the blue lights are turning out purple and washed out (kinda over exposed) and the rest of the tree is completely underexposed.

I've tried all the different W/B settings (asides from changing the Kelvin or white balance shift). And I just can't seem to get the blue to show up blue. Even when just trying to take a close up photo of some of the blue lights only, it always shows up a shade of purple. I've tried it with or without back lighting. Optimally, I'd like to take the photo without backlighting and the tree is already pretty bright, but I realize I might need some to show the details of the branches.

I've heard of this thing called HDR (combining multiple photos using photoshop?), but have no idea how to do it (although I do have photoshop CS4 and would be willing to try if that's what it takes).

Any help would be appreciated.

PS: of course i'm using a tripod ;P

Derrel · Dec 11, 2009

I would try setting the white balance to Incandescent, with a slow shutter speed like 1/2 to 1/4 second, lens at f/4, ISO around 800. A fairly small "pop!" of electronic flash will help illuminate the tree, which itself is quite dark. You can adjust the flash one of two ways, but you are actually in a situation where you need to make two exposures; one for the lighted lights, which is done by a combination of ISO, shutter speed, and aperture, and the flash exposure which is created by the combo of ISO, flash power level, and the lens f/stop in use; on the flash exposure, the shutter speed is largely irrelevant.

The problem occurs that when in most programmed or automatic mode, the flash popping up will cause the shutter speed to default to 1/60 second or even faster.

As far as purple rendering as blue and vice-versa...purple is a difficult color for many digital sensors to render accurately; I have a purple gel that photographs as blue. I think maybe the WB adjustment to Incandescent will help with that.

Pugs · Dec 11, 2009

Try figuring out what settings to use to properly expose the lights (even if that leaves the tree underexposed). Once you have the lights properly exposed, try those settings but also use a flash to expose the tree.

As for your WB problem, are you shooting raw? If not, try it so that you can adjust the WB in post. If you HAVE to shoot .jpg, try manually setting the WB on your camera. If blue is showing purple, it's a little too warm and you need to set a cooler (higher) WB temp. (MAN I hope I got that last bit right! If I didn't, PLEASE, someone jump in and correct me!)

victor_vvv · Dec 11, 2009

Derrel said:
I would try setting the white balance to Incandescent, with a slow shutter speed like 1/2 to 1/4 second, lens at f/4, ISO around 800. A fairly small "pop!" of electronic flash will help illuminate the tree, which itself is quite dark. You can adjust the flash one of two ways, but you are actually in a situation where you need to make two exposures; one for the lighted lights, which is done by a combination of ISO, shutter speed, and aperture, and the flash exposure which is created by the combo of ISO, flash power level, and the lens f/stop in use; on the flash exposure, the shutter speed is largely irrelevant.

The problem occurs that when in most programmed or automatic mode, the flash popping up will cause the shutter speed to default to 1/60 second or even faster.

As far as purple rendering as blue and vice-versa...purple is a difficult color for many digital sensors to render accurately; I have a purple gel that photographs as blue. I think maybe the WB adjustment to Incandescent will help with that.

it's actually my blue turning to purple, not purple to blue.

victor_vvv · Dec 11, 2009

Pugs said:
Try figuring out what settings to use to properly expose the lights (even if that leaves the tree underexposed). Once you have the lights properly exposed, try those settings but also use a flash to expose the tree.

As for your WB problem, are you shooting raw? If not, try it so that you can adjust the WB in post. If you HAVE to shoot .jpg, try manually setting the WB on your camera. If blue is showing purple, it's a little too warm and you need to set a cooler (higher) WB temp. (MAN I hope I got that last bit right! If I didn't, PLEASE, someone jump in and correct me!)

my problem is that I can't even figure out how to properly expose the lights. they just don't turn out the way I see them or even close. at best, it turns my deep LED blue to a baby blue color. I guess these LED are giving me the fits cuz they are a different technology. the old school lights I can probably just adjust the white balance to tungsten or incandesent and all would work. but since led's aren't based on either tech, it makes it difficult.

GeneralBenson · Dec 11, 2009

Post example pictures...

Dwig · Dec 11, 2009

Colored LEDs can be a problem to photograph. They emit light in very narrow frequency bands. Differences in how these match the sensitivity of each of the three sets of filtered photosites in a digital sensor compared to how they match the sensitivity of the three sets of cones in the human eye will frequently cause them to photograph different than they seem to the eye. There is not much that can be done to "correct" the differences.

One thing to watch out for is overexposure. Most holiday light pics overexpose the lights themselves. This happens because the rest of the scene is too dark compared to the lights. The best pictures usually result from having rather bright ambient lighting or flash. You should set the white balance for the dominant lighting, ignoring the holiday lights. If the room is lit with bright incandescent lights then set the WB for incandescent. If you are using flash then set the WB accordingly. You often want to underexpose the ambient or flash lighting slightly so that the room doesn't look too bright. You want the lights to dominate.

pharmakon · Dec 11, 2009

Get the closest you can on all other colors and then adjust the blues in adobe camera raw?? Isn't there a way to tweak individual colors somewhat? Not sure it would work without messing up another part of the image but it might be worth a shot. Don't have PS available to me right now so I can't say for sure.

craig · Dec 11, 2009

One of my biggest clients designs Christmas trees for Hotels and Country Clubs, etc.

I shoot Tungsten WB. Aperture Priority. Exposures are in the 20 @ 20 sec range; ISO 100.

The key is to light it like you would anything else. I use a diffused main "high at 45" barn doors or gobos are needed to keep the light from spilling all over. Add a bare hair light or kicker hitting the side only; for interest and to separate the tree form the background. Strobes or tungsten is fine. Mostly for the trees I use tungsten lighting because the ambient lights indoors is tungsten. He only uses clear lights, so I can only guess why your blue lights are not turning out blue.

You are in luck with a with an 8' tree. Most of the ones I shoot are in the 15' plus range. It is a challenge to say the least.

Love & Bass

Garbz · Dec 12, 2009

Sure that's called playing with the camera profile.

There's one big issue with LEDs. LEDs are pure lights. By that I mean they generate a single peak wavelength. This means they fall on the very edge of the CIE horseshoe diagram.

It has a few implications. Firstly, unless the LED wavelength falls on the exact wavelength of one of the R G B G filters on your sensor the camera won't otherwise know it's a pure light. Secondly because it's a pure light you have no means of recording or displaying it. Even with the ProPhoto colourspace you don't cover all of the possible colours, although in this case the blue would be covered. But that is academic since you won't be able to display it since most screens and printer produce gamuts that are a small fraction of the visible possible colours.

When I go out and take a photo, and later here convert that photo from AdobeRGB (the gamut of my screen) to sRGB (the standard gamut), 99% of the time I see no difference. However if I take a photo of LEDs, or Lasers there is a large night and day difference to the colours as they get shifted to fit within the sRGB spectrum.

Our ability to produce single lights are far beyond our current ability to produce or record entire spectrums

Anyway your best bet may be in photoshop to use the hue adjustment on just the tiny bit of the blue channel. If the colours start affecting the rest of the image then maybe mask it to just the LEDs.

GeneralBenson · Dec 12, 2009

I would certainly think that a grey card would solve your problems, no?

Skaperen · Dec 12, 2009

Dwig: How about post processing the LED lights? On tripod, shoot a well underexposed picture (at night, room lights off) to get ONLY the lights and nothing else. Shoot again at normal settings with the lights off (don't move anything) to get the tree. Color correct the lights-only shot as you like, even separately in each color channel. Merge with the tree shot at the desired ratio.

Dwig · Dec 12, 2009

Compositing two images, one with only the lights visible and the second without any lights but with a well exposed tree and surroundings is a workable approach if the environment can be controlled (no people milling around, indoors or no wind, ...).

Such compositing will allow very good control of the balance between the two shots, but it will do absolutely nothing to correct for the LEDs' narrow emission line spectra and their fit/misfit with the spectral sensitivity of the sensor's filtered photosites (the RGBG Bayer filter arrangement Garbz referred to).

Skaperen · Dec 12, 2009

Dwig said:
Such compositing will allow very good control of the balance between the two shots, but it will do absolutely nothing to correct for the LEDs' narrow emission line spectra and their fit/misfit with the spectral sensitivity of the sensor's filtered photosites (the RGBG Bayer filter arrangement Garbz referred to).

The corrections will be easier on just the photo with spots of lights in a few colors on a dark background. Correct color is only crucial on the lighted photo.

For blue lights that look purple, just apply a subtraction of the blue channel against the red channel. The red, yellow, and green lights stay the same, but the red is reduced for the blue lights. While lights will lose some red, and that could be countered with an addition to red of the product of green and blue. Selected values in a first and second order color mixing matrix would do that.

The color correction of the lights alone is also not so critical. You could even swap colors around and who would really know.:mrgreen:

I'd take the lights shot and duplicate it many times. For each one, I'd erase out random selections of lights. Then I'd compose them together in a sequence with a brief mix frame between pairs, and form a little movie making the lights twinkle and blink.