What color lighting gives best result?

[pilotgeorge]

I am using a Canon Rebel xsi DSLR to photograph coins. I have built a light box so I can control the light. The box is powered by a string of LEDs of unknown color temperature.
The pictures come out making the coins look grayish rather than their true color. Because they are grayish, the apparent contrast is off. The focus is good, but the pictures look like there is a gray haze between the camera and the object.
Can someone help a novice? I need to know what is the best color temperature to get a natural result? I just ordered some 6000K devices, hoping that would improve things, but I would love to get some input from someone that knows a lot more about lighting than I do.

 

[RAZKY]

I am using a Canon Rebel xsi DSLR to photograph coins. I have built a light box so I can control the light. The box is powered by a string of LEDs of unknown color temperature.
The pictures come out making the coins look grayish rather than their true color. Because they are grayish, the apparent contrast is off. The focus is good, but the pictures look like there is a gray haze between the camera and the object.
Can someone help a novice? I need to know what is the best color temperature to get a natural result? I just ordered some 6000K devices, hoping that would improve things, but I would love to get some input from someone that knows a lot more about lighting than I do.

Light box?? Sure you don't mean light table, or soft box? A light box provides back lighting for viewing negatives and transparencies. Ideally, you would want 5000-5500K lights, with the camera white balance set for daylight. You should be good with your 6000K lights, though - if they look a bit cool, alter your camera white balance a bit at a time to suit. You can also fake about any color you want in photoshop..

 

[pilotgeorge]

Light box?? Sure you don't mean light table, or soft box? A light box provides back lighting for viewing negatives and transparencies. Ideally, you would want 5000-5500K lights, with the camera white balance set for daylight. You should be good with your 6000K lights, though - if they look a bit cool, alter your camera white balance a bit at a time to suit. You can also fake about any color you want in photoshop..

My terminology may be wrong. I have built a box, with the camera "looking" in from one side. The object is mounted near the center of the box, and a rear wall contains numerous voltage controlled LEDs. The light bouncing off the walls illuminate the object being photographed [the coins]. This makes me independent from time of day, so the camera settings will work for any time of day. I have been trying many different settings, but this grayishness, and loss of contrast cause me to suspect that it is the LED color temperature that is hurting my efforts.

 

[RacePhoto]

I'm not sure this is the major problem, but just asking, are all the LEDs identical and at the identical brightness and color temperature? Otherwise mixed light is "impossible" to match. If there is any ambient light, you have mixed light. You might have natural light mixed with LED light. If there's a room light, now you have three different WB to match.

If you match the White Balance of the lights, and set the camera, using a grayscale card, then you have your answer to what's the right light WB to use. Auto WB can be fooled by the color of the subject.

If I wasn't clear. Set the color balance to the light source using a gray card (Grey Card) which is neutral. And then you will always have it right for your LEDs. If the voltage changes or the LEDs are not identical, the WB will change.

If you have multiple light sources mixed, things are going to be near impossible to correct for.

 

[adamhiram]

I'm not sure this is the major problem, but just asking, are all the LEDs identical and at the identical brightness and color temperature? Otherwise mixed light is "impossible" to match. If there is any ambient light, you have mixed light. You might have natural light mixed with LED light. If there's a room light, now you have three different WB to match.

I second this. The color/temperature of the lights isn't particularly important as long as they are all the same and you aren't mixing light sources. Take an underexposed photo of the LED lights and check that they all look to be the same color. When you shoot, avoid any sunlight from nearby windows and dim any lights in the room. From there, assuming your LED lights have consistent temperature, you should be able to adjust white balance in Lightroom or Photoshop afterwards.

 

[smoke665]

The pictures come out making the coins look grayish rather than their true color. Because they are grayish, the apparent contrast is off.

A little more information is required, are you metering your exposure, or is your camera on AUTO. Also posting an image will help diagnosing, but I'm not sure it's a temperature issue. I suspect a couple of things are happening. First you say "I have built a box, with the camera "looking" in from one side. The object is mounted near the center of the box, and a rear wall contains numerous voltage controlled LEDs." If you're on AUTO rather than metering and setting your exposure manually, you might be fooling the camera, much the same way that snow will. Camera meters work by evaluating light reflected off subjects and are standardized on middle gray (also known as 18% gray), any time a camera is pointed at something very dark, the meter will work the opposite way by brightening up the exposure, whereas a very bright subject will cause the meter to darken the exposure, resulting in white being rendered gray. "The light bouncing off the walls illuminate the object being photographed [the coins]" Light coming in from all directions is flat lighting, the subject is devoid of any shadows. To create a three dimensional looking object on a one dimensional image requires shadow to define the object. You only get shadow from directional light.

For photographing coins, I suggest ditching the box and the LED lights. Get a black felt mat, place the coin in the center raised off the cloth by 1/2" or so. Get a macro lens (or a cheap alternative like macro extension rings), so you can get down close to the coin. Mount your camera on a tripod that will allow you to point down and focus close. For lighting you can use the little goose neck clip on LED lights, they don't have to be overly expensive, just be sure they are the same so the color temp is the same. Set your camera to AWB, manual, meter for exposure, and save as RAW. I'd advise letting the first shot be a gray card (you can use it later to set your WB in post) gray will also help with exposure adjustments and color. You'll have to play with the lights for best look, maybe one on each side low or one low/one high, or both high. When you get the right amount of shadow detail, you're happy with shoot away.

Another method of lighting coins is Axial lighting, you shine light straight down on the coin in perfect axial alignment with the camera lens, which gives uniform light but lacks shadow detail that gives the coin a three dimensional look. The way around this is go with the straight down lighting, but angle your camera ever so slightly. Again it's an adjustment that will require some trial and error. For the light you could go with a ring lights. You'll spend a little more than the goose neck lights, but it may be worth it to you. The Pseudo Axial method will produce a better image of the coin.

 

[LWW]

As noted, as close to 5.5K Kelvin will give as close to daylight .

Being off 500 one way or the other is fixable in software easily, but I’m a firm believer that getting it as correct as is reasonable will yield the best result.