proper correction of color in LR4?

[nathancarter]

Originally Posted by mike_d

Keep in mind that depending on your shutter speed, the light might not be consistent from frame to frame or even within the same image due to the phosphors changing intensity and color with the power frequency.

This is something that's important when shooting under fluorescent. The voltage to the lights is 60Hz - or, 60 cycles per second - and the lights flicker at approximately the same rate. Too fast for most people's eyes to notice, but a camera with a fast shutter speed will be affected.

It's a tough shooting situation, for sure. If your shutter speed is faster than 1/60 (or 1/120? I forget) then you only capture a partial cycle of the fluorescent lights, which can result in erratic color and erratic exposure. But if your shutter speed is slower than 1/60 then you're almost guaranteed to get motion blur on human subjects.


To see it for yourself, set your shutter speed to something fast like 1/200, crank up the ISO and open the aperture to get a decent exposure, then fire off a burst mode and see how the color and exposure changes from shot to shot.

[the.forumer]

Originally Posted by nathancarter

This is something that's important when shooting under fluorescent. The voltage to the lights is 60Hz - or, 60 cycles per second - and the lights flicker at approximately the same rate. Too fast for most people's eyes to notice, but a camera with a fast shutter speed will be affected.

It's a tough shooting situation, for sure. If your shutter speed is faster than 1/60 (or 1/120? I forget) then you only capture a partial cycle of the fluorescent lights, which can result in erratic color and erratic exposure. But if your shutter speed is slower than 1/60 then you're almost guaranteed to get motion blur on human subjects.


To see it for yourself, set your shutter speed to something fast like 1/200, crank up the ISO and open the aperture to get a decent exposure, then fire off a burst mode and see how the color and exposure changes from shot to shot.

yup guys, i know what everyone is saying. problem is that even after getting the neutral point with the eyedropper in LR4.1, it still looks odd (which is what you already saw in the first picture). it's often a guessing game in punching in the right amount of tint/wb to make the photo look "Right".

this was taken under fluorescent lighting btw, not mixed.

[pknight]

Originally Posted by the.forumer

this was taken under fluorescent lighting btw, not mixed.

There could be a mix of different flourescent tubes, with different color characteristics, in the fixtures.

[kirkt]

Fluorescent light, in general, can be problematic because its emissive spectrum is not a nice continuous, correlated color temperature analog like most other light sources we usually shoot under. It has crazy spikes and flat spots in it, making the accommodation of the "color" of the light particularly troublesome. Add to that the often difficult mixture of it with daylight coming through a window or other mixed lighting sources and you have yourself a headache. To make matters worse, there are multiple favors of fluorescent (warm, cool, daylight balanced) that make the assumption of "fluorescent" precarious. Even a neutral target may not give you natural results. It is a pain in the butt.

From wiki:

Main article: Color temperature

The color temperature of different electric lamps

Correlated color temperature (CCT) is a measure of the "shade" of whiteness of a light source, again by comparison with a blackbody. Typical incandescent lighting is 2700 K, which is yellowish-white. Halogen lighting is 3000 K. Fluorescent lamps are manufactured to a chosen CCT by altering the mixture of phosphors inside the tube. Warm-white fluorescents have CCT of 2700 K and are popular for residential lighting. Neutral-white fluorescents have a CCT of 3000 K or 3500 K. Cool-white fluorescents have a CCT of 4100 K and are popular for office lighting. Daylight fluorescents have a CCT of 5000 K to 6500 K, which is bluish-white.

High CCT lighting generally requires higher light levels. At dimmer illumination levels, the human eye perceives lower color temperatures as more pleasant, as related through the Kruithof curve. So, a dim 2700 K incandescent lamp appears comfortable and a bright 5000 K lamp also appears natural, but a dim 5000 K fluorescent lamp appears too pale. Daylight-type fluorescents look natural only if they are very bright.

Color rendering index

Color rendering index (CRI) is a measure of how well colors can be perceived using light from a source, relative to light from a reference source such as daylight or a blackbody of the same color temperature. By definition, an incandescent lamp has a CRI of 100. Real-life fluorescent tubes achieve CRIs of anywhere from 50 to 99. Fluorescent lamps with low CRI have phosphors that emit too little red light. Skin appears less pink, and hence "unhealthy" compared with incandescent lighting. Colored objects appear muted. For example, a low CRI 6800 K halophosphate tube (an extreme example) will make reds appear dull red or even brown. Since the eye is relatively less efficient at detecting red light, an improvement in color rendering index, with increased energy in the red part of the spectrum, may reduce the overall luminous efficacy.[19]

Lighting arrangements use fluorescent tubes in an assortment of tints of white. Sometimes[weasel*words] this is because of the lack of appreciation for the difference or importance of differing tube types.[citation needed] Mixing tube types within fittings can improve the color reproduction of lower quality tubes.

Kirk

[the.forumer]

Originally Posted by pknight

There could be a mix of different flourescent tubes, with different color characteristics, in the fixtures.

makes sense - i didn't think about that till you said it.

any other trick in the bag we could use to avoid this? :/