Author Topic: Flourescent lighting == The Suck.  (Read 2650 times)

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riogrande491

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Re: Flourescent lighting == The Suck.
« Reply #15 on: December 30, 2009, 01:58:00 PM »
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Apparently there is some interest in the relative merits of different lighting technologies. It can be very difficult to describe in words the sensations that the eye and brain perceive. I happen to work in a related field, so I already had a few visuals prepared for an NMRA layout photography clinic I gave earlier this year. Perhaps these will be of some assistance.

One of the many challenges in fluorescent lights today is achieving a satisfactory CRI. As mentioned by others, the typically poor CRI is the result of spikes in the emission spectra. Smoother is better, and this measured cool-white tube is actually one of the "better" ones. Smoother also requires more expensive phosphors, and reduces the light output of the lamp. Since so many people suffer from "mononumerosis" disease, fixating on light output per watt, really good bulbs are fairly uncommon.



Even though this CWF tube is actually pretty good for a hardware-store light, let's illuminate a test scene under tungsten and then CWF fluorescent. First, the tungsten-lit scene.



Now the CWF-illuminated scene. Notice that the gray patches stay gray, and about the same brightness, but the colors, especially reds, look dull and lifeless. The effect should be easy to see on almost any computer monitor.



Of course there are some great benefits of fluorescent lighting, including a lower energy consumption and less heat in the layout room. That said, it is almost impossible for today's fluorescent fixtures to reproduce the crisp shadows of real daylight that make details "pop."

Here is an old NMRA Heritage car illuminated by a tungsten spot light. Notice how the details pop.



And here is the same car illuminated by diffuse fluorescent Lowel Ego photographic lights.



I hope this proves helpful. All the best.

Bob

Still fixing typos :o
« Last Edit: December 30, 2009, 08:50:44 PM by riogrande491 »

DKS

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Re: Flourescent lighting == The Suck.
« Reply #16 on: December 30, 2009, 03:07:26 PM »
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Bob, that's excellent information; very useful. Thanks for the post--and welcome to Railwire, by the way! I think it would be most illuminating (sorry) if we could have an emission spectrum plot of each fluorescent lamp type, folks could see how the spikes change in peak wavelengths and intensity, which affects our perception of their illumination. As a side-note, white LEDs function via the same process as fluorescent lamps, namely fluorescence, or re-emission. It would therefore be extremely useful to have their spectra as well. (This is not a request, just an observation.)
"Life's a piece of sh!t when you look at it."
                                       —Monty Python

riogrande491

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Re: Flourescent lighting == The Suck.
« Reply #17 on: March 11, 2010, 09:38:04 PM »
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Don't give up on fluorescent lights quite yet, although giving up on the cheap import stuff could be a wise move. Lately I've been experimenting with several different 4 foot linear bulbs available through various sources, and one seems to be a potential candidate.

For reference, here is a photo of a Macbeth color checker made under a 50 watt, 12 volt MR16 halogen track light. The color rendering index (CRI) of this bulb approaches 100.



Here is the same scene, illuminated by a Philips T32F8/TL930 fluorescent bulb. This bulb has a rated CRI of 95 and a color temperature of 3000K. By the way, the camera white balance in Adobe Raw was set to precisely the same settings as in the previous photo. The exposure time was different.



When comparing these two, except for the shadows they should appear fairly similar. The halogen produces a realistic sunlight shadow but the fluorescent does not (which could cause some modelers, in a futile attempt to better simulate reality, to dry-brush fake looking highlights on models.)

Now for an acid test. I digitally cut out small squares from the halogen photo and overlaid them on corresponding squares of the fluorescent photo. Got that? The big picture was shot under the test fluorescent lamp, and the tiny cut from the halogen illuminated photo just above.

Now for the comparison. How obvious are the cutout pieces?



From my experience of doing industrial color for over 15 years, this is an excellent visual appearance match under affordable lights. The light from the halogen flood lamp was not as even as that from the long fluorescent lamp. Some, but not all of the patches that do not match in brightness can be attributed to that. Also note that the halogen appears slightly greener; hopefully field testing on a layout will not show an objectionable difference.

I have not yet photographed a mix of this fluorescent lamp with ordinary tungsten track light fixtures. Since ordinary tungsten filament bulbs (i.e. "real light bulbs") are yellower than a halogen, we would anticipate somewhat-directional tungsten light to be yellower than fluorescent fill light, just as the sun is yellower than sky fill light. If so, that could be very good, if the visual color shift was moderate. The shift between cool white fluorescent (4000K) and tungsten (about 2800K) is too extreme to be visually believable.

Also note that the normal fluorescent lamps available from the "home store" have a CRI of 74 to 85. They produce a color appearance far from the more natural look of colors under CRI 95 or greater. Color under a CRI 74-79 lamp appears to my eye quite "dead" and dull (and I seem to become a sort of "zombie undead" under all cheap but common fluorescent lights!)

I have yet to measure any spiral compact fluorescent (CFL) lamp that was anything but extremely poor junk. That is not to say that a good CFL does not yet exist, but it does not (perhaps yet) exist in my personal experience. Surprisingly, the brand name from major brands to cheap in-house brand, did not matter. For the ones I bought and measured, they were all the same poor color but sold at different price points. When I measured their emitted lights spectrum (SPD in color lingo), all bulbs I tried at a given color temperature might as well have come off the same low-cost production line.

What's the next step? Field testing. If the layout owner approves, we move forward. Otherwise, I have a lifetime supply of bulbs for my home metal shop!
« Last Edit: March 12, 2010, 07:48:26 PM by riogrande491 »

riogrande491

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Re: Flourescent lighting != The Suck.
« Reply #18 on: March 15, 2010, 07:14:38 PM »
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A slightly more detailed discussion, with the same photos, at:
http://www.aorailroad.com/phpBB3/viewtopic.php?f=3&t=133&p=659#p659

Hope at least one reader finds this helpful. Fluorescent lights don't always have to, ahem, well I don't want to say it. They can be a useful tool when lighting a layout, if selected and applied with care.

All the best.

Bob
« Last Edit: March 15, 2010, 07:17:38 PM by riogrande491 »

Ian MacMillan

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Re: Flourescent lighting == The Suck.
« Reply #19 on: March 15, 2010, 08:55:15 PM »
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Bob,

Thanks, this has been great! I'm currently usin Phillips Sunshine T12s with a CRI of 92
I WANNA SEE THE BOAT MOVIE!