Higher CRI = unannounced Colour Temperature shift w/Fluorescents?

TPA

Enlightened
Joined
Aug 26, 2005
Messages
333
Location
Florida
Hi all,

Is it normal to have a colour shift in output when you go with a higher CRI?



I ordered TCP's 3500K/85CRI equivalent (F-32T8/835) and was unpleasantly surprised -- it appears almost as a 4100K bulb when in a fixture with existing Philips or Sylvania 3500K / 735 bulbs. Is such a colour shift normal when going to a higher CRI? The TCP appears more green in light output whereas the Sylvanias next to it in the same fixture have a pleasant pinkish colour to them. I checked the case of TCPs, all of them gave off the same green light. For now they've been relegated to the stairwell. Can't use them in the office space as I'll have to re-lamp an office whenever a bulb goes out. Yes, it's THAT different in appearance.



Anyone else come across this? I'd like to figure out what happened before re-ordering bulbs. I was hoping for a higher CRI to improve light quality, but I'll say the heck with that if I'm going to get this much of a shift.
 

LEDninja

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02-04-2011 02:43 PM #2 purduephotog

Originally Posted by TPA
Hi all,
Is it normal to have a colour shift in output when you go with a higher CRI?

I ordered TCP's 3500K/85CRI equivalent (F-32T8/835) and was unpleasantly surprised -- it appears almost as a 4100K bulb when in a fixture with existing Philips or Sylvania 3500K / 735 bulbs. Is such a colour shift normal when going to a higher CRI? The TCP appears more green in light output whereas the Sylvanias next to it in the same fixture have a pleasant pinkish colour to them. I checked the case of TCPs, all of them gave off the same green light. For now they've been relegated to the stairwell. Can't use them in the office space as I'll have to re-lamp an office whenever a bulb goes out. Yes, it's THAT different in appearance.

Anyone else come across this? I'd like to figure out what happened before re-ordering bulbs. I was hoping for a higher CRI to improve light quality, but I'll say the heck with that if I'm going to get this much of a shift.
If you're mixing bulbs by different manufacturers and different lots... then yes, they'll all appear different. There's no guarantee the other bulbs are actually what they state, either.

If you have a 'real' DSLR you can manually set the color modes- shoot a neutral gray patch (home depot, silver screen BEHR paint swatch) and measure the color temp at a known pick (say, 6500K).

Good luck- swap them all out and you should be good.

(higher CRI = more complicated phosphor = more 'aging' different shifts)

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02-05-2011 10:06 AM #3 TPA

purduephotog If you're mixing bulbs by different manufacturers and different lots... then yes said:
Actually, around the office we have Sylvania & Philips bulbs living side by side with no noticeable difference. I do have 4100k bulbs in the one room (light fixtures were replaced at one time, bulbs came with them), but that's an expected colour shift there. The 3500K TCPs appear VERY close to the Sylvania 4100K bulbs.

If you have a 'real' DSLR you can manually set the color modes- shoot a neutral gray patch (home depot, silver screen BEHR paint swatch) and measure the color temp at a known pick (say, 6500K).
I did take DSLR pics of the bulbs in the fixture and the room and sent them to my supplier. It's quite obvious that there's a color difference between them, enough that non-CPF-types would complain. I didn't take calibrated pics though. Might try that if/when I get bored.

Good luck- swap them all out and you should be good.

(higher CRI = more complicated phosphor = more 'aging' different shifts)
Eh, I really don't care for the way the TCP 3500k's look nor their light output. Really lacking in the red range. Reminds me of nasty hospital lighting or fluorescents of old. What do you mean by "more aging different shifts"? Higher CRI will mean more of a color shift as the bulbs age? If so, for general office work, would I be better off sticking with the lower CRI bulbs? I'm definitely sticking with Sylvania/Philips after this though.

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02-05-2011 12:00 PM #4 blasterman

The TCP appears more green in light output whereas the Sylvanias next to it in the same fixture have a pleasant pinkish colour to them
TCP is pretty low end, and I've obeserved the same thing with TCP, Feit, etc. They use the cheapest phosphor sets imagineable and get their lumen count via green-yellow. If you goal is higher CRI and you aren't buying a lot of them I strongly suggest spending a bit more money and looking for 90 CRI and higher which tends to eliminate the junk Fl brands. Anybody can claim 80'ish CRI and color can be all over the place. 90 and higher though tends to be a more exclusive category.

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02-06-2011 01:14 AM #5 TPA

Oddly enough, I've had good luck with TCP's CFLs. I relamped the wall sconces in an office building from a hodge-podge of incandescent & department-store CFLs to TCP 3500K CFLs. Instant improvement. Looked like we repainted the hallways/lobby and had the carpet cleaned. Best couple of hundred dollars we've spent in awhile.

Well, that all depends how you define "aren't buying a lot of them". We just had the first bulb in the office die (~3 years since this section of the office was remodeled), so I'm expecting the rest of them to all start going soon. There's approx 230 bulbs on that side of the office. I'm not displeased with the current Sylvania/Philips bulbs, just was figuring higher CRI automatically meant better quality light.

Whatever I buy, I'll need to be able to get them in T8 4 footers, U-tubes, and 2 foot linears. I'd love to shoot the interior designer for spec'ing U-tube fluorescent fixtures ($9/bulb). Especially when the same fixture was available as 2 ft linears ($1.50/bulb).
 
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