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Thread: New GE CFLs at Target

  1. #31
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    Not much difference from the 10 w - but somehow it seems that there is more contrast/saturation on the 15w? - could be just the exposure on my digicam - but it is more pleasant - the 10w seemed grayish - but the 15w does seem more daylight-like.......
    Your assessment seems to match what others have said regarding high-CCT lighting. Basically, you need a lot of it in order for it to look pleasant. At lower light levels, the 6500K looks dreary bluish grey. But crank up the light levels and its looks much whiter and more "normal". That's just the Kruithof curve at work. So if you plan to only get by with a 10 watt CFL, then 3500K or 4100K might look better. But if you have the room much brighter, then 6500K can look pretty decent.

    It's amazing also how yellow incands and soft white CFLs look when you shoot them under daylight color balance. And yet our eyes can eventually adjust to them so they look relatively normal (still yellow but not distractingly so).

  2. #32

    Default Re: New GE CFLs at Target

    I just went through this the other night and did a better round of tests. After years of testing film and shooting my own calibration targets I'll give you guys some advice.

    1 - Ditch the MacBeth charts and use a box of Crayons instead. The Crayons have a much broader gamut / brightness/contrast range than MacBeth charts using more common commercial pigments, and have a translucency that looks a bit like human skin. MacBeth charts are about only good for calibrating TV's at an appliance store.

    2 - Unless your camera has a full manual settings, comparison tests are subject to skepticism because you don't know what color balance and post processing the camera is doing. Much better off shoting RAW and applying corrections with a RAW converter.

    I shot a bunch of CFLs the other night, and after nulling out CCT differences found there was no difference between daylight (5000-6000k) CFLs and 3500, so it's obvious the same phosphors are in play, just different levels of them. However, neutral white LEDs yielded a different color rendition than CFLs, especially with oranges.

    GE Chroma 50's used to be one of my favorite tubes, but were actually closer to 4200k than 5000. Even though Vitalights at the time and had better lumen efficiency specs, the Chroma 50 wasn't nearly as green and much easier to live under.
    Last edited by blasterman; 09-09-2009 at 02:43 PM.

  3. #33

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by blasterman View Post
    1 - Ditch the MacBeth charts and use a box of Crayons instead. The Crayons have a much broader gamut / brightness/contrast range than MacBeth charts using more common commercial pigments, and have a translucency that looks a bit like human skin. MacBeth charts are about only good for calibrating TV's at an appliance store.

    2 - Unless your camera has a full manual settings, comparison tests are subject to skepticism because you don't know what color balance and post processing the camera is doing. Much better off shoting RAW and applying corrections with a RAW converter.
    It seems you know pretty much what you are doing - so this is not in anyway negative comments about your methods.

    1) Unfortunately the Macbeth Color Rendering chart is the standard that photography is using. I don't disagree with you that by eye it is hard to judge how one light source of the same CCT is better than another - other than in very subtle ways - and that is open to subjective interpretation. But Macbeth is the standard - and in a way I quite like the "subjective" aspect - which reflects real-life since I don't think there is any "universal" agreement to how accurate/pleasant any artificial light source is - those are always open to "subjective" interpretation anyway.....

    The CRI (Color rendering index) chart is even less helpful, with its fewer and less intuitive colors -



    " Note that the CRI by itself does not indicate what the color temperature of the reference light source is; therefore, it is customary to also cite the correlated color temperature (CCT).
    According to (Schanda & Sandor 2005), CRI is being deprecated in favor of measures based on color appearance models, such as CIECAM02 and, for daylight simulators, the CIE Metamerism Index. (Guo & Houser 2004) and (CIE 1995) note that CRI is not a good indicator for use in visual assessment, especially for sources below 5000 K.
    A newer version of the CRI has been developed (R96a), but it has not replaced the better-known Ra (general color rendering index). "
    (my highlight in Red )

    Out of interest what do you recommend as the box of crayons to use?

    2) RAW processing probably begs even more questions - not many people have digicams with RAW - and not only that a lot of people including experienced photographers do not use RAW on a regular basis to have become well versed with RAW.

    RAW actually requires even more Post-Processing by the user which means it is even more open to question. There is no such thing as a standard template conversion from RAW to a viewable format like JPG. The "default" conversion by most manufacturers is conforming to the camera's settings - which by-and-large basically means it receives the same processing as an in-camera JPG - so the user is no better off than if the picture was taken with jpg to begin with.

    For illustrating color/tints the all important setting that anyone needs to know is basically the white balance. Auto White Balance (AWB) maybe useful for general photography - but it is not much good in illustrating colors from an artificial light source (other than perhaps trying to mimic the way our eyes "might" see).

    The most commonly (but not always) useful setting for most of us here is the fixed daylight/sun white balance (equivalent to daylight white balanced film) this helps illustrate how a light source may deviate from average daylight (between 5500-6500 degK).

    Color temperature or CCT seems to be more "important" than any CRI which is not very well understood - see quote above from the Wikipedia -
    " note that CRI is not a good indicator for use in visual assessment, especially for sources below 5000 K. "

  4. #34

    Default Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    In your opinion who makes the best linear T8 tubes? (just curious) I'm referring here to commodity tubes like 741s, 850s, etc, not high-CRI specialized tubes like the Paralites.
    PRobably:

    G-E
    OSI
    Ushio

    In that order. However, if you asked about T5s, I wouldn't have listed Ushio's. Their F54T5HO's are not quality lamps. I've had quite a few returned to premature failure. For T5HO's, I'd stick with G-E or OSI. WIth teh exception of CFL's, I will generally take G-E over anyone, but Sylvania is a close second.

    FOr CFLs, I'd take Greenlite, Litronic's, and a company called Overdrive. I'm starting to stock Green Energy LIghting (formerly PEC-Phoenix) and am a fan of those too. Not that I dont' like G-E and OSI, it's just for the price v. quality I like the above companies.

  5. #35

    Question Re: New GE CFLs at Target

    Any opinion on

    Eiko SP30/955K

    it's a 5500K 30watt CFL that claims CRI=93....
    (there's also a 50 watt version in E26 medium screw base)
    and is supposed be for specifically ColorMaster Digital Imaging

    specs -
    Volts 120
    Watts 30
    MOL in/mm 6.3/160
    MOD in/mm 2.76/70
    Avg Life 10000
    Bulb T-4
    Base Medium Screw (E26)
    CT deg K 5500
    Replaces Std 150W Incandescent
    CRI 93
    Approx Initial Lumens 1500

    Thanks,

  6. #36

    Thumbs up Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    Not much difference from the 10 w - but somehow it seems that there is more contrast/saturation on the 15w? - could be just the exposure on my digicam - but it is more pleasant - the 10w seemed grayish - but the 15w does seem more daylight-like.......
    GE Daylight 6500K 15w CFL specs
    Mixed lighting.

    I left one of the GE Daylight 6500K 15w CFL in the room where I took the test shots of my home printed Macbeth color chart - but in the other light socket I thought I'd try a GE Soft White 2700K 13w CFL (this is one that was bought about 2 years ago rated at 825 (initial) lumens).

    Although it's pretty obvious that one part of the room is warmer - the overall effect balance seems quite nice.

    Just out of interest I took a photo of my home printed Macbeth color chart to see what it looked like -
    the Daylight 6500K 15w CFL (900 lumens) was a measured 58" from the center of the chart - the Soft White 2700K 13w CFL (825 lumens) was to the right and 93".




    A crude approximation of the intensity of each bulb on the chart is a ratio of
    900/(58x58) 6500K to 825/(93x93) 2700K
    = about 73.7% 6500K to 26.3% 2700K
    - which averages out to be about 5500K?

    Again the photo shows no dramatic difference - perhaps the grays on the bottom row are more neutral without too much tint shift/bias - it's certainly less blue than the daylight balanced shot when two GE Daylight 6500K 15w CFL's were used - the balance may be closer to that of the AWB version of 2x 6500K -

    But I was surprised to see that the reds seemed no more vibrant than the 6500K only shots.

    But these really are only look-see comparisons.

    Overall having those two differing bulbs does seem to make the room look more pleasant and the area directly under the 6500K can be for "simulated" daylight examination
    - I think I'll keep that ad-hoc mixed configuration for now.

  7. #37

    Default Re: New GE CFLs at Target

    Out of interest what do you recommend as the box of crayons to use?
    Box of Crayola (any size) work fine

    RAW processing probably begs even more questions - not many people have digicams with RAW - and not only that a lot of people including experienced photographers do not use RAW on a regular basis to have become well versed with RAW.RAW actually requires even more Post-Processing by the user which means it is even more open to question. T
    Sorry, but you don't have good ceonceptual grasp of RAW processing, and shooting MacBeth charts with a digicam in 'Automode' just doesn't prove much because you have no idea what the camera is doing. With RAW you can at least remove color temp from the equation. Also, you're confusing post processing with color space conversion, and while sRGB doesn't have near enough gammut range to brag about, it gets more muddled up when digicam algorithms distort colors on the basis of trying make colors look good in JPEG.

    Granted you have to make use of the gear you have, the MacBeth chart is still a near useless reference target - unless you're mixing paint. MacBeth charts are used to determine *consistency* between illumination sources at very specific and narrow points. Were trying to approximate visual and perceptual *differences* between light sources, and the best way top do this is with a real world subject. A human subject is the best reference, but Crayons are a good stand in because wax approximates human skin tone very well.

    It's possible for instance for two different light sources to reproduce a MacBeth chart that looks pretty similiar, but our eyes under real world condition would tell us the lights are very different. It seems for this type of test you want to use subjects that best approximate what humans see and not how specific patches of color are rendered.

    Proof of this is the fact most of us think the color of cheap, daylight CFLs above 5000k is horrid at the least. The MacBeth chart simply doesn't have enough range to show this, yet the 'oldschool' marketing reps are using MacBeth charts as a reference and hence why these bulbs are shoved on the public. "Well, the MacBeth chargt says it's neutral, so your eyes must be broke". Confusion here is our eyes see more colors than a MacBeth chart.
    Last edited by blasterman; 09-10-2009 at 05:05 PM.

  8. #38

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by blasterman View Post
    Sorry, but you don't have good ceonceptual grasp of RAW processing
    ....interesting comment

    In the RAW processing software (I have Canon and Pentax) -
    there is color temperature adjustment -
    but that is setting the camera's balance for a particular color temperature
    - so to make a pic cooler one sets a lower color temp and to make the shot warmer one sets a higher color temp.....
    so unless one has an accurate color temperature meter -
    the light source color temp is not known and to get the pic to "look like daylight" -
    is a matter of trial and error -
    of course we can guesstimate the color temp
    such as 2700K for household incandescent and perhaps use whatever the CFL are spec'd at
    - but that in itself is a variable .....
    but my purpose is not necessarily trying to make the pic "look like daylight".

    Quote Originally Posted by blasterman View Post
    and shooting MacBeth charts with a digicam in 'Automode' just doesn't prove much because you have no idea what the camera is doing. With RAW you can at least remove color temp from the equation. Also, you're confusing post processing with color space conversion, and while sRGB doesn't have near enough gammut range to brag about, it gets more muddled up when digicam algorithms distort colors on the basis of trying make colors look good in JPEG.
    No not full auto mode but set white balance to Fixed Daylight white balance - this is akin to using daylight white balanced slidefilm - I don't think many experience or professional photographers specially ones who are experts in color reproduction say for the cloth industry can be critiqued for not understanding color slide processing - they just understand the light sources and the film stock used. Using Fixed Daylight White balance is liken to setting the color temperature in RAW processing to ~6000K.

    Perhaps we may be talking cross purposes the whole point of presenting pics with fixed daylight white balance (like shooting with daylight balanced slide-film) is merely to show how the illumination diverges from "daylight" - whereas if I understand what you are saying - removing color temperature from the equation - kind of defeats that, as all pics are then corrected for the light sources and all balanced and look like daylight pictures -
    and we already know for example regular incandescent light bulbs at about 2700K do not look like daylight.....
    Our eyes may see it that way - but that's not what I was trying to illustrate.

    I am not trying to use photos as any kind of quantitative measurement - but merely as an illustration of what a light source on a target looks like when compared to daylight - and RAW processing is not necessary to do that for me.

  9. #39
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    Default Re: New GE CFLs at Target

    Those reveal CFLs have just shown up at my local Wally World.

  10. #40

    Default Re: New GE CFLs at Target

    say for the cloth industry can be critiqued for not understanding color slide processing - they just understand the light sources and the film stock used
    Nah, they just insisted on using the dullest slide stock, like EPN or EPP The result was Kodak following suite and engineering their main films to be only being able to handle low gamut ranges correctly. I'm still arguing with film heads about that.


    Using Fixed Daylight White balance is liken to setting the color temperature in RAW processing to ~6000K.
    That's fine with me - provided the camera in use is indeed locked into a specific setting, aka manual. My main grips is that digicams do an extreme amount of post processing automatically, and then dump the results to a JPG file based on color saturation algorithms that housewives consider in marketing tests makes their 4yr old have the best skin tones. RAW insures this crap is turned off, and the point of reference is decided by the shooter, not a doctored color chart in Sony engineering labs.

    As long as the shots are taken at a fixed color temp, and you know it's fixed along with color enhancements turned off, then it's a fair shoot in my book.

    Classic case of this are Fuji Digicams which are stroked to provide pleasing skin tones. DPreview shows all these little nuances with Macbeth charts as references. RAW is frequently the only way to insure totally neutrality because many digicams insist on cheating to provide the best skin tones with no user intervention.

    As a side note, if you want to try an interesting experiment, shoot the Macbeth chart under open sunlight outdoors. Then, use this as a reference for CFL and LED tests. This eliminates any camera or processing variables because the grey patch on the Macbeth at a daylight setting should register darn close to grey. Using this as a reference shows CRI limits with artificial sources especially.

    Using that 'sunshine' reference shows how goofy the color rendition of CFLs actually are.

  11. #41

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by blasterman View Post
    As a side note, if you want to try an interesting experiment, shoot the Macbeth chart under open sunlight outdoors. Then, use this as a reference for CFL and LED tests. This eliminates any camera or processing variables because the grey patch on the Macbeth at a daylight setting should register darn close to grey. Using this as a reference shows CRI limits with artificial sources especially.

    Using that 'sunshine' reference shows how goofy the color rendition of CFLs actually are.
    Thanks for that input.

    This is exactly what I've done the Macbeth shot marked "Daylight Control" -this was taken under open sunlight - on a clear bright sunny day sometime early afternoon. That's what I use as a reference - and it was indeed the gray patches that were the most revealing please see post #23 (also comparison with 15w in post #30)

    As I said all I am attempting to do is to show any large visible shifts - deviation from real daylight (which itself is variable) Fixed daylight white balance seems adequate for the illustration purposes.

    The shots I did with the GE Daylight 6500K CFL - does show the shifts are barely noticeable with the photos taken with Fixed daylight white balance - but the eyes do detect more - from unacceptable with the 10watt version to "quite nice" for the 15watt version - but I think this has more to do with my eyes conforming to the Kruithof curve.

    But to be honest, for my tolerance, the 10watt would have been OK if I used it strictly as a task lamp just for examining under simulated "daylight" - but because of this interesting thread I wanted to see how they look lighting up a room - and for that I guess it dropped below my threshold of acceptability - whereas the 15w managed to get just above.

  12. #42

    Arrow Re: New GE CFLs at Target

    Just saw the GE Reveal CFL's at my local WalMart - in packs of two at $10.

    GE have listed Reveal CFL on their website

    I am a little surprised that the spec says:
    Color Temperature 2500 K

    Can that be right?

    That's warmer than the typical incandescent and the Soft White CFL which are 2700K.

    I checked the color temp is the same 2500K for the specs of all the Reveal CFL's

    Also I was surprised to see the CRI=70 for these Reveal CFL -
    whereas the normal Soft White and Daylight CFL have CRI=82.

    What's going on?

  13. #43
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    Just saw the GE Reveal CFL's at my local WalMart - in packs of two at $10.

    GE have listed Reveal CFL on their website

    I am a little surprised that the spec says:
    Color Temperature 2500 K

    Can that be right?

    That's warmer than the typical incandescent and the Soft White CFL which are 2700K.

    I checked the color temp is the same 2500K for the specs of all the Reveal CFL's

    Also I was surprised to see the CRI=70 for these Reveal CFL -
    whereas the normal Soft White and Daylight CFL have CRI=82.

    What's going on?
    That 2500k rating has to be a typo. I'm guessing one of their marketing/packaging guys looked at it, thought "oh, it's a CFL therefore it's warm white" without paying attention to the whole Reveal slanted-towards-blue thing. I expect that they'll either correct this in subsequent packaging or produce stickers to cover up the incorrect rating on the existing packages. Or send the store employees around with magic markers.

  14. #44

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by PhotonWrangler View Post
    That 2500k rating has to be a typo. I'm guessing one of their marketing/packaging guys looked at it, thought "oh, it's a CFL therefore it's warm white" without paying attention to the whole Reveal slanted-towards-blue thing.
    That's what I suspected as well - but the color temperature for the Reveal range (even the incandescent) has been a mystery -
    it's ironic that when GE finally "reveal" its color temperature -
    they got it so obviously wrong......

    If I were guessing the color temp was probably meant to be 3500K -
    but that is only pure speculation.

    The other thing about "Reveal" was how well colors are supposed to be seen - so I was doubly surprised at the low CRI = 70
    when even their lowly Soft White and Daylight CFLs manage CRI = 82
    (which was nothing to write home about to begin with) -
    so are the Reveal CFL's really that poor with CRI ?
    A CRI=70 looks almost like white LED ratings.

  15. #45
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    The other thing about "Reveal" was how well colors are supposed to be seen - so I was doubly surprised at the low CRI = 70
    when even their lowly Soft White and Daylight CFLs manage CRI = 82
    (which was nothing to write home about to begin with) -
    so are the Reveal CFL's really that poor with CRI ?
    A CRI=70 looks almost like white LED ratings.
    According to this, the incandescent version of the Reveal has a CRI of 92-93. However, independent testing here (go to page 5) gives a CRI of 78 and a CCT of 2789K. But as we already know, CRI isn't a great measure of how color quality is perceived. FSI is among the proposed metrics which are superior. Despite the differences in CRI, the Reveal has an FSI of 5.6, compared to 5.3 for a standard incandescent (0 on the FSI scale is considered ideal, and large numbers mean poorer light sources), so it is only slightly worse. And on other measures such as the color quality scale (CQS), the Reveal may actually do better than a standard incandescent. Bottom line is that it's impossible to use CRI as the sole measure of light quality. CRI is simply a comparison to a blackbody at the same CCT. Obviously if the blackbody has a very low or high CCT then colors will be rendered poorly regardless of the high CRI. Measures like FSI, GA (gamut area), or CQS also take CCT into account.

  16. #46

    Question Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    According to this, the incandescent version of the Reveal has a CRI of 92-93. However, independent testing here (go to page 5) gives a CRI of 78 and a CCT of 2789K.
    Many thanks for the input and interesting links.

    The first link you gave - interesting as it was,
    unfortunately appears to have a pretty bad error -
    Quote: " The Reveal© bulbs produce CRIs in the neighborhood of 92-93, considerably better than ordinary incandescent bulbs' CRI of 80-85. "

    My understanding is that an incandescent bulb has CRI=100 - by definition.
    Surely their knowledge has to be better than my meager understanding?

    This is confirmed in your second link where they give -
    Incandescent
    60-100W A-lamp (CCT=)2800 (CRI=)100
    60W GE Reveal A-lamp (CCT=)2789 (CRI=)78

    still on that second reference (and what you quoted)
    CCT for Reveal incandescent seems to = 2789K
    - that's 11degK lower than their given CCT(=2800K) for an incandescent....
    this just seems intuitively wrong
    since Reveal is supposed to have significantly higher blue spectral content....

    So is there an explanation for these seeming contradictions?

  17. #47
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    still on that second reference (and what you quoted)
    CCT for Reveal incandescent seems to = 2789K
    - that's 11degK lower than their given CCT(=2800K) for an incandescent....
    this just seems intuitively wrong
    since Reveal is supposed to have significantly higher blue spectral content....

    So is there an explanation for these seeming contradictions?
    I'll guess (and I might be wrong) that the explanation has to do with the way CCT is calculated. Due to the coating, the Reveal bulb probably falls somewhat off the Planckian locus (i.e. the line in x,y color space corresponding to a black body). Nevertheless, as can be seen by looking at this diagram, a light source can have a CCT of 2789, and yet end up appearing very blue (or yellow) depending upon how far off the Planckian locus it is, and in which direction. In fact, I'd say this is likely the case with Reveal bulbs. By filtering out some yellow (but not necessarily a corresponding amount of red), you could end up with a much less yellow light source, and still not change the CCT by much.

    And yes, I was quite surprised by this info on the Reveal myself. Not necessarily by the CRI, but to my eye the CCT appears to be similar to that of a blackbody in the mid 3000s, not 2789K.

  18. #48

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    I'll guess (and I might be wrong) that the explanation has to do with the way CCT is calculated. Due to the coating, the Reveal bulb probably falls somewhat off the Planckian locus (i.e. the line in x,y color space corresponding to a black body). Nevertheless, as can be seen by looking at this diagram, a light source can have a CCT of 2789, and yet end up appearing very blue (or yellow) depending upon how far off the Planckian locus it is, and in which direction.
    That is a really good and reasonable sounding explanation -

    I looked at the typical colored version of the
    Planckian locus diagram (Wikipedia)
    Here's a crop from that to focus on the locus/line:

    it was hard for me to see that a position that tends toward blue that still would not have a higher CCT than one that was yellower ...

    However using your suggestion of less filtering of red (ie: more red) -
    should put the Reveal on the lower side of the locus
    since the parts below the locus tend toward red.....
    and those color temp lines (Tc) do slant toward blue
    extending a Tc line for about 2800K -

    maybe a position way off the locus of approx x=0.425, y=0.3 could have more blue than a light on or above the locus and still have approx the same CCT?

    EDIT to Add -

    Just saw this different representation of the Planckian locus (by CIE)

    this seems to make it easier to see a light with more blue but off the locus/line could have the same CCT?

    In fact looking at both diagrams since extrapolating those Tc lines which tend to converge -
    ultimately wouldn't it get to an area off the locus where tiny shifts could result in big differences in CCT/Tc?

  19. #49
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    maybe a position way off the locus of approx x=0.425, y=0.3 could have more blue than a light on or above the locus and still have approx the same CCT?
    Definitely. Those colors on the chart seem a little off compared to what our eyes might see. For example, 4000K appears more or less neutral to most people, and yet it's colored orange in the chart. Looking at the colors in that chart, the mid to high 3000s look orange, and so does a point roughly at x=0.425, y=0.3, except maybe it might have a bit more hint of purple/blue than a blackbody in the mid to high 3000s. And it makes sense the Reveal would fall there with the purple coating.

    Now if anyone who can measure x,y coordinates would do so on a Reveal, it would be very illuminating (pun intended) to the discussion at hand.

    In fact looking at both diagrams since extrapolating those Tc lines which tend to converge -
    ultimately wouldn't it get to an area off the locus where tiny shifts could result in big differences in CCT/Tc?
    Yes, and that's why I believe that light sources lying more than a certain distance off the Planckian locus generally aren't assigned a corresponding CCT. A good example of this are colored LEDs. The Reveal is probably one of those borderline cases where the CCT can be calculated, but at the same time it really doesn't correspond very well with how the light source appears visually.
    Last edited by jtr1962; 10-14-2009 at 03:27 PM.

  20. #50

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    Definitely. Those colors on the chart seem a little off compared to what our eyes might see. For example, 4000K appears more or less neutral to most people, and yet it's colored orange in the chart.
    Thank you again.

    Please take a look at my post above's "Edit to Add" there's another representation that seemed to make it easier for me to see - I haven't figured if the U/V axes bear any relationship with the typical X/Y axes.

    As for your comment about appearance of 4000K as neutral that probably has more to do with the way we see and the Kruithof curve.

    The colors on the typical Planckian locus diagrams are probably what the colors really are (eg: like taking a photo using Fixed daylight white balance, like comparing to daylight?)

    Just another thought occurred to me - if the Reveals are way off the locus -
    would that not go some way to explain why they have such lower CRI?

  21. #51
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    Please take a look at my post above's "Edit to Add" there's another representation that seemed to make it easier for me to see - I haven't figured if the U/V axes bear any relationship with the typical X/Y axes.
    Actually I commented on that in my last post. The new diagram does make it much easier to see how the CCT lines converge.

    As for your comment about appearance of 4000K as neutral that probably has more to do with the way we see and the Kruithof curve.

    The colors on the typical Planckian locus diagrams are probably what the colors really are (eg: like taking a photo using Fixed daylight white balance, like comparing to daylight?)
    I agree with both points. I'll also point out that unfortunately the gamut of colors which can be displayed by a typical computer monitor probably result in a lot of colors in that diagram looking very similar even though they might appear differently with a different type of display medium such as a printed page. For example, to my eye there is a marked difference between 3000K and 3500K, and yet on my monitor in the color CIE diagram the colors appear practically the same (3000K only has a hint more orange).

    Just another thought occurred to me - if the Reveals are way off the locus -
    would that not go some way to explain why they have such lower CRI?
    Yes, by definition any light source not falling on the Planckian locus will have a CRI less than 100. How much less depends upon the spectrum of course. And interestingly, falling exactly on the PL isn't a guarantee of having a CRI of 100 either. Look at our white LEDs, for example. Or better yet, you can take a yellow and Tokyo blue (~490 nm) LED, combine them to make a perfect white, and have a CRI in the single digits, practically like looking at a monochrome photograph.

    But in any case, the new diagram illustrates my point quite well. Good find, and also very interesting discussion!

  22. #52

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    and also very interesting discussion!
    Yes, ditto - thanks to you - made me look into this in more detail.

    That's the problem these days of skimming information and putting so much reliance on numbers.

    I had long doubted the validity of CRI with the way we see.
    Please see long debate in -
    Puny LED flashlights (Not!) + COLOR RENDITION Comparison

    Now I find even Color Temperature CCT may be misleading.

    I think may be some of these figures/numbers are valid within certain bounds -
    but get to, or beyond those boundaries
    and they may have no useful bearing on real-life usage.

    CRI is a very typical case in point -
    incandescent light bulbs have CRI=100 by definition -
    and yet most of us know that it is far from a perfect/ideal light source
    (but of course it is, when the benchmark is itself!).
    But if it is made clear that CRI is related to CCT, and one CRI can only be compared to another with the same CCT - then it starts to be of some value.....

    Of course we now also know that CCT/color temperature is not such an absolute either....

  23. #53
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    Default Re: New GE CFLs at Target

    Quote Originally Posted by UnknownVT View Post
    I had long doubted the validity of CRI with the way we see.
    Please see long debate in -
    Puny LED flashlights (Not!) + COLOR RENDITION Comparison
    I finally managed to read through that entire thread. Very interesting and I agree with almost all of it. One thing nobody mentioned regarding viewing things in sunlight is fluorescence. The amount of UV in sunlight may cause certain objects to fluoresce, and thus appear differently that they would even if exposed to light whose spectrum is identical to sunlight in the visible region, but lacking UV.

    What I'm taking away from this discussion (and the other one) at this point is that CCT is only meaningful if your light source is fairly close to the Planckian locus. CRI on the other hand seems to have little correlation with how useful or pleasing a light source is for most tasks. Obviously it's very useful if your task involves critical color matching, but then CCT also becomes important as different CCTs have different gamuts. However, if the goal is simply to have pleasant lighting, or better seeing, then high CRI or "full spectrum" doesn't necessarily mean better. Case in point is the improved seeing many experience with amber-tinted sunglasses. Another case in point are certain combinations of RGB LEDs. CRI in some cases is very low (in the 20s), and yet many subjects prefer these RGB LEDs to either broadband or typical fluorescent sources. There's still a lot we need to learn about how people see things.

  24. #54

    Arrow Re: New GE CFLs at Target

    Quote Originally Posted by jtr1962 View Post
    I finally managed to read through that entire thread. Very interesting and I agree with almost all of it. One thing nobody mentioned regarding viewing things in sunlight is fluorescence. The amount of UV in sunlight may cause certain objects to fluoresce, and thus appear differently that they would even if exposed to light whose spectrum is identical to sunlight in the visible region, but lacking UV.
    There is a whole area of color metamerism of trying to match colors under different light sources -
    see also What is metamerism?

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