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Thread: High CRI and its significance

  1. #61
    Flashaholic* yaesumofo's Avatar
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    Default Re: High CRI and its significance

    I have seen in some LED Light panels designed for video and film production the addition of AMBER leds mixed with the white emitters used on the panels. They are able to tune the panel to work best as a daylight source by adjusting the amount of amber light mixed in with the other emitters. I do not know how much latitude this gives them. There is no doubt that it is very possible to make a human being look terrible (on film and tv) and in person based simply on how you light them.
    I find it interesting how different all of this becomes when transitioning from standard daylight based lighting to "digital" lighting using leds as the primary light source. One thing which is almost universally true in making this transition is that Led's do not have anywhere near the same OOOMPH as HMI's or tungsten lighting.

    I tend to look at this from this perspective because this is where I see the technology being implemented ....slowly..
    More and more interior lighting will be based on Leds. IMHO it is important that when people are lit in this way they do infact look natural and good. I am sure this is the goal of the manufactures of the emitters and the fixtures for LED interior lighting projects.
    Yaesumofo



    Quote Originally Posted by 2xTrinity View Post
    This is why. Those probes are designed many years before they're actually built an launched, so most of the computer equipment etc. is already obsolete compared to the general market. In the case of LEDs, there's been a huge explosion in the efficiency and output of white LEDs between the time when that probe was likely designed, and now.


    This is just as true for a camera as it is for the human eye, as like the eye, the camera detects color as a combination of three primary colors, using color filters over separate black-and-white CCDs to create the different color responses.

    So that's why RGB and black body white will appear the same when looked at head on (such as looking at a computer monitor) however, the color of an object is determined by the reflectiveness of the object at different frequencies. This means for accurate results, a light source similar to our sun (continuous spectrum) must be used. Differences in color temp can be corrected for easily with whit ebalance, but voids in the spectrum cannot.

    Imagine for example an RGB scheme using 630nm (red), 530nm (green) and 430nm (blue) sources, with narrow spectral line width. Then imagine that there is an object that strictly reflects light at around 590nm. Under a continuous white light, it will appear yellow. Under the hypothetical RGB light I described, it will appear black.

    In this case it actually DOES improve CRI. There is a red deficiency in the white LEDs compared to an ideal sure (the CRI9 is -10)

    Only a tiny amount of red light is actually needed to correct the CRI, and doing this doesn't really change the apparent color temperature much. This is the way I use red mixed with white, in very small ratios. Beyond that point though, you'd be right, the purpose of your red LED would no longer be to correct a deficiency, but to "warmify" the output for aesthetics.


    Bad example. The CRI of a fluorescent light is usually around 80. The CRI of a candle is 100 by definition, as it is black body radiation.

    You are right though in many cases, accurate color reproduction is actually not preferred for aesthetic reasons, for much the same reason as many people prefer EQ settings on music that boost bass or treble, rather than a "flat" EQ.


    The sun which is by far the most significant light source is a black body radiator, and the effect of Rayleigh scattering where different amounts of blue light are filtered away at different latitudes and time of day behaves is similar to changing the color temperature. There are no natural light sources that produce light outside of the black body line (ie, the sun or moon never appear purple or green)

    Also, for the sake of computing CRI, true black body spectrum is only used up to 3700k (melting point of tungsten), above that, real world daylight samples at different times of day are used as test sources, then assigned the number of the theoretical black body temp that would appear to be the same color.
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  2. #62
    Flashaholic* Stillphoto's Avatar
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    Default Re: High CRI and its significance

    Well put Mofo.

    It's taken a few years to get even the 5mm based panels to become regularly used tools in the industry.
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  3. #63
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    Default Re: High CRI and its significance

    I'm coming in quite late to this thread,and this is off topic,but I think this needs to be said.One statement stood out to me more than all of the other information contained here:
    Quote Originally Posted by McGizmo View Post
    .....in the spirit of moving the "art" forward as quickly as our community can.
    That statement speaks volumes about your character,and I for one would like to say it is much appreciated.

    I have been puzzled at times with some posters unwillingness to disclose information that would be beneficial to the CPF community,that type attitude is strange to me considering the posters probably learned much from CPF and yet were unwilling to give back in return.

    The fact that this is a form of revenue to you and not just a hobby only makes the stament more profound.

    Thanks again,
    Michael

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    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    Thanks TexLite.

    It is interesting to consider that "competition is good" has a down side to it that is often not considered. Cooperation is not in keeping with heavy or aggressive competition and the "Art" is often retarded as a result. Consider these high CRI Nichia's for instance. I suspect the key is in the phosphor itself. Imagine if Cree or Seoul could easily get some of this phosphor from Nichia and cover an EZ1000 chip with it.

    It will be interesting to see what the take is on the SunDrops that are now getting out there.
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  5. #65
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    Default Re: High CRI and its significance

    Quote Originally Posted by McGizmo View Post
    Thanks TexLite.

    Consider these high CRI Nichia's for instance. I suspect the key is in the phosphor itself. Imagine if Cree or Seoul could easily get some of this phosphor from Nichia and cover an EZ1000 chip with it.
    Hmm, as far as I know SSC are already using High CRI phosphor technology on some of their P4 and P7 LEDs (for valid customers).
    http://www.optoga.se/file.jsp?id=000...0uv&lang=en_US

    http://www.optoga.se/general_newsdet...000000000000ut

    FYI, Optoga is the agent for SSC in Scandinavia so I am pretty sure that they are using SSC LEDs and not Nichia LEDs.
    Opto-King

  6. #66
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    Default Re: High CRI and its significance

    Sorry I have come so late to this thread. I did begin reading it a week ago, but my life has been a bit crazy and busy lately and I couldn't give this thread the full attention it deserved. Even now, I must admit that I didn't fully read ALL posts, so please accept my apology in advance if I say something that has been said already. However, I did fully read most posts, and I do want to emphasize a few points, which Don has already made.

    The main problem that grips us here is that CCT is defined based on black body curves. Corelated Color Temperature means that temperature of a theoretical true black body radiator which most closely approximates the curve or color rendering of the source in question. You correlate the source being tested to a plankian black body with a temperature "T" measured in Kelvin.

    As for Color Rendering Index, I honestly have no idea what algorhthms are used to come up with that number. As Don's high-80's CRIa measured for the Sun clearly shows, you shouldn't put your faith in a number, especially for something that breaks the mold, as it were.

    Quite simply, LED's don't "fit" with the incandescent scheme. And it's easy to forget that, and to talk about the CCT of an LED source as if that were somehow something stable, something secure, which you can grab onto. Yes, you can grab onto it like a handle, but, as Don points out, it's a handle which will break off if you put too much weight on it.

    The real test is the human eye--YOUR human eye--and the actual tasks you put your light to, and the real life performance that results from the interaction of your eye, your lighting task, and the light you bring to bear on it.

    For a long time now I have had a problem with the "scientific" attitude or myth, that is frequently dominant here on CPF in threads. It's an almost unexamined faith in instruments and numbers and scientific results. Set the camera up at the same shutter speed and same exposure and take a bunch of beam shots and because you have objectively and scientifically set things up, your results are somehow more valid than other ones. But, clearly, such beamshots fail to really capture what your eye really sees.

    In the same way, (as has already been mentioned) two sources with similar numbers could perform very differently in real life.

    The most important point in my mind is this:

    The "tint" of the light on a white wall IS NOT the same as its color rendering ability, nor a direct measure of how well it will perform for you for any given task (besides white wall hunting).

    Don,

    I'd love to see the Golden Dragon LED put into the mix here, if you have the time and inclination to do so. As I've mentioned elsewhere, despite the blue tint (or maybe because of it???) of the light on a white wall, relative to other LED's I own, it is actually the best color rendering LED I own. I never would have guessed this from the white wall test. In fact, I would have suspected the opposite. I never expected the GD to perform so well in so many applications. I even like it outdoors, although I still prefer an overdriven incan for outdoors use. But still . . . quite a good performer, that Golden Dragon, despite its white wall "statistics".
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  7. #67
    Flashaholic* BigHonu's Avatar
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    Default Re: High CRI and its significance

    Good post js.

  8. #68
    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    _js_,

    I was hoping you would weigh in here. Thanks!! I think you hit on a real significant problem or bone of contention I have, and that is the scientific aspect practiced here by many of us. I joke to friends that I engage in trailer park science with equipment I have. It's one of the reasons I am not interested in posting spectrum after spectrum or providing flux readings I gather with my equipment. I am comfortable making some relative comparisons using the equipment I have but beyond that, I have no certainty that a number I come up with is close enough to reality.

    Some of you may have followed the group of LED lights that were passed around for folks to measure with their light meters. This group of lights was first measured by a real lab. I don't recall the details or which light it was but in one case, Peter G told me that the lab was not comfortable giving out a measure without doing some calibration work on their equipment and I think it took a couple days!!! These guys are experts and they certify other's equipment!

    I recall PK telling me a couple years back about the new integrating sphere that SF purchased as they were getting into the LED side. This sphere had some incredible number of sensors within and I believe many were band specific VS full spectrum in nature. Prior to this, SF was involved in hotwire and they only had to analyze light sources which behaved in line and were confined to the plank curve.

    The LED is a new animal and defining it by the rules and measures as established by hot wires will ultimately fail.

    The only certainty I have gained so far is that the ability to render colors of different wave lengths is not a given or the same from source to source. The CRI system addresses this problem as it relates to hot wire and suggests a means of partially quantifying and qualifying a LED but only to some extent. Many have come to equate warm to high CRI and this basis is from hot wire and possibly falsely supported by the consideration that the yellow peak in LED's lends to better red rendition and may then imply better color rendition elsewhere which may or may not be the case.

    It makes sense to me that any new standards be based on sunlight and not an artificial source. I personally prefer the higher color temps and cool white. It may be that my old and tired eyes are already yellow enough! I find it promising that it is possible to have a light source that is 6000k and yet also capable of sun like, color rendering.

    Off the wall a bit but I bet there is some way to come up with a printed color card or chart that has a number of colors on it that are quite tight and band specific in their reflective emissions. With such a card, one could illuminate it with a light source and see which bands returned some color and which were relatively dark. The tint we see on a white wall is the sum total of all bands present as well as absent within the source and it doesn't really tell us shit about the actual spectrum of light being totaled. Such a test card could be designed to address typical band specific strengths as well as weakness found in our light sources. In other words, I would guess there would be particular points of nm interest.

    Taking this color test card even further, if the bands selected to be present could be weighted in intensity by say the spectrum of the sun on a relative measure then it might be possible to take a photo of the illuminated color card using a sunlight balance in the camera and then convert the image to gray scale. In my mind, you come up with a color card that photographed as illuminated by the sun and then converted to gray scale gives you an even band of gray across all colors. Some of you into photography might be following me here? Kind of a color mapped to gray scale zone system?!?

    If such a test card were possible or produced, it would also allow many of us to communicate on the same page and in looking at these cards with our own eyes, we might even learn how our eyes perceive relative to others?

    OK, I guess I left the reservation there!
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    *Flashaholic* precisionworks's Avatar
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    Default Re: High CRI and its significance

    ... some way to come up with a printed color card or chart that has a number of colors on it that are quite tight and band specific in their reflective emissions
    I'm not sure that Pantone color cards are wavelength specific, but Pantone probably makes a greater selection of color matching items than any other manufacturer.

    Go to pantone dot com, click on products, click on color control, and look at the Color Checker. Pantone says that all the color squares reflect light the same way in all parts of the visible spectrum. Might be a place to start. For under $100, it could be a useful tool.
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  10. #70
    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    Thanks for the tip! I ordered one and it will be interesting to see how it behaves under various lights. I will also see if I can get some spectrums of some of the chips reflecting sunlight.
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    *Flashaholic* precisionworks's Avatar
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    Default Re: High CRI and its significance

    Neat, I'm eager to see your results

    My employer makes products that have multi-color labels, and those go into cartons that have a logo that matches the primary label color. It's always a challenge to narrow the choice down to a dozen 'close' colors, pick the best one (which are most often printed on glossy white stock), and then try to match that color on carton stock (brown Kraft material).
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  12. #72
    Moderator js's Avatar
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    Default Re: High CRI and its significance

    Don,

    That's a great idea there, about the color strip and converting to grey scale.

    The problem that may arise is that the eye can be fooled--it isn't a spectrum analyzer. Combine a couple of wavelengths and you can fool the eye into interpreting the result as a color at a wavelength that is not present. So a green card, for example, could actually only be blue and yellow together. I know I read that sodium arc lights were one of the only spectrally pure sources of yellow light that most of us ever encounter in daily life. That was in my first year physics book, if I remember correctly. Also, I need to re-read Feynman's discussion of the eye and color vision in The Feynman Lectures on Physics (incredibly good stuff there, BTW). I'll be back after reading that and will post about it. I suspect Don already knows everything I will read there, but we'll see.

    Anyway, the point is that the color strip would have to be chosen with true spectral characteristics in mind, and not just what is perceived by the eye, which looses information in the process of seeing color. I think I'm not too far off in putting it like that

    As for the pantone comment about "all the color squares reflect light the same way in all parts of the visible spectrum" I'm wondering if they don't mean like glossy, matte, semi-gloss, vibrancy, and etc.??? I haven't checked out there web site yet, though. Maybe the context makes it clear.

    Finally, I remembered something my jewler said. LOL! "My" jewler. I should say "The jewler who made my wife's engagement ring". Anyway, he was talking about saphires and he said that he would only buy saphires under a fluorescent light, and NEVER under an incandescent light. He said you could tell so much more about the quality and type and characteristics of a saphire when viewing it under a fluorescent light source. Just thought some might find that interesting. I suspect that the saphire, being sort of monocromatic, benefits from the fluorescent's shorter wavelength spectral output. And if so, LED's might be great for viewing saphires (and maybe other gemstones as well?).
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  13. #73
    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    _js_,

    I understand your concerns and that is what I meant by narrow and band specific colors if I can use those terms. We don't want an orange sample that is a result of reflecting red and yellow but one that is a very specific band of orange only, being reflected. If the orange sample sends back orange light to the viewer it is because orange light is present in the source.

    I believe you can get pass filters that allow a very narrow ban of light to pass through. One could use a set of these in front of a light source and compare relative lux measurements of the power getting out in the various wave lengths to assist in getting a feel for the sources' spectral composition.

    Heck, the spectrometer is not a bad way of getting a spectrum.
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    Flashaholic* yaesumofo's Avatar
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    Default Re: High CRI and its significance

    Don have you measured the color temperature of the Sundrop or more specifically the High CRI 083?
    I did with my DP's color meter and it came out at 4150K.
    Does that sound right to you?
    I have noticed that while I use the sundrop (I know this is not a thread about the sundrop but it is my only knows Ch CRI flashlight)
    that like other flashlights the warmth of the light sort of fades and becomes normal. My gets used to it rather quick. At this point if I bring out another light with a "cool" emitter the difference becomes extremely obvious.
    I like how the eye "normalizes".
    LED emitters are at their WORST when they are compared to each other and are at their best when all alone IMHO.

    Thanks.
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    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    Yaesumofo,
    In post #12, I provided data from my spectrometer on one of these LED samples. The CCT was measured at 4308k. I have no idea of the accuracy here.

    I agree the the eye can readily adapt to the initial tint or hue of a single source light and you become blind to it quickly. The brain calibrates or normalizes and then moves on to more pressing matters.
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    Default Re: High CRI and its significance

    Don,

    Ah! Yes, of course that's what you meant and those were fine terms. Me just slow on uptake. Sorry.
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  17. #77
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    Default Re: High CRI and its significance

    Quote Originally Posted by McGizmo View Post
    Many have come to equate warm to high CRI and this basis is from hot wire and possibly falsely supported by the consideration that the yellow peak in LED's lends to better red rendition and may then imply better color rendition elsewhere which may or may not be the case.

    It makes sense to me that any new standards be based on sunlight and not an artificial source. I personally prefer the higher color temps and cool white. It may be that my old and tired eyes are already yellow enough! I find it promising that it is possible to have a light source that is 6000k and yet also capable of sun like, color rendering.
    It's been possible to do this with fluorescent lights so I don't see why not with LEDs. In fact, LEDs will lend themselves to the job better I think. Even high CRI fluorescents tend to have somewhat spiky spectrums which might make some objects reflecting a narrow band of wavelengths render poorly (same problem might occur with RGB-based LED sources). Phosphor-based LEDs, on the other hand, including the non-high CRI ones, have a pretty full spectrum but are mainly missing the longer wavelengths (there is also a valley around 500 nm but it's not a complete gap in the spectrum). Anyway, as we've seen already by your spectrometer results plus others I've seen, the current crop of cool-white phosphor-based LEDs manages CRI in the high 70s, perhaps even low 80s for the warmer bins approaching 5000K. This isn't bad. It's not super high CRI, but it's plenty acceptable for the majority of lighting situations. Add a small percentage of red emitters, my guess is the CRI goes into the high 80s at least , good for nearly all but the most critical lighting needs. If you want to also fill in the valley around 500 nm with a Tokyo blue LED I bet you can get CRI well into the 90s (and the blue LED will offset the reduction in CCT from the addition of the red LED). Like you, I hope development focuses on high CRI not just for warmer but also cooler color temps. I would personally find the ~4200K of the particular bin of 083s you ordered acceptable for generally lighting but would probably not like anything much warmer. 5000K-5500K would be ideal of course for my preferences.

    Off the wall a bit but I bet there is some way to come up with a printed color card or chart that has a number of colors on it that are quite tight and band specific in their reflective emissions.
    I can't say whether or not such a card exists but I know of an easy way to test one. Simply shine colored LEDs of various center spectrums from 660 nm deep red all the way through 450 nm royal blue and note how much light is returned. If an apparently yellow object reflects red and green light in addition to amber, then you know it's not a good candidate to test for absence of amber in your spectrum.

  18. #78
    Flashaholic* Stillphoto's Avatar
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    Default Re: High CRI and its significance

    The Gretag Macbeth color checker is pretty much the standard when it comes to color in the photo/video world.

    http://usa.gretagmacbethstore.com/in...ItemID/411.htm

    The materials are prepared to a specific reflectance. When handled you have to keep your hands off the colored squares because you guessed it, brushing your finger against the surface could not only soil it, but also slightly buff the surface, changing reflectivity.


    Also just realized you probably pick up a card of known reflectance from edmund scientific...who also sells the color checker.
    Last edited by Stillphoto; 06-13-2008 at 08:00 PM. Reason: extra comment
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    Default Re: High CRI and its significance

    Quote Originally Posted by Stillphoto View Post
    The Gretag Macbeth color checker is pretty much the standard when it comes to color in the photo/video world.

    http://usa.gretagmacbethstore.com/in...ItemID/411.htm

    The materials are prepared to a specific reflectance. When handled you have to keep your hands off the colored squares because you guessed it, brushing your finger against the surface could not only soil it, but also slightly buff the surface, changing reflectivity.


    Also just realized you probably pick up a card of known reflectance from edmund scientific...who also sells the color checker.
    That Gretag Macbeth color chart looks like just the ticket! The only question is whether to get the regular or the mini. Anyone have any thoughts?
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

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    Default Re: High CRI and its significance

    Not much difference in price between the two size charts. As much as I think something like these charts would be very useful, it goes against my grain to pay the better part of a C note for a piece of cardboard. Granted, this isn't a standard item you could make on any old printing press, but I still think it's grossly overpriced. $10 would be more like it. In the meantime if anyone is interested in printing there own, see here. Not as accurate I'm sure, but possibly "good enough" for many applications. I did one on my CLP-510 and it looks pretty good to me.

  21. #81
    *Flashaholic* McGizmo's Avatar
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    Default Re: High CRI and its significance

    Right or wrong, good or bad, I ordered the Pantone unit and will see if it has any utility that I can come up with. I am also going to load the spectrometer software in my new laptop and see if I can and get it configured so I can hopefully get some meaningful spectrums from reflected sunlight off the Pantone as well as possibly some other objects.

    I have no false hope that there will be any "Eureka" resulting but it might be illuminating in some regards.
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  22. #82
    Moderator js's Avatar
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    Default Re: High CRI and its significance

    jtr1962,

    Anything you print will be made from three colors (cyan, magenta, and yellow), and will not meet the needs of such a color chart. If it were that easy to make, few people would pay the better part of a C note to get one. Personally, I don't think it's overpriced at all. It ain't cheap, to be sure, but such a precision item will require precise work and work done by engineers and scientists, using expensive scientific equipment. I can tell you, that that just ain't cheap. Add to that the niche market, and it's easy to imagine the company needing to price it at $60 or $70 in order to make a profit.
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  23. #83
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    Default Re: High CRI and its significance

    Quote Originally Posted by McGizmo View Post
    Right or wrong, good or bad, I ordered the Pantone unit and will see if it has any utility that I can come up with. I am also going to load the spectrometer software in my new laptop and see if I can and get it configured so I can hopefully get some meaningful spectrums from reflected sunlight off the Pantone as well as possibly some other objects.

    I have no false hope that there will be any "Eureka" resulting but it might be illuminating in some regards.
    Don,

    Seeing the same sort of wording about how "reflecting the same for any part of the spectrum" or whatever it was on the pantone website, my money is on the pantone color set also being a true color set and not just an RBY mixed color-set. I was thinking of the Gretag Macbeth one just cause I assumed it would be cheaper, and also because they all fit in a relatively small area, whereas the pantone set is a stack of cards, if I remember correctly. But however all that may be, the pantone color set is well worth owning. I'd love to own it at some point! And I'm sure you can use tiles from it to do just what you want to do.

    It's really very exciting. I love your idea of photographing and converting to grey scale! I bet it's going to work really well. Heck, even before converting it may work really well, excepting for the differences between computer monitors, of course.

    I have to thank you for bring this whole subject into discussion around here. You are definitely advancing the state of the hobby, as it were. I never would have thought to buy a color checker before the threads here in this forum. Good work, Don.
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  24. #84
    *Flashaholic* precisionworks's Avatar
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    Default Re: High CRI and its significance

    This is just a little OT, but perhaps worth mentioning. The light meter used with my integrating sphere is an Extech EA31 - one of the many plain jane, no frills, $100 meters available. The users manual states Calibrated to a standard incandescent lamp at color temperature 2856ºK. Since all my lights are LED, most with color temps around 6000ºK, the lux numbers generated in my tests are different than those obtained with a meter calibrated for a LED source.

    Even with that in mind, the Sundrop (with its warmer color temp) produces lux readings that are about what I would expect, compared to cooler temp lights.
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  25. #85
    Flashaholic* Stillphoto's Avatar
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    Default Re: High CRI and its significance

    I want the mini gretag myself... Epecially because it's small enough to get it entirely in frame when shooting somewhat close up shots.

    We use the full size version all the time on photo shoots.

    Provides an instant "true" color source, and if they were shot in LA and being retouched in NY, the retouchers could take out their colorcchecker and know if colors were off by comparing.

    That's why they're expensive (same with the pantone stuff). All around the world, those colors are identical...no variations in printers etc.
    Time flies like an arrow, fruit flies like a banana.

  26. #86

    Default Re: High CRI and its significance

    Quote Originally Posted by js View Post
    Anything you print will be made from three colors (cyan, magenta, and yellow), and will not meet the needs of such a color chart. If it were that easy to make, few people would pay the better part of a C note to get one.
    ...
    While exploring the previous links to these cards, I also stumbled across this one
    http://pantone.com/pages/Products/Pr...px?pid=27&ca=1

    I have no idea how hard it is to find something that does CMYKOG/"Hexachrome" printing, but if you did you could supposedly reproduce 90% of the pantone system. Of course that still doesn't deal with any of the "consistant reflectance" issues mentioned.


    this could be interesting to play with as well
    http://pantone.com/pages/products/pr...d=265&ca=7&s=0
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  27. #87
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    Default Re: High CRI and its significance

    Go to pantone dot com, click on products, click on color control, and look at the Color Checker. Pantone says that all the color squares reflect light the same way in all parts of the visible spectrum. Might be a place to start. For under $100, it could be a useful tool.
    Quote Originally Posted by McGizmo
    Thanks for the tip! I ordered one and it will be interesting to see how it behaves under various lights. I will also see if I can get some spectrums of some of the chips reflecting sunlight.
    Quote Originally Posted by McGizmo
    Right or wrong, good or bad, I ordered the Pantone unit and will see if it has any utility that I can come up with. I am also going to load the spectrometer software in my new laptop and see if I can and get it configured so I can hopefully get some meaningful spectrums from reflected sunlight off the Pantone as well as possibly some other objects.
    Don,

    I just checked out the specific pantone product that precisionworks recommended and it is a Gretag Macbeth color checker in the larger size! LOL! I was thinking that all the pantone stuff was hundreds of dollars--and it is, for the most part. The cheapest full pantone color set I found on their website was $400. But apparently they sell the Gretag Macbeth color checker as well.

    Anyway, the point is that we are talking the same thing here! Which is convenient as we'll be using the exact same color squares.

    I think I will order the small one for the very reason mentioned above--that I can fit the whole thing in a hotspot without having to pull the light too far back. This is exciting. Even more so now that I see we will have the exact same color set. Neat!
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  28. #88
    *Flashaholic* precisionworks's Avatar
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    Default Re: High CRI and its significance

    Does anyone else find it funny that the Pantone color checker seems expensive to some people? Most everyone who posts in this section has at least $400-$500 invested in their McGizmo, with some members (not to mention names like Yaesumofo) investing much more.

    Starrett inspection tools (for machinists) are expensive because they are well made & can always be trusted. Pantone comparison charts are similar. Except that they are low in cost for what they provide - a standard that gives the user uniform reflectance & uniform colors. Not expensive considering what it provides.
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  29. #89
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    Default Re: High CRI and its significance

    Quote Originally Posted by precisionworks View Post
    Does anyone else find it funny that the Pantone color checker seems expensive to some people? Most everyone who posts in this section has at least $400-$500 invested in their McGizmo, with some members (not to mention names like Yaesumofo) investing much more.

    Starrett inspection tools (for machinists) are expensive because they are well made & can always be trusted. Pantone comparison charts are similar. Except that they are low in cost for what they provide - a standard that gives the user uniform reflectance & uniform colors. Not expensive considering what it provides.
    Yeah. That's a good point. I think the counter to it is that if its not something in your area of interest or hobby, and you don't envision using it very much, then the price becomes more of an issue. I will only use the color checker I buy for my review of the LunaSol 20, and for not too much else besides, I suspect. Although, my wife will probably find lots of good uses for the color checker--but she is a very thrifty woman, and would definitely NOT want me to buy a pantone set. Nor a LunaSol 20 for that matter (if she knew how much I paid).

    Still, point taken. But most of us here, given the choice between a nifty set of almost 2000 color tiles, and a LunaSol 20, would take the LS20 over the tiles in a heartbeat. Interest and desire play a very large part in defining what is and isn't "too expensive".
    -Jim Sexton, creator of the M6-R, the TigerLight Upgrades, Fixture-ring lamp potting, the SL60, co-designer of the B90 Upgrade, and proponent of the SF A2, the SF M6 X-LOLA, Titanium, the Haiku, and the LunaSol 20

  30. #90
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    Default Re: High CRI and its significance

    Honestly the pantone set is great when you're printing things and want to make sure that that shade of blue you picked when designing something is printed the same shade of blue...But I've never personally seen it used as a color reference tool as it will be used here (presumably in photos as a color ref).

    That said it will work just fine, and will have every color of the color checker and about 1000 in between each lol.

    All this talk is motivating me to get the standard mini gretag checker.
    Time flies like an arrow, fruit flies like a banana.

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