Daylight lamp as white reference? - Page 2

You will require manual control of the aperture and shutter speed and will need to be able to take a photo that is dimmer than the subject matter (in this case, a 100% white field or window) with as little noise (gain/grain) as possible.

If all you have is a smartphone, then forget it.

Yes, GE doesn't list the CIE color info on their site. I contacted GE Lighting directly, and they said they'd research it and get back to me... which they did a couple weeks later via email.

I believe the bulbs are simple tri-phosphor. And yes, they are just an off-the-shelf type thing. Like some others here, I've also tried out a number of different daylight bulbs, and the GEs seem to a have a pretty consistent (and pleasing, though that's not really the point) color compared to some other generic brands. So I don't think I'm too off base in suggesting this.

I've never put a meter on one though to measure it.

I put one on order so I can put a meter to it.

Also when I walked into the cal lab today I noticed it was litered with CCFL daylight bulbs, although we were doing CRI testing on them, I'm having them checked for chromaticity.

Without the actual data in front of me I was told that they are generally only ballpark close.

My guess is the tech at GE simply looked up D65 and reported it back to you with out any data.

so, after trying to match them by eye you didn't like the results and went back to defaults, which appear more natural... this is what most of us were trying to tell you and I guess now you've discovered why on your own

consider it a learning experience

^ ^ ^

No different then trying various calibration "methods" then it would seem.

He came to his own best conclusion. It appears everyone becomes "aware" of what others are trying to communicate at their own pace.

yes, though certain things obviously won't work and therefore it's just easier to follow the advice of those who know what they're talking about (aka Experts on the forum)

the following things are always wasted time and effort:

-copying settings from one display to another

-eyeballing grayscale, gamma, or gamut

-optical comparator approach to grayscale (not that different from eye-balling grayscale, especially if using a cheap light source and white card not up to snuff... to do this correctly you'd need to spend more $$$ than a entry-level meter/software combo and the results would not be as good anyways)

-visual "spot" patterns for setting/evaluating gamma found on many popular calibration discs... I've tried them and they are pretty useless, essentially a form of eyeballing gamma.

*

-copying settings from one display to another

"debatable, but sometimes better than nothing"

there's nothing to debate about wrong practices being wrong

-eyeballing grayscale, gamma, or gamut

"Also debatable as color purity was done this way for years and if VISIBLE errors in gray scale are present. . . better is better."

by what standard? the subjectivity of the user/'calibrator'?

-optical comparator approach to grayscale (not that different from eye-balling grayscale, especially if using a cheap light source and white card not up to snuff)

"There is another way. Using an emissive gray scale source such as a pure monochrome B&W monitor with the same signal source as a comparison. Color temperature and luminance may not be exact, but also has been used for years."

seriously? you need D65 and proper luminance

-visual patterns for setting/evaluating gamma on many popular calibration discs... I've tried them and they are pretty useless.

"Irrelevant and in your opinion. For a neophyte unskilled in a procedure perhaps not."

useless is useless to anyone trying to get a meaningful benefit out of such a pattern, which is not possible



overall, you seem to be stuck in the past with methods that are no longer valid or useful

like you mention, newer displays are much closer to references standards out of the box in their most accurate picture modes/presets and these older methods are too crude and imprecise to be effective... you may very well end up making things worse objectively, which is not good calibration

It's important to educate naysayers in how the procedures of TV calibration evolved and some owners may still benefit from these methods as alternatives to expensive, time consuming, and sometimes disappointing use of hobbyist calibration meters that can not possibly offer the accuracy of professional equipment costing in the thousands.

History is always a good teacher and only those who wish to remain ignorant discard valuable tribal knowledge.

Stop now, or " Death By Bunga Bunga "

It's the tribal way~

It is lecturing only if you choose to take it that way. The choice of attitude is an individual one. I offered information that others may find of benefit. An individual can choose whether to use or not use any information.

Sadly, this has now gotten far of topic and no longer beneficial to anyone. This seems to be the case unfortunately with those naysayers who choose to be arrogant rather than invest in all information that is of value.

Great! I'll be curious to see your results, esp. on the GE daylight CFLs.

The bulbs change color slightly as they warm up btw. In my tests, they appeared slightly redder in color when "cold" (ie just turned on) versus after some warm-up time. And it appeared to take about 10-15 minutes before they "settled in" to a fairly constant color (which I'm guessin is typical for fluorescents).

Not sure what the normal procedure is for reading bulbs, but it might be interesting to see both a "cold" (just on) and "warm" (on 15 minutes or so) color reading, to see the difference.


Possible, but I was pretty explicite in my request, and gave them the model # of the daylight CFL bulb, etc. So I'd give them a bit more credit than that. I believe GE lists CIE coordinates for some of their other industrial bulbs, so they probably just needed to dig around a little for info on the tri-phosphor daylight bulbs. Probably not the sort of request they get too often on their consumer products.

The CIE values they sent me (x=0.313, y=0.337) are also not a precise match to D65 (x=0.3127, y=0.3290). If the values they gave me are correct, then the bulbs should be a hair off D65 towards green. (There are couple suggestions on how to compensate for that here.)

^ Very nice page. Tks for the link.

Copying settings is not calibration and neither is eyeballing grayscale, gamma, or gamut... I don't know why you don't believe that or would provide advice to the contrary in a calibration forum. This is not my opinion, but rather what has been established in this forum long before I joined AVS and is fact. You don't have to take my word for it, though; you can ask the experts on the forum.

There are ways to foul up equipment-based calibrations as well, PlasmaPZ80U.

For example, how many users of meters and sensors here can state with confidence that the device they're using to output patterns to their display is 100% accurate? Not many I'd wager. I doubt most would even know what to look for.

If you understand the theory behind them, then the old eyeballing ways can give you an additional useful toolset to confirm and possibly even refine your equipment-based results (a notion I'm sure you'll find amusing ).

Also AFAIK, there is no software/hardware combination currently available that can tell you how to adjust the color on your display so it's perceptually correct for a given illumination environment. They all assume a daylight or dark surround, which is often not what's being used (or desired) in practice.

In the correct lighting environment, with a good reference eyeballing it is acceptable.

The color matching functions that take raw spectral data and convert it into XYZ data were created by having test subjects eyeball match solid colors to blended colors.

We may use high precision instruments, but in the end even those results are derived from somebody eyeballing it.

Interesting and very nice to know.

The proof is in the visual pudding apparently.

I know my PS3 is considered a reference BD player when used in YCbCr 4:4:4 mode with Super-White on. Also, I believe SmackRabbit has tested various BD players to see which are reference-quality (Panasonic BDT210 is one that comes to mind).

How expensive is it to have the correct lighting environment and a good reference, though? Likely more than that of most DIY meter/software combos with results that are not quite as good. Also, acceptable and optimal are not the same thing.

Still no replacement for using the proper equipment. Also, reference viewing is done in reference environment (dark room with dim surround) so altering your display to better match a less than ideal viewing environment isn't desirable.

Acceptable may be all you get out of a hobbyist meter also and is the "best you can do" compared to professional multi thousand dollar equipment and an experienced ISF/THX technician that really does accurate calibrations.

Visual comaparator verification for TV calibration is nothing new.

show me some actual data to back up those claims and not from a budget-meter like the D2... perhaps an colormunki or i1Pro spectro

Use pf professional calibration equipment that is regularly certified is the best way to go as long as a known experienced calibrator is performing it. That said, other equipment may give you charts, graphs and numbers and still may not look correct or, in fact, be correct as you say.

But I agree with you.

it goes both ways, though, eyeballing can give compromised results as well given that our eyes are terrible tools for measuring colors (possibly far worse than a cheap meter)

a lot more can go wrong with eyeballing grayscale than using DIY equipment, given the inherent subjectivity of the method.

Where is the "data " on this theory. Grasping as straws now I think.

Just another opinion.

not sure what you are going on about...

but if someone who has a spectro wants to put this topic to rest:

-use the optical comparator approach to calibrate grayscale (perhaps just 2-pt grayscale to keep things simple)

-then measure it with the spectro

-also, measure the default grayscale in the right pic mode and color temp preset

-see how much improvement, if any, the optical comparator approach made and then compare that to how much remaining error was left using the spectro the measure the end result.

Just to play devils advocate, how do you know the spectro is going to give better results? It may actually appear closer to the optical comparator than when aligned with the spectrometer.

Remember while the spectral data from the meter is hard data, the color matching function that converts that data into XYZ data was derivied from people eyeballing it. We know for sure that with certain kinds of spectrums you can get very dissimilar shades of white between ultra wide gamut CCFL and CRTs even when a 1nm spectro reports them both at D65. Switching from the 1931 CMF to one of the newer formulas allows you to match them with the meter, but now we've opened a whole can of worms.

this is going beyond what I know about calibration so I'll just briefly state the point I'm trying to make...

Calibrating grayscale/gamma and gamut is best done with meters/software. The optical comparator approach for grayscale will not provide comparable results in general and can be expensive when done properly (using high quality light source and white card).