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Author Topic: What do I need to be able to display light spectrums?  (Read 9606 times)

WayneLarmon

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What do I need to be able to display light spectrums?
« on: February 03, 2014, 06:45:12 AM »

I want to measure the characteristics of light sources.  Spectrum plots, CRI, color temperature, etc.   Like this



(The above screen shot came from http://photo.net/casual-conversations-forum/00cHcE?start=50 and scroll down to the post by Lad Lueck , Jan 10, 2014; 10:06 p.m.)

I'm trying to figure out better sources of continuous light.  I've already made a DIY spectroscope
http://wlarmon.smugmug.com/Other/DIY-Spectroscope/32099985_nMBQnS#!i=2788846720&k=BLnwZzj which works for determining spikiness, but doesn't tell me the shape of the spectrum, the color temperature, or the CRI.

I'm assuming that I need some kind of spectrophotometer with matching software.   The post I linked to mentions a "Gretag Macbeth i1 Spectrophotometer."  But Gretag Macbeth doesn't exist anymore.  XRite spectrophotometers  seem to be oriented towards profiling monitors and printers.  I don't need that (I already have a NEC PA241W, Spectraview II, and an i1DP for my monitor and I don't have a printer.)  I just want to measure light spectrums.  

Lab grade spectrophotometers seem to cost "send for a quote", which probably means that I can't afford one.   Budget is an issue.  What is the cheapest way to do what I want to do?

TIA.
« Last Edit: February 03, 2014, 06:48:22 AM by WayneLarmon »
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #1 on: February 03, 2014, 10:04:06 AM »

I'm assuming that I need some kind of spectrophotometer with matching software.   The post I linked to mentions a "Gretag Macbeth i1 Spectrophotometer."  But Gretag Macbeth doesn't exist anymore.  XRite spectrophotometers  seem to be oriented towards profiling monitors and printers.

Same company now, the older and newer X-Rite i1Pro can do this, best mated with BableColor.

http://www.babelcolor.com/#CTandA
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Andrew Rodney
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #2 on: February 03, 2014, 10:19:51 AM »

So if I bought new, I'd buy the cheapest XRite package that has an i1Pro spectrophotometer, which I think is the

X-Rite i1Basic Pro 2 Color Profiling Software Bundle $1,149
http://www.bhphotovideo.com/c/product/854476-REG/X_Rite_EO2BAS_11_Basic_Pro_2.html

+ the BabelColor software?

Or haunt eBay looking for a used i1Pro (1 or 2) Spectrophotometer?  ( + the BabelColor software.)

And this wouldn't do me any other good, because I already have the i1DP for my PA241W and I don't have (or intend to get) a printer.  Correct?

Um, do you know of anybody that is measuring LED lamps?  The only reason I want this is because nobody else is showing spectral plots and CRI ratings of LEDs.  We all pretty much know what CFLs are good for by now but LEDs are a wild card.  (i.e., some of them now have smooth spectrums, just like tungsten.  But maybe not shaped quite right.  Which may be fixable with a Rosco gel.  Maybe.)

Thanks.
« Last Edit: February 03, 2014, 10:33:45 AM by WayneLarmon »
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #3 on: February 03, 2014, 10:47:11 AM »

And this wouldn't do me any other good, because I already have the i1DP for my PA241W and I don't have (or intend to get) a printer.  Correct?
Don't understand the question. The i1Display-Pro is a colorimeter so no, you can't use it for the work the OP is asking about.

Quote
Um, do you know of anybody that is measuring LED lamps?  The only reason I want this is because nobody else is showing spectral plots and CRI ratings of LEDs.  We all pretty much know what CFLs are good for by now but LEDs are a wild card.  (i.e., some of them now have smooth spectrums, just like tungsten.  But maybe not shaped quite right.  Which may be fixable with a Rosco gel.  Maybe.)

I have measured and built plots of LED's using BableColor and the i1Pro-2 Spectrophotometer. BableColor will produce all kinds of reports to the qualities of the light measured.
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Andrew Rodney
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #4 on: February 03, 2014, 11:12:57 AM »

Quote
And this wouldn't do me any other good, because I already have the i1DP for my PA241W and I don't have (or intend to get) a printer.  Correct?

Don't understand the question. The i1Display-Pro is a colorimeter so no, you can't use it for the work the OP is asking about.

I meant that if I bought the  i1Basic Pro 2 Color Profiling Software Bundle (in order to get the i1Pro 2 Spectrophotometer to measure lights) that this Spectrophotometer would only be useful to me for measuring lights.  Because I already have the i1 Display Pro calorimeter to measure my PA241W (with Spectraview II).   I wish XRite wouldn't name everything i1[whatever] because it causes confusion real quick when discussing several different XRite products.

Quote
I have measured and built plots of LED's using BableColor and the i1Pro-2 Spectrophotometer.

Have you published the results?  And have you found any LEDs that are useful?  (Enough so that SoLux bulbs aren't needed anymore?)

In another thread (Medium Format DSLR as film scanner) you linked to a thread on photo.net about DSLR camera scanning.
http://photo.net/digital-darkroom-forum/00cKbq?start=0
 
I participated in that thread.  If you read that thread you will know what I am concerned about.  I'm trying to improve the SOTA for camera scanning.  Because quality film scanners have gone away and aren't coming back.  But garden variety DSLRs are already great imaging engines.   I know that great results are possible with camera scanning (which I demonstrated in that thread), but the techniques need perfecting.
« Last Edit: February 03, 2014, 11:15:13 AM by WayneLarmon »
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #5 on: February 03, 2014, 12:25:04 PM »

I only just recently measured the LED's in my office ceiling for a tutorial on DNG camera profiles. Absolutely doable in BableColor software.
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Andrew Rodney
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #6 on: February 03, 2014, 03:35:53 PM »

the older and newer X-Rite i1Pro can do this, best mated with BableColor.

The ColorMunki Photo with Argyll can do this also and is a much less expensive package.
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #7 on: February 03, 2014, 03:40:26 PM »

The OP can download the software shown in the first post for free. Even better? Of course, way more useful stuff in BableColor but if all he wants to do is measure like that screen capture, register i1Pro on X-rite site and download, it's free.
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Andrew Rodney
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #8 on: February 03, 2014, 03:51:54 PM »

But I thought he didn't have a spectro yet?   The i1 Pro is much more expensive than the ColorMunki.
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #9 on: February 03, 2014, 03:56:56 PM »

Quote
The ColorMunki Photo with Argyll can do this also and is a much less expensive package.

You mean this?

X-Rite ColorMunki Photo Color Management Solution  $449.00
http://www.bhphotovideo.com/c/product/550833-REG/X_Rite_CMUNPH_ColorMunki_Photo_Color_Management.html

It is a spectrometer but the Argyll docs says that ColorMunki Design or Photo is "UV cut only."  What is the significance of that?

I've used Argyll to convert ICC profiles to 3-D VRML files (using iccgamut and viewgam) but I didn't know it could be used to make spectral plots, do a CRI rating and give the color temperature of an illuminant.    Before I buy a ColorMunki Photo, could you give me some hints on how to do this with Argyll?

http://argyllcms.com/doc/ArgyllDoc.html
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digitaldog

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Andrew Rodney
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MarkM

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Re: What do I need to be able to display light spectrums?
« Reply #11 on: February 03, 2014, 04:06:54 PM »


I've used Argyll to convert ICC profiles to 3-D VRML files (using iccgamut and viewgam) but I didn't know it could be used to make spectral plots, do a CRI rating and give the color temperature of an illuminant.    Before I buy a ColorMunki Photo, could you give me some hints on how to do this with Argyll?

http://argyllcms.com/doc/ArgyllDoc.html

Wayne, I've used argyllCMS for making spectral distribution plots. You want to use spotread — it's part of the argyll package: http://argyllcms.com/doc/spotread.html
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #12 on: February 03, 2014, 04:11:45 PM »

Quote
Better deal (better instrument):...

Ah, thanks.  I was searching eBay for "spectrophotometer" and only getting lab type instruments.   That price is more reasonable for experimenting.



Quote
Wayne, I've used argyllCMS for making spectral distribution plots. You want to use spotread...

Thanks.
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #13 on: February 03, 2014, 04:37:29 PM »

Quote
I only just recently measured the LED's in my office ceiling for a tutorial on DNG camera profiles.

The reason I am curious about LEDS is


Standard soft white CFL


Expensive CFL with a CRI of 93


Regular old tungsten bulb (which we can't buy anymore)


Cree daylight LED.  CRI 80

It is this last that has me interested.  Note the smoothness of the spectrum.   This is only CRI 80.  They have a new "TW" version that they rate at CRI 93 and refer to as "full spectrum"  But it isn't available in my local Home Depot yet.  (It is only in California Home Depots at present.)

SoLux bulbs are neat and all, but they are very hot.  Trying to put four or so SoLux bulbs in a softbox would be, um, challenging.   (I can swing four 100 watt (equiv.) CFLs in a softbox.  But CFLs, well...

B&H (et al.) have inexpensive small LED panels that might do for camera scanning, if I put one close to the film.   But LED lights (under $1,000) have no CRI rating (nor spectral plots)  I'd like to experiment with those LED panels, but I'd really like to know what I am getting.    Hence, the interest in being able to do my own spectral plots.
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #14 on: February 03, 2014, 04:41:31 PM »

Spotread produces this:

 Result is XYZ: 48.533259 51.313619 46.795263, D50 Lab: 76.868594 -2.560387 -5.444825
 Ambient = 51.3 Lux, CCT = 5564K (Delta E 6.324134)
 Suggested EV @ ISO100 for 51.3 Lux incident light = 4.4
 Closest Planckian temperature = 5386K (Delta E 5.505304)
 Closest Daylight temperature  = 5499K (Delta E 2.036443)
 Color Rendering Index (Ra) = 94.1

And the attached plot of the spectrum (which I can't seem to preview so I don't know if it will show up or not...)

UV cut means it won't measure into the UV spectrum (partly that is the LED and partly it is the receive path).  The plot shows what it measures.

Anyway, just giving you some options.  I spoke up since it seemed you were heading down an unnecessarily expensive path.
« Last Edit: February 03, 2014, 04:48:09 PM by BCRider »
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #15 on: February 03, 2014, 04:52:46 PM »


Quote
Spotread produces this:...

Yeah, this looks like all the info I need.

Quote
And the attached plot of the spectrum...

Is this a plot of a CFL?   Spiky but still has a CRI of 94.1.  Which makes me wonder a lot about the meaningfulness of CRI ratings.   (The spectrograph of the CFL I displayed a few posts ago is very gappy, but is still rated at CRI 93.)
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #16 on: February 03, 2014, 04:59:29 PM »

Yes, it is a CFL with daylight mixed in.

FWIW, here is a plot of a Cree 100 Lumen LED (flashlight) I have sitting on my desk (measured CRI 72).

I don't think CRI is very useful.  Spectral plots tell the story.
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #17 on: February 03, 2014, 06:41:29 PM »

I don't think CRI is very useful.  Spectral plots tell the story.
It isn't useful and you're correct, the plots are.
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Andrew Rodney
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Re: What do I need to be able to display light spectrums?
« Reply #18 on: February 03, 2014, 07:53:26 PM »

Here's what I get from the office LEDs. Nothing special, about 2 years old and purchased at either Home Depot or Lowes, can't remember.
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Andrew Rodney
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MarkM

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Re: What do I need to be able to display light spectrums?
« Reply #19 on: February 03, 2014, 08:00:02 PM »

If anyone's interested, here's a set of plots of a Philips Hue variable color LED bulb set to various various color temperatures.
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