GE sunshine 5000K CFL

[blasterman]

If the object being viewed responds does not exhibit sharp difference based on light source, then yes

A big reason cool white LEDs generate less negative aethestic response than cheap high CCT CFLs.

 

[UnknownVT]

http://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html

Thank you so much for that very useful link -
going have to try and make myself one of those -
have may to wait til I empty a cereal box though!

Well, it really wasn't about how to take pics, but I took pics so I can show what I meant. To get a visual confirmation, I use the disc 6-7 ft away from the light source, then play with the disc as well as viewing angle.

I can get a separation good enough to tell if the source is triphosphor or continuous.

You'll see multiple clear lines while wide spectrum source looks smooth with no apparent lines (except for the green line, which comes from mercury emission). To get it on photo, just hold the disc the same angle,then look at it from where your eyes were looking from.

I tried with the CFL about 6-7 feet away - and could not get/see the sort of separated images as in your photo inset.

I do see colored images of the CFL spiral but they are set wide apart that I cannot get all the spectrum on one DVD.

A CD seems a bit better I can manage to get more on a CD - but still no where where I can get the full spectrum.

However this raises another question for me - looking at the link Blasterman provided for the homemade CD spectrometer - the light is through a very narrow slit 0.2mm(!) this obviously will NOT show the image of the light source (eg: CFL spiral) - ie: the light is via the slit independent of the sources' shape - and kind of makes sense since we ought to be looking of the spectrum independent of the shape of the light source - and if I remember my school spectrometers they were through slits....

Please don't take this as anything negative on what you have manage to achieve - I am actually very envious and jealous (and almost feel inept) that I cannot seem to manage to reproduce it.

However it does beg the question of what is it we are looking at, and for?

 

[Bright+]

A big reason cool white LEDs generate less negative aethestic response than cheap high CCT CFLs.

Winder spectrum distorts color in a different way, but wide spectrum doesn't mean better.

Traditional 60 CRI cool white has a much more continous output than a 86 CRI triphoshpor, but does not render color well in most cases.

Chroma 50 is almost continuous (referenced: http://www.gelighting.com/na/busine...esources/learn_about_light/color_matching.htm ) even though there's a few lines from mercury spectrum, just as white LEDs have activating blue pass-through and color shift based by variation of the chip itself.

LEDs also suffer from a substantial unit-to-unit chromatic deviation.

 

[UnknownVT]

Just a bit of "subjective" input -
I only have LED flashlights, but plenty of them - none I consider particularly pleasing light - but I accept that any light when there is no light is good.

Of all the LEDs - Cool Whites I feel are kind of harsh but of all of them I like the LumiLED Rebel 100 as in the Fenix L1D-RB100.

I have much more limited choices in Neutral and Warm White emitters.

But I like the Neutral White I have in the 4Sevens Quark series which I believe are Cree XP-E Q3-5A.

Warm White (Cree XP-G Q5-7A or 7B) I like because I know they perform well under certain condtions like distance outdoors - and they seem to enhance vision - not necessarily as better color rendition - but I just seem to see better clearer - like under sodium street lighting, which must have a horrible CRI - but I seem to see sharply and clearly - but obviously not good for color recognition.

I haven't seen emitters rated at about 5000K eg: Cree XP-G R5-3A - ut would really like to see one of those to see if I change my mind about Cool white LEDs

In the house for overall lighting I actually like the SoftWhite CFL (2700K, CRI=82) and regular SoftWhite tungsten bulbs.

But for examining things and for better color recognition I now really like the GE 5000K Sunshine CFL (CRI=82), followed very closely with the F20/T12 GE 5000K Sunshine (CRI-90) fluorescent tube -

I much prefer these to the original GE Kitchen & Bath F20/T12 tube (3000K, CRI=70) and for a short while I tried the GE "Cool White" 4100K F20/T12 tube (CRI=60!) (notice the difference in naming of lights - where in a fluorescent 4100K is regarded as "Cool White") - which I did not like that much.

In this long thread:
Puny LED flashlights (Not!) + COLOR RENDITION Comparison
I attempted at a summary in Post #73 (link)

- good CRI does not necessarily mean good color recognition, which
in turn does not necessarily mean seeing better.

 

[Canuke]

UnknownVT: when shooting CD's/DVD's you have to account for the sRGB "squeezing" of the color band into R, G and B, because those primary colors are the most saturated colors displayable under that system. Saturated yellows, cyans etc, because they must be approximated using those primaries, cannot be as saturated as they are in reality. Either the hue must be compromised towards the closest primary to achieve more saturation, or the saturation must be less than "right" in order to preserve the correct hue. Different cameras with different software will handle it differently in their effort to make it "look right".

See here.

Bright+ shows the method I use to assess spectra. CFL's show multiple images of the light in different colors, whereas truly continuous sources show a continuous spectrum.

I didn't know that there really were continuous-phosphor fluourescents -- though it makes sense to me: the phosphor in LED's gives a fairly wide band, why wouldn't the phosphors in tubes be able to do the same?

Another material that shows the difference between incandescent sources and lookalikes (CFL's and LED's) is any transparent material that has a brick-red color, such as certain lighter red wines. (My example with which I discovered this was a cabernet-franc icewine from Niagara.)

Because of the deep reds (>650nm) present in incandescent light, the wine shows its true brick-red color under such illumination. Warm-white LED's and CFL's, however, tend to render the wine to the eye as more orange. It's a really odd thing to see, given that CFL's/LED's tend to look pinker to the eye when seen directly.

However, the lack of deep reds means that the CFL/s and LED's must somehow achieve that hue using a mix of two other frequencies -- in this case, the readily available royal blue and deep orange. Mixed together, these yield pink, which is more or less the right hue -- but it's not the same wavelength.

So, CFL's/LED's might look a bit pinkish to the eye, but when filtered through the red wine, the blue component gets whacked, leaving only the deep orange. In fact, pink CFL's like I mentioned will give Caucasian skin a weirdly orange cast for the same reason.

 

[Canuke]

Warm White (Cree XP-G Q5-7A or 7B) I like because I know they perform well under certain condtions like distance outdoors - and they seem to enhance vision - not necessarily as better color rendition - but I just seem to see better clearer - like under sodium street lighting, which must have a horrible CRI - but I seem to see sharply and clearly - but obviously not good for color recognition.

That's due to chromatic aberration. Different wavelengths focus at slightly different depths. The human eye tends to bias itself to focussing red-green wavelengths, since it has the most of those cones, and relies on the lower-resolution blue wavelengths for color depth.

Monochrome light eliminates this source of blurriness, at the expense of color perception. It's roughly analogous to taking the filters off a camera sensor and using the subpixels as monochrome pixels in their own right. You lose color information, but gain overall resolution.

 

[UnknownVT]

when shooting CD's/DVD's you have to account for the sRGB "squeezing" of the color band into R, G and B, because those primary colors are the most saturated colors displayable under that system. Saturated yellows, cyans etc, because they must be approximated using those primaries, cannot be as saturated as they are in reality. Either the hue must be compromised towards the closest primary to achieve more saturation, or the saturation must be less than "right" in order to preserve the correct hue. Different cameras with different software will handle it differently in their effort to make it "look right".

See here.

Bright+ shows the method I use to assess spectra. CFL's show multiple images of the light in different colors, whereas truly continuous sources show a continuous spectrum.

Thank you very much for the helpful posts I particularly appreciate the explanation on some of the aspects why the camera may not be able to capture what I see - even though I know intuitively that the eyes do not see the same as a camera - it's nice to be able to quantify some of this.

I also really am grateful for your post #341 over at 4Sevens' CPF MarketPlace: XP-G Warm White Pre-orders! w/ GREEN Packaging! explaining why even RAW would not capture some of the tint differences I saw between warm white emitters and real incandescents - which is another aspect of this.

On DVD's I can see the separate colored images of the CFLs - but they are spread right across and beyond the full DVD width/diameter - and I just cannot seem to get them to fit on one half (ie: just the radius) of the DVD - CD's seem a bit better, but they still spread right across the diameter.

That's due to chromatic aberration. Different wavelengths focus at slightly different depths. The human eye tends to bias itself to focussing red-green wavelengths, since it has the most of those cones, and relies on the lower-resolution blue wavelengths for color depth.

Monochrome light eliminates this source of blurriness, at the expense of color perception. It's roughly analogous to taking the filters off a camera sensor and using the subpixels as monochrome pixels in their own right. You lose color information, but gain overall resolution.

Yes, for more than 12 years I have EDC'd a yellow Photon 2 just because I can see sharply under it and it seems to be low enough not to disturb whatever low light adaption I have acquired (obviously not as low as scotopic) and doesn't seem to attract attention as yellow light just seems more commonplace.

It may be regarded as myth by some - but the prevalence of amber shooting glasses seems like reasonable empirical evidence that yellow/amber does seem to enhance vision/definition.

My own personal experience is the use of Serengeti Drivers sunglasses that eliminates a lot of blue, but the tobacco colored lenses just seems to enhance my vision - reds jump out, and definition is definitely improved for me - especially for distant hazy conditions - I often see things that I did not with the naked eye, or through other sunglasses.

 

[Canuke]

On DVD's I can see the separate colored images of the CFLs - but they are spread right across and beyond the full DVD width/diameter - and I just cannot seem to get them to fit on one half (ie: just the radius) of the DVD - CD's seem a bit better, but they still spread right across the diameter.

The trick to using these is that you need a really small camera with a wideangle lens and small aperture that can see more like the human eye. I stick the CD right under my eye and use it as a mirror to look at the light source. My big honking 5D isn't the best for this, though the Sigma 12-24mm comes close

As for photographing spectra, the best way to capture hue is to superimpose it with some white (for example, put the light source against a white wall that is big enough so that it shows up in the surface reflection, which has a different angle from the diffraction reflection). This desaturates it enough to fit it into the sRGB gamut, so you don't end up with the colors collapsing into the primaries. It also helps to underexpose it so you get no clipping in *any* channel.

I'll post some examples if I can find some time this week :O

 

[UnknownVT]

The trick to using these is that you need a really small camera with a wideangle lens and small aperture that can see more like the human eye. I stick the CD right under my eye and use it as a mirror to look at the light source.

That's it -
now I can see it -
my eye had to be inches away from the DVD surface -
never thought of that
I was looking at the DVD/CDs from about 1ft away -
no wonder I got the wider than the diameter spectrum.

Thanks so much for the advice - much appreciated -
now I don't feel such a dunce....

 

[UnknownVT]

Now that I've had some time to live with both this GE 5000K Sunshine CFL and the GE 5000K sunshine F20/T12 Chroma 50 tube -
I had a slight preference for the CFL version ever since I had both lights -
even though I knew full well the CFL CRI=82, whereas the Chroma 50 F20/T12 tube is CRI=90.

I recently got a $1 GE plug in lamp socket adapter:

this allowed me to plug in the adapter on an extension cord and place any bulb almost anywhere.

So I was able to put the GE 5000K Sunshine CFL more or less where the fixed Chroma 50 F20/T12 tube was - thus I was able to compare these two lights directly.

Doing this confirmed for me that the Chroma 50 tube seemed to have a slight greenish tint in comparison to the CFL's slight pinkish tint -
and overall I prefer the CFL's tint - and this is despite/regardless of the fact the tube has a better rated CRI.

 

[purduephotog]

The CRI is a measure of calculated color distortion of eight reference colors. Another more technical term for CRI is called Ra8, with the eight pointing to the use of eight reference colors.

There are some materials that exhibit metamerism. Substances, especially minerals with very specific spectral absorption properties will look different depending on spectral contents of illumination.

It's possible for something to have two objects to look the same under one lighting, then another under a different source.

Neodymium glass is something with a very narrow spectral absorption properties. It has a hint of red and can look slightly ruby red under natural light or wide spectrum light like Chroma 50 (CRI rated 90).

An SPX50 lamp may have a CRI of 85, but the spectral contents is far different and any hint of red will go away.

Notice the blue transparent plastic and tinted glass doesn't change color, but neodymium glass shows drastic color change between Chroma 50 vs SPX50. There are art work made of neodymium glass and the appearance is different enough to make them look like they're two different things.

Wide spectrum/Chroma 50 (CRI 90), or under sunlight


Triphosphor (CRI 85, SPX50)

On the left is the spectrum of Chroma 50, and on the right is SPX50. You can see the distinct breaks in triphosphor lamp and absence of yellow and cyan light. The Chroma 50 has a pronounced line in green that didn't turn out in photo. This is one of mercury emission lines.

Ahhh, the cheap poor-mans diffraction spectrometer. A couple of razor blades, a good CD... and you're set. Add camera to mix to measure.

 

[purduephotog]

The trick to using these is that you need a really small camera with a wideangle lens and small aperture that can see more like the human eye. I stick the CD right under my eye and use it as a mirror to look at the light source. My big honking 5D isn't the best for this, though the Sigma 12-24mm comes close

As for photographing spectra, the best way to capture hue is to superimpose it with some white (for example, put the light source against a white wall that is big enough so that it shows up in the surface reflection, which has a different angle from the diffraction reflection). This desaturates it enough to fit it into the sRGB gamut, so you don't end up with the colors collapsing into the primaries. It also helps to underexpose it so you get no clipping in *any* channel.

I'll post some examples if I can find some time this week :O

http://sci-toys.com/scitoys/scitoys/light/cd_spectroscope/spectroscope.html