30V from 24V

On a sunny day (Mon, 10 Nov 2014 07:21:27 -0500) it happened Phil Hobbs wrote in :

But now seriously, and i am not in competition with your system, what is so special about Easter dye colors that a camera cannot distinguish? I understand you are looking _through_ an egg shell?

On a sunny day (Mon, 10 Nov 2014 07:43:50 -0800) it happened John Larkin wrote in :

The problem with RGB that you have to recalculate to YUV anyways, if you really only want color info. But it indeed has all the info.

Hi Jan, Phil outlined the spectrometer upstream somewhere. He's detecting a bump on the shoulder of another strong absorption feature at something like the 1% level (or was it 0.1% ?) Using two interference filters. (I think)

George H.

Except inbetween the R G and B.

On a sunny day (Mon, 10 Nov 2014 08:57:56 -0800) it happened John Larkin wrote in :

Well in normal camera filters those curves overlap a lot, like in the eye. It is not like a fluorescent lamp where you have narrow spectral lines.

The RGB imaging filters are quite wide. The difficulty lies in the fact that RGB colourspace is not a good match for human vision perceptual colour space so you have to convert into something else if you want to be able to compare just noticeable colour differences more uniformly.

To get flesh tones just right manufacturers lose any errors along the line of purples which can spell trouble for photographing certain flowers with unusual shades of purple bordering to magenta.

Famously all colour photographs of galactic nebulae were incorrectly photographed on colour emulsions as pink and pastel blue until 1971 when someone developed a true panchromatic emulsion that wasn't blind to the the strong OIII green line (a safelight wavelength). The Orion nebula is bright enough that the central region looks apple green but on classic film photographs as red and blue.

Most serious science is done by spectroscopy with the image being used to chose the most interesting place to put the slit.

S. N. R. ;)

Cheers

Phil Hobbs

Easter egg dye isn't what we're trying to detect, it's just a convenient surrogate. Have a look at my original post for a problem description.

Cheers

Phil Hobbs

A lot of it's done by drilling holes in a plate to bring multimode fibres from various interesting image points, and lining them up to form the input slit of the spectrometer. The equivalent etendue increase is pretty startling.

Cheers

Phil Hobbs

On a sunny day (Mon, 10 Nov 2014 12:23:30 -0500) it happened Phil Hobbs wrote in :

How to make 30 V from 24 V?

:-)

Right, sorry, it was a bit further down, in response to #1:

Cheers

Phil Hobbs

Visible light is a wavelength-division system: human visual discrimination has three bands resoluble, and there's a lot of information. RGB, or YUV, or CMY... are common designations for combinations of that three-element vector. The full spectrum of 'white' is completely spanned by three primary hues. But, Phil is dealing with a sharper color feature than the pigments of a human eye, his 'white' spectrum breaks down into a thousands of elements vector.

So, a 'color camera' would include a noise bandwidth hundreds of times what he's aiming for, and the signal would be inferred from a linear combination of the three-color elements. That might be widely variant in sensitivity, according to the camera's color filters' specific transmission at the spectral regions of interest.

A camera is a poor spectrometer. You cannot match Pantone colors to an object through a camera. You can get close with a spectrometer, but the final test, a human eye on an object and a standard sample, in controlled illumination (hopefully, white sunlight), is key. The eye, after all, will NOT care about a lot of the deviations a spectrometer will reveal.

You don't test your work in production? Come on!

Jamie

I am fine with that, it's when they start wearing lipstick that bothers me :)

Jamie

Especially the boy chickens. That's creepy.

On Mon, 10 Nov 2014 17:29:09 -0800, John Larkin Gave us:

No... for chickens... that is the right set. The hens are odd bird out wearing it.

I know it's deep, but some of you will get it.

You don't think there are any hens trapped in a rooster's body?

You

Did you really have to go there JL?

?-/

Well that is total nonsense. YUV is NOT a handy color space for anything but teefee.

?-)