Is an Assignment of Colors to UV-Wavelengths possible?

[Cadmium]

Some examples of trying to find reflected UV colors, how hard it is to fine any yellow in man made materials that even come close to the UV yellow from some flowers.

 

Top: IR, Center: Visual, Bottom: UV

 

Old box of pastels

 

IR

 

Visual

 

UV

[Andy Perrin]

Cadmium, you probably need organic materials. I have seen a sign that went yellow-green in UV:

 

 

[Cadmium]

That is my whole point!

That's not yellow, that is hardly yellow, like a GG420 filter, you can hardly see it. About like the yellow pastels.

I am talking about REAL yellows. Real colors, like the bandpass filters, like a rudbeckia, there is NO man made UV yellow.

[Andy Perrin]

Cadmium, some of that is my editing though? Like, that color is pretty similar to Dave’s flower. It’s not all that different from the Rudbeckia. I can make it “more” yellow just by upping the saturation slightly. It is not yellow like the band pass, though (or the visible light photo).

[dabateman]

Cadmium,

I like your tests with paints and oxides. That is kind of what I am hoping with the color checker. My crazy rationale is that the color checker is fairly standard. Mine should be the same as others. If I can see some difference and work out a protocol, my hope is that we could compare cameras.

However, thinking about it lighting really matters. It may not be possible to standardize a target and light to get similar images. I will first test my 4 different lights to see how they vary with the same filter. My 405nm led, 365nm led, compact fluorescent black light and Exo terra 200 26W bulb. If that has significant difference using what may be a common filter stack like Ug1 2mm with S8612 2mm, then I would have no hope getting a standard setup for others.

I think sun light varies too much with location, time of year and time of day, that it will not be a good standard light.

[Cadmium]

Let me scroll back to the previous page and look at Dave's beautiful flower in UV again, It's soft, soft, soft barely some yellow in it, but...not very yellow at all.

Try a rudbeckia or a dandelion for some actual UV yellow.

The point is, there is no man made yellow materials that are good for yellow UV targets. There seem to be a lot of man made UV blue targets, and black of course.

So good luck grinding up a rudbeckia and applying it to some UV color target to sell to UV photographers like a Color Checker or like the UVIVF target that Andra bought,

but those aren't for UV.

Maybe someone will find some material, but I have never seen any.

It would seem like there should be more UV color materials, at least as much as what we see with narrow UV bandpass filters, green, yellow, lavender, blue,

we don't even see UV green like the 340nm bandpass filter, not even in flowers.

Rudbeckia UV yellow (center)

[DaveO]

Here's an interesting paper I found

J Comp Physiol A

DOI 10.1007/s00359-017-1175-7

Why background colour matters to bees and flowers

 

which had this figure

 

The yellow curve is the reflectance spectrum of YELLOW paper - it looks very similar to the curve for Hibbertia flower petals I think. Must be something spooky going on.

 

Dave