multispectral fruit bowl

[Fandyus]

I have been posting a lot of multispectral images lately. These were made the same way all other ones were. I apologize for the fruit bowl not being very appealing, the fruits aren't exactly fresh. Good enough, used one of the bananas for some banana bread today.

 

visible:

 

one shot full spectrum:

 

full spectrum (all images combined), old method:

 

full spectrum made with a hybrid method I developed using advice from both @Stefano and @Andrea B. (found in this thread):

Main difference between this and the old method is that here, the green channel is shifted towards visual red. 950nm and UV bands have less influence overall, since they are extreme ends and our hypothetical full spectrum "eye" would most likely have less sensitivity for them.

 

IR tri color:

 

GBUV:

 

Aerochrome simulation:

 

850nm-720nm-red

 

Fluorescence trichrome:

(method described here)

[colinbm]

Very interesting Fandyus
Does the bottom of the bowl fluoresce white ?
I have been trying to find something that fluoresces white, if you can tell me some more about it please.

[Stefano]

The tomato(?) in the IR TriColour looks like a forbidden blue fruit (the light blue you see on fruit/vegetables in IR TriColours is probably due to water absorption), while the GBUV version transformed the lemon into an orange and the grapes into something similar to cherries. It looks tasty.

[Fandyus]

21 hours ago, colinbm said:

Very interesting Fandyus
Does the bottom of the bowl fluoresce white ?
I have been trying to find something that fluoresces white, if you can tell me some more about it please.

Thanks, the bowl does not fluoresce white, the white object you see in the bottom is an apple. Also, white fluorescence in the fluorescence trichrome is not indicative of the color of fluorescence in the real world. Check the linked post. I describe how I made the image there.

[Fandyus]

10 hours ago, Stefano said:

The tomato(?) in the IR TriColour looks like a forbidden blue fruit (the light blue you see on fruit/vegetables in IR TriColours is probably due to water absorption), while the GBUV version transformed the lemon into an orange and the grapes into something similar to cherries. It looks tasty.

I am almost certain that the blue color is due to water absorption, what else could it be?

Funny enough, you're not the first one to tell me the GBUV fruits look tasty. I agree, although the things you see there are not cherries. Close enough however, they're cherry tomatoes.

[colinbm]

@Fandyus This white.......

[Fandyus]

Yes, @colinbm, that's an apple. It is visible in the reference image. And not only there, I checked personally what exactly it is when I was taking the images. It's an apple.

[colinbm]

@Fandyus OK i can sort of see it now, it is white from the IR ?

[Fandyus]

1 hour ago, colinbm said:

@Fandyus OK i can sort of see it now, it is white from the IR ?

It is white because the amount of fluorescence is roughly same regardless of whether green, blue or 395nm is used for inducing it.

Edit: I must add: "roughly same" when it comes to its ratio to other fluorescent objects in the picture. Fluorescence images cannot be properly color balanced so I have no idea how the strength of the apple's fluorescence varies between green, blue and 395nm. I could figure out but I would need standardized lightsources that output the same amount of light regardless of wavelength, that's not the case with my cheap spotlights. I think the blue one I have is the strongest. Might be on par with the green one though and perhaps green just makes objects fluoresce less. I don't know since I can't measure the precise output of the spotlights. I am pretty sure the 395nm one is the weakest.

[colinbm]

Thank you, I will try it out.

[Fandyus]

@colinbmNo problem!

[cazza132]

I adore the permutations performed here. I like the IR tri-colour and the trichrome fluorescence. I am fascinated by all the variations and it's cool to make theories! I have been inspired! My gazanias and iris flowers are waiting! Thank you Fandyus for showing :)

[cazza132]

Fluorescent white?

Colour balance under UV black-light conditions once the light source and recepting sensor with barrier filters in place?

Under these conditions, the PTFE board will just show spots of pigmented fiber lint on a dark surface.

The closest thing to a fluorescent white I can think of is calcium carbonate.

There are some interesting variations though - in particular the Map Cowrie shell (Leporicypraea mappa) that fluoresces a pink colour. That is unique amongst the cowrie shells in my collection. Btw - I do not hunt molluscs for their shells - have them because I collected before the age of 15, then thought better :/ Most of these were collected as empty shells from the beach where getting one in good condition is rare, but collectible. If I could photograph a golden cowrie with it's mantle half deployed, that would mean more than to own it's shell!

Colour balance under any sort of fluorescence should (in my opinion) be the choice of the photographer - the photographer's prerogative :) I think calcium carbonate is a start.

[Fandyus]

@cazza132thank you very much for the compliments, I'm glad you like the post!

I agree with you on the colour balance for fluorescence being up for interpretation. I believe there have been debates on this theme here but I don't think we ever arrived to any sort of concensus about what a "standard excitation" is. I have no grasp on mechanics of physics that could define one, maybe someone here does though.

[DKoch]

On 8/19/2023 at 11:35 PM, colinbm said:

Very interesting Fandyus
Does the bottom of the bowl fluoresce white ?
I have been trying to find something that fluoresces white, if you can tell me some more about it please.

There are pigments that fluoresce " white" ( a sort of "cold daylight" white)...or do you mean more natural objects?

[colinbm]

42 minutes ago, DKoch said:

There are pigments that fluoresce " white" ( a sort of "cold daylight" white)...or do you mean more natural objects?

Thanks DKoch
Yes please anything that fluoresces white.

[colinbm]

8 hours ago, cazza132 said:

Fluorescent white?

Colour balance under UV black-light conditions once the light source and recepting sensor with barrier filters in place?

Under these conditions, the PTFE board will just show spots of pigmented fiber lint on a dark surface.

The closest thing to a fluorescent white I can think of is calcium carbonate.

There are some interesting variations though - in particular the Map Cowrie shell (Leporicypraea mappa) that fluoresces a pink colour. That is unique amongst the cowrie shells in my collection. Btw - I do not hunt molluscs for their shells - have them because I collected before the age of 15, then thought better :/ Most of these were collected as empty shells from the beach where getting one in good condition is rare, but collectible. If I could photograph a golden cowrie with it's mantle half deployed, that would mean more than to own it's shell!

Colour balance under any sort of fluorescence should (in my opinion) be the choice of the photographer - the photographer's prerogative :) I think calcium carbonate is a start.

Thanks cazza132
Yes you are correct, but there must be something that fluoresces white ?

[colinbm]

Another way to ask this....Is there a white mineral etc that is white in visible light but absorbs UV light ?
I have tried calcium carbonate before, but I just got some food grade Calcium Carbonate, quite white, but it still faintly reflects some UV.

[Fandyus]

@colinbmThat sounds like a pretty exotic material, I wonder if anyone knows of some.

[Andy Perrin]

On 8/25/2023 at 2:35 AM, colinbm said:

Another way to ask this....Is there a white mineral etc that is white in visible light but absorbs UV light ?
I have tried calcium carbonate before, but I just got some food grade Calcium Carbonate, quite white, but it still faintly reflects some UV.

Yes! Zinc oxide or titanium dioxide sunscreen reflect visible light as white but are very UV absorbing. That is not going to fluoresce white though. 

[colinbm]

Thanks @Andy Perrin
I have found this paper that describes these pigments & their reflectivity.
Now to find some & test them out. I want a good white balance target for UVIVF.
https://www.academia.edu/49510222/Spectral_Behavior_of_White_Pigment_Mixtures_Using_Reflectance_Ultraviolet_Fluorescence_Spectroscopy_and_Multispectral_Imaging

[Andy Perrin]

That article points out that the binder that's used to hold the pigment matters quite a lot to the resulting fluorescence spectrum (not surprisingly). Maybe trying zinc white powder would be a good start, then suspend it in different media. I would try yellow-tinted media, because it will absorb the excess blue light that everything seems prone to.

 

[colinbm]

Thanks again @Andy Perrin
I would like to remind readers that Lead White is highly dangerous.

"How poisonous is white lead?

Inhaling the compound or allowing it to come into contact with the skin causes lead poisoning, an illness whose symptoms include dizziness, trembling, paralysis of the limbs, impaired eyesight and coma. Long-term usage (particularly occupational) can result in death."

[Andy Perrin]

Re lead danger: You could keep it behind glass though. BUt it looks like Zinc is better anyway and a lot less toxic.

 

The zinc white powder has a peak at 500nm which is right where you'd want it...

[colinbm]

Thanks Andy
Yes Zinc White is the way to go.
I'll head off to my local art shop & see what they have in Zinc White & get some yellow to add a add to the mix.
I placed the Lead White poison note just in case someone wanted to experiment that one too.