Floral Variety in Many Wave Lengths

[colinbm]

Floral Variety in Many Wave Lengths, 255nm to 850nm.

PS, the distance is 4'-6" or 1370mm, from subject to sensor & LED lighting.

 

Sigma fp full spectrum converted, with Sigma 105mm lens in 5000k 6500k LED light. No filters needed.

 

The rest are with a Sigma fp mono converted, with a UV Nikkor 105mm lens with various LED lights with filters.....

255nm

 

308nm

 

367nm

 

white light 5000k 6500k

 

850nm

[Foxfire]

Amazing! 255 looks very well! Can you post UV tricolor?

[colinbm]

@Foxfire Thanks

That will be a new endeavour that I will attempt.

[Nate]

Nice Colin, very wide range. That 255 is Excellent.

[colinbm]

@Nate Thanks Nate
I forgot to mention this is 4'-6" or 1300mm, from subject to sensor & LED lighting.

[photoni]

@colinbm it's finally possible!

.
only one thing I don't understand: why is image 5 (white light 5000k) so contrasty?

it looks like a simulation of the wet plate (BG39+BG25) the yellow flower is white, red and black.
if I convert the first image to BW with standard values, it is much softer.

[photoni]

255+308+367 nm

.

[Stefano]

Nice indeed. You paired each LED with a filter on the lens if I understand correctly.

 

Interesting how flowers appear less "glossy" at 255 nm. That might be how they actually appear, or there could be a leak. You could test for this to be sure.

[colinbm]

@Stefano Thanks
The filters are on the UV LEDs, I haven't seen any IR leaks on the spectroscope.

[colinbm]

@photoni Thanks
"only one thing I don't understand: why is image 5 (white light 5000k) so contrasty?"

Different camera & lens ?

[Stefano]

13 minutes ago, colinbm said:

@Stefano Thanks
The filters are on the UV LEDs, I haven't seen any IR leaks on the spectroscope.

If the filters are large enough, I would mount them on the lens. Even if the filtered light is clean, there might be some fluorescence from the subject that you aren't filtering out.

[colinbm]

@Stefano Thanks
I didn't think of that 

[photoni]

9 minutes ago, colinbm said:

@photoni Thanks
"only one thing I don't understand: why is image 5 (white light 5000k) so contrasty?"

Different camera & lens ?

yes, but it doesn't look like a normal monochrom.
I was wondering how it behaves outdoors in landscape photos with and a BG38 2mm/t filter?
does it look like a Pentax K3 mono or a Leica mono?

.

This is something I wanted to ask @lukaszgryglicki too

[colinbm]

@photoni It is 1:20am here

I will look at it in the morning when I awake again.

[Foxfire]

While looking at the photoni tricolor, i downloaded the images too, to play around a bit. Got an idea from this that while doing tricolor images, maybe it would make sense to use also something for white balancing? Like this teflon tape that could be treated as a reference for a white in a composite tricolor image. 

[Andrea B.]

Interesting how flowers appear less "glossy" at 255 nm.

When photographing flowers, the glossy areas (structural reflections) can change dramatically with even a tiny change in the angle of illumination. So I'm thinking that more experiments would be needed to confirm actual changes at 255 nm.

[Andy Perrin]

Colin, can we see an example with some glass? Maybe a clear glass vase? That should definitely be different in 255nm. 

[Andrea B.]

Toni: only one thing I don't understand: why is image 5 (white light 5000k) so contrasty?

Col: Different camera & lens.

 

Also it appears that the first vis image was made with some additional ambient light given that the background is more evenly lit? While the second B/W image was made only with the LED illumination?

[colinbm]

@Andrea B. @photoni
When the camera is set at Mono, there is no White Balance.
Here is a late afternoon sun light photo, the floral arrangement has changed.
Sigma fp mono converted, UV Nikkor 105mm lens with a Kolari hot mirror Pro2, which is a good match to the cameras original.

 

[photoni]

27 minutes ago, colinbm said:

Kolari hot mirror Pro2, which is a good match to the cameras original.

now, yes, everything is "normal"
do you have an identical image without the Kolari filter?
I didn't realize there was such a big difference

.

In your opinion, what are the wavelengths that make this big difference?

[colinbm]

@photoni I don't know.

The original was a household 14.5watt 6500k LED light. I was mistaken that it was 5000k, other household LEDs I have are 5000k.

The first was relying on the RGB of the 6500k to keep within the visible range.
The second sunlight one I used the Kolari hot mirror Pro2 to keep within the visible range.
The sun has gone.

@photoni  Looking at the Kolari graphs, It appears that the 6500k lamp is a bit more red at 50% at 650nm.

[colinbm]

@Andy PerrinDefinately a difference.

255nm with the filter on the lens.

[Stefano]

The glass(?) vase doesn't look completely opaque at 255 nm. I'm not sure if this can or shouldn't happen.

 

Schott K7, which is UV friendly, has 9% internal transmission at 300 nm at a thickness of 10 mm, and transmission isn't specified at shorter wavelengths.

 

9% at 10 mm means a rather high 61.78% at 2 mm. If the vase is thin and made of crown glass, perhaps it is possibile for it to transmit just enough light at 255 nm to see through it in a photo, but I think it's unlikely.

 

To rule out a leak, try this if you can: put a 254 nm mercury-vapor lamp inside the vase (if it's possibile to move the flowers). I think you have such a lamp. Make things light-tight if possibile, so that all the UV from the lamp stays inside the vase. Then, try to see the 254 nm line with a spectrometer, through the vase. If you can't see it, or it is strongly attenuated (less than 1%), then the glass should look completely opaque at 255 nm, also because probably anything darker than OD 2 or so will look black in a properly-exposed photo. If instead there's some amount of 254 nm light escaping, your photo could be actually leak-less.

[colinbm]

@Stefano I will do the test with the mercury vapour lamp tomorrow when I will have to throw these flowers out as they are dyeing, then I can clean the vase & do the test.
I have just re-done the 255nm photo again with the filters on the LEDs, with a S8612 on the UV Nikkor 105mm lens to see if there was any UVA or visible fluorescence.
With a 30 second exposure at a 5.6 aperture opening the image was essentially black.

[lukaszgryglicki]

I don't think I ever made an image with pure UVC (255nm) as I only have Hg lamp as a source and I have no filtering possibility at 254nm - OK I do have some possibility but I think I'm seeing mostly (95% or more) leaks from higher wavelengths.... I don't have any 255nm diode that outputs ONLy UV-C - I would be happy to buy something that emits ONLY 255nm so no filtering would be needed - but I didn't find anything that has any usable output... I there is a device emitting pure UV-C at considerable power, I woudl go for it to test, for now I'm blocked by non-UV-C leaks that dominate neglible UV-C - also my camera is probably a lot less sensitive to UV-C than leaks.

:(