15 replies to this topic

[BruceG]

The flower dome is one place in Singapore where I can always find new subject for UV floral photography, the place is like a huge greenhouse however the glass ceiling almost completely blocks UV radiation from sunlight.

In order to take pictures in conditions like this, (and also in hope of shooting some videos) I assembled a circular UV LED light, and recently I finally got to test it.

I used 32 LED bulbs from 365 to 405, and adjusted their proportion to give similar white balance result as from the sunlight, the photos taken all used the same white balance setting I made in lightroom with some help from photoshop. In other software such as capture 1, a proper white balance will give more violet instead of blue. My different color is entirely a result of the software. However, I found the combination of yellow and blue aesthetically more appealing therefore I didn't try to change it.

I shot a range of flowers including many types of sunflowers, the light is strong enough for me to handhold to take pictures, and judging from the pictures, I think my LED light can resemble natural light close enough as far as UV false color is concerned, especially when the camera can only effectively record wavelength above 350nm.

The pictures are taken on a converted Sony A7S, with a 40/2.8 Seiko lens from a Mamiya rangefinder, 1st generation SEU filter was used.
Exposure setting: all phots are taken with 1/50 shutter and 5.6 aperture, ISO setting changes between 1600 to 4000 depending on the distance.

Edited by BruceG, 06 October 2018 - 17:33.

[UlfW]

Very interesting project.

I would be very interested in more details about it.
Can you please show the LED assembly and component types?

[BruceG]

I will share some details on my equipment in another thread here:
http://www.ultraviol...uv-led-project/

Edited by BruceG, 03 October 2018 - 16:23.

[dabateman]

I find the 6th photo really interesting. Do you have a visual spectrum comparison image? I am intrigued, by the 3 flowers that are blue in the black sea.

[Andy Perrin]

Fantastic photos, and really cool equipment.

[BruceG]

dabateman, on 03 October 2018 - 18:11, said:

I find the 6th photo really interesting. Do you have a visual spectrum comparison image? I am intrigued, by the 3 flowers that are blue in the black sea.

For all I can remember, they are the same type of daisy, dark red in appearance, different UV color might be because of the angle, or the color might change during different phases of flowering. Unfortunately a VIS comparison was not capture as converting my setup was a bit of a trouble.

[Cadmium]

Bruce, Very nice photos! :-)

[BruceG]

Cadmium, on 04 October 2018 - 06:35, said:

Bruce, Very nice photos! :-)

Thank you!

[UlfW]

Cadmium, on 04 October 2018 - 06:35, said:

Bruce, Very nice photos! :-)

I Agree.
I should have said that in my first post.

Do you have any exposure data?
Lens type, ISO, aperture setting and exposure-times would be interesting to know.

[bobfriedman]

nice work!

[JCDowdy]

An interesting source indeed!
You have some striking false UV-yellow and UV-blue from your polychromatic 365nm, 370nm, 395nm and 405nm LED array. Appears to correlate with the false colors of the typical "sparticle" filter arrays. Where is that greenish gold foil coming from, a metamerism perhaps?

[Cadmium]

'The Gold Look', I call it. I get that same gold look once in a while when I shoot UV, seems like usually in the late afternoon sun, natural light.
I have seen the same from other people also at times.
I have never figured out what makes that happen. It is not the way I white balanced it.
Here is an example.

[BruceG]

UlfW, on 04 October 2018 - 13:15, said:

I Agree.
I should have said that in my first post.

Do you have any exposure data?
Lens type, ISO, aperture setting and exposure-times would be interesting to know.

Thanks, I edited in the info and datas.

[BruceG]

JCDowdy, on 05 October 2018 - 00:18, said:

An interesting source indeed!
You have some striking false UV-yellow and UV-blue from your polychromatic 365nm, 370nm, 395nm and 405nm LED array. Appears to correlate with the false colors of the typical "sparticle" filter arrays. Where is that greenish gold foil coming from, a metamerism perhaps?

Where is the green? Do you mean the second picture?

[JCDowdy]

BruceG, on 06 October 2018 - 17:42, said:

Where is the green? Do you mean the second picture?

Yes and #6 also, the metallic greenish gold or goldish green to my eye at least.

[BruceG]

JCDowdy, on 07 October 2018 - 16:08, said:

Yes and #6 also, the metallic greenish gold or goldish green to my eye at least.

Well they occur to me as yellow. I did not have the chance do a sparticle test, but I have seen how a 310nm LED looks like on my camera, that green is more pure and easily separates form the yellow.