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Exp 3: Target-UV with Stock Cam, Filtered Lens & Filtered UV-LED

Fluorescence
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#1 Andrea B.

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Posted 03 June 2017 - 17:03

Update 14 June 2017
Added links to other experiments.




Target-UVTM with Stock Cam, Filtered Lens & Filtered UV-LED

Experiment: Test effects of filtration on both the Nichia 365nm UV-Led and the stock lens when shooting the Target-UVTM with an unconverted, stock camera and stock lens. Use an in-camera preset white balance made against the UV-GreyTM target for each filtration choice. Repeat using Daylight white balance. Two different UV-Led filters will be tested.

Conclusion:
The fluorescent UV-GreyTM target works really well to set an in-camera preset white balance under UV illumination. The UV-GreyTM is the target you would want to buy and use for accurate colour in general UV-induced visible fluorescence photography. The Target-UVTM is a more of a specialized target for determining the strength of a subject's fluorescence although its neutral patches can be used for white balance.

Comment: I can't shoot all the WB settings every time. This time I'll just use Preset and Daylight settings.
In later experiments I'll try to hone in on a good K setting.

Equipment:

Camera: Nikon D810, stock

Lens: Micro-Nikkor 60/2.8G
Lens Filter: None, Baader UV/IR-Cut


Lighting: 365nm Nichia UV-Led Flashlight
Lighting Filter:
None, KolariU, Stack of U-360 (2mm) + S8612 (2mm)

Kolari peak: 365nm

Stack peak: 360nm

UV-Led peak: 365nm

Not using the StraightEdgeU because its peak of 379nm is 14nm off the UV-Led peak.

Not using the BaaderU because its peak of 350 is 15nm off the UV-Led.


Settings:

Neutral [0] Picture Control, no sharpening
Nikon ADL = off
f/4 @ ISO-400, various speeds
White Balance Series:
In Nikon cameras, a white balance may be fine-tuned on a 2-dimensional blue-red/green-magenta grid.
The bracketed [0,0] indicates no fine-tuning was applied.
  • In-camera Preset White Balance
    Made against the UV-Grey Target under the 365nm UV-Led torch in darkness.
    A new Preset WB was made for each torch and lens filtration combination.
  • Direct Sunlight[0,0]
    That is, "daylight" or "sunny" white balance.
.
Description:

The experiment was conducted in darkness in my hallway coat closet. For each filter combination, an in-camera white balance preset was made against the UV-Grey Target under UV illumination. Then the Target-UV was photographed. For each filter combination, the Target-UV was then photographed in Daylight white balance. The torch was always kept at same distance from the target and aimed from the bottom of the camera. Live View was used to set exposure times.

Photo Preparation:
  • Conversion in View NX to preserve files as shot.
  • Minor edit in Capture NX2 to equalize white patch brightness across all files.
  • Composite and labels in PSE 11.
  • Resize in Photo Mechanic.
.
Observations:

1) The in-camera white balance presets made against the fluorescent UV-Grey target have been spot on every time so far. The fluorescent white patch on the Target-UV is not quite as accurate for setting white balance. (This time I did not test any grey patches on the Target-UV, but I'm thinking that the middle grey patch should be tested.)

2) When making a color sample or white balance sample on the UV-Grey target, you must be careful to avoid the embedded dark or blue bits. (Fluorescent targets are not always uniform.) The best kind of color sampler or white balance tool for use with these targets is one which uses a drag or a marquee to sample a large enough area to provide an accurate average color or white balance.

3) It was difficult to illuminate the Target-UV evenly when the torch was filtered - partly because the torch was awkward to handle when filtered (filter so much larger than torch). The unevenness can be seen by the variation in the blue or grey strip of the UV-Grey at the bottom of each photo. In some photos the strip is brighter than in others. I think I'm gonna need a bigger torch.

4) Obviously, the Daylight white balance setting does not produce accurate UV-induced visible fluorescent colours. All the photos have a blue colour cast. But, interestingly, I do not see much difference at all between the Daylight photos made with the four possible combinations of torch/lens filtration. I sampled the blue strip along the bottom of each photo in the same place (trying to avoid blue or dark bits) and labeled the location on the colour wheel. The readings are the same, give or take a degree or two.

5) The in-camera preset white balances made against the UV-Grey target for each torch/lens filtration combination do produce accurate UVIVF fluorescent colours. (See #1.) I sampled the grey strip along the bottom of each photo to look for colour casts but found none. RGB labels are shown.

6) Please do let me know of any errors or typos. I'll take any helpful hints on methodology for future experiments!!

Next up: Try to correlate a white balance Kelvin setting to the white balance preset results.

Daylight White Balance :: Baader UV/IR-Cut for Lens :: U-360 (2mm) + S8612 (2mm) for Torch
Attached Image: panel01-04_daylight.jpg

Daylight White Balance :: Baader UV/IR-Cut for Lens :: KolariU for Torch
Attached Image: panel05-08_daylight.jpg

Preset White Balance :: Baader UV/IR-Cut for Lens :: U-360 (2mm) + S8612 (2mm) for Torch
Remember: A preset WB was made against the UV-Grey target for each of the four combinations.
Attached Image: panel13-16_preset.jpg

Preset White Balance :: Baader UV/IR-Cut for Lens :: KolariU for Torch
Remember: A preset WB was made against the UV-Grey target for each of the four combinations.
Attached Image: panel09-12_preset.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.

#2 Andrea B.

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Posted 11 June 2017 - 01:40

Bump. Because I finally got this finished!
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 JCDowdy

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Posted 15 June 2017 - 21:33

Great job Andrea!

I have really been educated by this series!

Thank you!!

#4 Cadmium

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Posted 16 June 2017 - 03:52

They have some of the grey paint, but I can't figure out where to buy it.
Middle row, right.
http://1.bp.blogspot...0/golden_uv.jpg

Bottom of page:
http://uvinnovations...01_archive.html

Edited by Cadmium, 16 June 2017 - 03:54.


#5 JMC

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Posted 16 June 2017 - 06:59

View PostCadmium, on 16 June 2017 - 03:52, said:

They have some of the grey paint, but I can't figure out where to buy it.
Middle row, right.
http://1.bp.blogspot...0/golden_uv.jpg

Bottom of page:
http://uvinnovations...01_archive.html

Looks like these are the folks that make the paint;

https://www.goldenpaints.com/products

But from the photo on the UvInnovations blogspot, it looks like they are custom made for them by Golden, so chances are they don't sell it to anyone else. Perhaps try contacting Golden direct and quoting the custom paint code from the photograph and see whether they can supply it direct to you?
Jonathan M. Crowther

http://jmcscientificconsulting.com