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Nichia 033A UV LED: Shiny Metal Test for Visible Output

UV Lighting
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#1 Andrea B.

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Posted 24 February 2015 - 04:53

Camera: Df
Lens: Zeiss 60/4.0 UV-Planar
Uvir Block: Baader UV/IR-Cut Filter
UV Light: Nichia UV LED Haiku Flashlight, 033A Diode

All Photographs: ISO1600, Neutral Picture Control, in-camera Auto White Balance later reset in Photo Ninja converter, made in total darkness. The camera recorded these photos in the blue channel. In the editor I tried to re-produce the violet colour as best I could.

ADDED 27 Feb 2015: These photos need a tiny bit more blue in them to match what I saw with my good eye. But not so much blue as to make the spoon look "blue-violet". I do not have a name for the colour I can actually see. Perhaps "magenta-violet" describes it?

I cannot get rid of the visible light leak on this Nichia torch.
Either the Baader-U or the Hoya U340 on the torch does help cut it some.

1. Violet light leak, Uvir-block filtered lens, unfiltered Nichia torch. f/4 for 1.6".
Attached Image: dfSpoon_uvPlanarUvirBlock_NichiaNoFilt_f4ss1.6iso1600_20150223wf_9264pf.jpg

2. Violet light leak, Uvir-block filtered lens, Baader-U on Nichia torch. f/4 for 1.6".
Attached Image: dfSpoon_uvPlanarUvirBlock_NichiaUvBaad_f4ss1.6iso1600_20150223wf_9265pf.jpg

3. Violet light leak, Uvir-block filtered lens, Hoya U340 on Nichia torch. f/4 for 1.6".
Attached Image: dfSpoon_uvPlanarUvirBlock_NichiaU340_f4ss1.6iso1600_20150223wf_9267pf.jpg

**********

Just for grins, here is the spoon photographed with Violet UV-LED illumination.

4. Uvir-block filtered lens, violet LED. f/4 for 1.6".
Attached Image: dfSpoon_uvPlanarUvirBlock_VioletLed_f4ss1.6iso1600_20150223wf_9280pnPf.jpg
Andrea G. Blum
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#2 colinbm

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Posted 24 February 2015 - 05:21

Thanks Andrea
That is why I am using a GG420nm high pass filter, in addition to the UV/IR cut filter on the camera.
The Nichia NCSU033A LED 365nm, is very powerful & narrow band, but the slight leak into visible is able to overwhelm the camera, through the slight UV leak in the Baader UV/IR cut filter.
As it is with light, the longer waves are more photogenic :D
Col

#3 Andrea B.

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Posted 24 February 2015 - 15:12

Col, thanks for your comment! I'm going to look through my filters and see what I have to try to stem the violet leak for UVIVF work.

And I think I need to go back and relabel ALL my UVIVF photos to mention that there might be violet leak !!!! :D :) :P
I'm feeling a bit embarassed that I never tested specifically for this before. UVIVF was never my primary interest, but that's no excuse.

When I was sitting in the dark closet (!!!), it was interesting to see that I could see rather well by the light of the Nichia torch. We all have a smidgen of vision below 400nm, so I was likely seeing in a tiny bit of "official" UV and also all that violet light. As mentioned before (somewhere), my left eye has an intra-ocular lens implant and I can perceive blues and violet quite a bit better with the left eye than I can with my "old" right eye. When I looked at the output from the Nichia 033A with my left eye the actual colour looked almost like the photos above - a dark magenta - very difficult to get right in the camera or in the editor. With my right eye the violet colour was so reduced that it makes me wonder how many colour errors we all make as our eyes age. Well, colour errors around 400nm anyway.
Andrea G. Blum
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#4 colinbm

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Posted 24 February 2015 - 17:11

Thanks Andrea
That is good that you have an 'eye' for this violet. It has been one of my 'pet' subjects for a while now, but I am getting a handle for it.
I should write a little about it some day, soon.
Cheers
Col

#5 Damon

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Posted 25 February 2015 - 00:45

Good test. Dang photons are so hard to stop aren't they?

Col, you say that the Nichia NCSU033A has a slight leak into visible and is able to overwhelm the camera, through the slight UV leak in the Baader UV/IR cut filter.
Mine is a Nichia NCSU033B
Do you know what the difference is?

Do you think I have light leaks in my final B-Ray/LED comparison? And if so, what kind of light?

Thanks,


-D

#6 colinbm

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Posted 25 February 2015 - 01:07

I have the Nichia NCSU033B, I made a typo, sorry.
I have discussed the light leaks before & shown the graphs & asked you to do some tests for me which haven't been done or shown to me yet.
Andrea has shown & explained the leaks here, ask her about it.
Col

#7 JCDowdy

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Posted 25 February 2015 - 02:21

Ball bearings and spoons aside, what does your 1.25" 99% Spectralon reflectance standard look like?

#8 Damon

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Posted 25 February 2015 - 02:39

Meant to say mine is a Nichia NCSU033B. D'oh!
I will look into those test you described and see what I can do.

I guess one you are referring to is testing the Blak-Rays. For the record--my Blak-Rays have brand new filters. Not all of them--but the ones I use for photography
http://www.ultraviol...ce/page__st__60
Re:simple test
--I tried this with 4 Blak-Rays and got no reading at all for IR. Lots of UV but as soon as the contrast filter goes on--nada
--I also tried putting 5 of my regular lenses right up to within inches of the Blak-Rays I use and the other end was the UV meter--no reading
--I also tried the same test as above but with the New MTE light--needle moves slightly (MTE is more powerful)

I have performed quite a few tests recently and at least one specifically by your request. The one with the Hoya over the UV/IR cut and that was actually a great test for two reasons.
1. As John explained--It is an excellent negative control to confirm I was not imaging >720nm when I employ the UV-IR cut in that manner
2. It jump-started a great and involved discussion

I will gladly do more I just need to look through the forum to find what you asked.
It seems it is not as easy as I thought to do all the proper testing asked by everyone...
I have tons of respect for you so if I shirked something you asked it was not intentional!
-D

#9 colinbm

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Posted 25 February 2015 - 04:41

Damon, I must apologise for being a doubter of your Blak-Ray lamps, not putting out any IR, sorry.
But I would like to purchase the Blak-Ray lamp you sent to John for testing please.
I can pay with PayPal.
Cheers
Col

#10 Andrea B.

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Posted 25 February 2015 - 04:42

Ball bearings and spoons aside, what does your 1.25" 99% Spectralon reflectance standard look like?

It is a violet-blue colour, not quite as magenta looking as the above spoon.
Andrea G. Blum
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#11 Andrea B.

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Posted 25 February 2015 - 06:54

The Nichia 033A 250mW chip is older than the 033B which is higher powered but by how much I'm not sure.
Both have 1 die on the chip.
Nichia makes other UV LEDs.
Andrea G. Blum
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#12 DaveO

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Posted 26 February 2015 - 03:14

I have just posted a series of images of Eremophila cuneifolia including a UVIVF shot.

http://www.ultraviol...other-specimen/

Here is that UVIVF image from the camera
Ultraviolet Induced Visible Fluorescence: Pentax K-5 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens with Baader UV/IR Cut Filter, Nichia NCSU033A UV-LED with Baader UV-Pass Filter, 30.0 s @ f/11 ISO 200.
Attached Image: _DO54255_v2.jpg

Here is an image of a stainless steel spoon, in the same position as the flower with the unfiltered UV-LED at the same exposure 30 s @ f/11. The brightness of the blue outer image of the LED was R1, G1, B254. The central purple(?) spot was R126, G1, B255.
Attached Image: _DO54257_v1.jpg

Here is an image with the Baader-U over the UV-LED, with the same exposure 30 s @ f/11 The central purple spot was R83, G1, R124.
Attached Image: _DO54256_v1.jpg

All images were white balanced in PhotoNinja using a custom light source profile for a Metz 15 MS-1 exposure of a Color Checker Passport with a Baader UV/IR Cut filter over the same lens.

#13 colinbm

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Posted 26 February 2015 - 03:39

That looks really good Dave.
Col

#14 JCDowdy

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Posted 26 February 2015 - 04:13

Dave,

Placing the Baader-U on the 365nm LED really shows how much visible blue even the good LED's emit.

I have used a U-360/S8612 filter stack to similar effect on a 365nm LED.

#15 DaveO

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Posted 26 February 2015 - 09:12

John,

I had already done shots with Spectralon so here they are:

Visible Light: Pentax K-5 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens, Metz 15 MS-1 flash, 1/180 s @ f/16 ISO 200, Baader UV/IR Cut Filter.
Attached Image: _DO54181_v1.jpg
Image Reference: DO54181

Ultraviolet Light: Pentax K-5 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens, Nissin Di866 Mark II flash, 1/180s @ f/16 ISO 200, Baader UV-Pass Filter.
Attached Image: _DO54185_v1.jpg
Image Reference: DO54183

Ultraviolet Induced Visible Fluorescence: Pentax K-5 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens with Baader UV/IR Cut Filter, Nichia NCSU033A UV-LED UNFILTERED, 10.0 s @ f/16 ISO 200.
Attached Image: _DO54188_v3.jpg
Image Reference: DO54188

Ultraviolet Induced Visible Fluorescence: Pentax K-5 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens with Baader UV/IR Cut Filter, Nichia NCSU033A UV-LED Baader UV-pass Filter 10.0 s @ f/16 ISO 200.
Attached Image: _DO54189_v3.jpg
Image Reference: DO54189

​I'm suspicious that the Spectralon may be contaminated by the ubiquitous optical brighteners in our world, I also found a NASA reference where they had found Spectralon to contain a volatile organic contaminant that caused it to turn yellow under intense prolonged UV.

I was puzzled by the light on the wooden block, perhaps it is reflected from the Spectralon then by the mirror surface of the Baader U. Here's another spanner - should we flip the Baader U around again as the LED light is coming from the opposite direction to that in our normal UV shots???

#16 JCDowdy

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Posted 26 February 2015 - 15:31

Dave,

This is really nice! You have demonstrated a strong blue reflectance on the Spectralon from the unfiltered LED that is strongly attenuated by the filter. That is also approximately the appearance of my Spectralon under UV-LED filter stack. Spectralon has very good diffuse reflectance so it will uniformly reflect anything fluorescing nearby. I suspect that the wood block is showing some weak fluorescence but that appears less blue. Was anything behind the camera fluorescing in the reflected UV?

What is also interesting is that it seems that a couple of the squares on the ColorChecker are fluorescing. Especially intriguing is the darkest lower left square of the upper panel which is black in visible!

As I understood it, the need to flip the filter had to do with reflection back onto the lens surface causing flare. I tried mine both ways and never could tell a difference but gladly defer to our mentors who have experienced the need to do so.

#17 Andrea B.

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Posted 26 February 2015 - 15:53

Excellent examples, Dave. Thanks so much !!!! (I've been on jury duty and have not been able to photography my standards yet.)

Dave & John, one question: what colour were your eyes seeing? My spoon was definitely purple. The brief look I made of my standard was violet/blue - not nearly as blue as you show above.
Why is your spoon blue ???

I wonder if I picked a weird spoon?

**********

As I understood it, the need to flip the filter had to do with reflection back onto the lens surface causing flare. I tried mine both ways and never could tell a difference but gladly defer to our mentors who have experienced the need to do so

Yes, it's about potential flare. More likely to be seen shooting landscapes outdoors? Baader Planetarium somewhere notes (or once noted) that the shiny pink side is designed to face the incoming light when used with telescopes. So for a photographic lens that is reversed. Induction of flare depends on a whole host of things - lens interiors, camera interiors, direction of illumination, and so forth.
(I need to see where one places the BU when using it with a telescope. On the 'inside' end of the eyepiece?)

Anyway, there is a very interesting experiment for you John. Measure the transmission of a Baader-U both ways. Any differences? Prove that BU orientation does not matter except to reduce possible flare.
Andrea G. Blum
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#18 JCDowdy

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Posted 26 February 2015 - 19:51

Being of a curious nature, I have measured probably every filter I own. Some several times and some even flipped -vs- not flipped. :D
None of it is really presentation quality, mostly slipped in as an afterthought while doing some transmittance job. I do need to do them up right and post some comparisons.

One thing that has confused me is the Baader-U comes with the pink side facing backwards from the direction of the light as it would be mounted in a eyepiece. So reversing it would be the opposite of how it is oriented in a telescope. see: This page (last images near bottom) and this page. The stargazers generally don't think it matters except where reflections cause ghosting.

Such filters are not designed to handle much off axis light, certainly not as much as they see used in the manner we use them.

#19 DaveO

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Posted 26 February 2015 - 23:27

Andrea,
First a cautionary tale. When I entered university back in the dark ages they gave us all a pretty cursory medical which included the coloured dot test for colour vision. A couple of years later they called me back to do some more tests involving sorting coloured discs with similar shades of red and green. THEN they told me that my earlier test had shown that I had the typical male pattern red/green colour deficiency - thanks for that as a chemist, I never could see some of the colour changes in masked indicators.

SO, I never ever estimate ANY colour on screen or anywhere else. I am now looking at a monitor that I keep calibrated but I would never try to match by my eye any colour to what I think it should look like. I use a pair of good polaroid sun glasses (as sold by our ant-cancer council with the maximum UV absorption) so I couldn't tell you what colour I see from my UV-LED anyway. Sorry. Wiki tells me that violet is 380 - 450 nm and blue is 450 - 495 so who knows what colour I am seeing.

Since my Spectralon was an uncalibrated freebie it would be interesting if you took a shot of your genuine Spectralon discs under UV-LED with your D600 and did the same WB you use for sunlight or flash for your visible shots which is what I did. No tweaking in PN. (in other words the same as for my visible light image which was from the flash only but derived from the colour checker as a saved custom light profile).

Dave

Edited by DaveO, 26 February 2015 - 23:35.


#20 Andrea B.

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Posted 27 February 2015 - 15:08

Such filters are not designed to handle much off axis light, certainly not as much as they see used in the manner we use them.

The Baader-U substrate is coatings are dichroic, true. But it does not affect the imaging significantly. Klaus made some measurements to show this.
In the first chart shown, both the Baader-U and the Andrea-U show some attentuation of light which enters at a 45° angle.
http://photographyof...arch?q=Andrea-U

The interesting thing is that light entering thru the Baader-U at a 45° angle is more attenuated in the area around 400nm, thus cutting some violet leak. And the light goes deeper in the UV region.

Klaus' third chart shows that the UG11, an ionic filter, also attenuates some light which enters at a 45° angle.
Andrea G. Blum
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