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

[Andrea B.]

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".

 

2. Violet light leak, Uvir-block filtered lens, Baader-U on Nichia torch. f/4 for 1.6".

 

3. Violet light leak, Uvir-block filtered lens, Hoya U340 on Nichia torch. f/4 for 1.6".

 

**********

 

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".

[colinbm]

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

[Andrea B.]

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.

[colinbm]

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

[Damon]

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

[colinbm]

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

[JCDowdy]

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

[Damon]

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

[colinbm]

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

[Andrea B.]

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 B.]

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.

[DaveO]

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

 

http://www.ultravioletphotography.com/content/index.php/topic/1251-eremophila-cuneifolia-pinyuru-another-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.

 

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.

 

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.

 

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.

[colinbm]

That looks really good Dave.

Col

[JCDowdy]

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.

[DaveO]

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.

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.

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.

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.

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???

[JCDowdy]

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.

[Andrea B.]

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.

[JCDowdy]

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.

[DaveO]

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

[Andrea B.]

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 B.]

The stargazers generally don't think it matters except where reflections cause ghosting.

 

That is why it matters in photography - reflections/flare/ghosting.

 

In close work you might not ever see this?

 

**************

 

Dave - I will shoot my Labsphere discs and my white panel today. :D

I have profiled the colour of the D600-broadband for visible daylight work, so I shall apply that profile in PN.

But I'll show everyone the before and after also.

[rfcurry (1950-2024)]

Andrea,

 

Klaus's statements regarding the difference between ionic and dichroic filters in handling non-collimated light runs contrary to both the physics and statements provided by the filter makers themselves. Dichroic filters are designed for collimated light.

 

http://uvroptics.com/graphics/Bandshift400px1.jpg

[Andrea B.]

Here are my photographs of the Labsphere White Reflectance Standard that Dave wanted to see.

 

These poor standards have gotten so beaten up from falling in the dirt, being dropped, taken on long journeys and so forth. I probably need to take a little very very fine emery cloth to them.

 

Camera: Nikon D600-broadband

 

Lens: Zeiss 60/4.0 UV-Planar on Helicoid

Lens Filter: Baader UV/IR-Cut

 

Light: Nichia 365nm 033A UV-Led Torch

Light Filter: Baader-U UV-Pass

 

All photographs made in total darkness at f/8 and ISO-400.

 

Please do not make any conclusions based on the exposure speed, OK? It was left at 1.6" for convenience, and the torch may not have always been at the same precise distance from the white reflectance standard.

 

These photographs have not been in an editor. The jpegs were extracted from the NEF in Photo Mechanic, so they are exactly as photographed except for resizing and addition of a watermark. sRGB color space was used.

 

 

Set 1: Auto White Balance

 

Nichia torch not filtered.

With my 'good' left eye having an IOL, I see this as a bit more purple than in the photograph

but with more blue than my spoon shown above.

The photo is not too far off what I see with this good eye.

With my old 'bad' right eye, I cannot see much color at all while shooting this.

The lettering on the CC Passport is a bright fluorescent neon blue,

but the letters blow out in a 1.6" exposure so look whitish in all photographs.

 

Nichia torch filtered with Baader-U UV-pass filter.

Some of the violet/blue visible output of the Nichia torch is reduced.

 

 

Set 2: Daylight White Balance

 

Nichia torch not filtered.

With my 'good' left eye having an IOL, I see this as a bit more purple than in the photograph

but with more blue than my spoon shown above.

The photo is not too far off what I see with this good eye.

With my old 'bad' right eye, I cannot see much color at all while shooting this.

The lettering on the CC Passport is a bright fluorescent neon blue,

but the letters blow out in a 1.6" exposure so look whitish in all photographs.

 

Nichia torch filtered with Baader-U UV-pass filter.

Some of the violet/blue visible output of the Nichia torch is reduced.

[Andrea B.]

OK, I just put the SigOth in the dark closet with the spoon, the Labsphere standards and the Nichia UV-Led torch UNFILTERED. He is a good sport!! He reports seeing with the naked eye a somewhat dull "greyish" colour for the LabSphere standards and no purple/magenta or blue from the spoon. This is how I see things with my old right eye also.

 

So that was an informal sanity check.

 

The point to make, perhaps, is that is very difficult to judge the actual colour of the visible (unwanted) output from the filtered and unfiltered Nichia 033A UV-Led by using the naked eye, particularly if it is over 50 years old by which time there is basically a yellow filter through which everyone sees unless you have had an IOL implant.

[DaveO]

We don't have to "guess" colours if we are using Photoshop software such as Elements or CS3/4/5

In the Window drop down list choose "Info" which will put onto your screen the Info palette which shows the RGB values of the pixel on which your cursor is resting. Drag the Info palette off to the edge of your screen and leave it there. It's very handy to know what your pixel colours are and whether you have a blown RGB channel. I once read that using such software without the Info palette is like driving a car without a speedo.

 

In my filtered shiny spoon image the dim purplish blob was R83, G1, B124 which really is sort of violet, certainly not bright blue as for the unfiltered spoon which also has a blown blue channel (R1, G1, B255).