Paint Torch Reflector Black

[ulf]

Ulf,

That thing looks cool. I wonder how the output is compared to the bulb that Col and I have that he linked to. Ours is rated at 7W. Its uniform and I us it all the time.

The output depends on conversion efficiency of the LEDs and input power.

 

I think that the LEDs in the array I have used is of high quality and almost as efficient as the type from Nichia used in some of the Convoy UV torches.

The array can handle 50 W input power, but I have chosen to drive it conservatively at ca 35W.

If the LEDs in your 7W lamp has the same efficiency, then my array will emit ca five times more optical power.

 

I do suspect that your lamp's LEDs are less efficient, to make it cheaper to produce, as it is more of a volume consumer product, while my array appears to be designed for industrial usage.

[ulf]

Here is a comparison.

At least I and David can clearly see the difference in the image. It is just as I predicted.

As it is a jpeg it is not possible to do measurements of the difference in optical power due to the gamma.

 

Quick sampling in Photoshop still show differences with values from around 102-128 for the black-painted and 122-143 for the PTFE taped one.

 

The difference is affected by more that tape or paint.

Individual differences between LEDs and small differences in distance between lamp and paper can also affect the result

[dabateman]

Looking at that image is really interesting. The stock convoy has a ton of central power. But the PTFE, doesn't seem to be as evenly distributed with the same power. The black paint one is lower.

 

I wonder if you cut a 20mm disc of Lee 750 diffuser and add it to the stock reflector, do you still get the power amplification, but diffuse?

[Cadmium]

David, I will leave that test up to you.

 

Once again, the point of my test here is simply to remove the hot spot created by the parabolic reflector.

The design of the UV diving flashlights, like Eka is recently using, have no reflector.

For example, let me quote from one of the eBay diving torch listings:

 

"Reflector: no hotspot design, no reflector

Angle of light beam: 120°"

 

No reflector, and the LED's are 'out front' where they make a wider beam.

That was my intent here, to test those two ideas with multiple LED's using the Convoy flashlights I already have.

Although the Convoy doesn't exactly have 'out front' LED's, the torches still have a fairly wide beam, which I think is about 80 to 90 degrees.

The beam angle is good for this test, and quite adequate for real use also, and much more useful than the stock bean with the hot spot which reduces the 'real illuminated area' to a small angle,

and requires moving the beam around during exposure ('painting') in order to get a more evenly illuminated photo.

So in that aspect removing the reflector and grouping the torches worked good for this test, and I am encouraged by the results.

 

That being said, this concludes my tests in this topic.

[dabateman]

My tests with Jpegs straight from camera. Settings are:

EM5mk2 ISO 400, F5.6, 1/320 on the 30mm F3.5 Macro lens. Fixed white balance

Set to record Raw + Jpeg Normal 1024x768

 

Good Convoy (No IR leak) aligned with back exactly at 18 cm mark on a ruler

 

Convoy with U340 filter, reflector, No Lee 750:

 

Convoy with No U340 filter, No reflector, No Lee 750:

 

Convoy with U340 filter, reflector, Lee 750:

 

Convoy with No U340 filter, PTFE reflector, No Lee 750:

 

Convoy with U340 fitler, PTFE reflector, No Lee 750

 

I decided best configuration is PTFE on reflector with U340 fitler, No Lee 750 filter.

 

Since I cut the Lee 750, I now have it on my Convoy which has an IR center. It works to diffuse that light a little.

[Cadmium]

Good test, David.

 

How does the

Convoy with No U340 filter, PTFE reflector, No Lee 750:

compare with the

Convoy with No U340 filter, No reflector, No Lee 750:

side by side?

 

I tested those two with my Blak-Ray meter, and there is some difference, just hard for me to see any with my eyes.

[dabateman]

I only have one good strong working convoy and no UV meter. So can't do a side by side.

The advantage of my test above is all images from same convoy LED.

 

What I found interesting was that the U340 works to diffuse the light slightly. With the U340 filter, the circle is broader. I am not sure if the slight intensity drop is real though. As the camera will be less sensitive to the U430 filtered light than unfiltered light. So if I had a UV meter they maybe the same. Just a wider circle.

[Cadmium]

Blak-Ray 221 and 225. Lots on eBay. They are very handy for testing torches. Model 221 is more sensitive.

[Cadmium]

Blak-Ray 221 and 225. The 221 is more sensitive, compare meter scaling. Each has added sensitivity switch on the back.

Both are handy, since somethings will be off the scale of one or the other, even when back switch is switched.

 

[Cadmium]

Yes, I can see a bit of a difference between your No Reflector and your PTFE Reflector when I put the pics side by side.

I don't want to put the tape on my reflector again, that was no fun.

[colinbm]

have you looked to see if the reflector will push out of the heat-sink, or is it a solid piece ?

[colinbm]

The whole torch is a heat-sink & as such the reflector can be left out & the inside of the torch is black at this end anyway.

[Cadmium]

Yep, the Convoy works with/without the reflector, heat seems the same wither way, I tested that last night.

[ulf]

Blak-Ray 221 and 225. The 221 is more sensitive, compare meter scaling. Each has added sensitivity switch on the back.

Both are handy, since somethings will be off the scale of one or the other, even when back switch is switched.

 

Actually they are designed for different wavelength ranges too:

https://us.vwr.com/store/product/4548861/uvp-blak-ray-uv-intensity-meters-models-j-221-and-j-225-analytik-jena

[Cadmium]

And they both sense the Convoy. One more than the other of course.

The problem is, with the 221, it will read off scale in both A and B switch mode.

The 225 will read on scale with the Convoy, in either A or B switch mode.

So if you want to compare variations with the Convoy (and or other UV torches), you would be unalienable to compare with the 221 because any variation will be off scale in either A or B switch more.

It depends on the distance also,

[colinbm]

Steve

Have you got the attenuater ?

[Cadmium]

Here I used the Blak-Ray 221 at a distance of 15" in B switch mode. As a past reference.

https://www.ultravioletphotography.com/content/index.php/topic/2120-convoy-s2-uv-flashlight/page__view__findpost__p__15521

[Cadmium]

There is also the Solarmeter, Past reference shows I used it at 30mm distance:

https://www.ultravioletphotography.com/content/index.php/topic/2120-convoy-s2-uv-flashlight/page__view__findpost__p__15376

[Cadmium]

Steve

Have you got the attenuater ?

 

I might! What does your look like? Are you talking about the metal plate with the holes?

[colinbm]

Yes Steve

[Cadmium]

Yes I do.

[dabateman]

Yes, I can see a bit of a difference between your No Reflector and your PTFE Reflector when I put the pics side by side.

I don't want to put the tape on my reflector again, that was no fun.

 

Its easier the 3rd time. I put it on, then pulled to break and ripped it off the 1st time. The second time I slide it off.

The 3rd time worked. I wraped it around the top first, then down to the base. Carefully using a finger nail to push it down and spread it out. Once the U340 is in front it seems to act like a seal holding it in place.

I think I am done the tape plus U340 looks the best to me. So no need to do it again. Unless a buy an other flashlight.

[colinbm]

Just as an aside, I thought that Teflon was transparent to UV light ?

But it is probable its acting as a defusser ?

[JMC]

Perhaps there is some paint on Teflon stuff, would be whole lot easier to do.

 

Labsphere do a touch up paint for integrating spheres. I dread to think how much it costs though.

[ulf]

Labsphere do a touch up paint for integrating spheres. I dread to think how much it costs though.

Similar to this:

https://www.edmundoptics.com/f/pre-mix-white-reflectance-coating/11427/

 

It is a bit difficult to prepare and apply correctly.

The coating is intended to be applied with compressed air spray painting, not for paint brushes.

It is a modern version of the Eastman 6080 White Reflectance Coating based on Barium Sulphate.