UV light source shootout

[Andrea B.]

Yes, good old Roy G. Biv, a fine fellow. :D I will keep him in mind to remember to use the colour name 'violet'.

So thanks Johan. [[some words - like 'purple' - just stick from childhood I guess.]]

 

Thanks John for the confirm about silicon.

Kopp filters are new to me. Wonder if I should include a reference in the UVIR Filters Sticky?

[Andrea B.]

OK, I was interrupted there by a very long plane flight from Oslo Gardermoen to Newark Liberty with attendant security/customs checks at both ends. And after commenting last night, I realized I was too tired to write more.

 

So -- to get back to the last two rows - this time looking at the middle column.

 

What are the facts?

• We have a banknote which is designed to visibly fluoresce under UV illumination.
  
• Visible fluorescence (middle column) is observed in the banknote with the first 5 UV illumination sources.
  
• There is no reason to believe that visible fluorescence would not be induced by the last 2 UV illumination sources
  because they have the similar near-UV range (say, within 360-400nm) as the preceding 5 UV sources -
  although perhaps they have different UV-peaks within that range.
  
• However, no visible fluorescence is observed in the banknote in the last 2 (middle column) frames.
  

Thus, given that the UV illumination sources were turned on, we can only conclude that there was a:

• camera malfunction in the K5 which produced a black frame.
  
• exposure error which produced a black frame.
  
• filtration error which produced a black frame.
  
• some combination of the preceding 3 errors.
  

I'm assuming that the K5 is functioning properly else Johan would have reported/noticed some problems in his series of shots. But Johan can confirm that.

 

EXIF info would reveal whether there was some kind of exposure error when attempting to capture the visible fluorescence in the dark.

Johan can you confirm that there was a proper exposure (speed/aperture/ISO) dialed in before taking the shots which produced black frames?

 

Assuming Johan confirms proper exposure details and a properly functioning camera, then only some kind of filtration error can explain the black frames.

 

Perhaps the wrong filter was placed on the lens and visible light was blocked under the given exposure? Or perhaps a filter was not removed before adding the Baader UVIR-Cut, and visible light was blocked by the filter stack under the given exposure?

 

This is end of my explanation attempt for the last two rows - right column and middle column. :D :D :D

 

Obviously, as Johan has already suggested somewhere above, a repeat of the experiment for the last two rows will tell the tale of what went wrong.

[JCDowdy]

... how to explain the last 2 rows of post #10?

 

... Maybe I made a mistake, I'm wondering if I used Baader-U rather than Baader UVIR.

 

Occam's Razor, the simplest explanation should be considered first.

When I encounter befuddling results my first question is always - Did I do what I thought I did? :D

- John

[Andrea B.]

And even logic leads to the same result. "-)

[Johan]

Well I can either feel dumb or or be relieved by the last minute triumph of intellect over evidence, but it seems from some quick tests earlier today that as I'd suspected this is exactly what happened, I'd put the Baader-U on the camera rather than the Baader UVIR cut. Same weird filter size and they both have that yellow look. Note to self, never play photos and post at midnight after a full day at the office =). And, hearty thanks for thinking it through as well, Andrea =)

 

Occam's Razor is a perfect analogy as well, I live 5 miles away from Occam's birthplace after which he was named, the village of Ockham, and drive through there on the way from work regularly :)

[colinbm]

No worries Johan, it just shows you are a mere mortal like all of us on Earth :)

Col

[JCDowdy]

Occam's Razor is a perfect analogy as well, I live 5 miles away from Occam's birthplace after which he was named, the village of Ockham, and drive through there on the way from work regularly :)

 

That is totally cool :)

[Andrea B.]

Johan, no worries. We've all done such things as mis-stacking filters or whatnot in the pursuit of UV.

 

Interestingly, I never knew that Occam was a real person. :)

 

Sometimes I like to "think things through" just to be sure the old brainpan still functions logically. It has been a very long time since my mathematics days.