• Ultraviolet Photography
  •  

Infrared Infographic

Infrared
23 replies to this topic

#21 Andrea B.

    Desert Dancer

  • Owner-Administrator
  • 8,274 posts
  • Location: USA

Posted 09 July 2017 - 18:40

Ah, now, we have to be careful here. I most pointedly, clearly made the clear point above that "Mind you, I'm not claiming no UV gets through". [This time I've bolded that 'not'. :lol: ]

And I also said earlier:
"When both IR and UV light are permitted to reach a sensor, the Infrared light will "win" because there is so much more IR in sunlight than there is UV. So we really cannot make a IR+UV photo. Only the IR is recorded - no, mostly only the IR is recorded."
[This time I've bolded that 'mostly'. Maybe I should have crossed out the 'only' clause. Yeah, I should have. Oh well. :lol: ]

I'm arguing as a purist, as I said. With all that reflective foliage, I just can't see those IR+UV photos as anything other than IR. We are simply having differences over the amount of UV. At best I could only call those IR+uv photos. I couldn't call them IR+UV photos. :rolleyes:

:D

You know how I like to discuss things. And I can be persuaded. Sometimes. B)

[Having the worst internet connection today. Keep losing stuff.]
Andrea G. Blum
Often found hanging out with flowers & bees.

#22 Andy Perrin

    Member

  • Members+G
  • 3,667 posts
  • Location: United States

Posted 09 July 2017 - 23:18

I think without any equivalent of the Wood effect in UV, the IR blows away the UV most of the time in those photos, just because they are mostly vegetation. If some other subject were being photographed, I think the IR and UV might be on a more even footing, Andrea.

That's why I asked before if Steve had any photos showing IR+UV effects that are unique to those filters.
------

Bill's point about most people confusing thermal IR and near IR is well-taken, and I usually have to explain that to people aloud.

Edited by Andy Perrin, 09 July 2017 - 23:21.


#23 Cadmium

    Member

  • Members+G
  • 4,053 posts

Posted 10 July 2017 - 01:12

View PostAndy Perrin, on 09 July 2017 - 23:18, said:

I think without any equivalent of the Wood effect in UV, the IR blows away the UV most of the time in those photos, just because they are mostly vegetation. If some other subject were being photographed, I think the IR and UV might be on a more even footing, Andrea.

That's why I asked before if Steve had any photos showing IR+UV effects that are unique to those filters.
------

Bill's point about most people confusing thermal IR and near IR is well-taken, and I usually have to explain that to people aloud.

Again, the only one of those filters I showed that is UV + IR is the U-360 2mm filter. I showed the other two filters (RG9 and RG850) as IR + Visual and IR Only comparisons.
And, indeed the U-360 filter shots I have shown (other than the one stacked with the GG filter) all show a mix of UV and IR in the sky.
You may say, "IR overpowers UV", this is true, and we don't want any IR when we are doing UV Only, however it can be mixed, and that is why the U-360 shots have blue skies.
"Why does the sky get the UV and not anything else?" Because the sky is dark in IR, and the sky is bright in UV, it's rocket science! ;-)

Cutting off the UV with the GG filter is an excellent way of demonstrating just how much the UV transmission of the U-360 changes the photo.
You may not be able to demonstrate the opposite as exactly, because once you stack the U-360 with something that suppresses and removes all out of band transmission (Red/IR) and leaves you with only UV,
you will then also be suppressing some of the wide open UV that is present in the dual band UV + IR photos.

Regardless, my original point remains simple and the same, that UV does in fact mix with other things. If that were not true, then we would not be using UG5 or U-330 to get UV+Blue+Green.
In the same way that the UG5 filter has a tapered curve giving it stronger UV amplitude compared to the Blue and Green transmission of that filter, so also the U-360 has a somewhat similar ratio which helps to make the UV of the U-360 have more color influence of the sky.
Without that UV the sky is not blue.
Now you may say, "it is not UV, it is blue", but I cut that off at 400nm, and there is no blue sky.
So you might say, "it is high UV, just under 400nm", and I would have no issue with that.
The point is still the same, UV and IR are mixed in such a way with many dual band filters, and you can call that false color, but you can call UV only color false color, and UV+blue+green false color,
and you can call 590nm IR longpass false color. It doesn't matter if it is 'false color', the point is that without mixing UV with IR you don't get the blue skies with U-360 (UG1).
No mater what you call it it is still a mix of UV + . Remove the UV, and you will see the difference.

#24 Andrea B.

    Desert Dancer

  • Owner-Administrator
  • 8,274 posts
  • Location: USA

Posted 10 July 2017 - 16:59

OK, I'm somewhat more persuaded. But I'm afraid "newbies" will think they are getting way more IR than they really are. We have seen so many mis-labeled photos across the web.
Andrea G. Blum
Often found hanging out with flowers & bees.