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UltravioletPhotography

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David, I tried this here:

I used a Convoy S2+ Nichia 365nm UV torch, through a Tiffen #12, no UV makes it through.

The same using the DB850, there is the tinniest bit of barely detectable fluorescence, no LED image.

Stacked together there is nothing, just some fluorescing dust on the torch side of the filters.

That is with U-340 on the torch to remove any 400+nm light from the torch emission.

 

Does that help? Would you like some other test?

 

Actually doesn't help for a controlled study. I have no problem believing a filter expert whom knows the slightest difference in orange filters discussed in a different thread, would pick and own an excellent tiffen 12 filter sample.

 

However, I have know idea where Andy bought his Tiffen #12. Is it really a Tiffen filter or Chinese copy with small 2% leak at 380nm not normally detectable. To be sure I would want Andy to run his filter in a controlled way.

 

I guess I wasn't clear about that. I under stand that Tiffen filters are great. I like mine.

 

Also no offense intended to Andy. He is a smart guy. But we all buy stuff cheap off ebay and its quality can be questioned at times.

 

My Parks 38A filter is actually a #47 filter.

My Parks 47 filter acts exactly like a B370 filter. Don't know if the seller accidently switched them once when cleaning or if Parks makes them that way.

 

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Andy Perrin

It is a Tiffen brand filter from Adorama. It wasn’t from eBay. It has functioned normally in all prior instances.

 

Also, your comment that we all buy cheap filters on Amazon is at best half-accurate in my case. I prefer to know where my filters come from and the majority are from Cadmium or trusted manufacturers/sellers like Tiffen/Adorama. The only cheap stuff from eBay that I own is a 1000nm filter of unknown provenience and my Omega seconds.

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David, So in other words, you want Andy to shoot another picture out his window (nice view by the way), all the same except with a U-340 or some such on the front?

Same settings as the other shots,or as another comparison shot... And you know, it will be a completely black shot if the Tiffen 12 is not some kind of strange impostor with a UV blip.

Right?

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I have UG11 but no U340?

The difference is not much... UG11 lets in a bit less UV and a bit more deep red/IR, and blocks green better than U-340, at the same thickness.
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Andy Perrin
Unfortunately in this case you will definitely see the IR. It’s not a good test.
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So stacking it with S8612 (basically stacking it with a UV-pass filter) will solve the problem?

 

The point is to see UV, right? And maybe see what color it has with your aerochrome process.

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Andy Perrin

That is going to be one thick stack! To recap:

Tiffen12, DB850, UG11, S8612, and then the step rings because the Tiffen is 49mm and the others are 52!

 

Honestly I kind of want to try it just to make this Rube Goldberg filter contraption.

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Andy Perrin

Okay, okay, here you go.

 

First, a retake of the original image (keep in mind the rainbow photo was a pano, so the field of view will not be the same). The settings for all photos were F/8 1/250" ISO100, as in the original as best I recall, unless otherwise specified. Time of day was not the same.

 

DB850 + Tiffen#12:

post-94-0-12678100-1593878431.jpg

 

Next, let's put UG11 2mm and S8612 1.75mm on there.

 

DB850 + Tiffen#12 + UG11 2mm + S8612 1.75mm:

post-94-0-98184100-1593878572.jpg

 

Nothing. What if we do an autocontrast (Photoshop)?

 

DB850 + Tiffen#12 + UG11 2mm + S8612 1.75mm: + autocontrast:

post-94-0-24849100-1593878630.jpg

 

Noise. Let's try the UV photo alone, under the same settings.

 

UG11 2mm + S8612 1.75mm:

post-94-0-65694400-1593878681.jpg

 

Pretty underexposed! That's because there just isn't much UV in sunlight relative to vis and IR. If we adjust the time to 0.4 seconds we can see something.

 

UG11 2mm + S8612 1.75mm, with F/8, ISO100, 0.4":

post-94-0-84253200-1593878755.jpg

 

Here is the monster stack, for your enjoyment:

post-94-0-15212800-1593878800.jpg

 

ETA: Here are a couple more.

 

Let's let the full stack run for 30 sec.

 

DB850 + Tiffen#12 + UG11 2mm + S8612 1.75mm

F/8, ISO100, 30sec

post-94-0-33447100-1593879894.jpg

 

What if we autocontrast that?

post-94-0-81081500-1593879913.jpg

 

There ain't nothing there. You can see whatever light leaks I have in this setup, and that's it.

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Checking in late. Yes exactly what I want to see. Now we know you genuinely captured some really odd IR bands from that rainbow that aren't normally visible.

 

Not sure why you needed S8612 in your stack, as the DB850 filter cuts out the 680nm to 800nm IR leak from the Ug11, u340 or ZWB1 filters.

 

Now you you have me questioning the UV band capture from rainbows. I still haven't caught one. But how do we know when we think we have the UV bands we aren't really capturing IR bands that you caught.

 

I will have to make some rainbows with a garden hose and play with filters if I get a good clear high UV day again.

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Andy Perrin

Checking in late. Yes exactly what I want to see. Now we know you genuinely captured some really odd IR bands from that rainbow that aren't normally visible.

 

Not sure why you needed S8612 in your stack, as the DB850 filter cuts out the 680nm to 800nm IR leak from the Ug11, u340 or ZWB1 filters.

UG11 passes 800-900 at aroune 1%, so you will get an IR image if you push it.

 

There was never any doubt about the UV in any mind but yours...

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Thanks Andy, Well done. Although, I am starting to receive alien messages when I look at your static shot, and the conclusion I come up with should be obvious:

Some sort of two-phase liquid-vapor mixture is going on here... :cool:

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Thanks Andy, Well done. Although, I am starting to receive alien messages when I look at your static shot, and the conclusion I come up with should be obvious:

Some sort of two-phase liquid-vapor mixture is going on here... :cool:

So I am not the only one who started reading the book!
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Ha ha, Andy is a PhD, I think... so are a few others around here. Impressive indeed to me. Education, experience, training.

The book he uses in his photo shoot is probably not exactly random, it is at least a glimpse into his thinking.

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Andy Perrin
It's just the last thing I was working on the night before. Thermodynamics text. I am in the process of computerizing the tables in that book so I never have to look up anything in the back ever again.
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