Delta 400 & 720 Filter!

[Daniela]

Beautiful result, OP! The beauty of that light around the columns is breathtaking with this filter!

 

[Helge]

Found this intriguing patent, that AFAICS proposes the use of the Herschel effect for using bog standard film (IR sensitive film would actually be bad, again AFAICS) for recording pretty deep into the infrared spectrum. And what's more due to the desensitising effect of the Herschel effect the capture is a positive.

https://patentimages.storage.googleapis.com/01/02/fd/ee2c2e99e9ebb8/US4018608.pdf

The only catch seems to be that you need to give a brief post exposure flash right after, or in fact preferable as a continuation of the IR exposure. That could be tricky to achieve with a normal camera, but certainly possible.

Could this be a substitute for HIE?

Edit. A further possibility is that stuff like D400 could actually be faster in ”Herschel” reversal mode. Even with a 720 filter.
Would be pretty easy to test.
Who gets there first‽

 

[Ian Leake]

This is very interesting. Thanks!

 

[Sirius Glass]

Found this intriguing patent, that AFAICS proposes the use of the Herschel effect for using bog standard film (IR sensitive film would actually be bad, again AFAICS) for recording pretty deep into the infrared spectrum. And what's more due to the desensitising effect of the Herschel effect the capture is a positive.

https://patentimages.storage.googleapis.com/01/02/fd/ee2c2e99e9ebb8/US4018608.pdf

The only catch seems to be that you need to give a brief post exposure flash right after, or in fact preferable as a continuation of the IR exposure. That could be tricky to achieve with a normal camera, but certainly possible.

Could this be a substitute for HIE?

Edit. A further possibility is that stuff like D400 could actually be faster in ”Herschel” reversal mode. Even with a 720 filter.
Would be pretty easy to test.
Who gets there first‽

The best substitute is a real infrared film such as Rollei IR 400 shot at box speed and then adjusted for the filter.

 

[Helge]

The best substitute is a real infrared film such as Rollei IR 400 shot at box speed and then adjusted for the filter.

Doesn’t get you much beyond 720. And is quite slow.
Don’t get me wrong I love Aviphot, it’s a better film than HiE on many counts.
But on extension and speed it’s not.
If the Herschel effect can “fix” some of that, and even on regular B&W film it would be fantastic.

And it’s very simple to test on a single frame.
Hold the IR filter in front of the lens and expose. Slide a diffusion filter in front if the lens and remove IR filter and expose with “fill” exposure. Close shutter and develop film.

The exposures will have to be derived experimentally of course, so probably best to start with 135 Foma or the like.

 

[John Wiegerink]

In some of my examples, especially the one of all trees, the foliage is rendered white. That tells me that there is more going on than just extended exposure. It is very doubtful that this will happen to a film sensitised up to 650nm. The next sunny day, I'll go out with some HP5 and prove it.

I recently shot some Rollei Infrared, but when I was testing that I also found an old Hasseblad back with very old HP5+. I took a few shots using my SuperwideC and that old HP5+ with the 720 filter. I didn't write anything down exposure wise on those shots, since I figured there'd be nothing too good. You would be surprised how HP5+ and a 720 filter look. Certainly not HIE film, but certainly worth doing some more experiments with. JohnW

 

[reddesert]

Found this intriguing patent, that AFAICS proposes the use of the Herschel effect for using bog standard film (IR sensitive film would actually be bad, again AFAICS) for recording pretty deep into the infrared spectrum. And what's more due to the desensitising effect of the Herschel effect the capture is a positive.

https://patentimages.storage.googleapis.com/01/02/fd/ee2c2e99e9ebb8/US4018608.pdf

The only catch seems to be that you need to give a brief post exposure flash right after, or in fact preferable as a continuation of the IR exposure. That could be tricky to achieve with a normal camera, but certainly possible.

Could this be a substitute for HIE?

Edit. A further possibility is that stuff like D400 could actually be faster in ”Herschel” reversal mode. Even with a 720 filter.
Would be pretty easy to test.
Who gets there first‽

A close reading of that patent suggests that they were hitting the emulsion with enough mid-IR CO or CO2 laser light to heat and in the extreme test cases to actually damage the emulsion, leading to the desensitization.

To quantify this, their visible light fogging exposure was typically at surface brightness of 0.2 microwatts per sq mm for 1/50 sec, while the mid-IR laser exposure was at 3-10 milliwatts per sq mm for 5-10 sec. It is confusing because the table in Fig 6 uses "mw/mm^2" for both milli- and micro-watts (for which the authors should be punished), so one has to read the caption.

In 1975 this may have been interesting as a means to detect 5 to 10 micron IR light with conventional photographic emulsions, but today there are other ways of detecting mid-IR light. Pictorially ... Godspeed and good luck.

 

[Helge]

A close reading of that patent suggests that they were hitting the emulsion with enough mid-IR CO or CO2 laser light to heat and in the extreme test cases to actually damage the emulsion, leading to the desensitization.

To quantify this, their visible light fogging exposure was typically at surface brightness of 0.2 microwatts per sq mm for 1/50 sec, while the mid-IR laser exposure was at 3-10 milliwatts per sq mm for 5-10 sec. It is confusing because the table in Fig 6 uses "mw/mm^2" for both milli- and micro-watts (for which the authors should be punished), so one has to read the caption.

In 1975 this may have been interesting as a means to detect 5 to 10 micron IR light with conventional photographic emulsions, but today there are other ways of detecting mid-IR light. Pictorially ... Godspeed and good luck.

Yeah, I read the laboratory jargon and use cases.
Unfortunately the Herschel effect seems to have terrible reciprocity failure.
So perhaps an initial exposure with a destructive IR exposure following?

 

[Andrew O'Neill]

I recently shot some Rollei Infrared, but when I was testing that I also found an old Hasseblad back with very old HP5+. I took a few shots using my SuperwideC and that old HP5+ with the 720 filter. I didn't write anything down exposure wise on those shots, since I figured there'd be nothing too good. You would be surprised how HP5+ and a 720 filter look. Certainly not HIE film, but certainly worth doing some more experiments with. JohnW

I'd love to see that HP5 shot!

 

[John Wiegerink]

I'd love to see that HP5 shot!

Andy,
I'm at home and not at my cottage where everything is at. I'm going to the big city while I'm here and will buy a 4 or 5 rolls of HP5+. When I get back up north, I'm going to use a couple of rolls with the 720 filter. I'll keep track of exposure and development better this time. That old, old roll of HP5+ had mottling severely and it was the first time I have ever had a bad roll of HP5+. Certainly not Ilfords or anybody's fault but mine.

 

[Andrew O'Neill]

Andy,
I'm at home and not at my cottage where everything is at. I'm going to the big city while I'm here and will buy a 4 or 5 rolls of HP5+. When I get back up north, I'm going to use a couple of rolls with the 720 filter. I'll keep track of exposure and development better this time. That old, old roll of HP5+ had mottling severely and it was the first time I have ever had a bad roll of HP5+. Certainly not Ilfords or anybody's fault but mine.

My Urth 720, is sitting there waiting for me... I've just got so many projects on the go, I haven't been able to compare it to my Zomei 720 (cheap) filter...and the leaves are dropping like flies!

 

[Helge]

Yeah, I read the laboratory jargon and use cases.
Unfortunately the Herschel effect seems to have terrible reciprocity failure.
So perhaps an initial exposure with a destructive IR exposure following?

Even if the author of the patent vehemently denies or at least downplay any connection of his invention to the Herschel effect (for other than scientific reasons?), it is under any circumstances interesting to ponder if this effect or whatever combination of effects it might be, has some effect on tamping down highlights in naturally lit scenes? That is, scenes that lit but IR rich sunlight.
Artificially lit scenes especially neon and LED lit scenes, with about the same measurable contrast range as a sunny day, has a comparatively much higher tendency to burn out in the highlights it seems.