Seeking help on Infrared Flash Photography

[sevo]

Also, does anyone know to what wavelength refers the IR marking on Leica lens or in general?

The popular filters I had in HIE days were 820nm, and the film went on to 950, so I'd expect the marks to be tuned towards wave lengths rather beyond the scope of current film...

With digital - or HIE - you'd also have to factor in the dominant wave length of your illumination. The full 700-950 of HIE is a broader range than the entire visual band (and sensors go past 1000), so you may end up considerably off even when the filter matches the mark, so that means trial-and-error.

 

[ulrich.von.lich]

Thanks! I will certainly do that.

However, the dominant wave length is more a matter of the IR filter than of the film or of the sensor, right? Given the fact the IR sensitivity drops drastically as the wave length goes higher, it is ultimately the IR filter that pushes and postions, although not precisely, the dominant wave length, isn't it? If it is true, the IR filter will be my starting point of different tests.

 

[Kate-the-Great]

This fellow may be a good source of info on IR flash photography- http://www.kpraslowicz.com/

For a time he was using IR film (can't remember which one) in an M3 and Oly XA with an IR-modified flash to avoid drawing attention at music shows etc. The range of the flash was very limited, but the results have a great look.

 

[sevo]

Thanks! I will certainly do that.

However, the dominant wave length is more a matter of the IR filter than of the film or of the sensor, right? Given the fact the IR sensitivity drops drastically as the wave length goes higher, it is ultimately the IR filter that pushes and postions, although not precisely, the dominant wave length, isn't it? If it is true, the IR filter will be my starting point of different tests.

For IR significantly past the filter threshold, the filter is a piece of clear glass. The filters tend to be low pass type, and hard edge at that - it is pretty much nothing at 810 and all at 830 and on, down past what any film could ever record. So it is a matter of the film/sensor (and the spectral distribution in the illumination) more than the filter...

 

[ulrich.von.lich]

Ok sevo, I will remember it and rest my tongue and my still-not-so-convinced mind: after all, even a 780nm filter, low pass type if you want, would call for at least 4 stops of exposure compensation and that must be something. Just look at how opaque it is!

I think I will start with a Helopan RG780 (Wratten 87, 780nm) with the expired HIEs at ISO25 as it is suggested by Kodak:

http://www.kodak.com/global/en/professional/support/techPubs/f13/f13.pdf

(Page 3, Wratten 87, Electronic Flash or Daylight : ISO25)

And eventually goes down to ISO12 or 6, considering the film is expired in 2009.

I may come back to the thread in the future to share my findings.

 

[ulrich.von.lich]

This fellow may be a good source of info on IR flash photography- http://www.kpraslowicz.com/

For a time he was using IR film (can't remember which one) in an M3 and Oly XA with an IR-modified flash to avoid drawing attention at music shows etc. The range of the flash was very limited, but the results have a great look.

I saw his pictures a couple of years ago with a page of detailed instructions that he pulled off later.

I think he used an Olympus XA2, an A16 flash with IR modification (just stick an IR filter to it) and Rollei IR films. He pre-focused and fired flash at a constant distance (between 1m and 2m). I didn't know he used a Leica as well.

Hopefully the Vivitar will produce better results as its GN is 36m instead of 16m of the A16, as well as the HIE which, although expired, should surpass the Rollei.

 

[sevo]

Ok sevo, I will remember it and rest my tongue and my still-not-so-convinced mind: after all, even a 780nm filter, low pass type if you want, would call for at least 4 stops of exposure compensation and that must be something. Just look at how opaque it is!

As far as infrared is concerned, it is as clear as window glass - this is a 715nm filter photographed through a 720nm filter:

So even that small 5nm difference means that there is barely any attenuating overlap left. Seen with the bare eye, it is a disc of black glass. But from a (purely) IR device, this does not need exposure compensation...

 

[ulrich.von.lich]

Last time I checked, I couldn't see anything through the IR filter. There must be something wrong with either my memory, my eyes, or my filter. I have a Heliopan RG780 (780nm) which is only one and a third stops away from the RG715 (715nm).

Also, according to the Wratten number conversion page:

https://en.wikipedia.org/wiki/Wratten_number

My filter is closer to the Wratten 87C filter than to the 87 filter. It is ISO10 for the HIE under daylight or electronic flash.

 

[x-ray]

I started shooting Kodak IR in the 60's before it was high speed and have shot quite a lot until it was discontinued. This includes the Konica film which was great.

I currently have a Nikon D3100 I had modified by Kolarivision to 850nm. It's a fantastic modification and gives results much like HIE.

I used HIE in my commercial work from time to time. I did several campaign including one for Levi's for a retail fashion chain on Kodak HIE. All of this was location shooting. Another campaign was for a jeweler using a model in studio. It was beautiful how this film rendered.

I've had a lot of studio as well as location experience and would suggest you sacrifice a couple of frames. Do a test on two or three frames. Take the camera into the dark and clip out those frames. Make sure to never expose the cassette to visible light. The film pipes IR and the cassettes are not IR tight. They leak IR and your film will be ruined. Other films are less sensitive. Run your test and evaluate. It's better to sacrifice two or three frames than ruin a roll.

I think one poster is confused. Strobes do not have an IR filter, just UV which has no effect on IR. I Used an 87c filter on camera with both Speedotron and Norman studio strobes and several brands of hand held units and never had an issue.

If you disassemble a strobe be careful. It only takes 50 joules (watt seconds) to stop your heart. Most likely a portable wouldn't kill but it will give a very Nast shock and burn. Even after discharging the flash there can be residual energy in the capacitor that will shock.

 

[sevo]

Last time I checked, I couldn't see anything through the IR filter. There must be something wrong with either my memory, my eyes, or my filter. I have a Heliopan RG780 (780nm) which is only one stop away from the RG715 (715nm).

As I said, to the eye the filter is black. But when photographing it with a camera with another IR filter on, it has almost no attenuation left (and that in spite of little margin between the two filter curves I used). So when you use a IR flash (with a deep red or "black" filter), you do NOT have to apply any of the factors (more or less) applicable when dealing with visible light.

Also, according to the Wratten number conversion page:

https://en.wikipedia.org/wiki/Wratten_number

My filter is closer to the Wratten 87C filter than the 87 filter. It is ISO10 for the HIE under daylight or electronic flash.

That is a different matter. In general, beware of filter factors when you use a meter that reads a different spectral range - they are heuristics at the sunny 16 level, very far from anything resembling proper sensitometry.

According to that table ISO 10 is a working setting for HIE when using a 790nm filter, in direct sunlight, using a meter with a visual band spectral range. That number can be very different when you use IR LED illumination - or some IR free light source. It does not mean that HIE has a sensitivity of IR ISO 10 - all it says that given the relation between visible light and infrared under the given conditions (open sunlight or studio flash) on one hand, and the IR sensitivity of HIE on the other, that meter setting will give a good exposure. IIRC the proper sensitivity of HIE when used as a technical film with broad-band IR sources and IR meters is somewhere between ISO 50 and ISO 100. But normal humidity conditions (water vapour is a powerful near IR filter) attenuate the amount of IR radiation from the sun, so you get less of the IR HIE is sensitive to than you get of visible light.

 

[sevo]

I think one poster is confused. Strobes do not have an IR filter,

Hard to tell. Among the Metz flashes I've used for IR work, the older ones, prior to the nineties, had no filter, but the front glass (or rather, plastics) on the later ones positively acts as a strong IR filter. I don't know whether that is a conscious addition of an actual filter, perhaps obeying a safety regulation of some sort or acknowledging the high IR sensitivity of early digital cameras. It might also be a accidental property of the front window plastics they used from that point on, or of an enhanced UV filter, but regardless why, that thing has to come off or the later Metz flashes only let out a somewhat feeble amount of near IR and no far IR at all.

 

[ulrich.von.lich]

Sorry sevo I didn't read carefully your previous post. Although your answer makes great sense, it doesn't advise me much other than to test, test and test. Say, if you were me (somebody who has two expired rolls of HIE, a 780nm IR filter, a Vivitar 285HV, and some spare time), at what speeds would you be most likely to rate the precious films? Remember, I don't have 20 rolls of them, unfortunately.

The ISO10 is a friendly advice from Kodak, a rule of thumb only, not necessarily the reality. I must be really bad at photography because I'm still trying to figure it out, provided that the ISO10 is true, how to use the Vivitar flash since the lowest ISO value it accepts is ISO25.

Previously I have only used on an M6 an Olympus FL20 flash in auto mode (and I felt proud enough because it wasn't TTL). Perhaps I should figure out how to use the Sekonic L308 in flash mode first and draw myself a chart with distances and f values at ISO10.

So much to learn...

 

[ulrich.von.lich]

Hard to tell. Among the Metz flashes I've used for IR work, the older ones, prior to the nineties, had no filter, but the front glass (or rather, plastics) on the later ones positively acts as a strong IR filter. I don't know whether that is a conscious addition of an actual filter, perhaps obeying a safety regulation of some sort or acknowledging the high IR sensitivity of early digital cameras. It might also be a accidental property of the front window plastics they used from that point on, or of an enhanced UV filter, but regardless why, that thing has to come off or the later Metz flashes only let out a somewhat feeble amount of near IR and no far IR at all.

For the Olympus A16 flash, one just needs to add an IR filter; for the Vivitar 285HV flash, Shane asked me to remove the stock plastics before installing the IR filter, if that means anything.

 

[Dwig]

... It might also be a accidental property of the front window plastics they used from that point on, or of an enhanced UV filter, but regardless why, that thing has to come off or the later Metz flashes only let out a somewhat feeble amount of near IR and no far IR at all.

It could just as likely, or perhaps more likely, that the extremely low IR emission is the result of the reflector being transparent to IR or at least non-reflective at those wavelengths.

 

[ulrich.von.lich]

X-ray, what chance you had to buy fresh HIEs!! plus, at reasonable prices !!!

Thank you for your advices. I will pay extra attention to my HIEs. I'm afraid I won't make a test roll since I have only two of them. I will do bracketings instead.

I have seen many digital IR pictures but they look really nothing like HIE or Efke IR820 aura. Is Kolarivision anything special?

 

[x-ray]

No fresh IR now. It's all old stock and questionable quality.

Here are three IR shots from the Kolari conversion.

I'll have to locate some of people.

 

[wolves3012]

Very true, make sure you discharge the capacitor (firing off the flash) before you start taking it apart. Don't cross wires with screwdrivers and such. Take the batteries out before you start your disassembly.

Use a screwdriver that isolates your hand from the metal part of the tool (plastic handled) also a good idea.

Use your own good judgement as to if you can do it.

B2 (;->

Firing the flash will only discharge the capacitor to about 80V, leaving more than enough for a very unpleasant shock. If the capacitor is charged, there's enough charge stored for a lethal shock. The main advice would be: unless you *really* know what you are doing, DO NOT tinker with the insides of an electronic flashgun. The capacitor needs to be discharged completely and safely before working on one.

 

[Denverdad]

So a camera with 720nm IR conversion has a sensor that only respond to wavelengths above 720nm? That does spare the need to use an IR filter in front of the lens, but what about the other side of the spectrum? 720nm to where? 850nm? 950nm? Nobody says.

The sensor itself isn't any different; it's just how the filtration is altered. My understanding is that an IR conversion always starts by removing the IR blocking filter that most cameras come fitted with. Doing so makes the camera sensitive to the full range of visible and near-IR wavelengths that its silicon sensor (with its Bayer color filter) can detect. If that is all that is done you would then need to add an IR pass filter to the lens each time in order to do IR-only imaging. I'm not that familiar with these conversions but I assume it is also possible to have an IR pass filter fitted over the sensor in which case the camera becomes a dedicated IR-only imager, eliminating the need to add IR filters externally. Of course that also removes the option to make normal visible images. In any event, the spectral plots on this page give a pretty good summary of how this all works with digital cameras.
[EDIT: Looking back over the previous responses I realize I am mostly just repeating what others have said, just in different words]

The IR filters we're talking about are mostly "long pass" type, blocking visible but having good transmission from the cut-on wavelength on out. How far out you ask? Well it would seem typically a couple thousand nanometers beyond the cut on wavelength, so actually into the mid-IR region. As an example, the spectral plot for the Hoya R72 filter shows high transmission from its 720nm cut-on wavelength out to about 2700nm, while even passing some light as far out as ~4500nm. These wavelengths are well past the ~1100nm limit to which silicon cameras are sensitive.


Jeff

 

[shimokita]

Maybe as a reference... for my film "IR" testing, here is what I ended up doing...

Ilford SFX 200 which has extended red sensitivity (up to 740nm) together with a R72 Infrared Filter. For the test, I was using a Nikon F3P and AIS 50mm f/1.2...

Exposure... The Ilford SFX 200 data sheet recommends shooting in bright sunshine in order to obtain the best results. From different articles on the internet I found that a good baseline for my exposure tests would be to meter at ISO 6. The film is ISO 200 and the R72 filter does not have a fixed filter factor.

Note 01: ISO 200 film metered at ISO 6 is a 5 step difference = Filter Factor of 32

According to the filter maker, lighting conditions have an impact on the exposure... depending on what you are looking for as a final image... and true enough my tests when using SFX 200 and the R72 filter showed the following:

Note 02: in shaded sunny conditions meter at ISO 3 i.e. 6 steps / FFactor of 64

Note 03: in bright direct sunshine meter at ISO 12 i.e. 4 steps / FFactor of 16

... and even at that, there was some variance, so it's only a guideline... bracketing is recommended...