Modern Panchromatic Film and IR

[Fragomeni]

Hi all. I've made a few posts touching on the use of IR in the darkroom and those conversations have opened up more questions that I think would be best dealt with in their own thread.

As a primer, I'm interested in using IR technology in the darkroom. Not at all a new idea. I am trying to figure out the details of the materials and tools that I will be using and I could use some help understanding the things that I am unable to figure out or grasp hence my posts which so far have been very helpful.

I have a pair of IR goggles on the way (Nyte Vu). From my research, I believe these use IR LEDs which output at 850nm. This is low enough that I believe the IR LEDs will produce a red glow. I have some IR LED (from RadioShack) that I've been messing with to see some differences in what can be found locally. I have an 850nm IR LED and a 940nm IR LED. The 850nm IR LED produces a much more significant red glow then the 940nm IR LED. The packaging describes the 850nm and 940nm measurements as being "wavelength at peak emission" which I take to mean is the farthest into infrared that the light reaches. Is there a way to measure the range of wavelengths emitted (low to high)? Do I need to find someone with an infrared spectrometer? Basically, I'd like to know the lowest wavelength of light emitted so that I can compare it to the data in various film datasheets defining the film's spectral sensitivity. For example, if I'm reading it correctly Ilford's datasheet for Delta 100 (Wedge Sensitivity to tungsten light (2850K)) says that the film tapers off and becomes basically insensitive around 660nm. I want to know if the lowest wavelength produced by the red glow of an 850nm IR LED is anywhere near that 660nm mark. If I'm understanding things correctly, I know that 850nm is the max wavelength of this IR LED but I do not know what the min (red glow) wavelength is and if it is approaching the film's sensitivity range.

Can anyone offer any insight into this? Thank you very much!!

[johnielvis]

hey dude, I'm thinking the cheapest and best sensor is the film itself

do a test strip exposure at the time levels you'll be using with the equipment at the ranges you'll be using...you know...Tmax is the longest you'll be developing

do--darkslide open 1" for .1 Tmax
darkslide open for 2" for .2 Tmax....etc....

then develop with another sheet that's been unexposed (or a strip) for the same amount of time...same tray,tank, whatever....then compare...see if there's any difference..

I just did a FOUR HOUR exposure in regular roomlight due to the reciprocity....a 15' exposure would have done little I could see maybe--intensity of light makes a big difference for sensitivity. particulary in a relatively insensitive area....

take you 1 hour say to do the whole thing as soon as you get your equipment

[Oren Grad]

..."wavelength at peak emission" which I take to mean is the farthest into infrared that the light reaches.

No, this is the wavelength at which the light emitted is most intense - in other words, the wavelength at which the emission curve peaks. There will be emission both below and above this wavelength.

[Fragomeni]

hey dude, I'm thinking the cheapest and best sensor is the film itself

do a test strip exposure at the time levels you'll be using with the equipment at the ranges you'll be using...you know...Tmax is the longest you'll be developing

do--darkslide open 1" for .1 Tmax
darkslide open for 2" for .2 Tmax....etc....

then develop with another sheet that's been unexposed (or a strip) for the same amount of time...same tray,tank, whatever....then compare...see if there's any difference..

I just did a FOUR HOUR exposure in regular roomlight due to the reciprocity....a 15' exposure would have done little I could see maybe--intensity of light makes a big difference for sensitivity. particulary in a relatively insensitive area....

take you 1 hour say to do the whole thing as soon as you get your equipment
Thats exactly my plan when the goggles arrive. I'll just test it basically exactly as you described. I was posting here to see if anyone had any insight ahead of time or if anyone had any extensive knowledge of the LEDs and the various wavelengths.


No, this is the wavelength at which the light emitted is most intense - in other words, the wavelength at which the emission curve peaks. There will be emission both below and above this wavelength.
Thanks for the clarification Oren. So that leaves me with the same question as before if I want to know the high to low range of wavelengths.

[Jim Michael]

It might have been Leigh in the other thread that noted that LED emission is pretty pure, e.g. if they rate it at 850 nm then it should be pretty close to that, so the curve should be pretty narrow. The exception would be where the emitted light is used to excite a phosphor layer like they do for 'white' LEDs.

Another factor I don't know if you've looked into but which someone might have touched on is the output of the LEDs you are planning to use. IR LEDs are often used for things like remote controls where the intensity may not need to be very high. The idea of using IR sources intended for security system illumination would be worth looking into.

[BetterSense]

Is there a way to measure the range of wavelengths emitted (low to high)?

Yes


Do I need to find someone with an infrared spectrometer?

Basically. Or you could just do a test with film. By the way, all Lee/Roscoe filter gels are transparent to IR, so you could stack some of those up to block the red glow.

[cyrus]

Well I was under the (mis?)impression that LEDs produce light over a very narrow (so narrow that some sources say 'single') wavelength (which is why there are no true white LEDs) but if you're seeing the red then obviously that can't be true since by definition IR is supposed to be invisible to the human eye.

This guy (http://ledmuseum.candlepower.us/led/ledir.htm) compared LED output from various bulbs and charted the results for comparison. Based on my eyeball calculations, it shows that each bulb's output has only a 100nm spread, from low to high (the Radio Shak 940nm LED actually peaked at 925nm.)

[John Schneider]

each bulb's output has only a 100nm spread, from low to high (the Radio Shak 940nm LED actually peaked at 925nm.)

For deep red LEDs (I can't put my hands on any IR LED spectral curves right now), the spectral half-width is 20 nm and the curve peak has a tolerance of about +/- 5nm. This based on the info put out by Philips-Luxeon. Shorter wavelength LEDs have a much greater halfwidth for some reason I don't understand.

[Peter De Smidt]

I agree with simply testing film when your goggles arrive.

Recently, I tried using Acros, a not very red sensitive "regular" bw film with a Hoya RM72 IR filter, which I believe filters out light bellow 720nm. I did get a nice IR image, complete with the Wood effect, i.e. white grass and leaves, but I had to give 15 more stops exposure than normal in bright daylight. That's a lot of light.

[David R Munson]

Recently, I tried using Acros, a not very red sensitive "regular" bw film with a Hoya RM72 IR filter, which I believe filters out light bellow 720nm. I did get a nice IR image, complete with the Wood effect, i.e. white grass and leaves, but I had to give 15 more stops exposure than normal in bright daylight. That's a lot of light.

I would really like to see your results...

[Peter De Smidt]

See: http://www.largeformatphotography.info/forum/showthread.php?t=78561

[Fragomeni]

Great input everyone! Thanks for all the thinking points!

[R Mann]

Any thoughts/reactions/problems on the Nyte Vu goggles now that you have had them for a few months?

[Fragomeni]

Any thoughts/reactions/problems on the Nyte Vu goggles now that you have had them for a few months?
They are fantastic! An important point to make however is that I modified them considerably which was a part of the plan pretty much from the start. In order to meet my specific needs I had to make a few changes. First, the IR LEDs that come in the Nyte Vu goggles ouput 850nm. This wavelength produces a red glow that I was not comfortable with. I used film data sheets to determine the range where most 100 iso films stop being sensitive to red light and 850nm was a little too close for my comfort. I don't remember all the numbers but I wanted to be well outside of the film's sensitivity range. I think the data sheets show the films I looked at are sensitive up to around 700-750nm (don't quote me cause I can't remember at this point). I disassembled the goggles and replaced the 850nm IR LEDs with 940nm IR LEDs. 940nm IR LEDs are a fair bit deeper into the IR spectrum and produce very little glow from the visual spectrum at all. The glow is almost unnoticeable and it is certainly not enough to cause any exposure on 100 iso film during the time span it would take to develop film. I also disassembled the head brace and strap of the goggles and mounted them in a set of welding goggles with the glass removed. This provides a light tight seal on your face which prevents visible light produced by the screens in the goggles from reflecting off your face and exposing the film.

I tested everything and with the changes I made (speaking mainly to the LED switch) there is absolutely no visible or measurable exposure to the film with the use of the goggles. I checked to make sure there was no measurable exposure using an X-Rite densitometer.

There are a couple of tricks I’ve had to implement as well. I prefer to use my hands as opposed to tongs and I found that the white rubber gloves (standard hospital gloves) I use reflected too much IR and threw off the sensor cause a major loss of contrast and the inability to see much at all. The solution was a switch to dark blue/purple gloves that my girlfriend brings home from her job at the hospital. They are more opaque and much darker and do not reflect anywhere near as much as white gloves and therefore don’t throw off the sensor.

The most amazing thing about the experience was finding that under the IR goggles the negatives glow like they’re sitting on a light box! Complete sharp visibility! The image begins to come up within the first 10 seconds and then learning how to judge where the highlights should be was very easy. I set up the darkroom to develop some 4x5 test sheets (images of various contrast levels) using my already established time and temperature scheme. I did everything as I would normally do using time and temperature with the addition of the goggles so that I could observe what was going on visually. This gave me a very clear idea of where highlight placement belonged with various contrast situations and within 4 negatives I was developing by inspection like I’d been doing it my whole life. I really have no idea why this isn’t the standard method of development now. One more important thing to note is that typically when speaking of development by inspection (under green safe light as most people do it) you look at the base side of the film to see the highlights coming up through the milky base of the film. With the IR goggles that is completely unnecessary. You see every tone in the image as clear as if you were looking at it develop on a light box. Quite remarkable.

Well, that’s my experience so far :)

[Andrew O'Neill]

That's very interesting, Peter. Thank you.

[EdSawyer]

Pics of the goggles would be cool to see. Sounds like an interesting way to work in the darkroom!

-Ed

[Fragomeni]

Pics of the goggles would be cool to see. Sounds like an interesting way to work in the darkroom!
I'll take some pictures of the goggles tonight and post.
I'll tell you, it's really revolutionized how I'm approaching development and it's even having an effect on how I go about making exposures. My photographic experience is entirely based on my awareness of my environment and my ability to make visually objective decisions in relation to the mechanics and controls I have over the equipment. I've always had a major intrinsic problem with the development phase of my process. I've always used time and temperture very well and the negatives it yields for me are very good but my problem was with having everything "in the dark" (pun intended) i.e. not being able to visually observe and visually understand what was happing during development and not being able to make visually objective decisions during development. It took a couple of years for me to start to seriously investigate IR as a way of working in the darkroom and it was only when a friend introduced me to a very good photographer/printer who had begun to use it himself. I saw his work and spoke with him in depth about his experience using it and about the wavelengths of IR light and the sensitivity range of various films and I was convinced that this could be a solution to the visual gap that I always felt was holding me back from working the way I want to. Watching the negatives develop and observing how much control I can have simply through visual observation using IR in the darkroom has made me fall in love with photography all over again.

[Fragomeni]

Sorry for the delay. Things have been quite busy around here and I forgot to post the pictures.

http://francescofragomeni.squarespace.com/storage/P1030810.JPG?__SQUARESPACE_CACHEVERSION=1318216309492

http://francescofragomeni.squarespace.com/storage/P1030812.JPG?__SQUARESPACE_CACHEVERSION=1318216364115

[cyrus]

How easy was it to swap out the LED lights? Does it require special tools or electrical knowledge? Soldering?
Do you feel a need to kill Sarah Conner whrn you erar these?

[Fragomeni]

Hahahaha, it does feel somewhat Terminator-ish. They are actually very low profile so you don't need to worry about some long tube sticking out from your face (like with other night vision scope designs) and knocking into things.

Swapping out the IR LEDs wasn't overly difficult but I have moderate experience with soldering. You have to be careful not to touch anything other then the posts on the IR LEDs. I'm sure if you're sloppy you could end up shorting out the board. Basically, I used the soldering iron to head the solder holding the IR LED posts in place. Each IR LED has 2 posts (positive and negative). With heat alternating between posts, I was able to slowly shimmy the LEDs out of the holes they are soldered to. It was then fairly easy to replace them with the new IR LEDs. I just added a small bit of solder to reinforce the new bonds. Overall it was fairly easy but if you don't have experience doing something like this I wouldn't tackle it without a little help from someone who is more familiar otherwise you risk ruining the goggles and you're out of the money.

[polyglot]

Is there an affordable source for goggles like this? I've only seen them for $250-$600, which frankly would pay for quite a significant quantity of film.

[Fragomeni]

Use the forum search to find the various threads on the topic of IR goggles. There have been a lot of discussions on the various options and where they can be purchased from. I bought my Nyte Vu goggles from B&H for around $250 I think (think they were on sale). IR goggles can be had from as cheap as $60 for a pair of children's toy goggles (which do work) up to and in excess of $40k.

[Fragomeni]

HERE (http://www.francescofragomeni.com/homebrew-blog/2011/10/9/ir-darkroom-goggles.html) is a little write up I did for my website summarizing the process and what I ran into along the way. Thanks to everyone for the information and assistance along the way.

[Fragomeni]

For everyone following this, HERE (http://www.francescofragomeni.com/blog/2012/1/11/ir-darkroom-goggles-part-ii-refining-approach-and-developmen.html) is a follow up to the first write up I did on my website.

[Fragomeni]

For those still interested in this, here is an update.

I've refined the system a few times to make it easier to use. I replaced the strap of the goggles with an elastic thing that slides over the whole head. I removed the IR LEDs from the goggles because they caused major reflections during use which made it difficult to see. I've begun using an IR illuminator that I found on ebay (details and a link are on my website) and this has solved the reflection problems as well as produces a lot more IR light. The illuminator is 940nm so in line with the past tests.

Everything seems to work fine with 100 ISO or slower film but today everything I developed in 400 ISO film had fog in the film base and noticeably so. I developed both Tri-X 400 and Delta 400 and both fogged. I did not believe that 400 speed film would pick up the 940nm wavelength but it looks like I was wrong. It could also have something to do with how much IR is being output by the illuminator which has around 120 IR LEDs as opposed to the 6 that were built into the goggles. Quantity shouldn't be an issue here though as the wavelength is the same and distances and times with film in the path of the IR is the same.

The IR DBI journey has been a lot of fun and I've learned a lot. My primary purpose was to visually learn exactly how film develops and remove the mystery built into the traditional time and temperature methods. Now that that has been satisfied my next steps are to experiment more with DBI using the traditional green safelight as well as using Pinacryptol Green and Pinacryptol Yellow as desensitizers if I can find some. I've seen the benefits of using DBI and I don't plan on every going back to rigid time and temperature but I still need to isolate a method that works with all the film I use and is efficient.

[kathy82]

the 850nm (http://www.lightingnext.com/high-density-850nm-infrared-led-strip-light.html) ones glow a slight red which is only slightly noticable when the lights are completly off. while the 940nm infrared LEDs (http://www.lightingnext.com/940nm-infrared-led-strip-light.html) are virtually invisible to the naked eyes.