Colour Infrared

26th August 2004

I am shooting an entire feature on Color infrared, I am wondering if anyone has had any experience shooting this film. It is the Kodak EIR stock. One major issue I have is, does anyone know how to measure infrared light? Of course Infrared light is not visible to our human eyes, so is there a way to measure the amount of infrared light, does an infrared light meter exist?

Max Goldman

Most professional photographic light meters are designed to have a "Photopic" response, seeing light much as the human eye does.

All three layers of KODAK EKTACHROME Professional Infrared EIR Film are UV and blue sensitive, so a yellow filter is normally used in front of the lens. This leaves sensitivity to green, red, and infrared portions of the spectrum.

Here is the technical data for the film:

http://www.kodak.com/global/en/professional/support/techPubs/ti2323/

ti2323.jhtml?id=0.1.18.14.7.22.3.34.14.5&lc=en

Which says :

Exposure
Speed and FilterNon-Aerial Use
Use the exposure index (EI) numbers below with meters and cameras marked for ISO, ASA, or DIN speeds as a starting-point. Do not change the film-speed setting when metering through a filter. Metering through filters may affect light meter accuracy; see your meter or camera manual for specific information. For critical work, make a series of test exposures. Exposure latitude is limited to 1/2 stop.

A KODAK WRATTEN Gelatin Filter No. 12 (or equivalent) is required over the camera lens to prevent blue radiation from exposing the inherent blue sensitivities of all three emulsion layers. Similar filters may provide satisfactory or preferred results. Experiment to determine your personal preference in your application.

Since 2/3 of the image is formed by VISIBLE light, use of a normal photopic sensitivity light meter should yield good exposure information.

Be sure this film is processed in TOTAL darkness, and that the lab is not using infrared cameras or goggles in the darkroom, or infrared film/leader detectors on the machine.

Hope this helps.

John Pytlak
EI Customer Technical Services
Research Labs, Building 69
Eastman Kodak Company
Rochester, New York 14650-1922 USA
Telephone: +1 585 477 5325
website: http://www.kodak.com/go/motion

Max Goldman wrote :

> ... does an infrared light meter exist?

Yes - http://www.thedopshop.com/item.cfm?itemID=256 - but it won't work with color IR film which is very different from black and white IR film.

Best,

Anders Uhl
Cinematographer, NY
The DoP Shop
http://www.thedopshop.com

I used to shoot Kodak infrared B&W and color transparency stills in the 70's and, with the color, I used to follow the Kodak recommendations for a starting point.

As I remember, I tested first under different lighting conditions using an incident meter and established an film speed for each situation as the films responded differently to different lighting. I don't remember bracketing exposures much afterwards, so I must have been getting consistent results. I used a range of filters to change the look of the final result.

Sometimes I cross - processed the transparency to negative gave me a speed increase, great looks and greater exposure latitude.

You must be very careful with heat and with loading procedures to prevent fogging and , of course, all your focusing distances must be adjusted for the longer wave-length of infra-red.

Paul Hicks

You will have issues w/ chrome pressure plates, so you should use an older 2C or Mitchell. Also, if you're shooting w/ a 435/535 there is a problem w/ the led perf counters.

Also, I believe you must remark the lens to compensate for a shift w/ the back focus(if you're shooting at let's say F 11, 16 etc you'll have enough depth of field but below 8 or 5.6 it could be a problem.

Perhaps do some tests w/ stills if possible(?)

John F. Babl
Miami

>Also, I believe you must remark the lens to compensate for a shift w/ the >back focus(if you're shooting at let's say F 11, 16 etc you'll have enough >depth of field but below 8 or 5.6 it could be a problem.

Not Back focus, wrong terminology. The greater the depth of field the less the depth of focus, which is what you are referring to.

The lens has to be re-marked to account for the different focussing of the infrared light. Not a back focus issue.

Steven Gladstone
New York Based D.P.
www.gladstonefilms.com
East Coast CML List administrator

Hi Max,

I'm posting this on the list because I think that there are a few people who are interested. Color IR film (I assume that you are using Kodak EIR and processing in E-6) has a lot of visual light sensitivity and relatively, much less IR sensitivity. Kodak lists it as having a range of 380-900nm, but in the IR range (700-900nm) the density drops pretty low :

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

ti2323/f009_0537ac.gif

Kodak HIE B&W IR film on the other hand has much lower sensitivity in the visual range and excellent sensitivity from 700-900nm. For this reason, many argue that Color Infrared film is in fact, not a true IR film but a "near IR film". This is good news for filtration, focus and metering. It does not require as dense (visually opaque) a filter to produce a strong effect and a lightly modified meter with some testing should give you good results. Focus will require some testing, but since you are only shooting EIR (is that right?) and the IR range focuses short, you might be able to shim the mount and use the existing lens marks - I'd recommend a few short lenses and a well matched set.

There are other precautions to take as well regarding loading, temperature, camera, etc. Because EIR is a reversal film, your latitude is very slight and a lot of testing will help insure usable exposures.

Do you have a camera package in mind and have you spoken to your lab yet?

Best,

Anders Uhl
Cinematographer, NY
The DoP Shop
http://www.thedopshop.com

Steve wrote:

>Not Back focus, wrong terminology. The greater the depth of field the >less the depth of focus, which is what you are referring to.

I know the lens has to be re-marked, but I meant that if the depth of field is enough (depending on your stop) it won't be as critical. Since it will be different from using regular film, the lenses should be re-marked.

From Clairmont Cameras' very informative tips :

When using infrared film, the distance scales on the lens will not be perfectly accurate. If you are using a lens opening of F8 or smaller, there should be enough depth of focus to take care of the problem. It is possible to adjust the lens or put a new witness mark on the lens to compensate for the infrared. This correction is a change in back focus of .0025 percent of the focal length of the lens. A 25mm lens would have the back focus changed by .0625mm. It is better to just put a new witness mark on the lens using a collimator set closer to the lens by .0025 percent of the lens focal length. Most still camera lenses have a red mark to be used as a witness mark when focusing. Because of this focus shift, a zoom lens cannot be used.

John Babl
Miami

> you might be able to shim the mount and use the existing lens marks -

Scratch that, it would be much simpler to set a new witness mark.

best,

Anders Uhl
Cinematographer
ICG, New York

Thanks to everyone for the reminders about the change in the back focus, especially when trying to focus the longer wavelength IR alone. Also, keep the unprocessed film cold except when using it. Prolonged exposure to heat will adversely affect its characteristics.

Here are some additional links to infrared photography on the Kodak website :

http://www.kodak.com/global/en/service/scienceFair/

infraredPhotography.shtml

http://www.kodak.com/global/en/service/scienceFair/

infraredTechnical.shtml

http://www.kodak.com/global/en/service/scienceFair/

infraredRadiation.shtml

http://www.kodak.com/global/en/service/scienceFair

/infraredLighting.shtml

http://www.kodak.com/global/en/service/scienceFair /

infraredFilters.shtml

Remember, Kodak infrared films were designed for other product areas like aerial photography or scientific imaging, and so are NOT normally available in motion picture formats.

John Pytlak
Eastman Kodak Company
http://www.kodak.com/go/motion

Sam Wells wrote :

> If you stop down a lens you increase both.

Do you? I had always learned that as Depth of field increases, depth of focus decreases.

Steven Gladstone
New York Based D.P.
www.gladstonefilms.com
East Coast CML List administrator

>Not Back focus, wrong terminology. The greater the depth of field the >less the depth of focus, which is what you are referring to.

If you stop down a lens you increase both.

Sam Wells
Discovered this morning dragonflies hit their marks with incredible precision.

Steven Gladstone wrote:

>Do you? I had always learned that as Depth of field increases, depth of >focus decreases.

Not quite.

There is a teeter-totter effect -- the more Depth of Field a lens has (wider lens) the less Depth of Focus, and vice-versa for longer lenses.

But both increase when you stop down. Otherwise you'd be collimating wide lenses at f/22! That would be fun!

Jeff Kreines

The same confusion exists when you talk about PROJECTION lenses. In projection, "Depth of Focus" is more shallow with the SHORT focal length lenses required for short "throws". Many projectionists confuse it with camera lenses, where the depth of field is more shallow with LONGER focal lengths.

Here are links to some handy calculators for projection lens parameters :

http://www.schneideroptics.com/software/theatre_design_pro/

http://www.iscooptic.de/isco_new_e/downloads_e.html

John Pytlak
EI Customer Technical Services
Research Labs, Building 69
Eastman Kodak Company
Rochester, New York 14650-1922 USA
Telephone: +1 585 477 5325
Cell: +1 585 781 4036
website: http://www.kodak.com/go/motion

>The greater the depth of field the less the depth of focus, which is what >you are referring to.

Is that a direct relationship?

Blain Brown
DP
LA

I was apparently incorrect about the relationship between depth of field and depth of focus in regards to how f-stop affects each one.

Thanks again list.

Truly wonderful and invaluable.

Steven Gladstone
New York Based D.P.
www.gladstonefilms.com
East Coast CML List Administrator

(In regards to the Kodak links...if you have a problem with the linkls... just copy the entire link into your browser)