Conversion of a Kodak DC-3400 for IR capture

The conversion of a Kodak DC3400 point & shoot for infrared capture is not a very complicated operation. As far as tools go you do not really need anything else than a smal Phillips screwdriver and a pair of tweezers. A reasonable amount of manual dexterity is required too, be too heavy handed and you can easily wreck your little Kodak.

A clean desk and proper lighting are for obvious reasons also recommended. Some small containers for the screws you will be removing are useful, especially because the screws are not all the same length.

Take reasonable precautions against discharge of static electricity, these can wreck the electronics. If you do not want to spend ages to remove dust specks that have ended on your CCD make sure your work area is clean. Really clean.

Last but not least: don't poke in the inside of the camera where the flash circuitry sits. The voltage in the flash capacitor is nasty at best!

Note that my camera had suffered some gravity induced damage (== it was dropped, most likely multiple times) before I acquired it on eBay.de for a couple of EUROs. Some pictures are from the second camera I converted, that one looks better.

I have outlined how to accomplish it in a step-by-step photo shoot.

• Preparation steps: remove the batteries and the CF flash card from the camera.
• Once done, you have to remove the bottom cover of the camera. 3 Phillips head screws are holding it in place. Remove them, then remove the bottom cover along with the door of the battery compartment. The picture shows the resultant situation.

  

• Next remove the righthand cover of the camera. 2 screws are holding it in place. Remove the screws, then remove the cover.

  

• With the two covers removed you just have to remove the back cover by removing 5 screws holding the back cover in place. Don't forget the lone screw that lives on the bottom of the camera, next to the battery door hinge.

  Now gently remove the back cover to avoid breaking the left hand side of it that contains the door for the CF card. The buttons and selector switch on the back cover are connected to the electronics module in the camera body so don't wreck that flex wire. I opted to temporarily disconnect the flex wire from the main circuit board. This makes the rest of the operation much easier.

  Once you have done all this you are greeted by a plastic coated piece of copper shielding material along with a closer view of the LCD screen. The shielding is glued onto the back of the electronics with some dual-sided adhesive tape. Gently pry the shielding loose. The sticky tape will stay in place and can be re-used.

  

• Note that the copper shielding is connected to the electronics with a piece of wire (the blue wire just above the tripod socket). So you either have to unsolder it, or just gently push the copper shielding aside while keeping the wire connected to the camera. I did the latter.

  

• Once you have taken the shielding aside, you will find the CCD sensor in the middle, mounted on a copper colored piece of flex-wire circuit. The flex-wire is connected to the main (green) electronics module with a tiny (really!) connector. You have to unplug that connector from the corresponding socket on the green circuit board. It might have been unplugged already when you pulled the shielding out. Gently put a fingernail under the rim and pull gently towards you. The connection between the sensor and the green circuit board is now broken. Subsequently remove the 2 screws that hold the sensor module in place.

  

• Once the previous step is completed you can simply lift the sensor module and put it aside to the left. Keep dust, tools and finger prints far far from the CCD sensor.

  

• Peering inside you will see the IR blocking filter. It has a purplish tint on both sides of the glass. The picture below shows the filter sitting on the little rubber gasket. It is not glued in or whatever, you can simply get it out by holding the camera with its back down to mother Earth. Note: the filter is tiny, about 7.7x10mm. Thickness is about 1.75mm.

  

  You want to retain it, you need it if you decide to re-build the camera for conventional use. Apart from that, the optical system is designed to produce sharp images only with a piece of glas of appropriate thickness in place. A shot taken without any glas in front of the CCD sensor is really unsharp.

  

  The IR block filter appears to have a filter layer deposited on it (by CVD I guess). I could not find a piece of replacement glass of the correct thickness so I first tried a piece of slightly thinner glass cut (well, broken) from a microscope objectglass, subsequently ground to shape with wet&dry sandpaper. That helped a lot with sharpness already.

  But completely satisfying it was not. So, at a later stage I acquired some extremely fine polishing powder (thanks Andre!) This stuff is normally used by amateur geologists polishing their stones/gems. I gently ground the filter layers off the original filter. That solved the thickness problem.

  

  On my second camera I removed the original IR-blocking filter and replaced it with another filter I created myself from a 1.75mm thick coated UV filter. It took some head-scratching before I found a decent method to cut the round filter into the tiny rectangular shape I needed. I borrowed a small diamond cutting wheel for my Dremel (thanks Robert!), then cut the raw size out of the round filter. This is tricky, as the glass typically cracks once you cut through it halfway. Anyway, I ended with a slightly bigger piece of glass (approximately 12x9mm) that I subsequently ground down to the exact dimensions using 600 wet&dry sandpaper. A picture of this procedure is shown below.

  

  The home-grown filter is shown mounted in the camera below. Note the the tiny rubber gasket. Don't forget to re-install the U-shaped brass bracket when you re-assemble the camera.

  

  Initial testing showed good sharpnes, I need to do some further testing with daylight. The plan is to shoot side-by-side the #1 camera with the original polished IR-filter and the #2 camera with the home-grown filter.

Given that I wanted a flexible solution to mount various filters on the lens I turned a brass spacer ring on my lathe to mount a 35.5mm filter mount on the little Kodak. That brass spacer ring plus filter ring I glued on the front of the camera lens. I can now mount different filter types by putting them in a surplus 35.5mm filter ring (acquired for a 1 EURO each at a camera fair). In retrospect I would probably better have used a 37mm ring, as there are IR filters readily available in 37mm for IR work with video cameras.

My IR camera with it's lens extended next to its conventional brother with lens retracted

Image quality using a Wratten 87C filter plastic foil (0.4mm thick) that I bought from Willem-Jan I personally find very satisfying. These pictures are from the #1 camera, so with the polished-off IR filter.

Below an (uninspiring) test shot with the #2 camera. The DIY filter appears to work as anticipated.

A side by side testshot with the polished filter (camera #1) versus the one with the cut-down UV filter (camera #2) reveals that under difficult lighting conditions the #2 camera wins hands down. The polishing has left tiny scratches that give rise to flare with bright light directly entering the lens.

Further plans

Last but not least I would like to find a piece of suitable IR-blocking filter glass that I can use to make the converted camera behave "normally" again. Suggestions on where to find suitable glass are very welcome.

Feel free to send me email on the conversion.

© Wilko Bulte, 2007.

Last update: Sun Dec 2 13:49:05 CET 2007