Infrared Photography: Tips on How to Get Started Part 2

Photography Tips

Now is maybe a good time to explain some of the thinking behind the way in which I tackled my own IR camera project. By no means does this mean that you should be doing the same or even that you should agree with my logic. The following paragraphs may however go some way toward explaining some of the principles involved in the original project and why I did things the way I did. Here is the story of my own project, its constraints, and its outcome.

My Own Infrared Camera Project

I wanted a cheap digital IR camera. I had seen articles on how some other people went about modifying cameras. I was prepared to do most, if not all, of the work myself. I wanted to “hedge my bet” at getting a usable camera and thus decided to try not one, but a few, conversions. If the first attempt failed, it would leave me with a few more chances at getting a usable camera. If indeed more that one of the cameras worked, I would be able to compare their performance and characteristics and choose the better camera as my working IR camera.

I set myself the following targets and constraints:

• Use only cheap second hand point-and-shoot digital cameras. Some of these cameras have rather sophisticated lenses, zoom functions, and auto focus capability. They should serve just fine as a starter IR camera.
• Remove the “hot filter” from the camera, enabling higher sensitivity in the IR-region of the light spectrum. This should allow for acceptable exposure times, not limiting us to tripod-bound photos.
• I would mount an interchangeable high-pass filter in front of the lens rather than inside the camera (where it becomes a permanent fixture).
• Try to find cameras with some differences in function and resolution so we can experiment with these and try and find out pro’s and con’s of different functions.
• Try to find cameras which will allow for standardization of those parts I need to buy in. Settle on one filter size, standard non-supplier-specific batteries and if possible similar glass element components as replacements to the “hot filter”.
• Source components from the cheapest source possible without compromising the quality.

I started with a Kodak EasyShare CX6230. I already had this camera, thus out of pocket cost for the camera was zero. Things I liked about this option:

• It didn’t cost me a cent.
• The camera was proven to have taken good quality photos before. The only reason I abandoned it was because I obtained another which had a bigger MP value.
• It runs off standard AA batteries. Even though the camera may be approaching its end-of-life, I did not have to deal with the problem of an old non-reliable battery. (Which invariably is what happens with older cameras.)
• I could imagine fixing a 27mm screw thread filter to the front of the lens without too much difficulty.

Based on the measurements and configuration of the CX6230, I ordered a number of 27mm high-pass filters from a supplier in China. The filters sell for about $US 15 each, postage included. These filters turned out to be of good quality and quite suited to my needs. The filter rings I got did not carry any information on the filter’s cut-off value on the filter itself. It is important that you write the filter’s cut-off nm value on the side of the ring as soon as you unpack them. Otherwise they may get mixed up.

Before I even opened up the CX6230, I started looking for other cameras I could modify for IR work. Scanning through auction sites on the Internet, I found a few contenders. The way to get more information about a camera (its specifications, etc.) is to enter the brand and model number as a search term. You can use any which search utility you are familiar with (Google, Bing, etc). One of the results from the search result will most likely be a link to the website set up by the manufacturer. Visit this site and navigate to where the manufacturer provides technical support. You will most likely get the info you are after there. Even discontinued lines have their specifications preserved on these sites for many years. Unfortunately two of the important pieces of information we are after, cannot be found on these sites:

• How to take the camera apart without breaking it
• The dimensions of the “hot filter” hidden somewhere within the camera

After opening up the Kodak CX6230, I found it to contain a “hot filter” with a thickness of 0.5mm. I had difficulty acquiring glass of this thickness right away, so I simply removed the “hot filter”, closed up the camera, and tried it. More on the results later.

Note the 27mm filter glued to the lens housing. It moves with the lens housing and protrudes a bit further at start-up. It is not interchangeable.

I found a Nikon Coolpix 2100 on an auction site and put a ridiculously low bid in on it. The Coolpix 2100 is a 2MP camera of 2003 vintage.

Point-and-shoot digitals from the early 2000s go for a song, and they shouldn’t be hard to find either. If you do not have access to Internet auction sites, you can try second-hand shops, your local community notice board, or advertisements in the paper. I only had to push up my bid price once or twice to secure the auction on the Coolpix. You will be able to do the same.

Things I liked about the Nikon:

• I paid only a few dollars for it. It was dearer than the CX6230 because it had more features and cost more when it first appeared on the market.
• It was working perfectly and was in good nick. (You have to rely on some luck with your second hand purchases.)
• It suited my requirements for standardization in that it seemed feasible to fit a 27mm screw thread filter to the lens. It also ran off 2 AA batteries.
• It had the function to do manual white balancing before taking the photo. More comments on this later.

Things I did not like about the Nikon:

• It was even smaller than the Kodak and thus difficult for a ham-fisted guy like me to work on.
• When I opened it up, I struggled to get into the area where the “hot filter” was housed. When I finally got to it, I removed the filter and found it to be 1.8mm thick. This did not fit in with my plan of having standard internal replacement filter thicknesses!
• The Nikon uses a Compact Flash card. This did not fit in with my standardization plan for memory cards.

Note how this filter mounting protrudes out from the body all the time. A short length of aluminum tube was used to manufacture the section holding the first filter ring. The first filter ring is from a cheap 27mm UV filter. Simply take it apart and discard the glass filter. Then glue the filter ring to the tube or use a press fit to attach it to the tube. Another interchangeable filter ring with filter is screwed into the front of the assembly.

Thus far I had only tried 2MP cameras. Keen on getting something better, I secured another Kodak through an online auction. I got the Kodak EasyShare CX7330 for less than the price of a replacement for the SD card I got with it! The CX7330 was different in layout and construction to the CX6230. Its innards looked more like the Nikon’s. I was able to get to the “hot filter” easily enough and replaced it with a home-manufactured piece of glass in no time at all. More on this process later. The thickness of the “hot filter” in the CX7330 was 1.1mm. This lead me to believe that there are many different glass thickness “hot filters” out there. My plan of having a standard replacement glass element thickness proved to be flawed. If we are going to build our own IR cameras, we had better be prepared to search for different thicknesses of suitable glass. Read about the results obtained with this camera later on in the article.

Lessons Learned

These are the lessons learned after constructing three cameras and putting them through basic testing:

• I had one camera and bought two more at minimal cost. Cameras like these can be found easily and can be bought at low prices.
• By checking on the camera’s specifications we can determine its basic functionality and the size of photo it will be good for.
• A number of point-and-shoot type digital cameras have lens assemblies suited to the fitment of a 27mm high-pass filter. In some instances you may have to construct a connection element between the lens housing and the filter.
• Cameras like these can be dismantled, their “hot filters” removed/replaced and the camera be put back together again by anyone with basic practical skills.
• Replacement elements for the “hot filter” inside the cameras can be manufactured by anyone with basic practical skills and basic tools. (More on that later.)
• Cameras thus modified produce results of surprisingly good quality. The results are good enough to suit the needs of the amateur photographer and may even be used to get sizable prints, publish results on the Internet or the like.

Results

The photo shown below is one of the first photos taken with one of my IR cameras. It is a scene at a riverbank not far from where I live. It was taken with the modified Kodak CX6230. It is worth the while to note that the camera did not have any replacement for the “hot filter” in place when the photo was taken. The hot filter was simply removed, the camera closed up again and an 850nm high-pass filter glued to the front end of the lens. It doesn’t get much simpler and cheaper than that. The photo was downloaded to a computer by plugging the memory card into a card reader. The imagery was then manipulated using GIMP 2.6.8 and saved in slightly compressed format. It took me just about a dozen mouse clicks and mouse movements to get to the result you see in the photo. By then I knew the light distribution within the different color channels, had equalized these and converted the image to grayscale.

This camera does not contain a replacement part for the “hot filter” which was removed. The filter used was an 850nm high-pass. The Woods effect is clearly visible in the foliage. Note the dark sky. I think this photo is not half bad, considering the simplicity and low cost of the modified CX6230! For the CX6230, the complete project cost (excluding the tools) was less than $20 (New Zealand). This does not cover the cost of the camera. Cameras like this one (in perfect working order) can however be picked up for between $30 and $40 in New Zealand. In case you wondered about the “speed” of the CX6230 (its equivalent shutter speed under normal lighting conditions), you need not be concerned. The photo above clocked in at 1/236 second. To prove the point that shutter speed is not impeded, the photo below was taken. It shows a scene in the Manawatu region, on the other side of the island from where I live. The wind generators were going at the time and the blades were spinning wildly. They were however “frozen” quite easily in this photo due to the shutter speed of 1/276 second.

This camera does not contain a replacement part for the “hot filter” which was removed. The filter used was an 850nm high-pass. Note how the spinning blades of the wind generators were “frozen”. The shutter speed was recorded at 1/278. You need not be concerned about the exposure times needed for IR-modified digitals like the CX6230.

The Nikon Coolpix 2100 IR cost me a little more. The camera itself was bought for $60. I used two filter-and-filter-ring assemblies for this camera modification. Together they cost $20. I had to buy some aluminum tube and a small photo frame (so I could use the glass pane from it!) All-up the direct project cost of this camera was less that $100. For the extra expenditure I have a camera which allows me manual white balancing. I quite like this feature. See the photo below for an example of what the Nikon produces. The photo was taken at a local park.

It was overcast at the time. The filter was a 720nm high-pass. One of the advantages of manual white balance is that this picture is pretty much what you see when looking at the LCD at the time the photo is taken. There is one problem with the Coolpix IR-modified camera that you may need to consider. Because of the way that the filter holder was constructed, it may sometimes cause the edges of my photos to be cut off. The example below shows what this looks like. The photo is of a bronze statue in a local park.

The filter was a 720nm high-pass. It was slightly overcast at the time. Note the apparent vignetting in the bottom corners. This is most likely caused by the tube from the filter holder extending too far forward at this zoom setting. This problem causes me very little concern. I just need to remember to always “shoot wide”, then “crop back”. Note that this photo was not manipulated with photo editing software at all. What you see here is what you get straight out of the camera! This is what custom white balancing can do for you.

Proceed to Part 3: How to Build Your Own Infrared Digital Camera

About the author:
Pieter Albertyn is a self-confessed “tinkerer” and amateur photographer. He lives in Napier, New Zealand. Pieter has previously been involved in product development and systems engineering. He loves to modify utility products, enhance their features and develop basic logistical support systems for them. Though he works in an English dominated workplace, English is his second language.