Teardown: building an infrared camera

You've probably seen infrared photographs before: leaves of plants, for instance, emit a lot of infrared radiation and therefore appear very bright in infrared photos.

Infrared is invisible to the human eye, but it's visible to camera sensors. Nevertheless, you can't just take infrared pictures with digital cameras, as they have a cut-off filter that shields the infrared light. This improves the image quality because it only lets the light that we actually see reaches the sensor. Thus, a regular camera allows almost no light to reach the sensor.

In other words: to take infrared photos, the cut-off filter of a camera needs to be removed. This includes taking the camera apart.

Preparation

I won't sacrifice my regular cam for this teardown. It's the first time I'm doing this and my DIY skills aren't exactly legendary. Even if the camera survived my attempts to open it up and put it back together, a camera without IR filter isn't much good for normal use.

So I bought an old Nikon D90 for 150 francs on ricardo.ch. I used to have the same model myself for a long time and I know it’s a good camera – or at least, it was when it was released. SLR cameras that are even older would be unsuitable because they cannot display the viewfinder image on the LCD. This is necessary for infrared photography. I’ll get back to that later.

Of course I also looked around on YouTube – there are plenty of people who have converted a camera in the same way and posted videos of it. So I have a rough idea what to expect. But what's different is the details of every camera. On top of this, there's a big difference between watching a video and actually doing it yourself.

The operation, part 1: the nuisance

The conversion is filmed in our video studio. I take with me our iFixit tool set and an A3 sheet, which I use to lay out and label the screws. After all, I need to know where each screw belongs.

When disassembling the camera, I work my way step by step from the back of the camera to the sensor:

1. Unscrew the base plate.
2. Remove the back panel.
3. Detach and remove the circuit board.
4. Detach the second circuit board the sensor is mounted on.
5. Remove the IR filter.

After this, I put everything back together again in reverse order.

Sounds simple in theory. But the devil is always in the details. Besides, I feel the pressure of being filmed in the video studio and several people being involved in the project. The studio is available for exactly one day. That's my timeframe to get everything done.

The first problem isn't long in coming: the LCD of the back panel is connected to the circuit board by electronic cords. There are more connections on the other side of the board. I can't get to the sensor without disconnecting these wires. And I'm unsure how to disconnect them without damaging them.

At this point, I already feel a little stressed out. If I was doing this at home, I'd put everything aside and do some research on the internet. I might let it rest for a few days. Or at least take a break, relax and wait for the saving idea to come to me.

But in this situation, I can't do what I'd do at home. So instead of having Stephanie film me endlessly trying to figure it out, I get help by Kevin Hofer, our MacGyver when it comes to electronic things. There are three types of connectors. Kevin knows how to disconnect two of them. He doesn't know the third type, but it turns out we can leave them in place anyway.

The other problem that appears isn't as easy to solve. Some screws are stuck. I manage to get most of them out by pressing the screwdriver hard against the screw to prevent it from slipping off. But sometimes that doesn't work either and I run the danger of messing up the screw.

This is exactly what happens with the last of the three screws that hold the sensor board in place. When I try to unscrew it, I turn the cross slot into metal dust.

Since the nuisance of screw is almost out, I just want to rip it out, but Kevin thinks other stuff would come along with it. He tries to shred the screw from above with the power tool. It doesn't work, he slips.

Lunch break.

The operation, part 2: the solution

Time's going too fast. Time's going too fast. We haven't even finished disassembling the camera and reassembling will probably take even longer. Am I going to make it? Despite the time pressure, I'm glad it's lunchtime. I'm pretty tired. It's good to eat and relax.

On Kevin's advice, I buy a new metal drill in the right size. And indeed: it works. It knocks the head off the screw and allows me to remove the circuit board. Underneath it, I finally see the sensor. And the infrared cut-off filter.

The cut-off filter also features electronic connections. But since we don't need the cut-off filter anymore, I simply cut through them.

The only challenge when assembling is the circuit board. But it's a tough challenge. Whenever I've mastered one connector, I can't get to another one because I can't move the board around freely. All in all, I release it two or three times until it finally works. What's more, I'm never sure if the connections are plugged in far enough. What worries me most is that one slot remains empty. That's strange. Video producer Stephanie I go through the recordings to find out what was there in the beginning, but this slot is never in focus and I can't see what it's supposed to look like. After some pondering, I decide the slot will remain empty. And no matter if it works or not, there's no way I'm taking the board apart again.

Does it work?

As soon as I've put everything back together and reinserted the battery, I switch the camera on. It works! Both screens are running! I wasn’t expecting this, especially because of the empty slot. What a great feeling!

All screwed together, we get a lens and a take a few pictures. It works, although the photos are a bit blurry. As far as I know, that's normal if you remove the IR filter. When I focus with Live View (viewfinder display on the LCD), the pictures turn out focused.

Will infrared photography also work? I don't know yet. To find out, I have to put an infrared filter in front of the lens, which creates the opposite effect of an infrared cut-off filter: it only lets infrared light through. As the filter has to match the diameter of the lens, I need to decide which lens I want to use.

Not all lenses are suitable for infrared photography. Some have a hotspot, a bright area in the middle of the image. This compatibility list helped me.

The only suitable lens I own has a broken filter thread and won't allow me to screw anything onto it. Since this lens works well for infrared photography and I think it's a great product, I buy exactly the same one again on ricardo.ch.

The moment of truth: the first infrared photo

My first picture is of a plant. It's not a great photo, but it shows that the camera is suitable as an infrared camera: the leaves appear white.

The same picture with the unmodified D7500 turns out black because the two filters together (cut-off filter and high-pass filter) block the whole light spectrum.

If I expose for 30 seconds or even longer, some infrared will still come through. So even with an unmodified camera, it is possible to take infrared pictures. The long exposure times, however, make it impossible to take pictures without a tripod and videos.

This is what the image looks like with the modified camera and without infrared filter. The colours aren't far off, in my opinion. The blue in the background is also created with an unmodified camera, it has nothing to do with the IR cut-off filter.

Verdict: just do it

My teardown project is a success. It wasn't easy, but I have ended up with exactly what I wanted. And I'm new to DIY projects. If I can do it, you can do it! It's worth the effort: in a time where there are far too many pictures that look similar, this is a way to produce something that's more special and rare.

Of course, there's more to a good infrared photograph than the camera. Unfortunately, it's the wrong time of year for it right now, but I promise to follow up with an article on infrared photography in spring.