Infrared Camera Sensor Anti-reflection Coating Analysis

I had to pay extra to get my infrared-modified camera supplied with an anti-reflection coating on its IR-sensitive sensor cover. The company that converted my camera to 590nm infrared (it also passes some orange and red light) is called Kolari Vision. Did I waste my money getting this anti-reflecton coating option?

I wanted to show some examples of what the IR anti-reflection coating can do. I chose to shoot with a couple of lenses that are known to be poor choices for infrared use. I took photos with the same lenses at the same focal length and f-stop on two different cameras. My IR-converted camera is the Nikon D7000.

To be able to compare the IR anti-reflection coating effect against a camera sensor that doesn’t have a specific coating for IR, I chose to shoot with my Nikon Z9 camera. To shoot in infrared on both cameras, I used the same 850nm infrared filter mounted over the lenses being tested.

Lenses perform worse in infrared when you stop them down, so I chose to do all of my tests using f/16.  Zoom lenses perform worse at their widest settings with IR, so I tested the lenses at their widest settings, too. Lenses perform worse with longer infrared wavelengths. This may not be the worst-case scenario, but it’s close.

The first lens under test was the Nikkor 18-140 f/3.5-5.6 ED VR DX. This lens has a reputation as being a poor performer with infrared, especially when stopped down.

The second lens under test was the Nikkor 24-70 f/2.8 AF-S E ED VR. This lens has a terrible reputation when shooting IR, even though it’s quite expensive.

Nikkor 18-140mm at 18mm f/16 850nm Z9 camera

The 18-140 lens, which is a DX-format lens, yields a nasty white spot in the center of the picture when shooting at 850nm infrared on the un-modified Nikon Z9 camera. The white spot is due to IR light bouncing off of the camera sensor and going back into the rear of the lens. If I were to open up the lens aperture, the central white spot wouldn’t look quite as bad.

Nikkor 18-140mm at 18mm f/16 850nm D7000  IR camera

The same lens mounted on the IR-modified D7000 camera produces the barest hint of lightening in the central portion of the picture. I doubt that most people would even notice issues shooting IR with this lens. By opening up the lens aperture, the slight center light area would disappear.

The IR-modified camera with its IR anti-reflection coating over the sensor allows the infrared light to pass through, instead of bouncing around between the lens rear and camera.

Nikkor 24-70mm at 24mm f/16 850nm Z9 camera

This 24-70 f/2.8 lens produces horrible results with this unmodified Nikon Z9 camera. Totally unacceptable. Now you know why the 24-70 is legendary for being terrible with infrared. Even when you open up the aperture, this lens just can’t perform when shooting infrared on un-modified cameras.

Nikkor 24-70mm at 24mm f/16 850nm D7000  IR camera

Now take a look how this same lens with the same 24mm setting at the same f/16 performs. There’s a world of difference. There’s still a hint of central lightening, but this effect goes away when shooting about f/8 or wider. Since the D7000 is a DX format, the 24mm zoom setting looks like 36mm.

D7000 before IR conversion, 35mm f/1.8 AF-S DX at f/8 720nm

Here’s an example of the same D7000 camera before getting it converted to 590nm infrared. This shot used a 720nm Hoya R72 IR filter. This same lens, when stopped down to f/16, made shooting IR totally unacceptable. Even at f/8, I would typically have to use a radial filter in my photo editor to darken the central portion of my shots when using this lens.  More often than not, I used to switch to my old Nikkor 20mm f/4 AI-converted lens, which is excellent shooting infrared at any aperture.

Summary

The extra expense of the IR anti-reflection coating option on my camera when getting it converted into infrared was totally worth it. Most lenses that look awful when shooting infrared on my un-modified cameras perform just fine on my Kolari Vision 590nm converted camera, with its IR anti-reflection coating.

Beware that not every lens can work acceptably when shooting infrared, even with anti-reflection IR sensor coatings. My Tokina 11-16mm f/2.8 zoom is a poor performer under nearly every infrared scenario.

If you think about it, would you ever buy a camera lens that didn’t have anti-reflection coatings on it? Of course not. Then why would you want an infrared camera without IR anti-reflection coatings on its sensor cover?

Be careful if you get your camera converted into infrared. Not all companies offer an IR anti-reflection sensor coating option. In case you wondered, I’m not getting paid by anybody to sell anything.