Nikon D850 Infrared: Filter or Conversion?

The direct answer: for serious infrared photography with a Nikon D850, converting the camera is the better choice, while an external filter is a cheaper, less convenient alternative. A conversion removes the camera’s internal hot mirror and replaces it with a clear or IR-passing filter, allowing fast shutter speeds and normal viewfinder use; an external IR filter screws onto the lens and blocks visible light, requiring a tripod and long exposures because the camera’s hot mirror still blocks most IR.

Why the D850 Is a Popular IR Candidate

The D850’s 45.7-megapixel full-frame BSI CMOS sensor offers exceptional resolution and dynamic range, which carries over to infrared work. Its high-resolution live view and tilting touchscreen make focusing in IR easier, and its robust build suits outdoor field use. Many photographers choose the D850 for IR because the same camera body can serve both normal and IR duties if you buy a second one—converting one body and keeping the other stock is a common approach.

How External IR Filters Work

An external IR filter, such as a Hoya R72 or a 720nm long-pass filter, screws onto the front of your lens. It blocks visible light (below ~720nm) and lets only infrared through. The camera’s internal hot mirror—a glass element in front of the sensor that blocks IR to prevent color casts—still sits in place, so only a small fraction of the IR reaches the sensor. This means you need very long exposures: typically 2 to 30 seconds in daylight at ISO 100, even with a wide aperture. You also cannot see through the optical viewfinder because the filter is nearly opaque; you must compose and focus before attaching the filter, or use live view with the filter on (which is dark and slow).

How a Conversion Works

Conversion involves removing the D850’s hot mirror and replacing it with a clear glass or a dedicated IR-passing filter (e.g., 590nm, 720nm, or full-spectrum). A professional service does this—it requires opening the camera in a dust-free environment and recalibrating autofocus. After conversion, the camera behaves almost normally: you can look through the viewfinder, autofocus works (though it may need fine-tuning), and shutter speeds are normal—1/250s or faster in daylight. You still need an external IR filter if you choose a full-spectrum conversion (to select the wavelength), but with a dedicated IR conversion, no filter is needed at all.

Comparing the Two Approaches

• Cost: External filter: $50–$150. Conversion: $300–$500 plus the cost of a used D850 body.
• Convenience: External filter is slow, tripod-only, and hard to compose. Conversion allows handheld shooting and normal workflow.
• Image quality: External filter produces softer images due to diffraction from the filter and motion blur from long exposures. Conversion gives sharp, high-detail IR images.
• Flexibility: A converted camera is dedicated to IR; you cannot shoot normal color with it. An external filter leaves your camera fully normal when the filter is off.
• Autofocus: With an external filter, autofocus is unreliable because the filter shifts the focal plane. With conversion, autofocus works but may need micro-adjustment for IR focus shift.

Choosing the Right IR Wavelength

Common IR wavelengths are 590nm (golden/red foliage), 720nm (classic white foliage with deep black sky), and 850nm (strong contrast, almost black-and-white). A full-spectrum conversion lets you use any external filter to choose the wavelength after the fact, giving maximum flexibility. A dedicated 720nm conversion is the most popular for classic IR looks. If you want both color and IR, a full-spectrum conversion plus a hot-mirror filter for normal color is an option, though color quality may not match a stock camera.

Common Problems and Misconceptions

• Lens hotspots: Many lenses show a bright spot in the center of IR images due to internal reflections. Test your lens before converting; some lenses are known to be IR-friendly (e.g., older primes) while others are not.
• Focus shift: IR focuses at a slightly different plane than visible light. With a converted camera, use live view and manual focus or fine-tune autofocus. With an external filter, focus before attaching the filter.
• White balance: Even with a 720nm filter, the raw file is strongly red. Set a custom white balance on a green leaf or use a preset to get the classic blue-sky/white-foliage look.
• Metering: The camera’s meter may be inaccurate in IR. Use histogram and exposure compensation; start with +1 to +2 stops over the meter reading.
• Myth: “Any camera can do IR with just a filter.â€� Most modern cameras have strong hot mirrors; the D850 is no exception. Without conversion, only a tiny fraction of IR reaches the sensor, making exposures impractically long.

Costs and Practical Considerations

If you already own a D850, an external filter is a low-cost way to experiment. But for serious IR work, you will likely want a converted body. A used D850 costs roughly $1,500–$2,000; conversion adds $300–$500. That total is comparable to buying a dedicated IR camera like a converted Fujifilm or an older full-frame model. Consider whether you can afford to dedicate a body to IR—if you only shoot IR occasionally, a filter might suffice despite its limitations. Also factor in that a converted D850 loses its warranty and any weather-sealing integrity may be affected (though reputable converters reseal properly).

Alternatives to the D850 for IR

If you are not set on the D850, several other cameras are popular for IR: the Nikon D700 and D800 (older but cheaper), the Fujifilm X-T1 or X-T2 (mirrorless, with excellent live view), and the Sony A7 series (full-frame mirrorless). Mirrorless cameras are generally easier for IR because live view works with the filter on, and focus peaking helps. However, the D850’s high resolution and dynamic range remain a strong draw. If you want a dedicated IR camera without converting, some manufacturers sell factory IR versions (e.g., Canon had a 20Da for astro, but not IR). In practice, conversion services are the standard route.

Frequently Asked Questions

Can I use an external IR filter on a stock D850 without conversion?

Yes, but expect exposures of several seconds in daylight, a dark viewfinder, and soft images. It works for static subjects on a tripod, but it is not practical for handheld or moving subjects.

Does converting the D850 void the warranty?

Yes, conversion requires opening the camera and removing the hot mirror, which voids Nikon’s warranty. Reputable conversion services offer their own warranty on the work.

Will autofocus work after conversion?

Autofocus will function, but because IR focuses at a different point than visible light, you may need to fine-tune autofocus (using the D850’s AF fine-tune feature) or rely on live view and manual focus for critical sharpness.

Can I shoot normal color photos with a converted D850?

If you get a full-spectrum conversion, you can attach a hot-mirror filter to shoot normal color, but the color accuracy may not be identical to a stock camera. A dedicated IR conversion (e.g., 720nm) cannot shoot normal color without removing the internal filter.

What is the best IR wavelength for a beginner?

720nm is the most common and gives the classic IR look: white foliage, dark sky, and strong contrast. It works well for landscapes and is forgiving in post-processing.

How do I know if my lens is suitable for IR?

Search for “lens name IR hotspot� or test it yourself: mount an external IR filter, take a photo of a white wall, and check for a bright center spot. Prime lenses and older designs generally perform better than modern zooms with complex coatings.

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