Filming in UV, IR and Thermal — when your camera starts lying to you

If normal filming is “point camera at thing, press record, pretend you’re David Attenborough”… then filming in UV, IR and thermal is more like, “point camera at thing, press record, realise physics has other plans, and spend the next hour arguing with a lens cap.”

These worlds are brilliant for science, nature, kit testing and all sorts of “wow” shots — but they come with a special set of problems that don’t show up in ordinary visible light.

1) Your lens may not be telling the truth (or even letting the light through)

UV and thermal are the worst offenders here.

• UV: Most normal glass blocks a lot of UV. Many lenses transmit almost nothing useful in UV, so you end up with dim footage, mushy contrast, and lots of noise. Some lenses also create bright “hot spots” or weird flare patterns because coatings weren’t designed for UV.

• IR (near-IR): Many lenses work sort of fine, but you can get hot spots, reduced contrast, and soft corners. Some lenses shift focus slightly between visible and IR.

• Thermal: This is a completely different optical system (often germanium lenses). You can’t just “use your nice Canon lens” and hope for the best. Also: thermal lenses are expensive enough to make you treat them like crown jewels.

Result: your image can look soft, blotchy, low contrast, or oddly vignetted… even when you did everything “right”.

2) Focusing becomes a dark art (sometimes literally)

Autofocus is usually trained and tuned for visible light. In UV/IR it can hunt, miss, or give up and go home.

• IR focus shift is a classic trap: you nail focus in visible, flip a filter on, and suddenly everything is slightly off.

• UV often forces you into manual focus because the image is dim and AF can’t see enough contrast.

• Thermal cameras don’t focus on “detail” in the same way — they focus on temperature edges. Fine detail can vanish if temperatures are similar.

Practical fix: manual focus, focus peaking, test charts, and checking playback like a nervous parent at sports day.

3) Exposure is harder because the rules change

Your camera’s metering assumes the world behaves normally. In UV/IR/thermal… it does not.

• IR: foliage can turn bright (the “Wood effect”), skies can go dark, and reflectivity changes. Your histogram becomes a comedian.

• UV: everything is often dim, and you may need big light levels — but you also need to avoid frying your subject (or your eyeballs).

• Thermal: exposure is essentially a temperature scale (often with auto-gain). The camera may constantly re-map the scene if something hot enters the frame (hello, hands), making the picture “pulse” as it rescales.

Fix: lock exposure where possible, use manual settings, and for thermal learn to control level/span (or equivalent) rather than thinking like a normal videographer.

4) Reflections and “phantom signals” ruin your day

This one catches people out fast:

• Thermal reflections are real. Shiny surfaces can reflect heat like mirrors reflect light. You think you’re filming a warm object — but you’re actually filming the reflection of your own body heat. Congratulations: you’ve invented the thermal selfie.

• IR reflections off water, varnish, glass, and polished surfaces can be wildly different than in visible.

• UV can produce strange flare and internal reflections, especially with filters.

Fix: change angles, use matte finishes, add shields, and in thermal beware of glass (often opaque to long-wave IR) and reflective metal.

5) Colour becomes “false colour” (and your audience will believe it anyway)

In IR and thermal, colour is usually:

• mapped (false colour palettes),

• shifted (custom white balance in IR), or

• manufactured (UV fluorescence where the “colour” is actually visible light emitted by materials).

That’s fine — as long as you’re honest about it.

Fix: label what’s going on (“false colour thermal”, “near-IR”, “UV fluorescence”), keep palettes consistent across a project, and don’t imply “this is the real colour”.

6) Calibration, emissivity, and why thermal numbers can be wrong

Thermal cameras are amazing, but temperature readouts can be very misleading if you don’t account for:

• Emissivity (how well a surface emits IR radiation)

• Reflected apparent temperature

• Distance, humidity, and atmosphere

• Shiny surfaces (often low emissivity)

You can be “measuring” 70°C and actually be looking at a reflection or a surface that simply doesn’t emit well.

Fix: treat thermal temperature as a measurement with assumptions, not a gospel truth. Use emissivity tables, reference patches (matte tape/paint), and compare against known temperatures where possible.

7) Noise, artefacts, and the “why is the picture crawling?” problem

• UV/IR often require higher ISO or longer shutter times → noise, banding, hot pixels, motion blur.

• Thermal sensors can show fixed-pattern noise, drift, and “stuck” pixels; some cameras do periodic NUC calibration (that little click/freeze).

Fix: more light (UV/IR), stable support, sensible shutter speeds, and in thermal plan around calibration pauses.

8) Lighting can be the biggest headache of all

• UV lighting: needs proper UV sources, but also serious safety thinking (skin/eye protection, avoiding stray UV, and managing reflections).

• IR lighting: IR illuminators help, but can create hotspots and uneven scenes.

• Thermal: you don’t “light” it — you manage heat differences. Sometimes you need to create contrast (warm background, cool subject, or vice versa).

Fix: design the scene. In these bands you don’t just film reality — you engineer visibility.

9) Workflow: it’s slower, fussier, and needs more notes

When you mix UV, IR, thermal and normal footage, your edit can descend into chaos unless you keep track.

Fix: slate your clips (“IR 850nm filter”, “UV fluorescence 365nm torch”, “Thermal palette ironbow”), keep consistent LUT/palette choices, and grab some “normal light” reference shots so viewers know what they’re looking at.

---

The big takeaway

Filming in UV, IR and thermal is like gaining superpowers… with the small downside that your camera becomes a moody scientific instrument. Once you accept that you’re not just filming — you’re measuring, translating, and sometimes politely arguing with physics — it becomes hugely rewarding.