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Seek Thermal · Seek Thermal CompactPRO – High Resolution Thermal Imaging Camera for iOS
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A 320 by 240 thermal camera that draws power and processing from an iOS device, with a focusable 32 degree lens, a frame rate stated as under 9 hertz, a detection span from minus 40 to 626 F, nine palettes and four emissivity presets. Two of those published figures govern how the camera has to be used. Under 9 hertz is an export control threshold and a limit on how fast you can pan. Four emissivity presets is not an emissivity value, and the difference shows up in every spot temperature it reports.
Under 9 hertz is an export limit and a panning speed
The specification line gives the frame rate as less than 9 hertz rather than as a value, which is unusual enough to be worth explaining.
Nine hertz is a regulatory line, not an engineering one. Thermal imagers that refresh faster than that attract export control attention in several jurisdictions, which is why a large part of the consumer and trade market is deliberately built to sit underneath it. Writing the figure as a ceiling is the honest way to describe a camera designed to that constraint, and it is also a reliable way of telling which market segment a camera belongs to.
The consequence for the work is arithmetic. At nine frames per second there is about an eighth of a second between frames, so panning at any speed smears the image, because the scene has moved appreciably between one frame and the next. Thermal detectors also have a settling time of their own, so the smear lasts longer than the frame interval alone suggests.
The technique that follows is to move in steps. Point, let the image settle, read, move. It is the same discipline a slow shutter speed imposes on a visible camera, and it is a real constraint on how quickly you can sweep a ceiling or a distribution board rather than a detail.
Four presets instead of an emissivity value
The specification line ends with four emissivity presets. Note the wording: presets, not adjustment.
Emissivity is how efficiently a surface radiates infrared compared with a perfect emitter at the same temperature. A thermal camera measures radiation and has to assume an emissivity in order to report a temperature, so the assumption is part of the measurement rather than a refinement of it.
The spread across materials is large. Painted plaster, brick and most building materials sit high, around 0.9 and above. Oxidised and dirty metals sit in the middle. Polished aluminium, galvanised steel and bare copper sit low, and a low emissivity surface also reflects its surroundings into the lens, so the camera reports a mixture of the target and whatever is standing behind you.
Four presets cover four cases. If your surface is near one of them, the spot temperature is as good as the rest of the camera allows. If it is not, you are reading a figure that is wrong in a predictable direction with no way to correct it in the instrument. For building fabric work that is rarely a problem. For electrical work, where busbars and lugs are precisely the low emissivity metals that cause trouble, it is a real limitation, and our guide on setting emissivity covers the workaround of applying a known high emissivity patch to the target.
What 1,800 feet of detection works out to per pixel
The fourth bullet states a detection distance of 1,800 feet. Detection and measurement are different claims, and the published optics let you work out the difference yourself.
A 32 degree field of view spread across 320 pixels puts a tenth of a degree in each pixel, which is about 1.7 milliradians. Multiply that by distance and you get the patch of scene one pixel covers:
- At 1,800 feet, around 550 metres, one pixel covers about 0.95 metres, so a person is roughly one pixel of warmth.
- At 50 metres, one pixel covers about 85 millimetres.
- At 10 metres, one pixel covers about 17 millimetres, so a 50 millimetre target spans about three pixels.
- At 2 metres, one pixel covers about 3.5 millimetres.
That is what the detection figure means: at the stated distance a warm object is noticed as a bright speck. It is a true claim and a useful one if you are looking for animals in the dark, which the second bullet mentions.
It is not a measurement distance. A spot temperature is only valid when the target fills the measurement spot comfortably, which in practice means several pixels across, and anything smaller is averaged with its surroundings and reads cooler than it is. The useful spot measurement distance for a small target on this camera is metres rather than hundreds of metres, and that is a property of 320 by 240 over 32 degrees rather than a shortcoming of this particular model.
A focus ring sharpens the temperature, not just the image
A focusable lens appears in the specification line almost in passing, and it is the most valuable item on it.
On a visible camera, focus affects how the picture looks. On a thermal camera it affects what the camera reports. A defocused image spreads radiation from each part of the scene across neighbouring pixels, so a small hot spot is averaged with the cooler area around it and reads lower than its true temperature. Focus is part of the measurement chain, not a matter of presentation.
Many phone attachments in this class are fixed focus, set at a compromise distance, and ask you to live with whatever that gives at the distance you are actually working. A manual focus ring lets you make the measurement sharp at the distance in front of you, and it lets you work close, which is where the small pixel footprints listed above come from.
The same bullet notes that the camera needs no batteries or charging and that a waterproof case is included. Both are accurate and plainly put. The power comes from the phone, with the consequence that a long inspection runs the phone battery down, and a rugged case for a small attachment that lives in a pocket is sensible rather than a bonus.
The specification list is long and NETD is not on it
| Specification | In the listing |
|---|---|
| Thermal sensor | 320 by 240 |
| Field of view | 32 degrees |
| Frame rate | Under 9 hertz |
| Focus | Focusable lens |
| Detection span | Minus 40 to 626 F |
| Detection distance | 1,800 feet |
| Capture | Photos and videos |
| Measurement tools | Spot temperature, high and low temperature, threshold mode |
| Palettes | Nine |
| Span and level control | Automatic and adjustable |
| Emissivity | Four presets |
| Power | From the host device, no battery or charging |
| Supplied | Waterproof case, free application |
| Host platform | iOS, per the product name |
| Thermal sensitivity, NETD | Not stated in the listing bullets |
| Measurement accuracy | Not stated in the listing bullets |
| Pixel pitch | Not stated in the listing bullets |
| Connector type | Not stated in the listing bullets |
| Minimum focus distance | Not stated in the listing bullets |
| Radiometric file export | Not stated in the listing bullets |
The sensitivity figure is the significant blank. Noise equivalent temperature difference is the smallest temperature difference a camera can distinguish from its own noise, and it decides whether the camera sees the things building and electrical inspection depend on: a cold bridge behind plaster, a slightly warm termination, the faint edge of a damp patch. Resolution says how finely the scene is divided, sensitivity says whether the divisions contain usable contrast. Our explainer on NETD covers why a camera with a good sensor and a poor sensitivity figure disappoints.
The absent measurement accuracy sits alongside it. The camera offers spot temperature, high and low temperature and a threshold mode, all of which put numbers on screen, and the listing never says how close any of them are. Note also that the detection span converts exactly: minus 40 to 626 F is minus 40 to 330 C, another metric specification dressed for an imperial market.
The right owner for a phone powered 320 by 240
This is a good fit for an inspector or contractor who already carries an iOS device, wants a real sensor count rather than an upscaled low resolution one, and is prepared to work within a slow frame rate and four emissivity assumptions. A 320 by 240 detector with a manual focus ring will show building fabric problems, water tracking and a hot termination clearly, and the threshold and span controls are the right tools for pulling a small difference out of a scene.
It is the wrong tool in three cases. If your work is predominantly bare metal electrical terminations, four presets will get in your way and a camera with an adjustable value is worth the difference. If you need to scan quickly across a large area, under 9 hertz will frustrate you. And if your reports need a stated measurement uncertainty, neither an accuracy figure nor a sensitivity figure is published here, so you cannot source either from this page. Settle the platform question first though, since the product name says iOS while the opening bullet says smartphone or tablet, and the specific statement is the one to believe. Our roundup of iPhone thermal cameras compares it against the alternatives.
Recommended Tools
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Frequently Asked Questions
Why is the frame rate written as less than 9 hertz?
Because 9 hertz is a regulatory line rather than a design one. Thermal imagers refreshing faster than that attract export control attention in several jurisdictions, so a large part of the consumer and trade market is deliberately built to sit underneath it. Writing the figure as a ceiling instead of a value is the honest way to describe a camera designed to that constraint. The practical effect is about an eighth of a second between frames, which is enough to make a panned image smear.
What do four emissivity presets mean for accuracy?
They give you four assumptions rather than a value you can enter. Emissivity is how efficiently a surface emits infrared compared with a perfect emitter, and the camera uses it to turn received radiation into a temperature. Painted plaster, oxidised steel, anodised aluminium and bare copper are nowhere near each other on that scale. If your surface matches a preset you are fine. If it does not, you are reading a number that is wrong in a predictable direction with no way to correct it in the camera.
How far can it actually measure temperature?
Much less far than the detection figure suggests, and the two are different claims. A 32 degree field of view across 320 pixels puts about a tenth of a degree, or 1.7 milliradians, in each pixel. At the stated 1,800 feet of detection that is roughly 0.95 metres of scene per pixel, so a person at that distance is about one pixel of warmth. Detection means noticing something is there. For a spot temperature you want the target to cover several pixels, and at 10 metres a pixel covers about 17 millimetres, so a 50 millimetre target spans about three.
Does the focusable lens matter?
More than it would on a visible camera. A defocused thermal image mixes radiation from neighbouring parts of the scene into each pixel, so a small hot spot measured out of focus reads cooler than it is because its energy is averaged with its surroundings. Many attachments in this class are fixed focus and ask you to accept that. A manual focus ring means the measurement and not just the picture gets sharper, and it is the most useful single item in the specification list.
What is missing from a long specification list?
The sensitivity figure. No noise equivalent temperature difference appears anywhere in the bullets, and that number decides whether the camera can see the small differences building and electrical inspection depend on. A measurement accuracy figure is also absent, as are the pixel pitch and the connector type. The list is long and specific about features and silent about the two numbers that set the quality of the result.
Which devices does it work with?
The product name states iOS and the bullet underneath refers generically to your smartphone or tablet. Where a listing is specific in one place and loose in another, the specific statement is the one to act on. Read it as an iOS accessory and check the connector against your own device before buying. The listing also states that it needs no batteries or charging, which is accurate and means the phone is the power source, with the usual consequence for a long inspection.
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