Tuesday 2 June 2015

FLIR One Hands On

I've been hoping to have a closer look at one of the new breed of 'personal' thermal imaging cameras, and with the help of the Royal Photographic Society Journal I have been able to.

You may recall from earlier posts that this version of the FLIR One operates like a case for the iPhone 5 (more versatile versions are imminent) and uses the iPhone for viewing, operations and storage. The FLIR's case fits firmly onto the phone although it is in two parts so the thermal camera part can be easily unclipped if you don't want to carry it with you all the time. Fitting and removing the inner case to the phone is a little tricky and some users report breaking it ... so be careful. Clipped together the device is obviously heavier than the iPhone but not unduly so, and the whole thing still slips easily into a pocket. The two devices communicate via the Lightning connector and the thermal camera does not take any power from the camera; it has its own battery which is charged separately.

To operate the camera you pull down a slider switch half way until it clicks and turn on the free downloaded app. You are then prompted to pull and hold the slider a bit further, to calibrate the camera, after which you're ready to go. It's point and shoot, with options to change the colour palette, hold exposure, and select either a still photo, a panorama, time-lapse or a movie to shoot.

Thermal resolution is low, at 80 by 60 pixels, but the software neatly combines this with information from a coincident (almost) 640 by 480 visual camera, adding something like the Photoshop edges filter to form a hybrid image. For most purposes, this process, called MSX, completely ameliorates the low resolution thermal image. As the two cameras are not completely coincident there will be parallax errors if you shoot close-up. It is possible to correct for this (but sometimes I forgot). You can choose between several colour palettes. A thermal image is monochromatic but adding false colour can help show the distribution of temperatures. You can change the palette of a shot later, but for some reason the camera shrinks the image to 516 by 387 if you do this, which is weird. Another thing to note is that a FLIR logo is added to every image shot, which is slightly intrusive (imagine if Nikon or Canon did this) but is par for the course with their devices.

Straight out of the box you can shoot useful diagnostic images. For example, here is a shot that shows a cold carafe of water in the foreground and in the distance you can see a warm radiator and also the heat trace of warm pipes going up inside the wall above it. This uses a grey palette ... dark is cold and white is hot (relatively, the range is actually 12.8 to 21.2 degrees C).

Here's a shot with the temperature indicator turned on which shows heat spots of a group of transformers powering my broadband and phone equipment (iron palette). The FLIR One has a number of emissivity settings with a matte setting being the recommended one. Emissivity denotes how much infrared thermal radiation something radiates compared to what it should do if it were a theoretical 'black body'. Knowing the emissivity helps you know how accurate a remote temperature measurement is. The FLIR One has four settings for this, from matte to glossy, which is fewer that a fully professional thermal camera might have but is still useful.

I've no doubt a thermal camera such as this is a useful practical tool, especially in DIY for tracing heat loss and heating pipes (amazon.com buyers are notably enthusiastic about this kind of application), but I'm not so sure about its artistic possibilities. The low thermal resolution makes it difficult to take images as atmospheric as those that Joseph Giacomin takes, especially since I couldn't work out how to record only a thermal image with no visual embellishment. That said, it's easy to take fun thermal images and the images certainly attract attention.

I showed the FLIR One to a visiting heating engineer who immediately said he'd ask his boss for one, although for a professional with no need for panoramas or movies the new FLIR C2 [data sheet] is likely to be a better bet, especially since it is a self-contained unit with a similar price point and better analytical features.

The FLIR One in this form factor is available now from places such as the Apple store and Amazon (£180). I would wait for the newer model, which clips to the bottom of an Apple or Android phone or an iPad and should be a bit more future proof. From an artistic point of view I will pass, despite the low price. I think Joseph has convincingly demonstrated that a 640 by 480 thermal image has real artistic possibilities but I am less excited by the low resolution of the FLIR One. However this, and similar cameras, will show whether there is a market for less wallet-busting thermal cameras ... so I am delighted to see it and ignoring my arty pretensions I do think it's an impressive device and really easy to use.

To finish here are a few more results I got from the camera. Click for full size (640 by 480) versions.

The obligatory selfie. Normally with a thermal camera you wouldn't see my eyes through the glasses, but here the special processing does show them.

These thermal wavelengths (of the order of 10 µm) don't go through glass but they will go through some plastics. In this case you can see my hand inside a black bin liner. (The hand isn't touching the bag ... that would be cheating.)

The London Eye from Westminster Bridge. The thing growing out of the guy's head isn't a new tower block ... it's a lamppost on the bridge!

This shot, of the cab of a steam locomotive, demonstrates a colour palette that shows the very hot spots in red.

And finally some movie. Shooting a movie is straightforward, although in some circumstances you should lock the exposure (called span) to avoid changes to the palette mid-shot. The three scenes are of a London tube train (Victoria line) and a subsurface line (Circle etc) ... here you can see how the tube train, which runs deep underground, shows as warmer in relation to the platform than the subsurface one, which is at pretty much the same temperature. The wheels show very hot, as the trains are braking as they come into the stations. The third scene is of a loco at the Yarwell halt on the Nene Valley Railway, running to change ends before pulling a train towards Peterborough. I was surprised to see the hotspot at the front of the loco and by how relatively cool most of it was.