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The iPhone and Infrared - I made something of a discovery today. I'm probably not the first to realise this, but I can't be the last, so maybe this will be of interest.
Like many others, I was looking forward to the announcement of the iPhone 5 last week. It didn't materialise of course, but the iPhone 4S is on the way. I'm still undecided whether I'll upgrade from my 34GS at the moment.

Anyway, whilst looking at the specs for the 4S, I noticed that among the changes to the camera, an infrared filter has been listed as a new addition. Most cameras already have one of these fitted in order to block unwanted light from the IR spectrum. This implied that the previous iterations of the iPhone, and presumably the Touch too, do not have a built in IR filter.

Shooting in infrared on an unconverted camera generally requires very long exposures. The examples I put on my 'Rough Guide to Infrared' (https://plus.google.com/u/0/112750091316252656625/posts/JoAYY1ED7aF) range from about 1 minute through to 11 minutes. The reason for such long exposures on an unconverted camera is that the built in IR blocking filter stops most of the IR light from reaching the sensor. Getting your camera converted for infrared involves removing the IR blocking filter and replacing it with an IR filter which blocks visible light.

By now, you've probably realised that if you've got an iphone, and you've got an IR filter, such as the Hoya R72, you've effectively already got a camera converted for IR!
I tested this out today. The weather was completely overcast - not great for IR photography. I simply placed the Hoya R72 filter over the lens of the iPhone, and immediately the iPhone was displaying the scene in front of me in infrared. The lens of the phone is so small that it's pretty easy to put the filter against it so that no other light leaks through.

I'll reserve judgement about how good an IR image can be produced in this way, but if you're living somewhere with sunnier weather than me at the moment, you might want to give it a try!
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7 comments
 
Very insightful observation! That's fantastic. Now to find a tiny piece of IR filter material to tape over the lens for convenience!
 
Interesting information.If only I had an iPhone !!! Impressive image ☺
 
Mr. Locke, do you have any idea how I'd check for this capabilty on an HTC android, or indeed any modern digital point-and-shoot? I'm aiming in particular for anything between 760nm and 900nm for "remote sensing" of vegetation. It seems like yesterday that these bands were only covered on satellite radiometers! Thanks for pointing this out!
 
Funny I read a post from another G+ about handholding an R72 onto the lens of a Olympus C2020 at pretty acceptable shutter speeds. I bought one for Sam years ago......but sadly it broke a few months ago!!
Must try this on my Wildfire.
 
+Bill Morris I don't know sorry. You just need to know whether the camera includes an infrared blocker or not, but I don't know where you'd find that information about your HTC. The easiest thing would be to stick an IR filter in front of your phone and see what happens, assuming you have access to one of course.
 
Actually, the iPhone 4 and 4S work well with a Hoya R72 IR filter taped over the lens. Then use software to extend the shutter range.
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