Friday, 24 July 2015

Hot Photography part deux

I blogged recently about my attempts to create a DIY infra red camera.

I left it at the point where all appeared to be working, but I needed filters in order to complete the task and to reduce the amount of visible light that otherwise overwhelm the IR light we wanted.

One of advantages of the DIY approach is that it allows more flexibility in terms of the type of IR images you want to produce. By varying the filters on the front of the camera, you can let more or less visible light through allowing you to play with the effects. You can have an pure IR image, or by allowing a little colour through, you can get a bit of colour as well as the IR part.

I therefore ordered an 720nm and 850nm screw in filter and when I returned from holiday they were waiting for me.

The 1st thing you notice is that the filters appear black, like a ND filter to the naked eye. Of course this is the point, since they only pass IR, which is not visible to the human eye. Mounted on the camera, it is has little effect on the usable image and little noticeable effect on shutter speed.

The 720nm lets a greater amount of the spectrum through, just poking through into the visible spectrum, while the 850nm has a greater cut-off in the IR region, cutting almost all the visible spectrum out(filters cut-off are not perfect and there will always be some leakage).

Yesterday I had my 1st chance to try them out. IR photography works best with warm blue skies (preferable with a little cloud), and at the moment it is a bit overcast (the irony being that I had just come back from Crete where we had 7 days of rich blue skies which would of been perfect for IR photography), but I couldn't wait to try it, so I went to one of my favorite places, which had a old barn and plenty of foliage.

The 1st issue was the white balance. Since my chosen camera does not support RAW, and normal white balance is skewed by IR, I had to manually adjust the WB. Fortunately the camera does have a custom WB feature, and the advice is to take WB from a large area of grass. So with my 720nm filter on that is what I did.

The results were great.The image turned from uniform red, to the IR silver I wanted. These are the 1st images taken with the 720nm filter on.

I have processed them a bit, by compressing the levels. I also tried switching the red and blue channels. Without much blue sky there is not much contrast, but overall I am happy with the result.

Here is a similar image with the 850nm filter on. You can see the greater IR affect, with the corresponding reduction in visible colour.

Remember both these images are in colour, without any B&W processing

Here are a couple other images.  My only issues was some of the images came out out of focus. However I am not  sure whether this is a result of my modifications, the camera or my usage,

So far I am very happy with the results, and I am looking forward to playing with camera and seeing what it can do.

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