A Question of Filters

Although I stumbled quite a bit initially, when I converted my original M camera to shoot 720nm infrared it soon settled down, the ‘it’ being me rather than the camera to be fair. Because it was a consistent single wavelength once Sring had come, I soon discovered what worked and what didn’t both in taking pictures in the first place and processing the resulting images in post production software. However when my M10 camera returned to me in late October converted to a full spectrum camera but far later in the year and very many months later than I had anticipated, I hit a bit of a road block.

The obvious ‘problem’ was that with full spectrum conversions, you have an awful lot of variables to live with which of course is the reason that I went that route. The fact that this camera came back so late in the year when I was involved in other things especially a new/old 1D MkIII and the seasons were changing/already had changed so that I didn’t have the conditions to experiment or give my full attention to it, has been rather frustrating.

But all that said, I did despite unfavourable conditions make the effort to try and decide whether I was starting from a solid position to experiment with come next Spring when the light and foliage returnes because with infrared, it is the quality and variety of the light that gives the best results.

My Starting Position

I bought new UV cut filters for the lenses I would be using on this camera and in addition bought circular variable IR filters. The best way to describe these is to say that they operate like a Polarizing filter, there are two pieces of glass and you twist the front element to change the density of the infrared wavelength between 530nm up to 750nm. At this moment in time and largely because I haven’t had the ideal lighting conditions, I haven’t managed to create repeatable images that I could use to develop the post production settings in my software, there just seem to be far too many variables at play for me to feel that I’vd ‘nailed it’.

I decided that I needed to create a fixed starting point just as I have with my 720nm Canon M camera which captures light at a single 720nm wavelength and build out solutions from there. In addition and as the circular IR filters were 52mm, 55mm and 77mm diameter, I wondered how effective the two smallest sizes were anyway in practical use. So I hunted around until I found fixed IR filters the lowest value available being 680nm, something of a lower value around 500+ would have been better but it didn’t matter too much, at least I would have a fixed starting point and a known value to work from.

The interesting thing that I found was that these type of filters seem to be described as “X Ray” filters and run up to 950nm. I should say that as anyone who buys filters knows from experience, there are basically two grades cheap and expensive and I was definitely shopping at the cheap end here because I am ‘experimenting’ and I didn’t know if I was on the right track. If it turns out that a particular thing obviously works then spending more cash would be fine but then availability might well be the issue.

Along Came Orange

As I have mentioned in previous blogs on infrared photography, one of the ‘go to’ resources on YouTube is undoubtedly Rob Shea ( https://www.youtube.com/c/RobSheaPhotography ) , without any doubt when I first started down this road, it was Rob that became a ‘guiding light’ along the way. Anyway he had recently done a post on using orange filters on full spectrum converted cameras and that for me was a bit of a lightbulb moment ! I got hold of an orange filter and the results feature in one of the galleries below.

Orange Filter

The Results

Above and below are a couple of galleries that whilst not exciting images show the effect of 680nm filters and the orange filter, a bit nerdy but might be useful to anybody interested in doing something similar. By setting a baseline at 680nm and the ‘orange filter’, I have been able to ‘dial in’ a basic workflow in Affinity Photo for my post processing. With Affinity I’m using “Adjustment Layers” which if you like are a stack of filters which if saved in the native file format .afphoto I can later go back to, adjust, remove or add to change the end result which can then be saved out in a format like PSD or TIFF.

680nm Filter

I will later do the same sort of exercise with ON1 Photo and likely also play with RawTherapee and Darktable which are also excellent at manipulating infrared images. Even in these few images I have played around with them to produce visually different results which seems to indicate that both the 680nm and Orange filters offer greater ability in terms of colour compared with my 720nm camera. That said though and I will need to experiment further on this and I suspect that 720nm offers a better starting point for producing black & white images.

It is important for being able to control and visualise your images as you take them so that you can predict your end result at the time of capture. With the orange filters, you do not do the ‘standard’ for IR red/blue channel swap, with the 680nm, you do. Infrared photography with converted cameras is definitely one of those areas in photography where the post production goes hand in glove with actually taking the image in the first place and offers hours of fun, providing that you like post production image manipulation.