A couple of months ago, I put a film in my Pentex ME Super, took some photos and then got distracted for a little while. In that time, the box end on the camera back slipped out and I totally forgot what was in it.

When I returned to shooting, I assumed that the film must be Ilford HP5 plus – what I normally use – and went out to take some photos. Unfortunately, on rewinding the film, I realised that I’d made a mistake – the Film was not HP5, but Kodak ColorPlus 200.

This was disappointing because I was partially looking forward to seeing some of the photos I had taken in black and white. I guess I could have the film lab developed in colour and convert to B&W in Photoshop, but that feels wrong somehow.

That’s when I discovered, that not only had I been using colour film thinking it was B&W, but I had the camera set to ASA 400, when this was a 200 film, so now I have an entire underexposed colour film that I wish was black and white.

I contacted a couple of labs to ask if they could push process a C-41 film with no luck, I considered just having it developed at box speed and trying to fix in photoshop. I decided, though, to use this as an experiment and learn something from it (other than to pay attention to what you’re shooting with). I’d heard that you can cross process C-41 film in black and white chemistry, but searching seemed to indicate about as many people saying it hadn’t worked as had.

Then I came across this post, where the author used both the same film stock and developer as I had. In the post he had used the average development times for black and white film. I decided to do the same, developing at low temperature and doubling my normal development times from 6:20 to 12:40.

I also wanted to push process this film to compensate for my incorrect camera config, to do this I combined the “double it” approach from above, with a rule of thumb I remember reading once of “one minute per stop”, and added two minutes for a total development time of 14:40 minuets.

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