Monthly Archives: November 2014

Use of external IR filters

I have had a couple of similar conversations over the last week with people who had not appreciated the use of external filters in addition to sensor modification, which made me want to get this out on the blog.

Putting aside full-spectrum conversions, there is still a place for external IR filters with single-spectrum modifications. The quoted frequency for the modification, like “590nm” or “720” means “590nm and above (longer)”  or “720nm and above (longer)”; it does not mean just 590 or 720.

I.e a 590nm modification, with use of external filters, can do 660nm, 720nm, 850nm etc. 720nm, being longer, can do less, but can still do 850nm, 920nm etc.

The thing to add is that these external lens filters are relatively inexpensive, so trying different frequency ranges is easy and accessible. The only time it is not possible to use such additional filters is with ultra-wide lenses, like my M43 Samyang 7.5 fisheye, that would be cropped by any additional front filter; or when the camera does not have a LiveView capability (such as with older DSLRs), as filters like 720 and 850 are too dark to work with an optical SLR viewfinder – which is why I am not convinced generally that DSLRS make good IR cameras and favour mirror-less cameras.

There is a logical school of thought that if you just want to capture IR (and not UV as well), a modification of 590nm is the most versatile common frequency; allowing it to be used with 660nm, 720nm, 850nm etc. Personally, I support this thought and don’t want to be locked into just one or two frequencies – much of the fun comes from playing and seeing what comes from different frequencies.

IR frequencies

New camera arrives

Hurrah, the new modified camera arrives – Olympus PM2, modified for 660nm.

Am off to Switzerland for a couple of days, so will test it there. The plan is to basically keep a Panasonic 12-32mm pancake lens on it and use it as a travel light camera, carrying only a screw-in 850nm filter with it. All other planned IR & UV photography will be with the coming soon M5 full-spectrum.

The camera was picked up very cheaply off Ebay (sold as an ex demo with no charger or box bits) and converted, in the UK, by Funky Electronics ( who were very helpful over the phone and reasonably priced.

Why Funky Electronics (when the e-M5 has gone off to Kolari) ? I wanted to keep the conversion in the UK and try someone new; plus Oly Pen’s seem to be a relatively well kown and easy camera to convert (unlike the M5, hence going to Kolari in the USA). So far the job looks a good’un.

Pl2 -2