Ilford SFX/IR filter/KX - advice?

I recently bought and loaded a roll of Ilford SFX, and now the IR filter has arrived I've got all the stuff to use it. Problem is, the KX has a match needle display which you can't read with the filter in place! Any ideas? Someone out there must have used this stuff extensively and be able to offer advice?

At the moment I'm trying to work out how many stops the filter reduces by, so I can think in terms of setting the exposure normally, focussing, adding the filter and then turning the shutter speed down a bit to compensate. Ilford say to use smaller apertures as a way of compensating for the fact that focus can be different with IR light compared to visible wavelengths, so I can't really compensate by stopping up. Is this workable?

I do have an old handheld light meter which works, but tends to overexpose. Wondering if I could adjust it so that it reads as though it has an IR filter attached all the time, then take settings from that. It was a £5 ebay find which I've never used for anything else.

Right, as I've now shot and developed a roll of this stuff with apparently good results I can offer some pointers to others who might be tempted to give it a go!

Ilford recommend that you use the smallest possible aperture so that depth of field can cover for uncertain focussing caused by IR light being at a different wavelength, so I set the lens (K 28-50mm) to f22 or f16, then focus. Note the recommended shutter speed, add the filter, then take seven stops off the shutter speed (so if the camera recommends 1/125 your correct speed with the filter is a second).

You will need a tripod and some sort of remote shutter release - I used a plain old cable release. The self timer isn't entirely suitable as for many shots you'll have to set the camera to B and use the second hand on a watch to time the exposure.

Developing is fairly normal for B&W film, just follow the instructions on the inside of the box.

If you use the film without the filter it will behave much like HP5 - I did a couple of shots without for test purposes.

Don't forget that many older Pentax lenses have a red-mark for adjusting focus for IR. Cheers, Kris.

Yep, I should probably have used a lens with that (the 28-50mm doesn't have one)! Next time I'll probably make the effort to use my 55mm and 28mm primes, the 28-50mm lives on the KX as a good all-rounder.

I bought a cheap 52mm R720 filter from Amazon, you can probably get much better ones if you pay 4x as much but I wasn't inclined to splash out as I didn't know whether it would work terribly well. It turned out to be pretty decent aside from a bit of flare in one shot, although I'm still learning how to get the IR effect to kick in properly. I've since been informed that a more expensive filter would probably knock ten stops off - easy enough to check by waving your filter in front of a camera with some form of illuminated viewfinder display to see what it comes back with. I checked mine with a handheld meter and also an old A3 body, both of which suggested around seven stops.

It works best if you take shots with plenty of sunlight, as there isn't much IR about on cloudy days. Big shadows don't help, even lighting is better.

I quite liked this one - the IR doesn't jump at you but I think it works:




and this one shows the IR effect pretty well:




As with all new techniques it takes a while to work out what will and won't work. This looked much better in my mind's eye than it turned out...:




At a guess the exposure wasn't quite right leading to blown highlights, this one was thirty seconds timed with my watch IIRC. Interesting water effects though!