Digital Infra-Red

John, thanks. I have had some promising early results - I just wish I had started this earlier in the year when there were more leaves on trees for all of those white leaf effects!

Very interesting thread. A couple of questions:

1) What sort of exposures were required with the R72 filter?
2) Anyone tried a milder filter? I've got a wratten 29 gel which I used to use with IR film so I was thinking about giving that a try.

1) It depends on the amount of IR light and how sensitive the CCD is to it. With my Fuji S7000 the exposures run into many seconds and are not that good. With my Pentax *istDS hand holding is possible if the ISO is upped to 1600 or 3200. The results with the *istDS are excellent.

2) You can use a red filter of any sort, but that also allows red light through so the effect is not as strong. It is, however, perfectly valid as a technique. I suggest you try it and see what you think.

Canon DSLRs are not very good for these techniques as they have particularly efficient IR filters over the sensor - that is, they block the IR light from reaching the sensor. Ironically, some Canon film SLRs have infra-red film counters which is not conducive to using IR film! I wonder what Canon has against Infra-Red?

niblue, I have posted a couple of samples here http://uk.pg.photos.yahoo.com/ph/ammonyte579. I kept the ISO to 400 as higher values made it granier than I like, which puts exposures into the 1/2 to 5 seconds range. I haven't had much chance to experiment yet, I can't wait for the spring and a lot of leaves on the trees to get the full effect. The great thing about digital IR is that after the investment in the filter the only cost are for your batteries and your own time! The main downside is that you may not notice the speck of dirt on the lens or filter until afterwards! I think I have overcome the problem of composing and focussing shots by using a cokin slide-in filter which means less chance of disturbing the camera or lens than screwing a filter on.

Well I got an R72 filter and initial experimentation looks promising however I've a question about post-processing of the images. At the moment I'm just converting to B&W in photoshop elements but I'd be interesting in what other folks are doing to process the image from the camera.

I use PS7, and if you look at the channels, there will only be any image in the red channel. So I select the red channel and then go Image>Mode>Greyscale and say yes to "Do you want to discard other channels?" after which you have the one channel in monochrome.

No point in using Channel Mixer, as all the information in the green and blue channels has been filtered out at the taking stage.

I don't have any experience in shooting through an IR filter, although I've recently acquired one (Hoya R72) to try out later in the Spring. I found some useful info on the following website, which also refers to the processing in Photoshop.
http://www.jr-worldwi.de/photo/

Just a little reminder to all those thinking of dabbling with the IR - those fresh new leaves just coming out will be perfect over the next few weeks or so.

Have fun!
Dan

I can feel my filters twitching already - or that may just be the sap rising!

You can use a hotshoe mounted viewfinder, originally intended for rangefinders with interchangeable lenses. They are £5-£10 on ebay and have 35/85/135 framelines, which should be ok for estimating framing.

Just out of curiosity, do you still need to use the IR focusing mark on the lens? With film cameras, there was a slight shift of focal plane with infared light.

um, well I'd suppose so, because IR is still a different wavelength to visible light and therefore should focus at a different point compared to visible light. The problem is, most modern lenses don't have an IR mark!

Good question. As most (if not all) modern cameras have auto-focus, can they 'see' infrared? If they can, and one puts an IR filter between subject and lens, thus limiting the light that the AF system 'sees' to being in the IR range of the spectrum, does it focus correctly?

I have no idea, do you?

Hmmm, well there is one way to find out! (pardon me while I fiddle around in the background)

The camera does seem to "hunt" for the focus, and the tests shots were almost in focus (as they were of my very untidy office I'm not going to post them!)

Might be a different result outside on a bright sunny day.

My guess is, no, AF systems can't focus on infrared. If they did, they'd get awfully confused in daylight as there's got to be some infrared content in daylight. Icould be (read probably am) wrong.

I would try this myself . . . but I don't have any IR filters . . . yet.