Long long time ago I wrote: GM> I've an (non-tested) IR filter that on paper gives 80% transmission for GM> 900nm. It's made of acrilic of about 4mm thick and is heat resistant. GM> It's perfect for some stealth IR photography, since it's the good size GM> to cover a flash gun (the size of a 550EX). Doing it gives just a dim GM> red glow when flashing full power with the previously mentioned unit.
GM> Here is the deal: I've one to go for FREE, with the only condition that GM> you test it and report the usability to the list (or to me, or whatever GM> as long as we get to know something). I've no time at the moment... Dieter and Eric kindly informed me of their experience with the filter and Maco IR film. The results with Maco were dissapointing as the transmission of the filter for 820nm is only of about 15% (see http://www.serialporteng.com/). The results of Eric are available at: http://darkwing.uoregon.edu/~epederso/Photo/IR/Test.html#Stealth Well, after more than one year I finally had the chance to try this combination. The filter works great with HIE, and it's not surprising, given that the (unaccurate) transmission chart reports about 80% tx at 900nm. More important even is the fact that the E-TTL flash metering from my EOS camera works great at determining the right exposure for the IR flash!!! >From previous experience with EIR and Ilford SFX Filter I knew that I could take advantage of the infrared sensitivity of the metering system to determine an exposure (accurate??). The E-TTL metering system is able to 'see' the IR Flash if you increase the ISO above 1600 but from the tests, it produces a usable exposure at ISO 6400. Bracketing is still possible with the 550ex. By using FEL, it's possible to know if you can put out enough power to light the wanted scene (by checking the bolt icon in the viewfinder) but you have to meter from a IR reflective surface (such as human skin). The metering is easily fooled, though: I couldn't get readings from things such as dark clothing or hair. I still have to print some of the frames to let you see. The density of the film is quite OK. It was developed in Rodinal 1+50/12'/20oC. Eric & Dieter, I hope you didn't throw the filter away!! Get some HIE :-) Ross: In included you in CC as I thought you might be interested from the discussion in photo.net. Although this is mainly a IR discussion, I cross-post EOS for the obvious reasons. -Kind regards, Gerard. PS: I have the feeling that I forgot something ;-) ;-) * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
