filters on a IR Camera

[kiko]

just a random question,

the other week i picked up a circular polariser for my Nikon D50 which has been converted to infrared (720nm to be particular) and very few of my images came out that sharp or in focus....

has anyone else noticed this or was i just having a terrible day taking pictures? from the effects i don't notice enough of a difference between my photo with or without the polariser....



also extra which lenses do you use...

i'm currently using the Nikkor 18-70mm but i'm looking at replacing it for the cheapo of the range Sigma 18-200mm so it is a little more versatile

 

[Llamaman]

Problems can arise with IR because the light behaves differently to visibile light. You might have reflections between the lens and the rear of the filter confusing the AF of the camera. I assume you had no problems prior to using the filter?

Be careful about changing lenses - some will porduce "hotspots" when used with IR lenses. The 18-70 is supposed to be very good for IR use - other lenses might not work so well, so you may want to read up before you commit to buying (or buy 2nd hand so you don't lose much if you need to sell again).

FWIW, I just bought a IR-converted D70 but haven't had a chance to use it properly due to work commitments. I've done a few test shots (which I haven't had a chance to study in detail) with my current set of lenses (18-105VR, 70-300VR, 35) but I was thinking of getting the 18-70 if the 18-105VR is no good (or trading in the 18-105VR towards a 16-85VR to share between both bodies...).

I'll let you know what I find...

 

[kiko]

i had no problems at all without the filter, ACS adjusted the focus to be acturate in infrared, which is a bummer at higher focal lengths (300mm) as the viewfinder is more obviously out of focus, couldn't work out why it wouldn't focus to infinity but after checking the shots.

one tip if the D70 custom white balance doesn't actually give you a picture that isn't just red, use the histograms because it's so much easier. I can't remember if you have control over WB temperature if so just aim it at the lowest value and use PP to click white balance on foliage.

i've not been able to find a comprehensive list of lenses to either look for or completely avoid, at my old job i was tempted on my lunch break each day to take random lenses out and quickly test but the task was a little daunting.