Infrared White balance problem

Hi everyone!
I've got an issue with my pentax k-r. Whenever i take a picture of some grass with my hoya r72 on the lens to use as a custom white balance, the camera says the operation could not be completed correctly. Why is this happening. Thanks!

Probably because you've filtered out all the visible light, so the camera cannot work out a white balance. The picture is going to be red come what may.

Why were you trying to do this?

because setting a cwb like this means the picture has that surreal look rather than the ugly red tinted look. You can do this on the canon 450d so i thought u could do it on the k-r.

I'm not sure if there's an IR setting in the menus, but the usual method is to process in black and white in Photoshop. I would try out the black and white setting on the K-r, which might help.

If you want colour IR red images (false colour) then I'm not sure. I'd have to experiment if I wanted that effect and would probably look first to Photoshop.

i believe you take a picture of brightly lit grass without the filter on, set a custom wb using this to use when you use the filter, can be done on K5. don,t know how you set up a custom wb on kr but it will be in the manual somewhere.

It can be done with the filter fitted. I had this occur on my K7. You need to make sure that there is a LOT of grass inside the little square when taking a custom WB. I'd say it says it cant do it 7 out of 10 times-ish.

I found it easier to just set it as low as possible in camera, 2500. Then tweak it a little using the jog dial if you see what I mean.

Ok thanks everyone! I'll try out those tips.

Make sure the aperture is wide open and that the grass is sunlit. The filter blocks so much light that its probably not getting enough light to work out the WB. If you still have problems also set a highet ISO while you set the WB.

Ok it works perfectly now. The kr really is better than the 450d for infrared. Thanks for the advice!