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06-15-2010, 09:57 AM   #1
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Frustrated with KX Manual White Balance for IR...

Alright, I read the manual and searched the forum, but didn't find anything on this. I'm shooting IR with a Pentax KX, Sigma 18-50mm f/2.8 lens, and a Bower R72 infrared filter.

I'm fairly experienced with shooting IR landscapes and such (using previous cameras as well as the KX with the 18-55 kit lens and a Hoya R72 filter), but for some reason I can't get the manual white balance to set with my current lens, filter, camera combination. With the IR filter in place I point it at the grass, but then I get the message, "The operation could not be completed correctly". The only time it works is if I point it at something white or point it at the blue sky. I don't want to use white because I want the trees to be white and the skies an orange/pink color. I then later swap red/blue to get white trees and a blue sky. It doesn't matter if I point it at the grass, green bushes, green trees, etc., the manual white balance will not set on a green object.

Anyone ever encountered this before? It almost seems like it's an issue with the Bower R72 filter, but I'm not sure why the KX's manual white balance system won't set at what I'm telling it to. I mean, if I want it to set on black, it should set on black. What's the point in manual/custom white balance if it won't do what I tell it to do, right?

-- Chris

06-15-2010, 10:33 AM   #2
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The issue is that the filter is too dark for the camera to be able to take a proper white balance reading off the grass. Perhaps with the sky and paper it can see it well enough to take a reading (one that might be incorrect anyway?), but the grass itself is probably just too dark. I think in this case RAW is the answer, then don't worry about it, otherwise isn't tungsten close to the correct WB/color temp?
06-15-2010, 10:35 AM   #3
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I never did try the K-x with an IR filter while I had it - I can take handheld shots using the hoya r72 with the new *ist DL I just bought (yes new, not just 'new to me!'). What kind of shutter speeds can you achieve with the K-x? How is the Bower rated for IR? Is it true IR, or one of those ebay types that are really just a deep red?
06-15-2010, 01:24 PM   #4
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QuoteOriginally posted by pxpaulx Quote
I never did try the K-x with an IR filter while I had it - I can take handheld shots using the hoya r72 with the new *ist DL I just bought (yes new, not just 'new to me!'). What kind of shutter speeds can you achieve with the K-x? How is the Bower rated for IR? Is it true IR, or one of those ebay types that are really just a deep red?
The Bower R72 is admittedly suspect because it's inexpensive for its size (the 72mm R72 Hoya is like 5x the price of the Bower). However, I've seen IR shots taken with this exact same filter (72mm R72) and they turned out very well. The shots themselves turn out awesome with my KX and Sigma 18-50 f/2.8 except for the white balance. In my white balance trouble-shooting, I've managed to get something very close to what I can get from my Hoya R72 (55mm -- I use it on my 18-55 kit lens with a step ring). Again, the difference only seems to be white balance.

If I can't figure something out, I'll send it back. It was only $45, which might sound like an above average pricetag, but the same from Hoya is $200+ (too much money for a hobby -- I'd rather double it and buy the 40mm pancake!).

06-15-2010, 01:29 PM   #5
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This may help.. I know we aren't technically suppose to post from other forums but it's relevant.

Infrared Photography: Pentax SLR Talk Forum: Digital Photography Review

06-15-2010, 01:30 PM   #6
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QuoteOriginally posted by pxpaulx Quote
The issue is that the filter is too dark for the camera to be able to take a proper white balance reading off the grass. Perhaps with the sky and paper it can see it well enough to take a reading (one that might be incorrect anyway?), but the grass itself is probably just too dark. I think in this case RAW is the answer, then don't worry about it, otherwise isn't tungsten close to the correct WB/color temp?
Yeah, I've tried bumping up the ISO to 12,800 (or whatever) to get the grass visible enough to hopefully improve the reading, but it just won't do it. Strangely , I don't remember having any of these issues with my 18-55mm kit lens with a 55mm Hoya R72 filter.

I'll try Tungsten and then RAW. Like I said in my other post, I've seen this Bower R72 filter shoot some really nice IR shots, but it's giving me a lot of problems that my Hoya R72 does not give me.

I'll mess with it some more. If I can't figure out a work-around, I'll just send it back and chalk it up to a poor, not-entirely-IR filter. I really want to use the 18-50 f/2.8 for IR because it's a faster, brighter lens, but oh well!

Thanks for the suggestions!
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