Originally posted by Duplo Well easy now Leo. You come across pretty harsh to me.
I recall two currently running about IR, someone asking for a lighter IR filter than the Hoya R72 IIRC and this thread that I have come across lately.
Well I guess those making colour IR from their digital cameras will have to disagree with you, I have seen a few people doing that and with quite impressive results.
If you are using a stronger filter like the R90 you may be right, but the R72 actually let some green and blue light pass through too, why not use that as part of your Image?
I guess I do not see the point of excluding 3/4 of your imagedata.
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I did not mean to sound harsh, perhaps I should have explained my two points better.
I mentioned it is hard to search for IR threads. I just searched for my name. I've posted in seven IR threads and I'm fairly new at this forum so I'd say there are at LEAST seven IR threads since February. In one of the threads someone mentioned how they could not search for IR because it is too few letters, and Infrared is often not spelled out. Thus, the same questions come up regularly due to no fault of the questioner.
Infrared light, longer wavelength than 690 Nanometers, is on the opposite side of visible red than blue or green. The 720 nm Hoya passes very little visible light, the viewfinder is black on a sunny day. The red pixels respond to IR moderately well, especially in a modified camera like my K110D. The blue and green pixels contribute very little to an IR photo, only picking up a little light that "leaks" through the Hoya filter or, as Andrew suggested, enters the camera without going through the lens. Thus, to me, the Blue and Green are artifacts that are not IR and can not add to the photo. Andrew's original post was about blue streaks that were hurting his otherwise good image. Most IR images either convert to Black and White, use a false red, or use sepia. IR has no color, thus anything other than B&W is not IR but rather the photographers choice to colorize the photo. I happen to like to display IR as red knowing full well it is not.
Thus my suggestion: if you only extract the red pixels from the RAW file then you will have the IR without the junk. This thread was initiated to ask how to fix false blue in an IR image.
The slightly color images added to this thread after my post are the only ones I've seen. No real green trees or blue sky, but some color appears. The Pentax internal filter cuts IR so strongly that the green and blue have some chance to be effective. My filterless K110D is about 300 times better at IR than my K100D, I typically shoot at 1/3000 second on a sunny day.
Last edited by LeoTaylor; 09-12-2007 at 06:32 PM.
Reason: Added paragraph about now images in thread