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04-14-2010, 12:47 PM   #1
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K-x IR Photos Pixelated after PP

I finally got to go out and shoot some IR photos today using a Hoya R72 filter on my K-x for the first time. After PP, however, the picture's quality looks awful. I shot in RAW and used JPG in Photoshop to PP. Adjusting the white balance didn't affect the image quality, but the channel mixing did, which became very clear in higher contrast. Any suggestions or reasons for this?

Here is the before and after. As you can see, there is a lot of pixelated banding in the sky.

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04-14-2010, 01:30 PM   #2
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The ISO 800 is probably part of it. You probably shot jpeg? You should check to make sure you are saving it as *** or **** quality. When you get into PP, make sure you aren't saving it over and over repeatedly and that you are saving with the least compression (highest quality)
04-14-2010, 02:58 PM   #3
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Figured out what it was. For whatever reason, if the image came from Aperture, it would end up pixelated in Photoshop. If it came from iPhoto, it wouldn't. Don't ask me why. So here is a new version.

Now I have to figure out why most of my IR photos have those wide streaks straight from the camera. It's very noticeable after proper PP.

The streaks didn't happen in the second photo. Oh, and don't mind the blurred branches. It was too breezy for 30" shutter speeds, but I did it anyway.
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04-14-2010, 03:36 PM   #4
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A note on IR pixelation in general: Be aware that the IR-pass filter blocks most visible light. That means that very little data is received from the Blue and Green pixels on the sensor. The image data comes mostly from the Red pixels, which are only 25% of the total. (Blue is also 25%; Green is 50%.) So you've effectively reduced resolution of your Kx from 12mpx to 3 or 4mpx. That's just part of the cost of IR work.

But it's great fun anyway. I'm in a similar situation when I'm spectrum-slicing to emulate the response to actinic (violet-blue) light of old orthochromatic emulsions. A deep violet optical filter blocks-off the Green and Red pixels' data. And then I'm in Pixelation Nation, same as when I use a 720nm or deeper IR-pass filter. The workaround is either major surgery (remove the camera's hot.filter) or buy a forensic dSLR without a hot.filter (but those take Nikon lenses). Ah well...

Just a guess: Those wide streaks might result from a less-than-perfect Hoya filter (gasp!). Try rotating the filter (and/or the camera) to different orientations, to see if there's any banding problem within the filter glass.

And/or you could be recording some spectral absorption by atmospheric layers -- IOW, a thin cloud stratum could be blocking enough solar radiation that your filtered sensor renders it as those sweeps. I try to avoid getting lots of thin clouds or bare-looking sky into any picture, but especially when spectrum-slicing. IR filters make big puffy clouds look great. But bare sky, especially in IR, especially at ISO above 200, can too often get nasty.

With actinic-filtered light, it's an opposite nastiness: the sky gets washed out to nothingness. Old-time photographers in the pre-panchromatic era solved that by keeping negatives of real or fake cloud shots, and using those (masked) to superimpose nice skies into their prints. See, shooping has a long tradition...

04-14-2010, 04:18 PM   #5
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QuoteOriginally posted by RioRico Quote
A note on IR pixelation in general: Be aware that the IR-pass filter blocks most visible light. That means that very little data is received from the Blue and Green pixels on the sensor. The image data comes mostly from the Red pixels, which are only 25% of the total. (Blue is also 25%; Green is 50%.) So you've effectively reduced resolution of your Kx from 12mpx to 3 or 4mpx. That's just part of the cost of IR work.

But it's great fun anyway. I'm in a similar situation when I'm spectrum-slicing to emulate the response to actinic (violet-blue) light of old orthochromatic emulsions. A deep violet optical filter blocks-off the Green and Red pixels' data. And then I'm in Pixelation Nation, same as when I use a 720nm or deeper IR-pass filter. The workaround is either major surgery (remove the camera's hot.filter) or buy a forensic dSLR without a hot.filter (but those take Nikon lenses). Ah well...

Just a guess: Those wide streaks might result from a less-than-perfect Hoya filter (gasp!). Try rotating the filter (and/or the camera) to different orientations, to see if there's any banding problem within the filter glass.

And/or you could be recording some spectral absorption by atmospheric layers -- IOW, a thin cloud stratum could be blocking enough solar radiation that your filtered sensor renders it as those sweeps. I try to avoid getting lots of thin clouds or bare-looking sky into any picture, but especially when spectrum-slicing. IR filters make big puffy clouds look great. But bare sky, especially in IR, especially at ISO above 200, can too often get nasty.

With actinic-filtered light, it's an opposite nastiness: the sky gets washed out to nothingness. Old-time photographers in the pre-panchromatic era solved that by keeping negatives of real or fake cloud shots, and using those (masked) to superimpose nice skies into their prints. See, shooping has a long tradition...
Wow, thanks for sharing that information. I have always wanted to try my hand at IR photography and your information really helped me out.

Thanks for sharing.
04-14-2010, 06:18 PM   #6
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QuoteOriginally posted by Tuner571 Quote
Wow, thanks for sharing that information. I have always wanted to try my hand at IR photography and your information really helped me out.

Thanks for sharing.
the red streak could also be internal flare; light entering the eyepiece and bouncing around inside. Make sure you cover it up.
04-15-2010, 04:50 AM   #7
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QuoteOriginally posted by enoeske Quote
the red streak could also be internal flare; light entering the eyepiece and bouncing around inside. Make sure you cover it up.
Exactly right. Whenever doing long exposures, cover the viewfinder. Well, you could probably get away with it uncovered if it's night and the lens is pointed straight up and you're shooting star trails and there are no lights on nearby. But otherwise, the VF is just a light trap.

While I'm on long exposures (and I won't shut up) I'll mention that deep IR filters, and/or deep ND (neutral density) filters, have an interesting effect. Welder's glass can be bought cheap. Disassemble a cheap UV or Skylight filter, have the welder's glass cut to fit, and you've got a cheap ND 1000 filter. Put that on the lens. Lacking that, get one or more ND10 filters, and a 900mn or 1000mn IR filter, and put those on the lens. Put the camera on a tripod on a busy street. Take LONG exposures, like 10-20-40-80 minutes. However long you expose, the camera will take just as long to do its Dark-Frame-Removel processing, so be patient.

What happens? Anything that moves just disappears. Illumination and shadows change because of the sun's movement. You capture a really strange, unpeopled world. You can get a similar effect with interval shooting: take a long series of tripodded pics of a vantage over a post-sunrise-to-pre-sunset period. My K20D lets me shoot up to 99 over 24 hours. In PP, stack all those pics in layers, then shoop to remove all differences. It's like a photographic neutron bomb, removing people but leaving the infrastructure intact. Just be sure to cover the VF.
04-15-2010, 10:24 AM   #8
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QuoteOriginally posted by Tuner571 Quote
Wow, thanks for sharing that information. I have always wanted to try my hand at IR photography and your information really helped me out.

Thanks for sharing.
Agreed! That was quite informative and useful, thanks, RioRico.

QuoteOriginally posted by enoeske Quote
the red streak could also be internal flare; light entering the eyepiece and bouncing around inside. Make sure you cover it up.
I had no idea about this. I'll be sure to cover it up from now on. Thanks so much!

QuoteOriginally posted by RioRico Quote
Exactly right. Whenever doing long exposures, cover the viewfinder. Well, you could probably get away with it uncovered if it's night and the lens is pointed straight up and you're shooting star trails and there are no lights on nearby. But otherwise, the VF is just a light trap.

While I'm on long exposures (and I won't shut up) I'll mention that deep IR filters, and/or deep ND (neutral density) filters, have an interesting effect. Welder's glass can be bought cheap. Disassemble a cheap UV or Skylight filter, have the welder's glass cut to fit, and you've got a cheap ND 1000 filter. Put that on the lens. Lacking that, get one or more ND10 filters, and a 900mn or 1000mn IR filter, and put those on the lens. Put the camera on a tripod on a busy street. Take LONG exposures, like 10-20-40-80 minutes. However long you expose, the camera will take just as long to do its Dark-Frame-Removel processing, so be patient.

What happens? Anything that moves just disappears. Illumination and shadows change because of the sun's movement. You capture a really strange, unpeopled world. You can get a similar effect with interval shooting: take a long series of tripodded pics of a vantage over a post-sunrise-to-pre-sunset period. My K20D lets me shoot up to 99 over 24 hours. In PP, stack all those pics in layers, then shoop to remove all differences. It's like a photographic neutron bomb, removing people but leaving the infrastructure intact. Just be sure to cover the VF.
Very interesting, again. I would love to try it sometime. I actually wanted to do longer exposures yesterday with the IR and lower the ISO, but I was on a bridge, and the traffic was making it move just a little too much. My 30" exposures at 200 ISO ended up with shake. I'll have to play around with the longer 10-30' or so exposures. Definitely a cool way to get just the buildings or whatnot without any interference.

Thanks again!

04-15-2010, 02:59 PM   #9
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QuoteOriginally posted by Perrumpo Quote
Agreed! That was quite informative and useful, thanks, RioRico.
!De nada! !No hay problemo! And while we're at it, on this thread we're talking about some long exposure stuff, including Tokihiro Sato's intriguing photos. rparmar noted that it's just "long exposures and running around with a torch" and I responded,

QuoteOriginally posted by RioRico Quote
Hmmm, probably, yes... I'll have to try that when it warms-up somewhat here. Put the fisheye zoom on the K20D on the tripod on the back porch; B(ulb); wander about the edge of the forest (and into it a bit) with a very slow strobe; don't flee if a puma or yeti appears.

Hmmm, another idea. I've a 950mm IR-pass filter. The widest lens I can put it on is the 18-55 kit. And I've a Sony IR light, for use with NightShot cams. So, same setup, but before the chill of night has fallen, I probe the forest (no pumas now) and trigger the light, see how long it takes to register through the filter. Hmmm...
So there are other ways to torture IR images. Day or night, use an IR flash or light, or such with an IR filter over it, to paint or spot a scene. IR gel filters can be bought for much less than glass filters mounted in rings. Or get gel filters and old rings, cut and mount them, save mucho dinero. I've done that with actinic filters.

Oh, another thing to keep in mind: Even with a deep 1000nm IR-pass filter, we're still dealing with near-IR. Far-IR, the kind you see in adventure cine where the heat of living humans is tracked through walls and forests etc, is a whole different thing. Except for STRONG sources of IR and IR-generating LEDs, all we get with this technology is reflected near-IR, mostly from sunlight. The color and tone effects we see result from materials' differences in absorbing and reflecting IR, differences we don't normally see because our eyes aren't made that way. Sometime I dream of having an eyeball lens replaced with IR-passing glass, so I could see more spectra without a camera. Borg me up, Scotty.
04-18-2010, 02:16 PM   #10
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QuoteOriginally posted by RioRico Quote
!De nada! !No hay problemo! And while we're at it, on this thread we're talking about some long exposure stuff, including Tokihiro Sato's intriguing photos. rparmar noted that it's just "long exposures and running around with a torch" and I responded,

So there are other ways to torture IR images. Day or night, use an IR flash or light, or such with an IR filter over it, to paint or spot a scene. IR gel filters can be bought for much less than glass filters mounted in rings. Or get gel filters and old rings, cut and mount them, save mucho dinero. I've done that with actinic filters.

Oh, another thing to keep in mind: Even with a deep 1000nm IR-pass filter, we're still dealing with near-IR. Far-IR, the kind you see in adventure cine where the heat of living humans is tracked through walls and forests etc, is a whole different thing. Except for STRONG sources of IR and IR-generating LEDs, all we get with this technology is reflected near-IR, mostly from sunlight. The color and tone effects we see result from materials' differences in absorbing and reflecting IR, differences we don't normally see because our eyes aren't made that way. Sometime I dream of having an eyeball lens replaced with IR-passing glass, so I could see more spectra without a camera. Borg me up, Scotty.
Cool idea. I hadn't thought of doing that yet. The Surefire helmet light on my Kevlar has IR, so I could use that, and I know I have an IR flashlight around here somewhere. I'll have to play around! I'm not sure how it would work, though. I feel like you'd need an actual IR camera to pick up IR light in darkness since the flashlights with an IR filter are barely visible. Maybe I'm missing something.

Last edited by Perrumpo; 04-18-2010 at 02:24 PM.
04-18-2010, 04:32 PM   #11
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QuoteOriginally posted by Perrumpo Quote
The Surefire helmet light on my Kevlar has IR, so I could use that, and I know I have an IR flashlight around here somewhere. I'll have to play around! I'm not sure how it would work, though. I feel like you'd need an actual IR camera to pick up IR light in darkness since the flashlights with an IR filter are barely visible. Maybe I'm missing something.
An IR-modded camera should be able to see fairly dim IR light. A straight camera with just the IR-pass filter on it will also, it'll just take longer. Try this: put the filter on the Kx. Boost the ISO way up and turn on LiveView (the Kx has LiveView, right?) Take a TV remote and aim it at the filtered lens and hold down any button. You should be able to see its IR light on the LiveView screen. Now try your IR flashlights. This will give you some idea of the filtered cam's sensitivity to IR light sources.

And beside the Sony IR boost light I use with my NightShot P&S (which flips the hot.filter out of the way for untrammeled IR use) I know that IR flashes exist. I haven't looked for them lately and I don't have time right now, but you could try to find one. Or as I mentioned above, get an IR gel filter and put it on a standard flash.
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