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Old Nov 18, 2009, 10:27 PM   #1
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Default Infrared and cameras lessons

Took a few minutes at lunch time to play some more with my new R72 filter, and learned a few things.

The K-7 (and the earlier K20) have several options for their in-camera b&w conversion. You can set the camera to simulate using colored filters and one of the options is supposed to simulate using an IR filter. So I decided to put it to the test, and also to see how the K-7 does with an IR filter.

First, the scene - it looks pretty boring in color:



I was shooting the scene in raw+ with the K-7, so the color version is the raw file converted with ACR.

Here's the in-camera b&w/infrared jpg file, showing how the camera thinks an IR picture should look like:



Now here's the real thing - taken with the K100 and the R72 filter, converted with ACR and converted to b&w in photoshop:



Then I put the lens and filter on the K-7. The first thing I noticed is that I had to have the camera at 2000 ISO to get the similar shutter speeds I had been getting at ISO 400 on the K100. The next thing I noticed was that I didn't get the same colors and contrast. It's obvious to me that the anti-IR filter on the K-7 blocks quite a bit of IR light that the K100 doesn't. Here's a K-7 photo taken at ISO 2000 and run through denoise before the same type of processing I did for the K100 shot.



Another difference is that while EV +2 gets you close to the right exposure with the K100, it's more like +5 or something like that with the K-7 (I was using manual mode and adjusting the shutter speed).

A color version with the red and blue channels switched, taken with the K100:



And with the K-7 using the same process:



My conclusion:

1. The in-camera b&w "infrared" setting for the K-7 isn't close to real IR pictures taken with the K100. I wouldn't be surprised if the setting is the same as the one available on the K20. While they can give you nice results, they aren't the same as shooting real IR on the K100.

2. The K-7 is not a good IR camera, it blocks too much IR. It looks closer to what the in-camera filter came up with that it did to the K100's pictures, not worth the time to set it up. I'm very glad I kept the K100 now.
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Old Nov 19, 2009, 1:41 AM   #2
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Thanks for sharing this. I know these are test shots, but they are cool. Is the filter something special? I have an IR filter from my old film SLR, wonder if it fits onto any of my current lenses or would even work. hmmm.
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Old Nov 19, 2009, 3:33 AM   #3
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=( yeah to get ir results from my k7 had some pretty long exposures - thought it was normal but i guess not

thanks for your tests - still wont given up on ir but seems like k7 gonna make me work for it =)
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Old Nov 19, 2009, 10:24 PM   #4
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Whether your old IR filter will work or not would partly depend on which one it is. Some, like the R72 filter I bought, allow some red light in with the infrared, while others block more. If yours blocks more light than the R72, it might not work. All digital cameras have anti-IR filters in front of the sensors, otherwise there would be a color shift. As cameras have progressed, the manufacturers have been using filters that block more and more IR. As you can see from my pictures, the K-7 blocks more IR than the K100, so it doesn't record the reflected IR light off of the palm fronds like the K100 can. If you are curious, dig it out and try it. There's a number of resources around the internet that give you some things to do to help, or let me know and I'd be happy to explain what I've done.

John - your long shutter speeds are normal for that camera. I couldn't believe the difference between the K100 and K-7 when it came to shutter speeds, and I had already read other people say there would be a big difference. Good luck with it, perhaps you'll have better success than I did. I'm not going to work at it with the K-7, just have fun playing with the K100 once again.
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Old Nov 20, 2009, 1:30 AM   #5
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I'll have to locate my old filter cases and see what's in there. If it's the right IR filter, I guess I'll give it a try on the K100d.
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Old Nov 20, 2009, 11:06 PM   #6
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Hi Harriet, I have a friend that does IR photography in digital but he sent his camera in and had the IR filter taken off the sensor. Now the camera is not able to take regular images and longer, but does IR very well. I think all digital camera's have this filter since the sensors are somewhat sensitive to IR without it.

I have not done any digital IR photography, but did quite a bit with IR film quite a few years ago.

Your shots are great even with the IR filter over the sensor, looks like great fun.

Tom
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