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03-13-2011, 08:10 PM   #1
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K20D IR Fail?

IR fail? - a set on Flickr

hey guys -
got a new IR filter this weekend and went to try it out this afternoon.
some of them are fine - others have a gnarly yellow streak running through them. all exif info should be available for everyone to see -
could it have been that i didnt screw the filter on tightly enough and light leaked in? any help is appreciated! thanks!

03-13-2011, 08:16 PM   #2
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Out of curiosity, did you cover the viewfinder with something? Sometimes light goes through the viewfinder and can cause strange light.
03-13-2011, 08:23 PM   #3
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no - i didnt cover the viewfinder on any of the shots i tried today.
03-13-2011, 08:25 PM   #4
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i actually thought that could be it too because i was in full sunlight when the harshest one occurs but then one from the same spot was fine. maybe the longer exposure time was too long? the shot that has the most obvious yellowing was 15 seconds long but i am sure others were longer than that...

03-13-2011, 08:34 PM   #5
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Looks like flaring to me. Covering the viewfinder may help but with these types of photos you really have to be mindful of how the light is hitting the lens. You might also want to set a custom white balance with the filter in place.

03-13-2011, 10:31 PM   #6
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any ideas on what the white balance settings should be for this kind of filter?
03-13-2011, 10:52 PM   #7
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QuoteOriginally posted by insulinguy Quote
any ideas on what the white balance settings should be for this kind of filter?
Take a photo with the filter in place and have a gray card or other neutral color paper in the scene. Then use your custom white balance settings to measure that particular part of the test shot and set it as your custom WB.

Your RAW files will still be incorrectly colored when you load them into processing software like Adobe Camera Raw, but it will be a lot closer to neutral than the hyper-red tone you have now. It will also be easier to correct if you are trying to make them black and white.

Most RAW processing software only goes down to a color temperature of 2000, which is still too "warm" for the custom white balance set by shooting the test image with the gray card. In my tests with early digital IR the only RAW software that can handle anything lower than 2000 is Raw Photo Processor (free for the Mac, I don't know if it's available for PC). Unfortunately, image processing with RPP is not real-time. You set values and refresh the image preview. It's actually quite good software, but the GUI leaves a bit to be desired.

Also, I agree with the previous posters; your streaks are most likely a result of light getting in through the viewfinder, something that has plagued me in the past with long exposures. Good luck, and stick with it!
03-14-2011, 12:28 AM   #8
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QuoteOriginally posted by LowVoltage Quote
Take a photo with the filter in place and have a gray card or other neutral color paper in the scene. Then use your custom white balance settings to measure that particular part of the test shot and set it as your custom WB.
This method is not gonna give good results from my experience.
IR photography relies on capturing subjects that reflect a lot at the IR spectrum (eg. green leaves or green grass) so a custom white balance should be done by taking a reading from such a subject.

You will then be able to do a channel swap and get results like this:
https://www.pentaxforums.com/forums/post-your-photos/136601-landscape-horse-tree.html

03-14-2011, 05:29 AM   #9
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Yeah WB for IR should be taken from the foliage for proper exposure. Best way is to shoot raw so that you can tweak to your preference in PP.

I'd have to say the streaks could be either from light in the VF or flare depending on the quality of the filter. On that note, I have both a cheap ebay IR filter and also a hoya r72 - the cheapie ended up being a deep red rather than true IR; it still gives the same effect, but some of the more interesting layering type of IR shots could not be achieved with that filter.

The longer exposures definitely exaggerate any flaws in the light hitting the sensor (and from any source), so definitely cover the viewfinder for IR shooting.
03-14-2011, 06:17 AM   #10
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It looks a whole lot like lens flare.
03-14-2011, 07:01 AM   #11
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it is a hoya r72 as well. im just wondering if it is from the viewfinder why wouldnt it be in every shot?
03-14-2011, 07:33 AM   #12
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QuoteOriginally posted by insulinguy Quote
it is a hoya r72 as well. im just wondering if it is from the viewfinder why wouldnt it be in every shot?
Is the light coming from precisely the same angle in every shot?
03-14-2011, 08:08 AM   #13
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QuoteOriginally posted by Wheatfield Quote
Is the light coming from precisely the same angle in every shot?
In the gallery there are shots at different angles, and the light bleeds are the same (more or less, depending on exposure, but the same spots).

I've read that sometimes the lens itself can have characteristics that result in flare like this, but I still think it is a result of light from the VF.

I have a 52mm Hoya R72 that ended up getting a small pressure crack on the edge of it. If I shot away from the sun it was fine, but anything with the sun in the frame (or even where it would reach the glass element) would result in similar flare eminating from the edge where the crack in the glass was. I'll see if I can find an example this evening.

Either way it'll take some experimentation to find out.
03-14-2011, 08:32 AM   #14
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It looks like you are using the 18-55 for those shots. I have the WR version of that lens and had no issues with an IR filter, though I was using a cheap Opteka on the K-7, not the Hoya on a K20. Since some of your images are fine it looks like the streaks are lens flare or viewfinder input, though the recent comment about a crack in the glass sounds like it could be the issue as well. You can do a quick check and cover the viewfinder, check for cracks, and maybe use a lens hood to see if you can eliminate the streaks. Also, I think the WB issue is not related to the streaks. Good luck!
03-14-2011, 06:45 PM   #15
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K, I had another look, and I have a theory that may tell you where to look at least.
And it could, as pxpaulx says, be bleed past the mirror.
Image 9995 makes me wonder though, since the viewfinder would be in shade in that image.
It's also showing a lot of veiling flare, but that's another matter entirely.
I'm kinda thinking it may be something in the mirror box or around the sensor that is reflecting off the lens and back to the sensor.
A good check to pin it down is to try to make it happen again, and then take another picture with the lens cap on and the lens at minimum aperture.
If the artifact is still there, it's the viewfinder.
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