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06-30-2014, 01:03 PM   #1
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Infrared Conversions

I just had my K-7 converted to infrared with a 665 filter. The conversion was for live view focusing so that I could use all of my Pentax lenses. Everything with the conversion looks good except for an interesting difference in view between the optical viewfinder and live view.


When I first used the converted camera a few weeks ago I had to use the optical viewfinder because it was too bright outside to properly use live view. Since then I have started to use a Hoodman loupe and that problem is solved; the loupe enables me to use live view for framing under all lighting conditions. However, in those first few pictures I noticed a difference between what I framed in the optical viewfinder and the final photograph. The final image was always higher than the viewfinder image (in horizontal mode), as if I were pointing the camera slightly upwards after framing and before taking the picture. Sometimes there was also an image shift to the left and sometimes to the right; these left and right shifts were with different lenses.


I can send the camera back to be checked; but before I do that, I want to be sure this is a real problem. The optical viewfinder is dealing with visible light while the image sensor is now dealing with some visible light but also light with a much longer infrared wave length. Are these image shifts a result of the longer wave lengths being recorded? Is refraction a contributing factor because of the longer wave lengths and the different types of glasses in the lenses?


Has anyone else experienced the same optical viewfinder/sensor image differences with their own infrared converted cameras?

07-01-2014, 03:04 PM   #2
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Did you send a lens with the K-7 conversion? If you did, that lens should have been calibrated for IR and should work fine. Are you experiencing this same issue between the optical viewfinder and live view with a calibrated lens? Other lenses may not fare as well with the differences between visible and infrared light wavelengths and this could be a reason for what you are experiencing.
07-01-2014, 04:25 PM   #3
cpk
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Thanks for getting back to me. No, I did not have my camera calibrated to a single lens. My idea is to use live view for all my framing and focusing, so the camera was calibrated for live view use, not a specific lens. I am trying to confirm the truth of your last statement. If it is true, then I have no need for any further camera adjustments; I simply ignore the optical viewfinder.
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