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Thread: Infrared photgraphy with DM22

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    Infrared photgraphy with DM22

    What filter should I get? I am not sure what IR sensitivity the sensor got. With film I could read the spec, and find out what filter to get, but with the digital back I have no idea.

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    Re: Infrared photgraphy with DM22

    A normal DM22 has a very strong IR block filter. Trying to do True IR work with such a back will be quite hard especially given its poor long exposure capability.

    If you have an IR-modified DM22 (like these IR backs) then you can throw on any filter you want. Sensitivity will drop off quickly but you can get out to around 900-950nm without getting crazy low in effective ISO.
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    Re: Infrared photgraphy with DM22

    I would remove the filter in front of the sensor when I would try to take infrared photos.

    I'll try som cheap filters first the , and see what result I get.

    Tnx :-)

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    Re: Infrared photgraphy with DM22

    I swapped the regular IR block filter on my Aptus 65 to a 650nm pass filter and it works fine - a filter on the lens obviously would have a similar performance. Just remember that whatever filter you use that you'll need to account for the shift in focus. Easy to do but obviously the viewfinder is inaccurate. The other thing to watch for is lens hotspots too - something you'll just have to try as each lens is different.
    Last edited by GrahamWelland; 22nd March 2014 at 15:19.
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    Re: Infrared photgraphy with DM22

    My Mamiya ZD Back featured a user removable IR absorption filter which I removed and replaced with Schott WG280 clear glass of the same thickness. I made two filters and sent one to Mamiya for evaluation and they subsquently offered a factory clear glass filter option. The clear glass allowed required the use of filters on the camera lens but permitted full spectrum photography. Since your DM22 Back doesn't have an easily removed IR filter, I suggest you contact Graham regarding his source for his conversion.
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    Re: Infrared photgraphy with DM22

    Quote Originally Posted by fotophil View Post
    My Mamiya ZD Back featured a user removable IR absorption filter which I removed and replaced with Schott WG280 clear glass of the same thickness. I made two filters and sent one to Mamiya for evaluation and they subsquently offered a factory clear glass filter option. The clear glass allowed required the use of filters on the camera lens but permitted full spectrum photography. Since your DM22 Back doesn't have an easily removed IR filter, I suggest you contact Graham regarding his source for his conversion.

    I don`t really understand why you need a glass in front of it?.. Other then protecting the sensor offcourse. But different focus because of it, I don`t get. The sensor is placed the same place with or without glass.

    on the DM22 the glass is removed by 4 screews and flip the lid off with the glass. so the plan was to do this when I wanted to do some IR shots and have a filter on the lens.

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    Re: Infrared photgraphy with DM22

    Quote Originally Posted by IBICO View Post
    I don`t really understand why you need a glass in front of it?.. Other then protecting the sensor offcourse. But different focus because of it, I don`t get. The sensor is placed the same place with or without glass.
    A flat layer of glass having a different index of refraction as air will move the plane of focus when introduced between a lens and a sensor.



    (source)

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    Re: Infrared photgraphy with DM22

    Ah. Forgot about that. So if I put a 720nm filter in front of the sensor with same thicknes, that would fix it.

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    Re: Infrared photgraphy with DM22

    The safest approach to avoid sensor surface damage would be to cut the 720 nm filter to the external dimensions of the original IR absorption filter and use the clip and 4 screws to hold it in place. With the removable filter system on the ZD Back I have trouble keeping all four glass surfaces dust free.

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    Senior Member ondebanks's Avatar
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    Re: Infrared photgraphy with DM22

    Quote Originally Posted by IBICO View Post
    Ah. Forgot about that. So if I put a 720nm filter in front of the sensor with same thicknes, that would fix it.
    That should do it. It does assume that both filter glass types have the same refractive index; they will probably be close enough that it hardly matters.

    Ray

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    Senior Member ondebanks's Avatar
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    Re: Infrared photgraphy with DM22

    Quote Originally Posted by fotophil View Post
    With the removable filter system on the ZD Back I have trouble keeping all four glass surfaces dust free.
    Three surfaces? (front & back of filter, front of sensor cover-glass).

    I have the same issue with my DCS645M back. But it's a minor hassle in comparison to the benefits of easily changing filters at will on the back.

    Only Kodak and Mamiya ever provided this wonderful capability. The European back makers, PhaseOne/Leaf/Imacon-Hasselblad/Sinar, seem to be anal about the dust issue; to the point of denying users a really valuable switchable visible/full-spectrum/IR feature without VF blackout. It's a mindset that reminds me of someone who will never use a valuable item for its intended purpose, for fear of temporarily dirtying it.

    Ray

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