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IR filter for DSLR(Canon)

mazza . , Jan 01, 2005; 11:18 a.m.

I was just wondering which IR filter is recomended for the DSLR? How do you use them exactly? Is it just to slap on the front of the lens and then you got yourself an IR photo after pressing the shutter release? Seems to work great anyway. Would like some tips on which filters are good and cheap. Thank you


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Leslie Cheung , Jan 01, 2005; 12:34 p.m.

Why not do it in photoshop?

Bob Atkins , Jan 01, 2005; 12:48 p.m.

With advice like that, who needs enemies.

A Hoya R72 is the answer. Be prepared for fairly long exposures (several seconds is typical).

Leslie Cheung , Jan 01, 2005; 01:55 p.m.

bob, I guess it came out wrong. It was a question actually. why not do it in photoshop? I haven't really done IR especially with a dslr.

Liam Strain , Jan 01, 2005; 03:19 p.m.

leslie - you can't just do it in photoshop because in order to get a usable amount of IR data, you would have way too much visible light, and would overwhelm the sensor.

You need the filter on the camera to block most of the visible spectrum and let the IR sensitivity of the camera sensor do it's thing.

Then you can balance and adjust in Photoshop...

David Manzi , Jan 01, 2005; 04:09 p.m.

Does the DSLR have a "hot filter" in front of the sensor? If so, doesn't it make the camera fairly useless for IR work? I've read of users modifying their camera by removing the hot filter, but then the camera is good for *only* IR. Also, other cameras, like the Sony 828, allow you to temporarily remove the hot filter (nightshot mode) so IR can reach the sensor. But doesn't it take more than a filter?

Bob Atkins , Jan 01, 2005; 05:56 p.m.

As explained above, you can't do it in PhotoShop because the camera has an IR bocking filter in front of the sensor.

However the IR blocking filter isn't perfect. It doesn't block 100% of the IR, just maybe 95%. So if you add a filter that blocks visible light (Hoya R72) but allows IR to pass, and you expose for long enough, that 5% that gets through the IR blocking filter will be enough to form an IR image.

If you remove the IR blocking filter from the sensor by performing some fairly delicate surgery on the camera, the camera becomes useless for regular work - unless you put an external IR blocking filter on the lens. Then it works OK, though the colors will be off and will need come custom correction curves in PhotoShop

Barry Passaris , Jan 01, 2005; 08:02 p.m.

I know there are 2 types of IR Hoya Filters the R72 and R90. Does anyone have any images using both to compare?

Bob Atkins , Jan 01, 2005; 08:59 p.m.

You won't get any light through the R90 and the built in IR blocking filter. Even with the R72 not much (but just enough) light gets through.

Paul Sokal - Dallas, TX , Jan 01, 2005; 10:08 p.m.

The Hoya R72 is the way to go. The first thing is to test your camera's IR sensitivity. Take you TV IR remote and fire it at your camera and take a pic. It you see lot's of light coming out, your camera is sensitive to IR. Then slap on the R72 and you're good to go. Since you can't focus, use a high F stop and bracket and experiment starting at least four stops added to your metered reading. Expect to wind up shooting in seconds, rather than fractions.

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