Infrared photography questions - focus shift and ND filters

Started 4 months ago | Discussions thread
ken_in_nh Senior Member • Posts: 1,995
Re: Infrared photography questions - focus shift and ND filters

Auf Reisen wrote:

So i have dabbled with IR photography for a bit, using an old converted Panasonic MFT camera (to 690nm I believe).

It's been great fun but I have run into two problems:

1) I cannot focus to infinity with my Samyang manual focus lenses. I know that there is a focus shift with IR light, but I simpyl cannot focus any further with those lenses. And stopping down too much quickly induces diffraction. Any way around this?

Only by getting new lenses.  But watch out for IR leaks.  Not all lenses work well with IR.  Lifepixel.com has more information.   Keep in mind you can probably buy a used lens and save...

2) I very often have a problem with too much light reaching the shutter speed limit on my camera. This often forces me to stop down way too much. Can I use normal ND filters to cut down on the light or do they have to be special IR filters?

In theory, normal ND filters would work, but you'd need to test them, as they weren't designed for IR work.  Look at uniformity too.

This is an odd problem - not one that I've seen in my converted camera, which seems to have roughly the same speed as an unconverted camera.  Do you have the camera's ISO setting at the lowest setting?

Thanks!

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