Infrared photography questions - focus shift and ND filters

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Auf Reisen Contributing Member • Posts: 830
Infrared photography questions - focus shift and ND filters

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?

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?

Thanks!

ken_in_nh Senior Member • Posts: 2,003
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!

OP Auf Reisen Contributing Member • Posts: 830
Re: Infrared photography questions - focus shift and ND filters

ken_in_nh wrote:

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...

I feared as much. Thank you!

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?

I'm an idiot, it was set to 400. Thanks!

robgendreau Veteran Member • Posts: 9,336
Re: Infrared photography questions - focus shift and ND filters

ken_in_nh wrote:

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!

It is odd. Never had that problem with my converted cameras, and I've used lots of M43s, although all Olys. Might have been close to the limit before the conversion.

Kolari has a very long list of tested lenses; hotspots are issues with some.

Kolari also makes NDs specifically for IR use. Understandably most ND makers don't care about the near IR wavelengths, so you might find some cheaper NDs splotchy.

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