IR without LPF

Englischdude · Jul 15, 2014

the problem with IR photography with "traditional" DSLR's is that the exposures are quite long due to the low pass filter blocking alot of the required IR light. The way around this is to get a camera converted where the LPF is removed and replaced with an IR filter which only lets in IR light.

Question: what is the situation with a camera WITHOUT a LPF like the D7100? My D7100 has just arrived but unfortunately I dont have a screw on type IR filter to test with.
@BackdoorHippie : maybe you could do a test with your new D7100?

Thanks for your feedback

BackdoorArts · Jul 15, 2014

Sorry, Martin, but all my IR is done with the converted D7000 and I don't have an external filter. Regardless, it's not the OLPF that blocks the Infrared, it's a separate filter within the stack. I couldn't find a diagram for the D7100, but here's the configuration of the D800 and D800e stacks...

As you can see, the second layer of both is where the IR blocking occurs, and it's this piece of glass that's replaced in an IR conversion, either with plain glass for full spectrum, or a visible light filter of predetermined wavelength.

Englischdude · Jul 15, 2014

BackdoorHippie said:
Sorry, Martin, but all my IR is done with the converted D7000 and I don't have an external filter. Regardless, it's not the OLPF that blocks the Infrared, it's a separate filter within the stack. I couldn't find a diagram for the D7100, but here's the configuration of the D800 and D800e stacks...

As you can see, the second layer of both is where the IR blocking occurs, and it's this piece of glass that's replaced in an IR conversion, either with plain glass for full spectrum, or a visible light filter of predetermined wavelength.

understood, but it is the removal of this stack (which is to all intends and purposes 1 piece) which enables the IR light to reach the sensor. Or are you saying that even though the D7100 has no LPF, the IR filter is still there?

John P · Jul 15, 2014

I shoot with a hoya R72 screw on filter with a D7100.
Shutter speeds average 5 to 20 seconds.

Englischdude · Jul 15, 2014

John P said:
I shoot with a hoya R72 screw on filter with a D7100.
Shutter speeds average 5 to 20 seconds.

ok, so no change in that respect. thanks for your feedback.

Thumper_6119 · Jul 15, 2014

John P said:
I shoot with a hoya R72 screw on filter with a D7100.
Shutter speeds average 5 to 20 seconds.

This is how I do it as well. You pretty much have to line up your shot prior to putting on the filter as it is (near) impossible to see through the filter. I am just getting started in IR, so I don't mind using the Hoya filters. If IR is something that I decide that I want pursue more heavily, I might consider sending one of my spare bodies off to LifePixel. But that will be down the road quite a bit. For no more than I shoot IR right now, the filters are fine.

John P · Jul 15, 2014

Older DSLR cameras are more IR sensitive.
For example with my old D70, and my wife's D40 I was able to cut these shutter times in half. The hot mirrors have gotten better over time unfortunitly.
A converted camera is definitly in my future.

BackdoorArts · Jul 15, 2014

Englischdude said:
understood, but it is the removal of this stack (which is to all intends and purposes 1 piece) which enables the IR light to reach the sensor. Or are you saying that even though the D7100 has no LPF, the IR filter is still there?

There is always a filter stack on all DSLR's and it contains an IR filtration element. The D7100's (and other Nikons w/o the OLPF) stack differs from the D800e stack in the way that it deals with the low pass filter removal, but the results are the same, and there's still a stack of filters over the sensor which includes the IR filter. When you send your camera off to Lifepixel or KolariVision they disassemble the stack and insert a visible light filter in place of the IR filter (or clear glass for full spectrum), then reassemble. When I got my D7000 back it still had the OLPF filter on it - it's just the second piece of the stack that was replaced.

Both companies are now also offering the option of removing the OLPF as well (at $400-550 depending on the camera), which would involve replacing the top and bottom pieces of the stack, likely with an arrangement as above. Lots of questions on how badly those conversions suffer from moire, which is one of the things keeping me from sending my D600 off.