How To: IR modify an old camera.

[Garbz]

Ok so I have it all done and put back together with the film piece between the sensor and glass, but the photos have a purple hue to them. Is this something weird or should that be the case?

Purple is due to the fact that cameras white balance algorithms can only be pushed so far. Some cameras when you use autowhite balance they come out great, but for the most part the trick is to either convert it to black and white, or set the white balance to manual so you can do something with the weird colours that come out.

An easy way to check is to take a photo of the tree compared to the sky. The sky should be darker than it would be in a black and white shot.

To illustrate this here's a shot from the IR modified camera. I am holding a 720nm IR filter up. The picture was shot with autowhitebalance and came out very purpleish. In post processing I've slid the tint slider to 90% green.

If you stuffed up the IR conversion the filter being held up would look completely opaque. Same with a film leader. The other way to check to see how well it worked is to take a photo of someone wearing sunglasses. Most sunglass lenses (not the psycho reflective surferdude style though) are transparent to IR.

My old Nikon point and shoot is about to be cracked open.
Thanks guys.

OMG what have I started.

I hear a disturbance in the force, as if thousands of point and shoots cried out and then ... nothing.

 

[Tim N]

OMG what have I started.

I hear a disturbance in the force, as if thousands of point and shoots cried out and then ... nothing.

We've all upgraded cameras over time and I have a hard time parting with them, but not a hard time PARTING them. I love to tinker and this project looks like the best I've seen in a long time. Thanks to all for answering my silly questions. Hope the end result is near. And my new old D70 showed up at the door yesterday. Early Christmas for me!

#1 First outside attempt / Auto Level PS

#2 Snow and Green Plant / Auto Level PS

Will cloudy skies still be white? I'm getting white. I'm guessing a blue blue sky will turn to black? Have to wait on that one.

 

[Garbz]

Yes clouds are still white. (See my beach picture above).

IR usability is a bit like polarisers. They work best on clear sunny days for maximum effect, or taking photos of things that you know don't reflect IR light (such as water).

 

[kimmik]

I've done a similar mod of my canon A480 a while ago. I've found a funny effect that i'm wondering if you guys experience as well. I have three external IR filters - 720, 850 and 950nm.

If i take a photo with the 720nm filter, the picture turns out a bit out-of-focus like (when focused as well as possible).

when taking a photo with 950nm filter, the picture is pixel sharp.

i believe this is due to the achromatic lens, which will focus at 450-650nm simultaneously for visible light photos, but not simultaneously in 720-1200nm. thus if using a 720nm filter, the lens has to try to focus a much wider spectrum than if using a 950nm filter.

any thoughts?

what sucks for using the 950nm filter, is that the camera is much less sensitive than with the 720nm. however the positive is the more accentuated IR look - trees are whiter, skin is whiter.

 

[Garbz]

Focus is dead on for me with the 720nm. Lots of effort is put into correcting aberrations in the visible spectrum, but none is put into IR wavelengths and beyond. How a lens element behaves in the IR spectrum is anyone's guess as it's outside of normal design bounds.

However this shouldn't make too much of a difference. The Canon A480 has a contrast detect autofocus system like all point and shoots. Unless it physically can't latch a focus point it should be reasonable at identifying the correct point as the point with the most contrast is the point where the picture is sharpest, and the method involves simply moving the lens about till that point is reached.

If anything contrast based AF is one of the most reliable ways to focus in IR.

 

[kimmik]

Interesting that focus is perfect for you. Like you say, each lens will be different as they're being used outside of design criteria.

However one point I disagree with, is that I believe some lenses "my a480 included" cannot focus at 720 and 1000nm simultaneously, as some lenses are not corrected for dispersion outside of the visible spectrum. Thus if a leaf reflects the entire IR spectrum, then my image will be like it has a soft focus filter on. But if the leaf is lit with monochromatic IR eg at 800nm, then the image is sharp.

Anyway, my original reason for posting was to see if other cameras had the same problem with dispersion induced soft focus. It appears the answer is not always lol.

Thanks

 

[Garbz]

Yes soft focus is quite different from being unable to focus which is what I thought you were referring to

The contrast detection should still provide the sharpest image, maybe stacking a highpass filter on a lowpass filter will help you. Unfortunately you'll only get those from optical labs and not camera stores. Then they naturally assume you have university grant money or do R&D for a multination and as such will proceed to rape your wallet