Pentax dSLR conversion to Infrared

[macona]

Since I recently bought a Canon 60D I have a spare dSLR lying around, my old Pentax K10D. It not particularly valuable so I decided to convert it over to IR. This is the third one I have done. Forst was an old Kodak DC210, then I did an electronic modification on my Sony DSC-v3 that allowed me to move the hot filter out of the way with a tiny button.

This one was a bit more complex. Lucky for me I had the service manual for the camera.

Took the camera's case off. Desoldered the main board and removed it. Then pulled the CCD block off. This block holds the sensor as well as the linear motors that do the shake reduction. I then removed the clip that holds the IR cut filter in place and pried off the IR cut filter. It was held in place with a adhesive foam gasket.


K10D Infrared Conversion by macona, on Flickr


K10D Infrared Conversion by macona, on Flickr


K10D Infrared Conversion by macona, on Flickr

The IR Cut filter was only 1mm thick. The IR filter I had planned on using was 2mm thick. I found a dichroic filter made for astronomical use and they are only 1 mm thick. I got it and cut it to size with a diamond ring saw. Unfortunately the corner broke. So I just cut the thicker one to size and used a diamond file to fine tune it.


K10D Infrared Conversion by macona, on Flickr

[macona]

At work we have a little portable clean box so I used that to reassemble the sensor block with it's new filter. When I got home I reassembled the camera. I used gauge to set the comparator stage up to set the sensor block to the height as speced in the manual. This ensures the sensor is the right distance from the lens and parallel to the focal plane of the lens. Sealed the screws in place with some nail polish and proceeded to re-solder the main board back in place. RoHS solder sucks!


IMG_0154 by macona, on Flickr


K10D Infrared Conversion by macona, on Flickr


K10D Infrared Conversion by macona, on Flickr

Got it all back together and found the battery. It turned on! I took a shot of something about 4 feet away and it was out of focus but something 6 feet away was in focus. So I had massive front focus due to the thicker IR filter in front of the sensor as well as the different refractive index of the glass at the longer wavelengths.

To solve this I put the camera into debug mode which has a mode for adjusting the focus offset. I had to increase it 700 microns to get the auto focus to work as it should. But everything seems to work now. The only funny thing is the camera is not commanding the aperture to the right spot. If I set it to max on the dial it still closes down. No big deal, really, since I can override with the aperture ring on the dial.

Here one pic I took yesterday. Looks like you can see some corona or something on the power lines.


IMGP6652 by macona, on Flickr


Pics of the conversion are here:

http://www.flickr.com/photos/6729211...7626377651582/

and the last 8 pictures in this set are done with the new conversion, the rest were done with my Sony:

http://www.flickr.com/photos/6729211...7624024513397/

[Evan]

Nice work getting all that done and still ending up with a working camera. I does still work, yes?

One day real soon now I am going to do the same to my Canon 300D since I have two DSLRs to rely on. The nice thing about the 300D is that there are meticulous step by step instructions available, right down to each and every screw and where it goes and how many threads it has. Also, I don't need to replace the filter with anything since I want the IR as well as the visible and focus is not as large an issue. Red (hydrogen) emission nebula don't contain much visible and any that is there is, um, red. One can always use an external filter if needed.

The effect on the power lines is very odd. Corona only emits in the UV, not IR. There are daytime Corona Cameras but they use a severe high pass filter that eliminates everything up to near UV.

BTW, where did you buy the vacuum tweezers?

[macona]

Well, looks like it works to me.

I know people have done the Pentax k100, which is the lower end version of the camera I have without the shake reduction. There are some people that use a base k10d and then use an ir filter in front of the lens and a very long exposure time, but the results are not what I want.

The Canons are a good candidate since they have live view so you can focus through that. That allows you to use a clear glass over the sensor and an infrared filter on the lens, or for that matter, specific spectral line filters. If I tried that with mine I would have to make a lot of shots just to find focus. You will be able to just look at the screen.

I have no idea whats going on with the power line. I might try going back during dark and seeing if I get anything then. Like you say, it should be UV coming out.

I got the tweezers with a kit of parts from the LASIK machine I took apart a couple years ago.

[macona]

I took a look at the power lines and there is some sort of white thing covering the lines near the tower, that's whats reflecting the IR.

[aostling]

I had a look at your full-size image, and was impressed with the sharpness at the pixel level. This speaks well for the Pentax lens and its performance at infrared wavelengths.

What IR filter are you using in front of the camera lens?

[macona]

I had a look at your full-size image, and was impressed with the sharpness at the pixel level. This speaks well for the Pentax lens and its performance at infrared wavelengths.

What IR filter are you using in front of the camera lens?

No filter on the lens, the IR filter is on the sensor itself. If you use a IR filter in front of the lens you cant use auto focus nor see through the view finder. That and combined with the focal length shift due to IR it would be real tough to focus.

[aostling]

No filter on the lens, the IR filter is on the sensor itself. If you use a IR filter in front of the lens you cant use auto focus nor see through the view finder. That and combined with the focal length shift due to IR it would be real tough to focus.

That's amazing. Reading your post more carefully I see you adjusted the focus offset to compensate for the IR focus shift. Its nice to have a camera which allows for this.

What is the 50% cut-off wavelength of the filter in front of the sensor? It looks somewhat like results from a 720nm lens filter, but much sharper.

[macona]

Its a 760nm filter.

[Gussman]

Great work! I am a Indianapolis electrician so am somewhat competent with these types of mods, and have been wanting to do some modifications to my camera. Maybe I will give it a shot after I get another camera, which I am planning on doing soon. Thanks for the very detailed explanation of your work, I have found it to be very inspiring.