Hello everyone,
As this is my first post, I'd like to start by saying thank you to the CHDK developers for their excellent work. I hope I'll be able to contribute.
Some 2 years ago I started playing with infrared photography using a mono CCD (which I normally employ for astroimaging) and an IR-pass filter. I liked the results, so last year I decided to try and remove IR-cut filter from my old Sony DSC-H10. It worked, but not very conveniently. There is of course no RAW support and not even a custom WB setting. As you can imagine, any post-processing of JPEGs quickly brings out denoising and compression artifacts, so in practice the images had to be downsized from 8 to 2 MP to look acceptably.
I had a plan to make another conversion, this time of a mirrorless camera, but then started reading about problems with wide-angle focusing requiring replacement of the sensor glass (Micro 4/3: 4 mm thick!) - doable, but expensive. I prefer to use my existing IR-pass filters.
Luckily I remembered the CHDK and started hunting for an adequate Canon compact; finally I chose the IXUS 230 HS. RAW support works great, though saving was slow on my old SD card (CHDK benchmark showed ~8 MB/s and RAWs are ~18 MB). After replacing it with a new 32 GB SDHC ("40 MB/s" sticker, ~20 MB/s in benchmark) the saving time is much better.
After disassembling the camera it turned out the sensor assembly screws are secured with glue drops (see
sensor1.jpg). I used a small scissors blade heated repeatedly over flame to carefully scrape some of the glue away. Finally I turned the screws which cracked the remains.
The IR-cut filter wasn't attached in any way, it just rested over the lens. I verified its function by taking a photo with a mono CCD without filters and with an IR-pass (>742 nm) filter held in front (
test12.jpg).
