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S2 IR filter removal

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S2 IR filter removal
« on: 21 / January / 2010, 12:47:00 »
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After months of humming and hawing, I decided to plunge into removing the IR filter from my old S2.  I finally figured it was a good camera, but I wasn't actually using it so I might as well try (I also did some disassembly practice on a non-working G7 beforehand).

Through patience and care I got the camera disassembled to the filter.  (Why so many screws of different sizes?  Be sure to document where they all go and in what order you remove the pices/ribbons/connectors, you will forget).  I found the filter glued in rather tight and was unable to remove it without cracking it, but I had already resigned myself this was a one-way trip anyways.
And finally reassembled the camera (with one leftover mystery screw).

With the filter removed, I could immediately see the added IR effect on the pictures, but unfortuneately the focus problem as previously discussed was present, I couldn't focus, manual or auto.  Over the next day, I did some searching to find a suitable replacement for the filter (it wasn't a spacing problem, but an optic/refraction problem).  I finally found some clear plastic from a cheap Ikea picture frame, it was nice enough to have protective plastic on both sides so it was fairly smooth with no serious scratching that would effect image quality however it's not anti-reflective, so there may be lens flare issues. I know it would have a slightly different IOR index, but I figured I might as well try it before having to source out some glass.

Got the camera reassembled (and found where the mystery screw came from) and found that the focus issue appeared more or less corrected.

At this stage, the photos would get visible spectrum and IR lighting, so I wanted to try filtering.  As can be found on the net, developed colour film negatives can be used as a cheap effective IR filter, blocking a lot of visible light, so I found some negatives. Use the blank trailer at the beginning of the film that has been over exposed and looks dark. Layering 2 of these together, I could only faintly see bright light sources through it.  Holding the double layer up in front of the modded camera lens, the camera coud easily throug it, confirming that it was blocking most of the visible light and that the cameras IR sensitivity had been increased.

This is as far as I have got at the moment.  I may post some pics after I get experimenting a bit.  I think I will end up trying to build a makeshift external IR filter from the film negative rather than adding it internally, as it will be nice to have the option of using visible light or not as well.

I may also try to put together a disassembly guide in the future if anyone is interested.

Note, this is not a minor undertaking!  Care must be taken so as to not permanently damage the camera such as damaging cables and ribbons.

Re: S2 IR filter removal
« Reply #1 on: 21 / January / 2010, 13:00:47 »
Do you have any bits of the filter available to measure their thickness with a digital vernier ?


Re: S2 IR filter removal
« Reply #2 on: 21 / January / 2010, 14:19:11 »
I do still have the filter (it is only cracked and chipped).  I'll have to see what I can do about measuring it.  I only have a cheapo digital micrometer, but I'll see wht it can tell me.

It is also notable related to this that the IR spectrum will have a different refraction property anyways compared to visible light, so it may be difficult to calculate an exact 1:1 replacement for IR.

I imagine that you don't really need a 1:1 replacement optic-wise, as long as it's close enough to bring it back in the focus range that the camera can handle.  It seems to be working in my case.  I'm not sure what the IOR is of the plastic I've used relative to the glass it's replacing.  I do think you may also be able to fix the focus problem by setting the CCD further, however you would need to calculate how much.  This may not be the best solution as well as it may allow a gap for dust to get in between.



Re: S2 IR filter removal
« Reply #3 on: 22 / January / 2010, 23:23:19 »
You might want to consider microscope-slides as a good source for very thin and nearly optical-flat glass. Generally 1.0-1.2mm in thickness. But well-slides (have a small depression for thick specimens) are sometimes thicker. If that's not thin enough, then you might be able to assemble the right thickness from microscope slide cover-slips/cover-glasses, which can be bought in varying thicknesses, 0.13mm, 0.16mm, 0.19mm & 0.2mm. You could conceivably stack the right amount cemented together with optical cement or even Canada-balsam specimen mounting cement. If using Canada-balsam be sure to let it dry for a few weeks before trying to trim the stack and using it. If a microscope slide is too thin, then again you could stack some cover-slips on that to make up the difference. I wouldn't stack them without cementing, due to the air/glass interfaces between each layer robbing your image of a lot of light and contrast. Look into some of the UV-curing optical mounting cements as a faster method than using Canad-balsam if wanting to use these materials. When exposed to strong UV light they harden into an optically clear solid. Edmunds Optical (somewhat pricey) and even some inexpensive surplus suppliers on the net are good sources. Hunt around.

« Last Edit: 22 / January / 2010, 23:25:48 by NewbieToobie »


Re: S2 IR filter removal
« Reply #4 on: 22 / January / 2010, 23:57:08 »
You might want to consider microscope-slides as a good source for very thin and nearly optical-flat glass. Generally 1.0-1.2mm in thickness. But well-slides (have a small depression for thick specimens) are sometimes thicker. If that's not thin enough, then you might be able to assemble the right thickness from microscope slide cover-slips/cover-glasses, which can be bought in varying thicknesses, 0.13mm, 0.16mm, 0.19mm & 0.2mm. You could conceivably stack the right amount cemented together with optical cement or even Canada-balsam specimen mounting cement. If using Canada-balsam be sure to let it dry for a few weeks before trying to trim the stack and using it. If a microscope slide is too thin, then again you could stack some cover-slips on that to make up the difference. I wouldn't stack them without cementing, due to the air/glass interfaces between each layer robbing your image of a lot of light and contrast. Look into some of the UV-curing optical mounting cements as a faster method than using Canad-balsam if wanting to use these materials. When exposed to strong UV light they harden into an optically clear solid. Edmunds Optical (somewhat pricey) and even some inexpensive surplus suppliers on the net are good sources. Hunt around.
Thanks.  I may look at some glass some time (bit more tricky to cut).  The plastic is working for now.  As I said above, I don't thin it is important to get an exact replacement, as long as it is close enought to get back within the focal range (plus the added issue of IR having a different focal distance than visible light to begin with).
Some good optical glass should certainly give clearer and sharper images than the plastic as the plastic does have micro scratches in it that I can see in the light, and likely more that i don't see.
I did look at the Edmund's site.  What would be really nice would be some glass ~1-1.2mm thick that is anti-reflective.  However, this may not be effective if the antireflectivity doesn't work in the IR range.  I do seem to get more lens flare effect now that may be from the existing antireflectivity not affecting IR, as it seems more than just the plastic insert should cause.

Re: S2 IR filter removal
« Reply #5 on: 23 / January / 2010, 01:06:13 »
I don't think that an AR coating will be as much of a concern deep within the optical-train as it would be on the outer lens elements, as those are subjected to light-rays coming from many external directions. All the spurious light-rays have already been diminished deep within the lens already. Worst-case scenario would be in very bright lights where light reflecting off the sensor would hit the back of the glass. However, you could always get some of those thin-film screen protectors for MP3 players and palm devices, some are sold with an AR coating on them for greater visibility of their screens in sunlight. Adding a layer of this to the sensor-facing surface (where it would do the most good) would add to the thickness but maybe not enough to matter.

Cutting thin slide-glass is actually pretty simple. Score with any cheap glass cutter and snap it in two on the line just using your fingers. Or place a straight uninsulated semi-thick wire on your work-surface, place the glass score-line up aligned with the wire, then press down gently on the glass on both sides of the wire. The wire acting as your fulcrum where the glass should break. Microscope slide-glass, being as thin as it is, it is also easy to grind to final shape using any emery-cloths or hobby-drills with sanding or grinding bits on them. If using a hobby-grinder just don't press so hard that you build up enough heat to crack the glass. You don't need optically-clear polished edges, just scratch-free clear front and back surfaces. Blacken the rough edges that you grind to shape with a black sharpie marker to prevent light rays trapped in the glass from reflecting back from the rough edges, which could rob your image of contrast.

Re: S2 IR filter removal
« Reply #6 on: 13 / February / 2010, 00:48:43 »
OK, I finally found a place that had microscope slides (turned out to be much more difficult to find than I woulda thought) and I replaced tmy plastic spacer with a glass one.  The Pics look a little clearer in my opinion, but I really can't be sure.  The microscope slide glass is ~1mm thick replacing the previous IR cut filter which was ~0.83mm thick.  Autofocus works both unfiltered, plus woth my film negative filter.  Over the next week or so, I will try to do some outdoor pics for testing.

On a side, note, when I did find the microscope filters, it came in a 72 pack, so I have quite a few extra (really didn't have the option of only buying a couple.  If anyone is interested, I am willing to forward some of my extra slides (will likely be by regular mail, so no guarantee that they won't get broke, but free is free).  If interested, please send me a private message and I will try to arrange to send a few, otherwise they'll sit here gathering dust.

Re: S2 IR filter removal
« Reply #7 on: 12 / March / 2010, 00:54:31 »
This place has some very detailed instructions for DIY IR conversion. They also sell replacement filters designed for specific cameras.
http://www.lifepixel.com/IR.htm


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Offline colinbm

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Re: S2 IR filter removal
« Reply #8 on: 23 / May / 2010, 22:24:55 »
Hi barberofcivil
I have a dead S2IS. It looks like the shutter is stuck, but some say a dead sensor is possible too ?
I would like to get inside & have a look, but have been baulking at doing this.
Are you able to share your experience at disasembling the S2IS Please.

I have just found CHDK & have made a remote release for my S5IS.

The S2IS exercise will give me some experiance to tackle IR with the S5IS later.

Cheers
Col

 

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