[shuttertalk]

Hey here's a brief step by step guide on converting a PC webcam into an infrared camera! Pretty cool... looks like the major steps are simply removing the IR filter, and adding -- get this -- a piece of film (negative)!

Maybe you could do the same with a digital camera?

http://homepage.ntlworld.com/geoff.johnson2/IR/

[Kombisaurus]

Hey ST,

Good news, the same principle does apply to digital still cameras.
Simply take out the IR-cut filter and replace it with some good quality glass OF THE SAME THICKNESS. That last point is very important or else it will throw out the focus. Apparently microscope slides are a good source of glass in a lot of cases (and you can use shims to adjust their thickness),

Here's a link to some really useful info on this kind of mod:
http://www.jr-worldwi.de/photo/modding.html

And here is a guy with some lovely IR galleries (scroll down, the IR galleries start 1/2 way down the page):
http://www.kleptography.com/

Cheers
Adrian

[adam]

I used to play with a piece of film over my digi-cam before I got my R72.


and some more in http://dpnow.com/cgi-bin/forum/forum.pl/read/11622

It's in that forum that I found shuttertalk

[adam]

I'd really like to take IR photographs with my DSLR - was quite disappointed when I found that my 300D couldn't take IR pictures (R72 was the first filter I bought )

The mods shown on these pages:
http://ghonis2.ho8.com/rebelmod.html
http://www.pbase.com/terrylovejoy/300d_mods

Seem nice, but I'm so scared to try it on my dear 300D
Maybe when it's time for it to retire, then I'll attempt to convert it to IR camera, so if it dies in the process, I won't mind as much (although the shutter is most likely to die first!)


I'm just looking at the page now, that you posted the link to Kombisaurus, and realised that the two links I posted above are the two links for 300D modification also hehe


thanks

[shuttertalk]

But you still need an IR filter right?

I wonder whether using the film instead of a filter will work..

[adam]

I looked at the link for modifying the D70, they put an IR filter over the sensor! so it's always an IR camera and then it means you can use the viewfinder!! (good idea)

If you want to shoot IR only, then using IR filters to block out the visible light may help. - from what I've read, not that I've done any calculations

[Kombisaurus]

ok.. first things first before we get confused.

There are 2 types of IR filters... the one that most digital cameras are built with in front of the sensor is an IR "cut" filter. It lets visible light through and blocks IR light out. They put this filter in cameras because digital camera sensors are sensitive to IR light, but our eyes are not. If they don't filter it out then it mucks up the colours and luminance for all "normal" photography.

The other type of IR filter is an IR "pass" filter. It blocks out visible light and *only* allows IR light through. If you want to do IR photography, you need to buy one of these filters and stick it on your camera, or else the visible light spectrum will still dominate the image.

So in order to take good fast IR photos, we ideally want to remove the IR cut filter (and thus allow a lot more IR light to reach the sensor), and then add an IR pass filter (so removing as much visible light from the image as possible).

Ok... but things being what they are, most IR cut filters used in cameras don't block ALL the IR out of the image, and similarly the most common IR pass filter (R72) allows some of the very top-end of the visible spectrum of light through, so if you hold it up to a very bright sky you can see a very dark red tint through it.
Because of this, you can usually stick an R72 filter onto a digital camera and it will take IR photos, but the two filters on top of each other give the effect of having an extremely dark ND filter - so expect very long exposures and don't even think about not using a tripod, even in very bright sunlight.
Personally I quite like this look, it blurs clouds and foliage and can give really interesting effects on water... but it is also noisy and quite restrictive if you want to take photos of anything other than static landscapes.

So that's where these modded cameras come into it. Removing the IR cut filter will effectively remove the ND filter effect from your IR photos and allow you to take IR photos in normal light with normal exposures. But you still need an IR pass filter to block out the visible light, or else you'll end up getting both IR and visible light and the photos will just look blech..

Now ST's question about whether you can use 35mm negative film as an IR filter material was an interesting one. Certainly it can block out visible light fairly effectively, but the question is.. how well does it pass IR light?

Well... you got me so curious I did a little experiment.
Below are a series of photos taken with various combinations of no filter, a black piece of 35mm negative as a filter, and an R72 IR pass filter. Comments are below each photo. I used auto-exposure for each pic, which varied from about 1/1000th sec when using no filter to 4secs with the IR filter in place. The only editing I did was to resample them down to 640x480 for uploading.


This is just a normal photo with no filter. The reason for all the crud in the image is because I couldn't be bothered walking outside or opening the window, and the window was filthy. Sorry, deal with it.


This is the same photo but with the IR flter in place. You can clearly see the IR effect in the way it lightens the foliage of the trees and gives the sky more contrast.


This is the same photo with no IR filter, but holding the 35mm negative in front of the lens and exposing through it. You can see it doesn't seem to lighten the trees like the R72 did, but it does add considerable contrast to the sky.


Ok, so this shot shows the 35mm neg and a normal pic in the same shot, so you can clearly see that the 35mm neg blocks out an awful lot of light when given the same exposure as the non-filtered image, meaning it does seem to act as a pretty good filter to cut out visible light.


And this is the crucial image. is the same shot as above but with the IR filter in place (ie the 35mm neg takes up the left half of the frame). It is clear that although the neg does cut some IR light, it is a lot more "transparent" in the IR spectrum than in the visible light spectrum.

Conclusions?
Well, it seems that 35mm negative material does behave as an IR pass filter, but pic #3 shows that it doesn't seem to give quite the same effect as a "real" IR pass filter, with foliage anyway.
I'd still recommend buying an IR pass filter if you want to explore this kind of stuff. By all means try to borrow an IR filter from somewhere first if you aren't sure if it will work with your camera, but for $50-odd it is probably one of the cheaper specialities you can explore in photography.

Here's where I bought my R72 from (and they're in Melbourne, ST):
http://www.centre.net.au/Infrared_R72_R90_0007VB.html

btw, do not buy an RM90 unless you have removed the IR cut filter from your camera, as it blocks out more visible light than the R72, and with the IR cut filter in place you might just end up with blackness. Plus the RM90's seem mega-expensive too!

Adam, can you not take IR photos *at all* with your 300D and an R72?? Have you tried 30sec or longer (bulb) exposures? I'm sure I remember seeing some on the web somewhere from a 300D? hmm.. perhaps I'm mistaken...
My Oly maxes out with 16sec exposures, and I regularly have to crank the ISO up from 50 to 400 to give me just enough light to get a reasonable exposure, even in regular daylight. I'd be interested to see what you can do with your 300D, particularly as I've just ordered a 350D for myself.
Obviously exposures this long have limitations, but they also have a dream-like beauty about them that I really like.

Check this:
http://www.maxmax.com/aXNiteCanonRebel.htm

It seems people are selling pre-modded 300D's now! I'm particularly interested in perhaps buying one of their "XNite CC1" filters, as this would allow a modified camera to take normal shots when you need it.
I'm not sure if you're aware, but Canon has also released a special version of the 20D in Japan, called (amazingly) the 20Da, which has the IR cut filter removed and another couple of tweaks, aimed at astronomy photographers.

oops.. this post has turned into an essay. Sorry for rambling.

Cheers
Adrian

[shuttertalk]

Heheh thanks for the info, Kombi. Very helpful indeed - especially the experiments!

You're getting me back for the polarizer stuff aren't you? I knew it...

[Kombisaurus]

hahaha.. nonono.. believe it or not, that never occurred to me!

But, if I'd had thought of it.... then... yeah!

I just did the experiment coz I was curious, and I tend to regurgitate what I *think* are facts to other people in the hope they will invariably correct me if I'm wrong

Seriously, if I hadn't have gotten things mixed up in that polarizer thread then I would never have learnt the differences between linear and circular, and never considered that cameras always AF at the widest aperture, no matter what it is set to for the photograph.
I've learned a lot from the short time I've been on this forum, and am grateful for how I've been accepted. I know I dribble on a lot, and I'm glad it doesn't seem to annoy people too much.

ok.. enough typing for me.
Cheers
Adrian

[adam]

wow! Thanks for that explanation Adrian
Was a good read

When`I mentioned about putting the IR filter over the sensor, I was referring to the last image on this page: http://www.lifepixel.com/IR.htm
Where it seems that they have removed the hot mirror filter and replaced it with an IR pass filter, instead of replacing the hot mirror filter with some glass and then using an IR filter over the lens. I saw the advantage in this as allowing the camera operator to use the viewfinder; instead of shooting blindly, or composing the shot and then screwing on the filter. The downside to having the IR pass filter replace the hot mirror filter is that the camera is permanently an IR camera, and it's not as simple as just screwing off the filter to take normal pictures.

Compared to my older digital cameras which did not seem to have any IR blocking filter, I could even do IR videos, and the shutterspeed required was not that long, whereas with the 300D, it required much much longer shutter speeds to get a similar effect, and because of this, I believed that it was just the light coming through the filter being coloured by the dyes used in the filter, giving the pinkish effect (since it doesn't completely block all visible light (only up to 720nm?)).

I saw on a website which had a list of lenses which they thought were good and bad for infra-red pictures; and the kit lens: EF-s 18-55mm was in the bad category, while the 50mm f/1.8 II was in the good category, but my R72 filter is a 58mm filter and when I went looking for a stepping ring, the shop near by didn't have any - and I haven't had time to go to other shops (this was many weeks ago already).

Whenever I'm walking at uni, and I see trees and nice clouds and things like that, I always wish my camera was able to capture that in IR

[adam]

on the maxmax page "Our modified Canon 300D cameras can take infrared pictures at very high speeds in comparison with a stock camera. For example, the camera can take an IR picture with a F1.2 lens using a 1000nm cutoff filter in daylight at 1/4000 of a second. The modified camera is very fast to the point that it can become a problem if you are using too fast of a lens."

I want! I want! apart from having to use a F1.2 lens to get that (the 85mm f/1.2 = $$$$$$);

I want the fastness! haha, like that which I experienced on my other digicams

but it seems that once you remove the IR cut filter, you'll need an IR cut filter on all your lenses when you want to take 'normal' pictures.
I may dedicate my 300D to taking infrared images if I can get another body. (that means I must operate and remove the IR cut filter!)

[adam]

I shall go through my backup discs and find that video demonstration I did with IR leds and a piece of film with classical music in the background....


haha! i was bored

[Kombisaurus]

Hey Adam,

Thanks for that info, I see what you mean now about the D70.
I'd still imagine that replacing the IR cut filter at the sensor with clear glass would be more flexible, as if you want to use the camera as a "regular" camera again, then you can buy an IR-cut filter to screw on the front of the lens. Also, I think the focus point changes between visible and IR light with most lenses, so you might have problems with AF that way, and might have to compensate when focusing manually (ie focus a bit in front or behind your subject). But I totally see your point about the benefit of being able to see through the lens, and the focus compensation is an issue that needs to be dealt with people who use a screw-on R72 filter too when they focus manually.

You are right that the R72 does let some visible light through, and I'm sure that has a lot to do with why all my IR pics are tinted pink... but I still get a good IR effect, even though it isn't as good as many cameras.

It's very interesting what you say about the various lenses being better or worse for IR, as that's something I haven't been able to play with (seeing as my Oly has a fixed lens).

Along with my new 350D (which comes with an 18-55mm that is optically identical to your 300D kit lens), I ordered the 50mm f/1.8 (and the 75-300 USM IS) and step-up and step-down rings to allow me to use my set of 55mm filters on all three lenses. And you can bet I'll be testing them all for IR-capability when they arrive (a few weeks away )

Cheers
Adrian

[Kombisaurus]

but it seems that once you remove the IR cut filter, you'll need an IR cut filter on all your lenses when you want to take 'normal' pictures.
I may dedicate my 300D to taking infrared images if I can get another body. (that means I must operate and remove the IR cut filter!)

Yup.
If I can get my hands on a 55mm IR-cut filter, then I'll definately be performing this surgery on my Olympus when the new Canon arrives.
If I can't get that filter, I may still do it and use the camera for IR-only.

Keep us posted if you give it a go!

Cheers
Adrian

[adam]

It'll be a while before I get a 2nd body; or maybe I'll try to get a body which doesn't require me to modify; I'll feel safer that way, but then it'll mean that it's already sensitive to IR and the IR will interfere with pictures unless I use another filter to remove it (like the 20Da?)

I'll be sure to keep you all posted on whatever happens
Although I want my fast-near-IR-capable-camera... like... NOW! haha

The list of lenses I got from http://heim.ifi.uio.no/~gisle/photo/ir.html

Can't wait for your 350D to arrive

[slejhamer]

Adrian's experiment reminds me of an old trick: take black slide film (shoot a few frames with the lens cap on and then develop it) and tape it over your camera's internal flash. Instant IR slave trigger! Put some cheap IR slaves on your external strobes and you've got a wireless lighting rig. The IR film on the camera flash will block any light that would have affected the image, but will still pass IR light to trigger the slaves.

You'll still have a problem with pre-flash triggering the slaves, but if your camera has custom functions you might be able to turn the pre-flash off.

[Kombisaurus]

Hey, I just found this...

http://www.adorama.com/TF55HM.html

Exactly what I need for my Oly to take "normal" pics after I remove the hot-mirror and convert it to IR-only.

I reckon I'll give this conversion a go in a couple of weeks... maybe try replacing the hot-mirror with microscope slide glass and some of that special glue and shims to adjust the thickness.
I've found links to the procedure for another Olympus camera that uses a very similar casing to my C750, so I'd imagine the steps would be almost identical. It looks a bit easier to modify than some other cameras, and the procedure is reversible.
I'm pretty careful with these things, so I can't go too far wrong... (famous last words)

The only thing I would still need to compensate for is the fact the hot-mirror in front of the sensor is tinted cyan. I'd need to manually offset the white-balance (which can be done in-camera, even when using the auto-WB setting), but I'm not sure if this works when in "full auto" mode, and it might also have other undesirable effects. I'd imagine that if the correction could have been done completely with software then Olympus wouldn't have tinted the hot-mirror in the first place.

Cheers
Adrian

[shuttertalk]

Tip from a friend:
http://www.a1.nl/phomepag/markerink/mainpage.htm

Apparently this is the "industry interest group bible for all IR photography"...