Anti-ir lens coating

[thomas_endlein]

Hello folks!

I would like to take infrared-images with my EOS 20D and my EF-Lenses

but I picked up that some of these lenses (e.g. 16-35, 28-70,

[10-22?]) have anti-infrared coatings that would cause artefacts in

ir-images. Does anybody has experiences with that gear and IR?

Thanks a lot!

[bobatkins]

The only problem with IR (apart from very long exposure times) is that some lenses "hot spot" in the center of the frame. EXACTLY why this happens hasn't ever really been nailed down, but it's definitely related to the IR blocking filter that covers the sensor, since when it's removed the problem goes away. It could be related to reflections - or not.

<p>

There seems no way to guess which lenses will work and which won't. The 28/2.8 is fine, but the 24/2.8 isn't. The 28-135 is fine, but the 28-105 isn't. The 24-70/2.8L is fine, but the 28-70/2.8L isn't. The 17-40/4L is fine, but the 16-35/2.8L isn't. The original 50/1.8 and the current 50/1.8 II are fine, but the 50/1.4 isn't.

<p>

 

Removing the IR filter isn't something you want to try at home by the way, not unless you have an extra $1500 to buy a new 20D when you screw the first one up.

<p>

Otherwise, stick an R72 filter on the lens, be prepared to exposures of several seconds or more and go for it. You'll get an IR image from any lens.

<p>

See this thread for more details:

<p>

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007ewk">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007ewk</a>

[Brad_]

A little OT, but has anyone here had their dRebel or 10D modified to permantly remove

the IR-block filter? Any first-hand experiences?

[._._z]

I doubt if it can be done, Brad.

 

The IRfilter is part of a a multi-layer device consisting of one glass plate and three

crystal plates. The IR plate is sandwiched in the middle, between low-pass filters, a

phaser layer (which converts linearpolarized light into circular), and a dichroic mirror.

 

If it gets damaged, Canon USA charges something like $800 for replacement part and

service.

[bobatkins]

You doubt wrongly my friend.

 

There are a few outfits who will remove the IR filter (and probably the anti-aliasing filter) if you want them to. This is done for both IR photographers (who want IR images) and for astrophotographers (who want extended red sensitivity).

 

I think they charge around $500. It does void the warranty of course...

 

I've even seen "do it yourself" instructions, but until I can get my hands on a Digital Rebel for $250 (any day now....) I won't be trying it myself.

[Brad_]

<I> I've even seen "do it yourself" instructions, but until I can get my hands on a Digital

Rebel for $250 (any day now....) I won't be trying it myself.</I><P>

 

That's what I'm hoping for. My sony works pretty good within its limitations, but would

love to have a higher-quality full-time IR cam.

[bobatkins]

Well, let's hope Canon soon bring out the Digital Rebel mark II (in black of course) with an 8MP sensor and a $750 price tag. That should drive used Rebel prices down to a point where the risk of failure while experimenting is acceptable!

[awindsor]

I have a 20D and have been trying IR photography using a B+W 092 filter. I have used it with the 17-40/4 and the 28-135 IS without the appearance of hot spots. I was photographing on a sunny Austin day and found I needed exposures of less than a second (or rather that my multisecond exposures were all blown out in the red channel). Since the 20D does not have a per channel histogram you will need to estimate correct exposure.

[bobatkins]

The B+W 092 lets through more red than the Hoya R72, which is probably why you're blowing out the red channel and getting fairly short exposures.

 

I think the 092 has a 650nm cutoff, wheras the R72 is 720nm.

[Brad_]

I use a B+W 093, that cuts off around 830 nm (1% transmissive at 800 nm, 88% at 900 nm)

- visibly dead black. The B+W 092 blocks up to 650 nm and transmits 50% at 700

nm.<P>

 

 

I get pretty good results with my sony f707 cuz the internal IR-block filter gets flipped out

of the way in a special mode. But, there is a max shutter speed of 1/60, apparently so it

can't be used as a "see-through-clothes" cam - ha!. So, I'm usually shooting at 1/60

second, sometimes with an additional ND filter.<BR><P>

 

<center>

<img src= "http://pages.sbcglobal.net/b-evans/Images%205/Silos1.jpg">

</center>

[rayn]

There is a conversion tutorial for the Nikon D70 <a href="http://www.lifepixel.com/

IR.htm">here.</a>

 

<p>You might be able to extract some information that would apply to your Canon.

Generally,

Canon bodies are harder to convert than Nikon bodies.

 

<p>The hot mirror on all newer Canon digital bodies is very strong. It hardly lets any IR

through. I've done extensive tests, and using a Hoya 072 on a newer Canon digital body is

a crock. You basically are taking a picture of the visible red light, which is why sample

pictures with this combo only look slightly like true infrared. To get true infrared, you'll

need a B+W 093 and that will give you extremely long exposure times. The Hoya gives the

illusion of shorter exposure times because a large part of the image is formed by the

visible spectrum. Believe me, very little IR is getting through that hot mirror even with a

15 second exposure.

 

<p>You'll need to remove the hot mirror if you want to take true IR pics with a newer

Canon body and exposures under 30 seconds. Removing the hot mirror will give you

exposure times that you can easily handhold in daylight, even at f/11.

 

<p>The guy who runs <a href="http://dpfwiw.com/ir.htm">this forum</a> should be

able to tell you which Canon lenses have hotspots. Send him an e-mail and post back for

us.

[chrisjb]

Hope this site helps

 

http://www.naturfotograf.com/UV_IR_rev00.html#top_page.

[chrisjb]

sorry wrong link this one mentions canon lenses with IR

 

http://dpfwiw.com/ir.htm#pg0

[._._z]

<i><blockquote> I think they charge around $500. It does void the warranty of

course...

</blockquote> </i><p>

 

And if they accidentally damage it during conversion, will they cover the $800 repair

cost?