20D IR photography help

[matt_stevens2]

I have a 20d with a 24-70 L lens. I have been given a hoya r72 IR filter (77mm so very expensive!)

I have never done IR photography and seem to be having touble getting a decent shot with this setup.

Is anyone able to help?

thanks.... Matt

[steve_unsworth1]

I don't think the 20D is sensitive to IR light.

[mike_earussi1]

Most, if not all, digital cameras have a UV blocking filter built in the them, as UV can have a negative affect on the accurate processing of normal color. Those who are shooting digital UV have had an "operation" on their cameras to have the filters removed. This makes them sensitive to UV but ruins them for normal color photography.

[jcolwell]

The filter in front of the sensor stops IR light. I plan to get my 20D converted to IR later this year, after I pick up a 5D. Your question got me thinking though. I just did a few test shots and discovered something interesting, but probably of little practical value.

 

Camera 20D, ISO 100, lens Tamron SP 180/2.5 at f/2.5, filter 87 (IR), subject translucent vertical blinds backlit by exterior sunlight on light overcast day.

 

For shutter speeds as long as 20 sec, there is no image at all, but the light meter indicates that the shot is very overexposed at t = 20 sec. This means that enough light energy is getting through the 87 filter (which is fully opaque to the eye) to register on the light meter. The meter may be reacting to the IR light or to the very low levels of near IR light (i.e. dark red) which may be getting through. Anyway, on a film camera, this is how you can calibrate the metering for IR film, but the sensor filter is preventing the IR from getting to the sensor, so it doesn't help with my 20D.

 

With the 87 filter on, the 20D meter indicates correct exposure at t = 5 sec, and this goes to t = 1/640 sec without the filter. This difference is 11.5 stops, which is a whole lot of difference (FWIW).

[jcolwell]

Of course, my comment above about calibrating the camera for IR film is bogus, as I should have realized before typing it in (hands faster than brains). This approach will calibrate the meter sensitivity to light as filtered by the 87 filter, but the typical IR film is way more sensitive to IR light than the typical camera meter.

[JeffOwen]

I believe the 20D has a IR blocking filter in front of the sensor and therefore will not take true IR photos. It is possible that the metering sensor has a different IR sensitivity and therefore will give an exposure that is incorrect when using a deep IR filter over the lens.

 

 

I think there is a 20D version that is IR sensitive, I am not sure but could be the 20Dr or you could do the conversion yourself see link http://www.lifepixel.com/ir-tutorials/canon-20d-digital-infrared-conversion-instructions.htm . Obviously with your version camera taking true IR photos will be very difficult so the only way that I can think is to use a deep red filter (not totally visually opaque) and do some exposure experiments to see if you get the desired results.

[bob_osullivan]

I had this same questin about a month or two ago. Search for older threads. Someone referred me to lifepixel.com they convert Canon EOS cameras to IR for $350. I'm keepig an eye out for an old 10D for this purpose.

[bobatkins]

The 20D can be used for IR work, but it's not very sensitive and you'll get a hotspot with some lenses.

 

For sample IR shots with the XT and 20D see http://www.bobatkins.com/photography/digital/eos_digital_rebel_xt_review2.html

 

For a list of hotspotting lenses see http://www.lensplay.com/lenses/lens_infra_red_IR.html

 

I've never been very happy with IR shot with conventional DSLRs. You really need them converted to IR use to get good results.

[slichtyler]

The 20d isn't great for IR, but it'll work. (Except for the old D30, Canon DSLRs have been very

good about blocking out most IR light.)

 

On a bright sunny day ("sunny-16" conditions), I'd start with ISO 400, f/4.0, and about 8s for

the exposure on the 20d, and use the histogram from there. You'll need a good bit of post-

processing -- the images will have very low contrast -- so it might be a good idea to shoot

in RAW.

[dave_powell2]

And you'll need to get used to carrying a tripod around...without "modding" the camera for IR, there's no way around that!

 

Dave