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View Full Version : How to post process photos taken with an IR filter



Mperko
10-02-2004, 06:12 PM
Several of you guys have asked me what my techniques are for my IR shots. I thought I'd make a post here and describe the process. It all starts with a Hoya R72 Infrared filter. I use it on my 50mm f/1.8 lens, on a digital rebel. You have to be careful which lens you buy the filter for. Some lenses will leave a large "hotspot" in the middle of the frame. I'll post a list of good lenses at the end of this post.

Most digital camaras have an IR blocking filter over the sensor. This blocks some of the IR, with the intention of reducing noise. It doesn't block it all however. What you need to do in order to compensate is to always shoot in full sun, which maximizes the amount of light in the IR spectrum, and shoot longer exposures. Focusing is a tad different in IR as well, so to ensure a sharp photo, you should always shoot at at least f/8, and smaller. This will typically require then an exposure at ISO 200 f/11 (what I normally shoot at) of about 10-20 seconds on a bright sunny day.

The infrared filter itself is a dark red filter, so your shots come out reddish in tone. I color balance the raw file by selecting a white point. With ir photos, green plants and vegetation reflect lots of IR light, and will usually appear white in a normally balanced photo, so I select a nice leaf on a tree as a white point. Then I convert to tiff and open in photoshop.

Once there, I duplicate the background layer, invert it, and set it's blend mode to color. This changes most of the remaining reddish browns to bluish cyan. Then I will use a color balance layer and add more cyan and blue until I make the leaves and trees as white as possible. (Removing a yellowish/pinkish tint usually) You are pretty much done then, at that point. What I like to do for a lot of my IR photos, to add a little something extra, is to soften them by duplicating the background layer again, (this layer will be inbetween your background and your color invert layer), and gaussian blur it at 6 pixels, then set the opacity to about 30%. Then I duplicate the background again, and sharpen it with the USM. I oversharpen it, because it has to cut through the softening. I like to do something like 10%, 100 pixels, then 40%, 20 pixels, and then 300%, 0.3, and finally 500%, 0.2. Since I have this on it's own layer, I can adjust the opacity as desired. It gives it a nice effect of being sharp, yet dreamy. Sometimes I will duplicate the background again, and run a diffuse glow on it, (make sure white is your background color) with settings like 0, 12, 10, and then fade it's opacity as desired. This will add to the dreamy effect, if used subtly.

I hope this all makes sense. Feel free to ask any questions you have. The real trick to IR is to find an interesting subject to shoot, a nice landcsape with lots of green trees to reflect the light.

PS. Here's a link to my IR gallery on my website for examples. I've posted a few examples in my galleery here as well.

http://www.anti-rejection.com/photography/infrared/

Mperko
10-02-2004, 06:13 PM
Here's a list of popular Canon lenses and how they fall with regard to IR hotspotting:

No Hot Spot Problem.
EF 17-40mm f4L
EF 24-70mm f/2.8L
EF 28-135mm/3.5-5.6 IS
EF 28mm f/2.8
EF 50mm f/1.8 Mk I & II
EF 70-200mm f/4L
EF 75-300mm f/4.0-5.6 IS
EF 135mm f/2L
EF 100-400mm f/4.0-5.6 IS L
EF 100mm f/2.8 macro

With HOT SPOT
EFs 18-55mm f/4-5.6
EF 16-35mm f2.8L
EF 20mm f/2.8L
EF 35mm f/2
EF 24-85mm f3.5-4.5
EF 28-70mm f/2.8L
EF 28-105mm/f3.5 - 4.5
EF 35-80mm f4.0-5.6
EF 50mm f/1.4
EF 50mm f/2.5 macro
EF 70-200mm f/2.8 IS
EF 85mm f/1.8

Mac
10-02-2004, 07:00 PM
I really like the pics from an IR filter...I have not yet looked into them yet...still working on learning the camera first...but are there specific brands you find are better then others, or ones that you would avoid?

Your gallery is awesome by the way...some great shots...:-D

Mperko
10-03-2004, 12:58 AM
Thanks Mac. As far as brands, I use the Hoya R72. I can't really recommend any other brands specifically, because I haven't tried their filters, but pretty much any major company makes an IR filter, and they are all probably equally good.

Thor
10-03-2004, 01:34 AM
Great pictures! I had never heard of anyone shooting with an IR. Something I'd like to give a try.

Mperko
10-03-2004, 09:11 AM
Thanks Thor. :)

ap.
10-04-2004, 01:44 AM
Great write up, Matt. I've also placed a copy of this in the "Knowledge Base" forum due to the heftly weight of all the above info. Beside, I'll need ot know where to find it when I give this a shot.

Thanks!

Mperko
10-04-2004, 08:25 PM
Thanks ap. I should have put it in that forum to start out with. It's been a while since I've been here and I forgot it even existed. I hope some people try this out. Digital IR is a blast :D