Infrared photography—why are green leaves not appearing as white?

Question

I'm new to IR photography. I'm trying to get the white colour out of green plants (leafs, grass etc.).

Here is my setup:

• Canon EOS 100D full spectrum - IR filter in front of sensor removed
• Samyang 24mm f/1.4
• Zomei 680 nm IR filter

I'm using Digital Photo Professional 4 to set the white balance.

Below a photo where white balance is set on the green colour of plants.

The second photo white balance is set on a white sheet of paper.

Am I missing something? Why I'm not getting the white colour like on all of the photos on the internet?

I don't have any experience in post-processing and I do not own Photoshop or Lightroom so if there is something else I should edit in the RAW files please suggest what software I should use.

Is there something else in the camera or lens that might be blocking the IR light?

Here is a link to RAW file of the above photos: RAW photo

EDIT: I did a small experiment. I used a filter that was removed from my camera which should block all IR light. I did two photos: with and without the 680 nm filter. So in theory the camera filter should be completely black when taking a photo with 680 nm filter which blocks all visible light. Here is the result:

As you can see the camera filter is not completely dark so either the 680 nm filter is passing some visible light or the camera filter is passing the infrared light (or a mix of theese two?).

Can that cause the plants being not white in the IR photos? Maybe I should try a deeper infrared filter like 850 nm or 950 nm?

Answer 1

Ok guys, here is an answer. It turns out that the weak point of my IR photography setup is... Zomei IR filter. I bought a high quality Hoya R72 (720 nm) infrared filter. I was shocked by the result.

• The first photo is made using the Hoya filter. White balance set on green leaves.
• The second photo is made using Zomei filter with exactly the same
  settings (exposure, ISO, aperture, white balance) as the first photo.
• The third photo is made using Zomei filter. Changed exposure time and adjusted focus slightly. Rest of the parameters unchanged.
• The fourth photo is made using Zomei filter. Exposure slightly
  changed. White balance set on a green color.

There was no post processing of any kind made to these photos except setting the white balance.

I do not know where all of these good reviews about Zomei filters come from. For me, the filter I received from Zomei is totally useless in terms of infrared photography.

I hope my investigation will help others.

Answer 2

You're not missing anything - some epic post production is pretty much always used to create digital IR images.

Life Pixel is a company that does conversions, but they've also put together an extensive list of video How-To's for post.

To boil it down, you need to use a program like Photoshop or Gimp and get familiar with the channel mixer. When converting to black and white using this tool, you get to select which color channels map to the brightness of the black and white. This allows you to select which colors become white and which colors become black, and every shade in between.

There are other ways, of course, as there always are with post. But, this should get you started.

Answer 3

I've used a few cameras with the hot filter removed, including a Canon DSLR. In your case, the problem is twofold:

• On Canon DSLRs, the sensor stack seems to be somewhat insensitive to IR. There is likely an element on the sensor stack (other than the hot mirror) that blocks a significant amount of IR. Based on a diagram in this modification guide, a potential culprit is the low-pass filter.

  

• You are using a 680nm filter which lets red and orange light through. You will need to use a high-quality 720nm filter that does not let visible light through, so that the IR-insensitive sensor is not distracted by it. The less visible light, the more monochromatic the image will be. If too much visible light is allowed through, the filter will behave like a deep-red filter and foliage will not be bright.

  

You'll get best results by using in-camera white balance.

• For IR, use something that reflects pretty much everything, like concrete pavement. Then swap the red and blue channels in post for faux-color IR with golden-colored leaves.

  

• You can get a different look by setting white balance on grass or other foliage.

  

• For visible light, any white surface should work fine. No need to use a hot filter because the filter stack is already so insensitive to IR.

Other suggestions:

• Use Live-View mode for both focus and exposure when capturing IR images.

• Use manual focus and focus bracketing because autofocus doesn't have enough light to work with through near-IR filters.

Answer 4

I have the Zomei 680nm filter. On unmodified Canon camera it has no infrared effect. On my Canon FullSpectrum it looks like a 720nm filter, with the white foliage effect. Everything indicates that the wrong filter was removed, the Low pass and not the hotmirror. You have to remove both filters and put a transparent one to focus.