My IR Post Processing Workflow

As many know, I’m lucky enough to have a Canon that can access Magic Lantern. This means I can maximise the quality of the captured photons through tools such as RAW Spotmeters and RAW-based ETTR. I also have diffraction corrected focus feedback in my Live View and thus, ‘all’ I need to worry about is composition.

This last week I’ve been re-acquainting myself with Infra Red photography, using my trusty IR-converted 50D.

Today’s post is all about how to post process IR captures in B&W.

First, as anyone who has shot IR knows, it’s difficult to focus and set exposure. From my experience the only sensible way to capture an IR image is to use the camera’s LV. If you don’t have a DoF app that allows you to explore IR frequency focusing, such as TrueDoF-Pro (http://www.georgedouvos.com/douvos/Intro_to_TrueDoF-Pro.html), then simply select a focus point beyond the visible band HFD. 

It's almost always best practice to 'never' focus at (sic) the HFD, as this guarantees only acceptable focus at infinity. For example, a non-App-based approach to focusing with a wide (sic) lens, is to focus on infinity and set the aperture for resolving the smallest near-field detail. For example, with my 10mm lens , on the 50D, if I set my aperture at, say, F/10, I would be able to resolve details as small as 1mm, ie FL/N. But don't push things much beyond, say, F/10 on a crop sensor (F/16 full frame), as that diffraction will get you!

As for IR-based exposure, I always seek out a Magic Lantern ETTR solution, as this maximizes the tonal data and the dynamic range. Also, as you are shooting IR, and most likely shooting in bright sun, it is very unlikely you will need to bracket. 

Here is the RAW capture and what the LR histogram looks like, showing the ETTR bias:

The first job in LR is to get rid of the red cast and get the best out of the RAW data. The way to do that is to use a custom Camera Calibration Profile. These are easy to create using the Adobe DNG Profile Editor (free from Adobe). 

To set up a custom IR profile simply save your RAW file as a DNG (sic) and open this file up in ADPE (you only need to do this once). 

In ADPE (having closed LR) go to the Tone Curve and rather than the Base setting, choose Linear: this will pull the maximum data out of the highlights. For a non-IR image stop here and save your profile for use in ACR, PS or LR. For IR we need to make one more change, namely go to the Color Matrices tab and adjust the Temperature and Tint, usually move them over to the left. This allows addition colour temperature adjustments in Lightroom, ie beyond which you can do without this tweak. Save the profile and re-open LR, where you will see the new (IR) custom profile.

Using the above custom profile, the above image now looks like this:

Because we have used a linear, rather than gamma-based, curve in the profile, the image is very flat, and thus can handle (and needs) a lot of tonal enhancement: which works well for B&W processing.

Next, after switching to B&W processing in the LR Develop module, I would typically (and did with this image) go to the Effects tab in LR's Develop Module and move the Dehaze slider to 100%.

I would then play around with the other develop sliders, eg contrast and clarity, as well as the zonal exposure adjustments, until I had the look I was going for. In this case, I ended up with this image of the church, taken in IR at a FL of 10mm, F/7.1, ISO100 and at 1/50s.