© ravenswood-services-2017
Infrared Imagery
I
n 2016 I saw some stunning blue and white images taken by a friend and decided to invest
in an infrared converted camera . It was the start of my journey into Infrared imagery.
Infrared digital imagery is achieved by use of cameras where the manufacturers filters to reduce Infrared
light from visual spectrum standard photography have been removed and replaced with filters which
allow more light from the infrared spectrum to pass onto the sensors. This is achieved by removing the
infrared blocking filters from the camera body and replacing them with filters of specific wavelengths in the
infrared spectrum. Or replacing the filters in the camera body with a full spectrum filter and using screw
in or square filters in various infrared frequencies on the front of the lens.
Filters of 590nm are close to the visual spectrum and produce the faux colour images , where greens
after processing become golden. Filters in the 690nm to 720nm range produce red and white images
which when channel flipped produce the classic blue and white images. 850nm and up produce strong
black and white images where vegetation glows as the camera captures reflected infrared light.
I originally started with Nikon D70 850nm converted ,and then got a 720nm d50 , finally got a
d50s converted to 590nm camera. However carrying 3 cameras just for infrared and the limited megapixel
count in the older models was limiting, not to mention changing lenses every time i wanted a range
of images of the same subject.
So i decided to bite the bullet and invested in a D3200 Nikon converted to full spectrum Infrared by the
folks at
T
So now i carry just the one camera and wide angle lens, with 590nm, 680nm,720nm, 760nm,850nm
and 950nm covering the whole range. I am often asked how these images are obtained , so have written
this page to show some of the work-flow and a few workarounds in particular for the D3200.
In order to obtain the results shown requires some work not only in the field but in post processing.
Software for digital cameras and indeed the firmware on board the camera is designed for the visual
part of the spectrum. As such working with hot infrared filters tends to produce very red rich images
which are often outside of the usual working range for software.
Whitebalance
White balance is often overlooked in visual photography as the on board automated firmware does
an excellent job for most conditions and cameras offer white balances for sunny, cloudy, shade, tungsten,
and fluorescent lighting on most models. Shooting in RAW format allows use of software to correct most
lighting situations, although file sizes are much larger and it can slow frames per second, although this is not
usually an issue in infrared.
Some infrared photographers work in raw format and dont worry too much about getting a white balance in the field.
White balance is however very important especially in 720nm -760nm range where the aim is to produce vivid white
foliage and a deep blue image. At 590nm white balance is usually taken off a white or grey surface which then allows
the goldie effect in post production. For 720nm white balance is taken off a green surface, fresh green grass to give the
effect.
My previous cameras where a tad tricky to get a white balance, but by stepping up and down a few ev on exposure compensation,
or even going down a f stop or 2 eventually it was possible to set a custom white balance. Its the PRE setting on Nikons which
allows you to measure your own custom white balance. However on the D3200 which has a different sensor than the older models
it was almost impossible to set a white balance. After much Internet searching and trying various RAW shots through lightroom 6,
results where still poor. I managed to get a custom white balance at night off of halogen bulb in the kitchen which improved things
but still not ideal. I sourced an 850nm infrared torch for use with night vision infrared sights, and tried using that in the field to take
a custom white balance..and it worked, and gave a white balance much closer to the conditions on the day. It appears that some
sensors require a lot more light to get a white-balance and the torch provides this. Important safety point 850nm is outside visual
so do not look at the torch directly unless its through an infrared filter. With filter in place look through the viewfinder and focus on
the torch then attempt to get a PRE white balance on your camera.
I shoot in RAW which on the camera showed a classic yellow sky and blue vegetation image , experience with my previous 590nm
camera told me when this is channel flipped in Photo-shop, or GIMP it gives the Goldie effect. Unfortunately light room imports turned the
images back to red and orange, and the limits of temperature range in light room meant i could not cool the image sufficiently get the image
i was after.
Another surf of the Internet and I found an article which describes how to generate a custom camera profile for your camera which
massively expands the temperature range in light room and once set up works for any RAW infrared image.
In case this is of assistance to any other infrared images out there I will share a work flow here for the D3200 or any other camera where
custom white balance or red imagery is an issue.
Stage 3 to 8 will only have to be done once to generate a custom camera calibration for infrared images in lightroom. Comprehensive guides
to producing custom camera profiles are available online.
Stage 1…use IR torch to get custom white balance in field
Stage 2 Image off back of camera, slightly orange
but blue foliage and neutral tree close enough to work
Stage 3 RAW image imported into lightroom,
this will result in a blue washed out image when channel
Stage 4 export Red image as a digital negative
and remember which folder you saved it in.
Stage 5 Download Adobe Digital negative Profile
editor if you dont have it. Its free software from Adobe
Stage 6 open the DNG file from stage 3
and then open the colour matrices tab. Go
to the white balance calibration and slide the temperature
to the left between -75 and -100 works.
Stage 7 go to the options tab and name the profile for that
camera, you will need one profile per camera you use.
Stage 8 Export your camera DNG profile, to the directory
it suggests, and close the editor once successfully exported.
it will be in
users\yourname\AppData\Roaming\Adobe\CameraRaw\Cameraprofiles
Stage 9 restart light room and go to development module. Drop down to
camera calibration and click on it and pull up your infrared calibration profile.
You will notice an increase in the temperature range for white balance of the RAW file now.
Please note stage 4 to stage 8 is a one time only per camera , once that profile is in place work flow is from stage 3
import of RAW file and straight to stage 9 use your custom Camera Calibration
Stage 3 ( A) image imported into lightroom in RAW format, but
with a custom camera calibration installed allowing a much wider
temperature range for white balance.
Stage 4a slide the temperature into the blue cooler and match tint slider to give
a convertible image. For 590nm blue foliage and yellow skies are about right,
once happy I save an original and export a JPEG image to work off.
stage 5 a The image will need to be channel swapped to give the final effect, I use GIMP as its cheap or even free , but photo-shop and other software have this facility.
Open the channel mixer and set red on the blue channel to 100 and then open the red channel and set the blue to 100 and then save that Chanel mixer profile..IR channel swap or something similar.
This will convert the image to faux colour as shown below. After that i save the file in GIMP and then import that JPEG back into light room for adjustments, or even edit them further using the various
filters available from the awesome NIK collection. Again available for free download and imports straight into light room and photo shop. The NIK collection allow you to let your artistic side out to further
change the effect on the image, there are some excellent black and white modules in NIK as well.
Hope this little page gives an introduction to the world of infrared and use of IR torch for white balances, feel free to contact me if you are struggling with the guide , although
there are many in depth articles out on the net for each stage if you need help.
