Wednesday 14 May 2014

Colour - Colour Profiling from Digital Images - A Summary


Here is a quick summary of my earlier posting.

Challenge: Cameras and computers don't display colour as the human eye sees it.
Solution: None.  We must accept that digital images are only representative and work with that.

Challenge: No two cameras are the same.
Solution: X-rite colourchecker passport DNG profiles will iron out the differences between cameras.
Check out this excellent presentation by Andrew Rodney HERE

Challenge: DNG profiles must be created for different illuminants.
Solution: Correct.  We only need one DNG profile for outdoor use - a Daylight DNG Profile.
Scroll through to point 9 mins. 30 secs. on Andrew Rodney's excellent presentation HERE

Challenge: Birds are highly variable in colour due to a range of factors.
Solution: Very true.  One of the possible uses of this tool would be to try and make sense of the variation within different species, in different places and at different times of year.

Challenge: White balance.
Solution: Grey card.

Challenge: Multiple illuminants in the same environment (shade, foliage, water, flowers, etc.)
Solution: Must be avoided.  Try and photograph out in the open and not under foliage or exposed to other illuminants.  If photographing a bird in shade ensure the grey card is also in shade.

Challenge: Camera exposure.
Solution: This is the big one.  The X-rite colourchecker passport takes care of hue but not saturation and luminosity.  My solution is new.  Create a template for a species/complex with pre-set saturation and luminosity settings.  Paint the template in the correct hues.  The results is not a photograph.  It is a Colour Profile (CP).

Here is an example of a CP template for Chiffchaffs.

To use the Chiffchaff profile apply the following steps:-

(1) Create a daylight DNG Profile for your camera setup by photographing an X-rite colorchecker outdoors in daylight and create the profile using the X-rite software available online.

(2) Bring a Grey Card with you into the field and photograph under the same lighting conditions as your subject (it doesn't have to be in the same frame, thankfully).  Shoot in RAW.

(3) At home apply the DNG profile and white balance correction to your RAW images and save them as PNG files.

(4) Download the Chiffchaff CP from this blog HERE.

(5) Open up the Chiffchaff CP file and a number of your images in your image editing software.  For simplicity I use MS Paint.

(6) For each of the 9 sample points in the Chiffchaff CP sample an equivalent point from your Chiffchaff image(s).  You might need to sample from more than one image to get them all, depending on how cooperative the subject was.  Most important point is to ensure the point is reasonably properly exposed and not in shade or under a colour cast eg. from nearby foliage.

(7) To sample a point use the sampling technique HERE.  I recommend using MS Office postarizing tool "Cutout".  I can't guarantee other postarizing tools will achieve the same result.  Please get in touch if you intend using a different postarizing software tool so we can quickly validate that one against Cutout.

(8) Having sampled and postarised a sample paste it into the box in the Chiffchaff CP template coinciding with the sample location.  Next select the pasted sample with the sample dropper and open up the "Edit Colours" window.  Here note down the Hue number.  Next change the Saturation and Luminance numbers to those pre-defined in the Chiffchaff CP template.  Last step is to select the bucket fill tool and fill the box.  The colour will fill the box plus the relevant parts of the bird.  Repeat for the other 8 sample points.

(9)  Last step is to fill in details about the bird, date, location etc. plus validation information including the DNG profile and Grey Card.

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