Exercise 13: Managing Colour

As this exercise is all about the color accuracy, (though it may differ depending on the personal perspective) I have calibrated my monitor again.

For this exercise, I had to choose 2 or 3 images that had significant color cast. I need to correct it through the processing. I have decided to stick to Lightroom 3 (I also have CS4, but I prefer using it only for extensive corrections).

Selection:

I have selected 3 images from the archives. These images were taken as the test shots and had significant colour cast. 2 of them also had an expected grey surface, and one did not. I guess I would use this last image for the RAW processing method. (I am aware that the JPG process can also be applied on the RAW files).

Original Images

Judgement

Image:1 Thumbnali-1 This image has obvious yellow and magenta colour cast and needs correction. On the extreme left the sky has the grey colour that will be helpful in stabilizing the colour tone of the image.
Image:2 Thumbnali-2 Here in the picture the tint of blue is quite visible, due to that the picture looks pretty dull. With the help of the colour dropper and the R, G, B channels I will try retrieving the picture and bring it to close to the original scene.
Image:3 Thumbnali-3 This Image showcases the strong yellow tint. Image also doesn’t have any obvious greys. Hence I am planning to rectify this image by using the already worked out white-balance settings. Looking at the image I also think I might have to use some local adjustments in the foreground.

Processing:

I had RAW + JPG formats for all the 3 images. Instead of repeating the explanations and the processing on all the images I have decided to divide the processes between the above images. The exercise explains three methods to correct the colour tone.

  1. By using grey dropper and adjusting the R, G and B channel. I will use the image # 1 for this process.
  2. By adjusting the opposite colour (of the colour cast) channel. I will use the image # 2 for this purpose.
  3. By selecting the pre-existing white balance settings in the software.  Alternatively adjusting the WB and hue slider and/or local adjustments. Note: the last option is meant for the RAW format.  I will be using Image # 3 for this.

Method: 1

The image details are as below:

  • Exposure:                 1/125 sec @ f/3.5
  • ISO:                           1250
  • Focal length:           36mm
  • Handheld

I opened the JPG image in the Lightroom 3. The image definitely had a strong magenta tint. I selected the grey dropper (Screen shot doesn’t show the dropper hence, I have pointed the selection area with the blue line) and picked the grey colour from the sky. It was like magic the colours were neutralized in one click. Check the image comparison in the image below.

Ex-13_Method-1b

You can see the drastic change of colour tone between both the images. Please note that on my computer, this different is even more prominent. In the above screen shot, the WB (highlighted with the blue oval) has changed to “custom” and the values for the temperature and tint sliders have also altered. I also experimented with the R, G and B channel and made the following changes.

Red Orange channel Green channel Blue channel
Hue:              0
Saturation:  -13
Luminance: -20
Hue:               0
Saturation:    +3
Luminance:   -31
Did not make any
changes, all the values
were left to: 0
Hue:            +38
Saturation:       0
Luminance:   -65

Final Image:

Ex 13-Final-1

Method 2:

This image was shot in Singapore and captures the iconic Marina Bay Sands. It has a strong blue colour cast all over it. I remember I was playing with the white balance before settling with the final selection. If I remember correctly, I had selected customized white balance and had also modified the values. Obviously it had not gone right. On top of that, I was still working on the right angle. Hence this image was never used for my website.

However, it is an ideal candidate for the 2nd method mentioned in the exercise. In spite of having an expected grey in the image, when I tried using the “grey dropper” there was no noticeable difference. I had to move to the next option of making a correction by dragging the sliders of the opposite colour (R, G and B). See the image below. In the beginning, values for all the channels were 0. Note I have used the JPG format here.

Red Orange channel Green channel Blue channel Purple channel
Hue:           +21
Saturation:  +61
Luminance: +23
Hue:              12
Saturation:   +40
Luminance:   +60
None None Hue:            +35
Saturation:   +29
Luminance:   +35

I also had to change few basic values to make the image more realistic. Further to that I also applied “Graduated Filter”.

Camera setings “Basic” adjustments
  • Exposure: 1/6 sec @ f/3.5
  • ISO: 100
  • Focal Length: 21mm
  • Tripod
  • Temp: +7
  • Exposure: +0.15
  • Recovery: 48
  • Fill Light: 14
  • Black: 6
  • Vibrance: +11

Ex-13_Method-2b

One can see that there is not too much of difference in the sky area. However the foreground details have surely benefited from this processing. It would also be interesting to see, when I use the same processing on the RAW format, what kind of results the processing will produce?

Final Image:

Ex 13-Final-2
To see another version of the same scene please click here.

Method 3:

The image details are as below:

  • Exposure:                 13.0 sec @ f/8
  • ISO:                           100
  • Focal length:           21mm
  • Tripod

According to the exercise guideline, this method needs to be performed on the RAW file. The RAW file keeps all the settings separate from the image capture. The white balance and the hue settings were easily accessible. To start with I chose the “Tungsten” WB however, it made the picture look very cold (bluish). Definitely did not do justice to the scene. I decided to settle with the “Fluorescent” WB. It remarkably corrected the colour tone of the picture. However, some manual adjustments were required. Compare the adjustments, I have made to bring the picture, close to the reality.

Before After
  • White Balance
  • Temperature
  • Tint
  • As Shot
  • 5650
  • +24
  • Custom
  • 3800
  • -8

 

  • Exposure
  • Recovery
  • Fill Light
  • Black

 

  • 0.00
  • 0
  • 0
  • 5

 

  • +0.15
  • 31
  • 24
  • 6

 

  • Brightness
  • Contrast

 

  • +50
  • +25

 

  • +60
  • +25

 


Ex-13_Method-3c

Method 3 has worked beautifully here. It has retrieved the colour tone of the picture and now the picture is quite usable.

Final Image:

Ex 13-Final-3
Conclusion:

I found this exercise a great learning and very enjoyable experience. This exercise emphasizes on the importance of the correct colour tone in your overall composition. Understanding how to manage it can surely help me in improving the quality of my photographs. Above mentioned all the 3 methods are excellent help in restoring the correct colour tone, yet I feel it is advisable to use our own judgment in accepting the changes done by the tools. This is specifically true when using the “grey dropper”. I found that in general it gives very good results. However, if the grey sample pixel has slight colour tone, then the result can vary.

“ Arguably the greatest problem with the colour in photography and in art is the notion of rightness and wrongness” this is what Michael Freeman says in his book – “The photographer’s eye – composition and design for better .., http://www.scribd.com/doc/20149783/the-photographer-s-eye-composition-and-design
-for-better-digital-photos-2007-by-michael-freeman
(accessed January 31, 2012). I will write in details about my learning separately.

I have also observed that when the images are converted to put it up on the web, the compression weakens the appearance. This can be the result of the colour space difference. This means I need to be aware of this constrain when the target display medium is the web.

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