Monday, 24 December 2012

Exercise: Correction

The first part of this exercises focuses on dust correction. I used to have much more of a problem with this, before I started cleaning my sensor myself. So I have delved into my archives for a great dusty image, taken in France on our roadtrip of 2007, in Avignon.
Image with many examples of dust spots clearly visible
The night-time conditions are particularly suitable for dust – long exposure against a clear sky and reflective water.

The dust spots were quite simple to remove, using the clone stamp in Lightroom. When zooming in at 100%, I also noticed a small bush in the lower left hand corner which I had not previously noticed! The dust marks were all quite obvious in this image, though I’m sure I have missed some on the buildings and other areas where it would not be possible to tell which was dust and which real. To be honest this does not bother me – I choose to remove things that I think should be removed, though I realise this is because my images are only created for me, not for journalistic or other purposes.
Dust spots were fairly quickly removed using the clone tool in Lightroom
I also cropped and tweaked the image slightly and display below.

Image has been cropped, optimized and slight adjustment of curves in Lightroom

The second part of the exercise is looking at lens flare correction. I chose an image that I took recently at Mt Coot-ha Botanic Gardens specifically with this exercise in mind. The image is looking up at a large tree, with the sun behind one of the branches.
Lens flare down the centre of the image
Most of the lens flare was removed relatively easily in Lightroom. I used an adjustment brush set to desaturation and underexpose by about half a stop or so (adjusted as necessary). This effectively removed most of the lens flare, for example on the trunk below.
Example of colourful lens flare on tree trunk

Desaturation has removed the colour effect

The clone tool finishes off the job

More difficult was the area at the top of the image which included some sky which was a different colour as a result of the flare, and some awkward to remove flare on the trunk – the trunk was noticeably paler than it’s surroundings. So I went into Photoshop with my image from LR and did some further adjustments using the clone tool. I set it to darken as suggested in the notes, and used it to adjust the colour of the sky and trunk. The result is quite convincing, though I can imaging it would be more difficult with other subjects (I recall seeing someone’s wedding photos with flare over half the wedding party’s faces – that would be a bit tricky!) I think it might be possible to remove using colour management – for example using tinting or colour balance in a mask, but I have not tried that for this exercise.
Difficult to remove flare on tree and sky
Desaturation works effectively on the trunk, but the exposure is still wrong
The finished result in Lightroom, but I know it needs further work with the tools of Photoshop
Bringing the image into Photoshop, and using the clone tool on the sky (to adjust the colour) and trunk
The finished product in Photoshop looks convincing even at this zoomed in scale
The finished result, optimized slightly in Lighroom (before it was taken to Photoshop) and all the flare removed.
Note that there are some other colour abberations on the trunks - are these considered flare? I don't know... I guess it's personal and needs to be considered depending on the use case for the image perhaps. it certainly would be difficult to remove for all the branches in this image!
Colour fringing on tree trunks - is this flare? 
I think in general it is best to avoid taking photos with flare if you don’t want to include it creatively. It can add to an image, but it is a bit painful to remove. In terms of what I think is ethical – if it is for personal use or if it is stated that there is some removal of photographic artefact then there is no problem. A problem may come about with use for journalism for example.

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