|P1. The base image showing the area where the highlight alert has started to flash on the camera.|
(ISO 100, 1/160 @ F5.6 105mm. The image has had no processing done other than a RAW conversion to JPG.)
|P2. The base line image.|
|P3. Base line + 1 stop.|
|P4. Base line - 1 stop.|
|P5. Base line - 2 stops.|
|P6. Base line - 3 stops.|
At this stage I think I would be happy to accept the base image or image P4.
For the second part of this exercise I am going to process the image using the recovery sliders, which are called simply 'Highlight' and 'Shadow' in the Canon RAW converter.
In practice I found that the controls in the Canon software did not offer the range of adjustment that other software offers. On the bright side this does encourage accuracy at the time of taking the picture! To complete this exercise I switched to Adobe Lightroom, my version being 2.7.
Starting with the base image I turned on the highlight indicator and adjusted the recovery slider. At +19 the red highlight alert had completely gone. I did this several times paying attention to the rest of the image. Interestingly the base image has a larger area of highlight alert in Lightroom than it does in the Canon RAW converter. We must be seeing software differences in the way the linear data capture is being translated. When adjusting the recovery slider, our original warning area is the last to disappear.
Moving on to the second image (P3) which was exposed at +1 stop. This image has the whole sky coloured red as a clipping warning. The recovery slider has to be moved all the way up to +34 to lose the alerts. On this occasion all the red disappears at almost the same time. Even when all the clipping has been eradicated,the image still looks over-exposed.
On the final three pictures, there was no highlight clipping as they were under exposed. I still played with the recovery slider to see what effect it would have. It was noticeable that the lighter areas such as the sky were affected and became darker whereas the foreground wooden fence stayed very close to it's original exposure.
I checked the rest of the image for noise and digital errors and to be fair to Lightroom, I found virtually no evidence of this. What I did see is that the transition from dark to light happened more quickly when I ramped up the slider. This was apparent in areas such as the side of the gutter.
Here is the edit I chose as most favourable. It is 1 stop under the base image and didn't need any adjustment either way. There is detail in the shadow areas and the highlights were not clipped.
|The final choice. 1 Stop under the base image.|