Adobe Photoshop CS5 for Photographers - Martin Evening [192]
Shooting tips
As I mentioned, the flat field capture image must be evenly lit. Since the high-end display I work with has good uniform brightness, I got good results by photographing the computer display with a white desktop. I shot at a low ISO setting to keep the noise to a minimum. I also bracketed the exposures so that I had the opportunity to choose the most suitable image – one that was bright enough to apply a Divide blend mode calibration and required minimal further image adjustments to the brightness.
What is this technique good for?
One of the reasons I chose to include this technique was to show what the new Divide blend mode could be useful for. In all honesty, I think the easiest approach would be to use the Camera Raw Lens Corrections adjustments to take care of the vignetting and use the remove spots tool in Camera Raw to remove the dust marks and synchronize the spotting adjustments across all the other affected photos. This could certainly work well for an image like the one shown here. On the other hand, if you have a problem with a particularly dusty sensor or the dust marks fall on top of areas where it would be tricky to retouch, the flat field calibration technique might just save the day. As you can see in the close-up views in Step 2 opposite, I was able to do a good job of removing most of the spots. However, I was only able to partially remove the big dust mark in the top left corner. It would have been unrealistic to have expected a better result than this for such a large sensor mark.
1.
The first step was to capture an image of an evenly lit white surface, exposed so that the center was 100% white. The key thing was to make sure the illumination was even and defocus the camera so as not to pick up any subject texture. It was also important to capture this image at the same aperture as I was going to shoot with since this would affect the definition of the sensor dust picked up by the camera.
2.
I placed the flat field calibration layer above the Background layer of an image shot with the same camera at the same lens aperture and set the blend mode to ‘Divide’ at 100%. The net result was a modified image in which the added layer canceled out the sensor marks that were present in the original and removed any lens vignetting. However, it was important to fine-tune the brightness of this layer using a clipping Curves layer so that the calibration layer in Divide mode precisely canceled out the sensor marks on the layer below.
Portrait retouching
Here is an example of a restrained approach to retouching, where only a minimal amount of Photoshop editing was used. Of course you can retouch portraits as if they were fashion shots and some publications may demand this, but I thought I would start off by showing a more subtle approach to portrait retouching.
1.
The top photograph shows the unretouched before version and below this you can see the results of the initial retouching in which I mainly used the healing brush to remove some of the skin blemishes. The key thing here was not to overdo the retouching. What I did here was more like ‘tidying and grooming’ rather than ‘digital surgery’.
2.
For this next step I wanted to lighten the eyes. To do this, I used the lasso tool to define the outline of the pupils. In the Adjustments panel I clicked to add a Curves adjustment and adjusted the curve shape to lighten the selected area. I then selected the whites of the eyes and applied a separate Curves adjustment. The aim here was to add more contrast to the pupils and make the eyes slightly lighter.
3.
You don't want the eyes to be too light, so for this step I reduced the eye adjustment layer opacity slightly. Lastly, I wanted to adjust the shapes of the eyes. To do this, I used the command to create a