FLASH TOO DISTANT

To follow this part of the tutorial make sure that the Undo system is enabled under File > Preferences > General Program Preferences > Undo/Redo and then load Wedding.psp. This is the classic wedding photograph problem. Wedding photos are hard to do well at the best of times because of the strong contrast between the white typically worn by the bride and the black worn by the groom. When the bridal couple is at the end of the room the flash doesn’t reach well and only the white reflects much light. In this case the bride is wearing a shiny satin dress that exacerbates the problem. Additionally the image looks too blue for the incandescent light in the scene, such as the one visible behind the groom’s head, and the colors are dull.

Summary

The difficult part of the correction is maintaining all the highlight detail while drastically increasing the brightness of the image. We do this by thresholding the image and using the result to create a selection for the region whose brightness we want to modify. Once this is done, contrast adjustment is completed with conventional Automatic Contrast Enhancement and Clarify filters. After balancing the color and optimizing its vividness, some defects are removed, grain is reduced and the image is sharpened.

Step 1 – Adjusting the contrast

Normally we start by adjusting color. However, the image is so dark we are unlikely to get good color correction, so contrast adjustment comes first. Select Colors > Histogram Functions > Histogram Adjustment, press Reset and examine the histogram of the image (below). There are some very large peaks in the left half of the histogram and a flat plateau on the right. The large peaks for the darker image intensities simply reflect the fact that the image is mainly dark. Now let’s take a look at the plateau. Slide the Low clip limit (black triangle slider) to the right just past the big peaks, say to a value of 122. Now slide the High clip limit (white triangle slider) down to meet the Low clip limit at 124. In this way we are effectively thresholding the image at an intensity of 123. Press the Autoproof button and examine what happens to the image. The plateau region appears as white and the rest of the image as black.

Toggle the proofing (eye symbol) on and off repeatedly and you will see that the plateau corresponds mainly to the woman’s dress, shoes and hat and the man’s shirt. Additionally, the white area contains the woman’s earring and the gleam from her teeth, as well as the reflection from the man’s shoes. It also includes the reflection from the glasses of the girl in the background. The objects in this white area are rather bright and we would like to restrict the brightening of the image to the black region so as to preserve all the detail in the folds of the wedding dress. Unfortunately we can’t use what we have because the white area also includes a part of the woman’s upper arm and the lower edge of her hand, so her skin will only be partly corrected and will have unnatural blotches. We have to slide both of the clip limits to the right until none of the woman’s skin appears in the white region of the thresholded image. A little experimentation shows this can be done with a Low clip limit of 142 and a High clip limit of 144. Press OK to receive a thresholded image. Now select the region of the image to be corrected by clicking the Magic Wand on a black pixel of the background and save the selection to disk using Selections > Save To Disk with Wedding.sel as the file name. Now you have a selection of everything in the image that needs to have its brightness adjusted without ever having to carefully draw around anything in the image.

The selection is what we wanted, so Undo twice to get the original image back. Now load the selection from the file using Selections > Load From Disk, specifying Wedding.sel as the file name, and fire up the Histogram Adjustment dialog again. Press Reset to discard the settings we used to threshold the image. Make sure Autoproof is on and slide the Gamma (gray triangle) slider to the right. If you move it a long way (e.g. to around 4) you will see the image brighten and the wedding dress will seem to become gray because it isn’t being affected by the Gamma value. Choose a final Gamma of 1.6, setting the Low clip limit to 3 (0.045%) and the High clip limit to 252 (0.036%), which gives us a reasonably bright image but keeps the groom’s clothing dark.

Finally remove the selection marquee with Selections > Select None and then invoke Automatic Contrast Enhancement from the Effects > Enhance Photo menu. Once the we have a fairly reasonable image brightness distribution, Automatic Contrast Enhancement usually does a better job than any manual adjustment. Run this filter with the default settings by pressing Reset. As a last step, run the Clarify filter (Effects > Enhance Photo > Clarify) with a setting of 5 to add some drama to the image. You should receive a result like Wedding1.psp.

Step 2 – Correcting the color

As noted earlier, the image has a bluish tinge. To eliminate, it choose Effects > Enhance Photo > Automatic Color Balance and press Reset when the dialog appears. The default Strength of correction is fine but we want to add a warmer effect to the light. This can be done by picking an Illuminant temperature of 5500 K. The result is Wedding2.psp.

Step 3 – Adjusting the saturation

The image colors are dull. An appropriate vividness can be obtained with Automatic Saturation Enhancement in the Effects > Enhance Photo menu. Press Reset to set the filter defaults and check Skintones present to receive natural but saturated colors, as shown in Wedding3.psp.

Step 4 – Removing defects

There is a distracting reflection from the girl’s glasses, as well as a bright spot a little more than half way up on the extreme right of the image. Now is a good time to get rid of them with the Scratch Tool. Zoom in on the defects and surround them with the Scratch Tool selection box. A width of 5 pixels works well on the reflection and 8 is good for the other defect, but instead of setting these in the Tool Options Palette you can simply use the PageUp and PageDown keys to set a convenient size a pixel or so wider than the defect. The result is Wedding4.psp.

Step 5 – Grain reduction

After all these adjustments, the image has developed a grainy look. This is the result of some image noise in dark areas that has been enhanced by the brightening of the image. We could reduce the grain with the Edge Preserving Smoothing filter but, since the wall behind the couple appears to be textured, a slightly better choice is the Texture Preserving Smoothing filter under the Effects > Noise menu. The default setting of 50 is a good compromise between suppressing grain and retaining texture. The result is Wedding5.psp.

Step 6 – Sharpening

The final step is to sharpen the image using Effects > Sharpen > Unsharp Mask. The following settings work well: Radius 1.5, Strength 70 and Clipping 15 to give Wedding6.psp as the result.

The final before and after comparison is shown below.