Simone Maranzana personal portfolio

This is the first of a short series of tutorials concerning the basic correction and improvement of a picture in a non-destructive way.
In a picture, the correct balance of black & white is a matter often disregarded in favour of the improvement of the picture itself.
Before starting to work on our example picture (provided by Andrea - here the original image on flickr), let’s focus on the tools we’re going to use:

• Point sampler tool
• Info palette
• Threshold
• Curves

Point sampler tool

By this tool we can get some information, like RGB/CMYK/LAB, from a precise point on our picture; this values will be then visualized in the info palette. The maximum number of points identifiable at the same time in the info palette is 4, and you can choose readout options from the pop up menu.
For a more accurate info palette tool description go to Adobe online docs.

When you take the white point and the black one, remember to set previously the eye dropper tool to catch information only from the selected pixel, by choosing point sample from the pull down menu.

Threshold

From Adobe Photoshop CS3 Guide:

The Threshold command converts grayscale or color images to high-contrast, black-and-white images. You can specify a certain level as a threshold. All pixels lighter than the threshold are converted to white; all pixels darker are converted to black.

Curves

For a more accurate curves tool description go to Adobe online docs.

Ok now let’s start!

Part 1

Precisely individuate black and white

• Open the example picture.
• 
• Click on the button smart filter in the tab layer and select threshold.
• 
• Move to the histogram towards the extreme left (i.e. towards the dark side of the picture) and slowly run to the right until you reach more or less the value 20.
• 
• Let’s place our first point by keeping pressed the button shift.
• Repeat the same also for the white point, now shifting to the right up to the value 210 and then place another point.
• 
• Once you’ve done this, press cancel on the threshold window.

Part 2

Curves

• Click on smart filters then curves.
• 
• Now we have to interpret the RGB values derived from the control points we have placed and shift the curves of the single channels as a consequence.
  Our aim is to get a RGB value like 10 10 10 for black and 245 245 245 for white, in order to have a margin to increase the contrast without the values to clip.
• Let’s move to the first channel corresponding to the red channel and move the point placed more down left corresponding to the black until the value in the info tab under R become 10.
• 
• Repeat it for the other channels.
• At the end click on OK.

Part 3

bonus: contrast boost (not necessary)

• Edit your smart filter curves and, in RGB channel, place 2 points as displayed in the picture below, try to move the highest towards left and the lowest towards right to increase the contrast
• 
• Here you can see the final result.
• 

thanks to Jessica for helping me with translation.