Making Picasa Sliders Reduce Values

Picasa is a very neat, very quick, photo-processing tool, providing the tools to make most basic adjustments to photographs. For reasons known only at Google, many of the controls allow only increases in adjustment – you can’t make a decrease in the value. You can see this below, where the Fill Light, Highlighs, and Shadows sliders are all the way to the left.

Look at the Color Temperature slider though. It allows both increases and decreases in values. We’ll change the Picasa configuration file to make the other sliders mimick this behavior allowing both increases and decreases on the sliders. So now instead of just being able to darken shadows, we can now lighten them too, as well as being able to both intensify highlights and dull them, etc.

Step-by-Step

Here’s what you need to do:

Close Picasa. Don’t have Picasa running when you make these changes.
Make a copy of filterdesc.xml. This will be your backup if things go wrong, or you want to undo your changes. This is located in different directories for different operating systems:
- Windows: C:\Program Files\Google\Picasa3\runtime
- Ubuntu (running Wine): /opt/google/picasa/3.0/wine/drive_c/Program Files/Google/Picasa3/runtime
Edit filterdesc.xml using Notepad, or whatever non-Word editor you have. (In Windows you could right click on filterdesc.xml, select “Open with Notepad”.)

There are 3 sliders we’re going to change; we’ll add an offset value to the Fill Light, Highlights, Shadows sliders. (The Color Temperature already has a centered slider.) Look for the section labeled !-- TUNING2 new version with Kelvin color temp -- – about 1/3 of the way down the file. This is where the sliders are defined. Replace the existing section with this, which simply adds an offset value for the three sliders, giving us a basic centered slider:

    !-- TUNING2 new version with Kelvin color temp --
    filter id="finetune2" mode="soft" zerostate="zero"
        labelTuning/label
        cursor type="dropper" persist="0"/
        colorcircle id="0"/
        sliders
            slider id="0"
                labelFill Light/label
                range1.0/range
                offset0.5/offset
            /slider
            slider id="1"
                labelHighlights/label
                range0.48/range
                offset0.24/offset
            /slider
            slider id="2"
                labelShadows/label
                range0.48/range
                offset0.24/offset
            /slider
            slider id="3"
                labelColor Temperature/label
                range2.0/range
                offset1.0/offset
            /slider
        /sliders
    /filter

Save the file.
Restart Picasa.

Here’s what you should now see:

The Details

Each slider is defined with a number of settings. You’ll notice that in the original the sliders for Fill Light, Highlights, Shadows don’t have an offset value, whilst the Color Temperature does.

<label> defines the text label for the slider. No need to change this.
<range> defines the total amount of effect – the range between the upper and lower bounds. Changing from 1.0 to 2.0 will produce a much larger effect with the same movement of the slider.
<offset> defines the slider starting position. Typically you’d want the slider to start in the middle so set the value to 1/2 the value of range. You might also want to provide a little more room for increasing values, so set the slider to 1/4 of the value of range.

If you don’t set an offset the slider will start all the way to the left, basically the default behavior.

Alternate Settings

If you find the that moving the slider a little applies large changes and would like to make more use of the whole range of the slider, try these values (first number is range, second number is offset):

Fill Light:
```
range1.5/range
offset0.375/offset
```

Alternately:

Highlights:
```
range3.0/range
offset1.5/offset
```

I like to add some shadow to my images, so here’s what I prefer to use:

    !-- TUNING2 new version with Kelvin color temp --
    filter id="finetune2" mode="soft" zerostate="zero"
        labelTuning/label
        cursor type="dropper" persist="0"/
        colorcircle id="0"/
        sliders
            slider id="0"
                labelFill Light/label
                range2.0/range
                offset0.5/offset
            /slider
            slider id="1"
                labelHighlights/label
                range0.48/range
                offset0.24/offset
            /slider
            slider id="2"
                labelShadows/label
                range1.0/range
                offset0.5/offset
            /slider
            slider id="3"
                labelColor Temperature/label
                range2.0/range
                offset1.0/offset
            /slider
        /sliders
    /filter

FAQ

Error: Cannot create filterdesc.xml

In Windows Vista you might get an error “Cannot create the C:\Program Files\Google\Picassa3\runtime\filterdesc.xml file”, “make sure path & file name are correct”.

In Vista you must run with administrators rights in order to make changes to filterdesc.xml.

I don’t like the new settings

Simply delete the changed filterdesc.xml, and rename you backup copy back to filterdesc.xml.

Things went horribly wrong…

In the worst case you can reinstall Picasa. That should overwrite everything to new as it should be. Your previous settings will not be deleted – this is the same as what happens when you install a new version of Picasa.

References

This information was primarily based on prior posts from dpreview and Picasa Groups.