You can find a very important dialog for configuring your scan in the very first place in your tool dock:
In this dialog, enter the name for your image along with the file path, select the file format and define the resolution for the scan. "Format" defines the dimensions for the output. If you select "user defined", the output format conforms to the format of the red frame in the preview.
The resolution is influenced by several factors:
The preset: The preset indicates the desired output resolution, particularly for printing later on. A conventional home printer is capable of up to 300 ppi, and this value is therefore set as standard.
The resolution slider: The resolution slider addresses the resolution supported by the scanner so that you can work without interpolation. The very last resolution offered is an interpolated one. Next to the resolution slide, you can see the resolution actually used for the scan.
There are several ways to work with this dialog:
Set fixed output size
As an example, let's take a scan of a 35mm slide that you want to enlarge to A4. The red frame is adjusted to the size of the slide which results in the displayed input size. You leave the preset at 300 ppi. Now manually enter the larger value in the appropriate field under Output, allowing for a small margin if necessary. The second value is automatically adjusted, preserving the aspect ration of the selected frame.
SilverFast automatically calculates the magnification factor and sets the resolution required to print at the selected 300 ppi in the selected output size. Of course, you can also switch from cm to pixels and specify a fixed pixel size, as is common with digital images.
Set resolution using the resolution controller
You can alternatively set the resolution by using the slider to set the output size. As an example, let's take the slide again. You want to print the image again afterwards, but you are not sure how large you can enlarge the slide without the quality suffering noticeably. Your home printer, prints at 300 ppi as in the previous example. You select your slide in Preview, so again you set 300 ppi as your output preset.
Now you slide the resolution slider to the right and you have the output size and the display next to the resolution slider in view. You now move the resolution slider further until the desired image size is reached. The output size and the resolution are linked and SilverFast automatically adjusts the other value when you change the resolution or the output size. When doing this, make sure that the resolution slides does not go into the red area if possible. The red area means that the resolution is interpolated. The red area indicates that the optical resolution of the scanner has been exceeded and an algorithm is enlarging the image by multiplying the existing pixels. This generates computational information that is not contained in the actual image.
Interpolation should only be used in cases where the additional size is actually necessary. Since interpolation can also be used after scanning, it makes sense to scan images at the maximum optical resolution and to use interpolation on a case by case basis. This reduces processing time and memory requirements.
So, if possible, move the slider to the orange range at most. The output size then shows up to which size you can print your image at 300 ppi without loss of quality and without interpolation.
A slide of 1.37 x 0.91cm is scanned and enlarged. An 8x magnification (800% zoom) allows an output size close to A4 format at an output resolution of 300 ppi.
Set resolution manually
However, it is recommended to enter the desired resolution manually in the box next to the Preset menu if you already know the resolution that you want to work with. To do this, leave the resolution slider at 300 ppi and zoom at 100%. If you now enter a value manually, this is displayed as a user-defined value in the Preset menu. The value given as the preset is also the one that is displayed when you open your image with another program following the scan.
Resolution slider or manually input?
If you work with the preset and the resolution slider (left screen), SilverFast saves the set print resolution for this in the file's metadata so that programs with which the image is later opened display the selected print resolution and output size. If you enter the value for the resolution manually (right screen), this value is stored in the metadata and is displayed later as the resolution when the images are opened.
The Scan Dimensions and Resolution dialog summarizes the relationships between input resolution, magnification, output resolution and output size in operable tools and provides a practical solution for most workflows by offering various ways to deal with resolution.