Top 5 Scanning Mistakes

Top 5 Scanning Mistakes

Whether you’re using a mobile phone scanner app or a multi-purpose office machine, try to avoid these Top 5 scanning mistakes.

1. Scanning to the wrong resolution

At the top of our list of Top 5 Scanning Mistakes is using the wrong resolution.

Scanning resolution is measured in dots per inch (DPI). In simple terms, the bigger the value the sharper your image will be. However, a bigger DPI value also means a bigger file and a slower scan, so it’s essential to find a good balance.

It is almost universally accepted that 300 DPI is sufficient for standard text documents (provided that the text size isn’t absolutely tiny) so this should be your standard setting.

If you are scanning a detailed document that contains small text (eg. a map or an architectural plan) or important detailing (eg. a photograph) you should probably use a higher DPI setting for that document so that the detail can be legibly read from the scan.

Sample Resolution Output

2. Scanning to the wrong colour scheme

Broadly speaking there are three options here: Black and White, Greyscale, and Colour.

Black and White will scan a document to two colours – black and white.

Greyscale will scan a document to many shades of grey.

Colour will scan a document to full colour.

Scanning in colour will produce a larger file than scanning in greyscale, which in turn produces a larger file than scanning in black and white.

If you use the ‘colour’ setting when scanning a black and white file (eg. a letter) you will end up with a much larger file than you need.

If you use the ‘black and white’ setting to scan a greyscale picture (eg. a monochrome photograph) you will lose a lot of detail and your scan will be of little use to you.

Greyscale vs Black and White
Greyscale (L) and Black and White (R)

3. Incorrect Orientation

If you’re using an unfamiliar scanner it can be hard to know which way to place the document that is being scanned. This leads to upside down or sideways scans, which can be very difficult to read later.

If you’re using an unfamiliar scanner I’d recommend scanning a test page first to see what the output looks like. Better to do that than to run a 100-page scan only to find the whole thing is upside down.

If you can’t run a test scan then you can use software (see our course on PDF Manipulation) to rotate the pages after the scan is complete.

4. Accidental Cropping

This happens most often when you are using a mobile phone or tablet as your scanning device. It can be difficult to exactly capture the document/image you want to scan, which can lead to accidental cropping (by which I mean accidentally cutting out part of the document you are trying to scan).

For a very small fee you can obtain excellent scanning apps for mobiles and tablets that will automatically detect the borders of the document and crop your scan perfectly for you.

I use a free app called CamScanner and paid a small licence fee to access the full features. It’s extremely handy to have in my pocket and it gets regular use when documents are handed to me on the fly (in court, at meetings). Here are two screenshots showing how CamScanner detects the borders of a document and, one click later, crops the scan perfectly.

5. Slanty Scans

These happen for one of two reasons – (i) the page has not been laid correctly on the scanner, or (ii) the page feeder (if your scanner has one) is set too wide and is allowing the pages to be drawn into the scanner at a slight angle.

To avoid slanty scans either (i) lay the page carefully on the scanner at the outset, or (ii) always check that your page feeder is set at exactly the right width.

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