SCANNING FUNDAMENTALS FifthTuna Data Workshop (TDW-5) 18-22 April 2011, Noumea, New Caledonia SESSION 7 SCANNING FUNDAMENTALS This is a brief presentation looking at what we might envisage a regional auditing system of tuna fishery data collection and management systems to involved (or comprise) … Oceanic Fisheries Programme (OFP) Secretariat of the Pacific Community (SPC)

Scanning Fundamentals – Session Overview This session will look at The technical details of scanning Common problems with scan image quality Some ways to resolve some scanning problems

Scanning Fundamentals – Technical Details The output and quality of a scan is determined by The scan resolution The scanning mode (Black and white, grayscale, colour) The file type (TIF, PDF, JPG) The brightness and contrast settings

Scanning Fundamentals – Scan Resolution Scan resolution is usually expressed as DPI (dots per inch) This represents how many dots, or pixels, are used per inch of the source document. Typical scanning resolutions are 150, 200, 300, and 600dpi For Example: An A4 page is 11.69 inches long, 8.27 inches wide(21.0x29.7cm) The number of dots used to create the scanned image can be shown in the following table: DPI Dots across page width Dots along page length Total dots on page 150 1,240 1,753 2,173,720 200 1,654 2,338 3,867,052 300 2,481 3,507 8,700,768 600 4,962 7,014 34,803,468

Scanning Fundamentals – Scan Resolution Less dots on the page means the dots are bigger, so scanned text will look ‘chunkier’ More dots on the page will mean the dots are smaller, so the scanned text will look smoother Example (from about 1/2 an inch on the page) 150dpi 200dpi 300dpi

Scanning Fundamentals – Scan Resolution Resolution Summary Higher DPI (more dots) is better, and gives a smoother and easier to read scan Higher DPI means more dots = bigger file size! 300dpi scan has 4 times more dots than 150dpi, so the file size can be up to 4 times bigger 600dpi scan has 16 times more dots than 150dpi, so file size also can be 16 times bigger. We find that the recommended scanning resolutions are: 300 dpi for Black and White scans (more on this next) 200 dpi for Grayscale scans If file size is not an issue, use 300 dpi

Scanning Fundamentals – Scanning Mode There are 3 main scanning modes Black and White Grayscale Colour These are often referred to by their ‘Bit Depth’ Bit depth refers to how many ‘bits’ are used per dot (or pixel) of the image, to record the colour. This affects the file size of the image. Scan mode Typical Bit depth # bits in an A4 scan at 300dpi Size in megabytes (uncompressed) Black and White 1 8,700,768 1.0 MB Grayscale 8 69,606,144 8.3 MB Colour 24 208,818,432 24.9 MB

Scanning Fundamentals – Scanning Mode The more bits there are to record the colour of a dot, the more colours can be shown, and the image will generally look better. Scan mode Typical Bit depth # Colours Good for Black and White 1 2 (black or white) Clear text documents Grayscale 8 256 shades of gray Documents Colour 24 16,777,216 Photos, magazines Others Scan mode Typical Bit depth # Colours 4-bit Grayscale 4 16 shades of grey 16-bit Colour 16 65,536

Scanning Fundamentals – Scanning Mode Black and White is by far the most economical in terms of file size, but will have problems when scanning images, or light pencil, because for every dot it must decide whether the dot is black or white. Grayscale is good for scanning images and light pencil Colour is not necessary for scanning tuna data Example: Grayscale B&W B&W dark

Scanning Fundamentals – Scanning Mode Scanning Mode Summary Higher bit-depth (more bits per dot (pixel)) is better, and gives a higher quality and easier to read scan Higher bit-depth means more dots = bigger file size! We find that the recommended scanning modes are: Black and White scans for logsheets that have clear and dark text Grayscale for pages that have been filled in with pencil, especially light pencil Slops uses 4-bit grayscale, to reduce the file size If file size is not an issue, use grayscale

Scanning Fundamentals – File types and compression There are a 3 different file types that are commonly used to save a scan TIF JPG/GIF PDF Characteristics: File type Multiple pages Best for scanning Notes TIF Yes Documents Good for document scanning JPG/GIF No Photos and Images Don’t use for scanning documents PDF Documents but OK for images Good for document scanning, usually embeds the scan as a TIF file

Scanning Fundamentals – File types and compression The files usually use ‘compression’ techniques to make the file size smaller without losing data. TIF has special compression algorithms for different scanning modes: Characteristics: Scan mode Compression algorithm Uncompressed file size (A4 page scanned at 300dpi) Typical compressed file size % of uncompressed size Black and White CCITT 4 1.0 MB 100 KB 10% 4-bit Grayscale LZW 4.1 MB 400 KB 8-bit grayscale 8.3 MB 800 KB

Scanning Fundamentals – File types File Types Summary TIF and PDF file types are best for scanning documents Using compression reduces the file size by about 90% Compression is usually automatic with scanning software, but sometimes is optional

Scanning Fundamentals – Brightness and Contrast The quality of a scan can be enhanced greatly using the brightness and contrast controls of the scanner These can be changed via the scanning software They can be used together for the greatest effect

Scanning Fundamentals – Brightness and Contrast Brightness Effects Brightness Setting Effect -100% Scan is totally black and is unreadable -50% Scan is darker, lighter text will be easier to read but page is gray. 0% Scan is normal brightness +50% Scan is lighter, light text might disappear +100% Scan is totally white and is unreadable

Scanning Fundamentals – Brightness and Contrast Contrast Effects Contrast Setting Effect -100% Scan is totally black and is unreadable -50% Scan is darker, lighter text will be easier to read, page is gray 0% Scan is normal +50% Scan is lighter, light text might disappear +100% Scan is totally white and is unreadable

Scanning Fundamentals – Brightness and Contrast Combined Brightness and Contrast Effects Brightness Setting Contrast Setting Effect 0% Scan is normal -40% +50% Scan is enhanced, light text is darkened but page is white -80% +100% Light text is greatly enhanced, page still looks white

Scanning Fundamentals – Brightness and Contrast Example: Brightness -50% Contast + 75% Original Brightness -50% Brightness +50%

Scanning Fundamentals – Brightness and Contrast Brightness and Contrast Summary The scan image can be enhanced using the brightness and contrast controls You can adjust the darkness of an image using either the brightness or the contrast control (e,g, set to -50%), but the entire page will become darker Adjusting brightness darker, and contrast higher, makes the text on a page darker (e.g. pencil), while keeping the page white Brightness and contrast have greatest effect on Grayscale images Slops automatically adjusts brightness and contrast for grayscale images, to enhance the image Note: The best brightness and contrast settings will vary from scanner to scanner. For the Canon DR-2010C, the best setting is Brightness -80%, Contrast +100%, but this will not necessarily work best with other scanners

Scanning Fundamentals – Common Problems The most common problems with scan image quality are The writing is not visible The writing is visible but difficult to read The file size is too big The scanning software is confusing or difficult to use The scans are saved with only one page per file

Scanning Fundamentals – Common Problems The writing is not visible Causes The source document has been filled in with a light-coloured pencil The scanner settings need to be adjusted How to fix Scan the document in grayscale Adjust the brightness and contrast to enhance the writing Use darker pencil In SLOPS, choose one of the ‘grayscale’ templates

Scanning Fundamentals – Common Problems The writing is visible but difficult to read Causes The scanning resolution is too low The scan image is not dark enough How to fix Increase the resolution of the scan Adjust the brightness and contrast to enhance the writing

Scanning Fundamentals – Common Problems The File size is too big Causes The scanning resolution is too high The file hasn’t been ‘compressed’ How to fix Reduce the resolution of the scan Save using the appropriate compression algorithm (e.g. CCIT 4 for black and white TIF files)

Scanning Fundamentals – Common Problems The scanning software is confusing or difficult to use A lot of scanning software are complicated and can be difficult to use Hopefully this presentation will explain some of the technical terms you will encounter with scanning software and make it easier to follow SLOPS takes the complication out of scanning, so it is recommended to use this software The scans are saved one page to a file (i.e. if 40 logsheets are scanned, the result is 40 files, rather than 1 file with 40 pages) The scanning software settings need to be changed

Scanning Fundamentals – Summary The main elements of are scan are Scan resolution, in dpi, e.g. 200dpi, 300dpi. Scanning mode (related to bit-depth), e.g. black and white, grayscale. The file type, TIF, PDF. Brightness and contrast settings, to enhance the writing in a scanned document

Scanning Fundamentals – Summary OFP Recommended settings Logsheets that are clear to read and have dark writing Black and white, 300dpi, multi-page TIF or PDF Scans filled in with pencil and / or on waterproof paper (e.g. port sampling or observer samples) Grayscale, 200dpi (or 300dpi), multi-page TIF or PDF Brightness and contrast set to enhance writing Recommended software SLOPS, which makes scanning easier by applying all the settings for you (resolution, scan mode, brightness and contrast, file type, compression)