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Sunday, January 23, 2011

Photoshop Tutorials : Lesson # 1 = Scanning, saving and set-up

To scan images into your computer, you need a scanner attached to your computer
and scanning software installed onto your computer. Scanning software is supplied
with the scanners, often Photoshop.  You can also buy Photoshop independently.

To scan a picture
1. Place the original material on the scanner glass. It should be face-down. Your
scanner manual will tell you which way round to put it.
2. Launch the scanning software: Photoshop, Photo Deluxe, ScanWise, etc. If you
already have Photoshop running, you can launch the scanning package from
within Photoshop by choosing File > Import > and select the scanning package
(eg ScanWise).

3. Your software may automatically preview (scan) your document so that it
appears on the right hand side of the scan window. If not, you will need to  click
a Preview button to pre-scan the document.
4. The scanning software will automatically select options for destination, image
settings, file format, etc. You may change this if you wish from the buttons on
the left hand side of the scan window.
6. Click the Scan button.
7. Save the image in the desired format (see page 7). If your scanning package was
launched from within Photoshop, your image will automatically appear in a
Photoshop window.

What scanning software is installed on the PWF Macs and PCs?
Graphics; Agfa ScanWise (can also be invoked from within Photoshop)
Text; TextBridge Pro (full-featured), OmniPage LE (basic, limited features)

Scanner/Photoshop error messages
Scanner could not be detected: caused by the computer powering-up before the
scanner or by a poor cable connection. Shut down everything, check  cables and start
again. If problems persist,  contact the Helpdesk, or your local support.
Scratch disc full/clipboard full/Photoshop out of memory:
1. These messages may be caused by the Clipboard being full with a large image.
To avoid this, if you Cut, Copy or Paste a large image,  immediately afterwards
copy a small image twice.
2. Free-up hard disc space as Photoshop uses the hard disc as temporary storage
space. If using a Mac with OS 9 or previous,, turn Virtual Memory off and
restart the Mac. OS X manages memory in a better way so this problem is less
likely especially if your Mac has a huge-sized hard disc.
3. With pre OS-X Mac, assign Photoshop enough memory (highlight application,
choose File > Get Info > Memory and allocate at least 64Mb RAM for
Photoshop 6.0 and 128Mb if you also want to use ImageReady, Adobe’s web
production software bundled with Photoshop 6.0).
Cannot complete the requested operation: caused by having the wrong layer “live”
(for more info please see Layers page 10) or by Photoshop running out of memory
(memory fragmented).  If out of memory, close down and restart the computer.

Work in Photoshop must be saved after every operation. It is surprising how much
space even a quick, simple operation such as changing a background colour can take
up. Never carry out more than one operation on a file without performing a save.

Pre OS-X Macs: Virtual Memory and Scratch Disk
Photoshop is a hungry application and uses lots of computer memory (RAM). During
each operation it also temporarily uses empty space on the hard disc (Scratch Disk).
Virtual Memory (virtual RAM) also uses empty space on the hard disc. Only enable
Virtual Memory if you have lots of empty hard disc space.  Real RAM is better and
quite cheap to buy.

File size and resolution
Big is not always best: an A4-sized colour photo scanned at a resolution of 300 dots
per inch (dpi) takes up 28Mb! PostScript printing adds another 50% to the file size.
Where will you keep it? How will you transport it? Using a lower resolution reduces
the file size.  Set your resolution according to the end use of your image and output
Screen use (eg. web page): 72dpi
Posters, monochrome, line art: 100dpi
Colour printing in documents: 150dpi
High quality printing/microscope enlargements: 300dpi or higher

If you need eventual output of several images on one page, scan each as a separate
file. Then paste both images as pictures into PowerPoint, Word, PageMaker or
Quark.  This makes the eventual file size smaller because the “white space” around
the images in Word is blank whereas in Photoshop it contains information.
Always crop extraneous material from the borders of images (see page 13). If you
want a white border, copy and paste the picture into Word and then print  it.  (Word
ignores empty white space whereas to Photoshop, every space is recorded as
information, even if blank).
Use RGB as your colour format unless you require colour separations at printing time
(in which case use CMYK).  CMYK is not available in Photoshop LE, a cutdown
version of Photoshop often supplied with scanners.

File formats
1 Photoshop (.psd): for “working” images in Photoshop
2 TIFF: for exporting to other printing applications.  (24bit colour, loss-less
compression possible, channel masks saved).
3 PICT: for exporting to other printing applications (Mac only).
4 JPEG: for exporting tone-based web-images. Note, JPEG compresses the file
by losing file information so file cannot be reworked.
5 GIF: for exporting line-based web-images
6 PNG: emerging web standard to replace JPEG and GIF but not widely used yet.
6 EPS: encapsulated Postscript, for printing or inclusion in printed materials.

Configuring Photoshop on your computer
• Use a computer with powerful processor, large memory and hard disc
• Do not run other applications at the same time
• Pre OS-X Mac:-  allocate Photoshop plenty of RAM (64Mb for Photoshop only,
   128Mb for Photoshop and ImageReady* to run concurrently)
 - only enable Virtual Memory if enough empty hard disc space.
• PCs and OS X Macs automatically set the above settings for their applications
• Save after every operation in Photoshop to minimise scratch disc use

thank's for your attention.

(to be continued to lesson #2)

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