Adobe Photoshop 7.0 for Photographers
34
Ideally this information needs to be known before the image is scanned (or digitally
captured). Because if you calculate that only 10 MB worth of RGB data will actually
be required, there may be no point in capturing more image data than is absolutely
necessary. If the printer’s specification is not available to you, then the only alterna-
tive is to scan or shoot at the highest practical resolution and resample the image
later. The downside of this is that large image files consume extra disk space and
take longer to process on the computer. If a print job does not require the images to
be larger than 10 MB, then you’ll want to know this in advance rather than waste
time and space working on unnecessarily large files. On the other hand, designers
like to have the freedom to take a supplied image and scale it in the DTP layout to
suit their requirements. Use the ×2 halftone factor, and there will be enough data in
the supplied file to allow for a 20% scaling without adversely compromising the
print quality.
Inkjet output resolution
I said earlier that the pixel resolution of an image should be clearly specified using the
numbers of pixels per inch (ppi) so as to avoid confusion when using the number of dots
per inch (dpi) to describe the imagesetter output resolution (although sometimes dpi is
used to refer to the number of halftone cells per inch). Inkjet printers also use the term
Figure 2.3 The New document dialog.
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Resolution
35
‘dots per inch’ to describe the output resolution of the printer. The dpi output of a typical
inkjet will range from 360 to 2880 dpi. And although this is a correct usage of dpi, in this
context the dpi means something else yet again. Most inkjet printers use similar methods
to lay down a scattered pattern of tiny dots of ink that accumulate to give the impression
of different shades of tone, depending on either the number of dots, the varied size of the
dots, or both. The principle is roughly similar to the halftone process, but it is not really
the same. If you select one of the finer print resolutions such as 1440 or 2880 dpi, you
should see smoother print outputs when they are viewed in close-up. The optimum pixel
resolution should ideally be the printer dpi divisible by a whole number. The following
pixel resolutions could be used: 144, 160, 180, 240, 288, 320, 360. To make large inkjet
prints for viewing at a greater distance, use a low pixel resolution. For smaller sized
portfolio prints I normally use a 240 ppi pixel resolution. I doubt very much you will
notice any improvement in print quality if you choose a resolution that is higher than this.
Creating a new document
If you want to create a blank new canvas in Photoshop, go to the File menu and
choose New This will open the dialog shown in Figure 2.3. In Photoshop 7.0 you
can select a new preset setting. This will automatically configure the physical size
dimensions for your new image. However, Photoshop will not adjust the resolution
for you, this must be entered manually. Advanced users can create their own custom
document size presets by going to the Presets folder and following the instructions in the
New Doc Sizes.txt document and editing the values for the height, width and units.
Altering the image size
The image size dimensions and resolution can be adjusted via the Image Size dialog,
shown in Figure 2.4. By default the dialog will open with the Resample image box
checked. This means that you can enter new pixel dimension values to increase or
decrease the image size. Or if you enter new physical dimensions, or change the
image resolution, you can also increase or decrease the image size (and you will see
the pixel dimensions adjust simultaneously). Remember the rule I mentioned earlier:
the number of pixels = physical dimension × (ppi) resolution. You can put that rule to
the test here and use the Image Size dialog as a training aid to help understand better
the relationship between the pixels, dimensions and resolution. The constrain pro-
portions checkbox links the horizontal and vertical dimensions, so that any adjust-
ment is automatically scaled to both axis. Only uncheck this box if you wish to
squash or stretch the image when adjusting the image size. Any adjustment made to
the image will not alter the total pixel size. If you adjust the dimensions the resolu-
tion value will adjust to compensate and vice versa.
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Adobe Photoshop 7.0 for Photographers
36
When Resample Image is checked the image can be enlarged or reduced by making
the number of pixels in the image greater or smaller. This resampling is also known
as interpolation and Photoshop can use one of three methods when having to assign
(approximate) values for any new pixels that are generated. The interpolation options
are located next to the Resample Image checkbox. Bicubic interpolation provides
the best image quality when resampling continuous tone images. Photoshop will read the
values of neighboring pixels, vertically, horizontally and diagonally to calculate a
weighted approximation of each new pixel value. In other words, Photoshop guesses
the new pixel values, but does so with a modicum of machine intelligence. Bilinear
is a less sophisticated form of interpolation, reading only the horizontal and vertical,
neighboring pixels. Nearest Neighbor is the simplest interpolation method and yet I
use this quite a lot, such as when I want to enlarge a screen grab of a dialog box for
this book by 200% and I don’t want the sharp edges of the dialog boxes to appear
fuzzy.
I consider ‘interpolating up’ an image in Photoshop to be preferable to the interpola-
tion methods found in basic scanner software. Digital files captured from a scanning
back or multishot digital camera are extremely clean, and because there is no grain
present, it is usually possible to magnify a digitally captured image much more than
you would to a scanned image of equivalent size. There are other programs like
Resolut and ColorShop which are used to good effect when interpolating digital
capture files. Interpolation works most effectively on a raw scan – one that has not
already been pre-sharpened. Unsharp masking should always be applied last as the
file is being prepared for repro. Interpolating after sharpening will enhance the im-
age artifacts introduced by the sharpening process. If you need to apply an extreme
Figure 2.4 To change the image output resolution without altering the physical size, check the Resample
Image box and enter a new resolution. To change image output dimensions without altering the
resolution, leave the Resample box unchecked. Auto resolution will help you pick the ideal pixel
resolution for repro work based on the line screen resolution.
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Resolution
37
image resize either up or down in size, I suggest you consider resizing the image in
stages rather than all in one go. Increase or decrease the resolution by 50 ppi at a
time. For instance, start with an image at 300 ppi (or make it 300 ppi in the Image
Size dialog box, with Resample Image checked) and reduce to 250 ppi, then 200 ppi,
till the pixel dimensions get close to the desired number. This is not something I
recommend you must do with every picture. I will probably only use this method when
sampling down a large image that is destined to appear prominently on a web page.
Once an image has been scanned at a particular resolution and manipulated there is
no going back. A digital file prepared for advertising usages may never be used to
produce anything bigger than a 35 MB CMYK separation, but you never know – that
is why it is safer to err on the side of caution – better to sample down than have to
interpolate up. It also depends on the manipulation work being done – some styles of
retouching work are best done at a magnified size and then reduced. Suppose you
wanted to blend a small element into a detailed scene. To do such work convincingly,
you need to have enough pixels to work with to be able to see what you are doing.
For this reason some professional retouchers will edit a master file that is around 100
MB RGB or bigger even. Another advantage of working with large file sizes is that
you can always guarantee being able to meet clients’ constantly changing demands.
Although the actual resolution required to illustrate a glossy magazine double-page
full-bleed spread is probably only around 40–60 MB RGB or 55–80 MB CMYK.
Some advertising posters may even require smaller files than this, because the print
screen on a billboard poster is that much coarser. When you are trying to calculate
the optimum resolution you cannot rely on being fully provided with the right advice
from every printer. Sometimes it will be necessary to anticipate the required resolution by
referring to the table in Figure 2.7. This shows some sample file size guides for
different types of print job.
Figure 2.5 If Image Size is proving too confusing, the Resize Image assistant is on hand to help guide
you. This wizard is located in the Help menu and can be used to resize images both for print and for
the Web.
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Adobe Photoshop 7.0 for Photographers
38
Figure 2.6 The above table shows a comparison of pixel resolution, megapixels, megabyte file size
and output dimensions at different resolutions, both in inches and in centimeters.
Figure 2.7 Here is a rough guide to the sort of file sizes required to reproduce either a mono or
CMYK file for printed use. The table contains file size information for output at multiples of ×1.5 the
screen ruling and ×2 the screen ruling.
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0002x0003 6 BM5.71 BM5.32 01x51 52x5.73 5.6x01 71x52
0052x0053 57.8 BM52 BM5.33 5.21x5.71 13x44 5.8x5.11 12x92
0582x0004 4.11 BM5.23 BM5.34 41x02 63x05 5.9x5.31 42x5.33
0023x0054 4.41 BM14 BM5.45 61x5.22 04x65 5.01x51 72x5.73
0004x0005 02 BM75 BM67 02x52 05x5.26 5.31x5.61 5.33x24
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Resolution
39
Practical conclusions
Amid all the conflicting opinions on how large a digital file should be, I find the
guidelines given by some of the photographic picture libraries instructive. Photogra-
phers who submit digital work are asked to supply digital files of around 40–50 MB
RGB. The thinking is that for the vast majority of picture purchases, these file sizes
will be ample and in fact the majority of pictures purchased are probably printed
using 20 MB of RGB data or less anyway. You can be sure that in any magazine
publication you care to look at, it does not matter how large the original scans were,
the same amount of digital information was eventually used to make the halftone
separations on each page you are looking at. There are photographers and also cli-
ents who insist nothing less than a high resolution scan from a 5 × 4 or 10 × 8 sheet
of film will provide good enough quality for advertising work. I do believe an over-
obsession with ‘pixel correctness’ gets in the way of appreciating just how good the
technical output quality can be from smaller format cameras or what can be created
on a modern computer desktop setup in the hands of a talented artist.
In theory the larger a picture is printed, the further away it is meant to be viewed and
the pixel resolution does not have to alter in order to achieve the same perception of
sharpness. There are limits though below which the quality will never be sharp enough
at normal viewing distance (except at the smallest of print sizes). It also depends on
the image subject matter – a picture containing a lot of mechanical detail will need
more pixels to do the subject justice and reproduce successfully. If you had a picture
of a softly lit cloudy landscape, you could quite easily get away with enlarging a
small image through interpolation, beyond the normal constraints.
An enormous industry was based around photographers supplying films to clients,
who made positional scans for layout purposes. They in turn then sent the film for
repro scanning at the bureau to make the final separations. Along comes a photogra-
pher armed with his or her computer loaded with Photoshop, offering to cut out a
large chunk of the repro process, supplying repro quality digital files themselves.
Tread on somebody’s toes once and they won’t like you very much. Stamp all over
them and they begin to squeal (loudly), especially if they believe you don’t have a
clue what you are talking about. Obviously, repro specialists should know best when
it comes to getting the best printed results, but remember they have a vested interest
too in keeping the likes of you out of the equation. This leads to occasional ‘spoiling’
tactics, designed to make you look foolish in front of the end client, but I reckon
companies with attitudes like these are dying out now. The smart businesses recog-
nize the digital revolution will continue apace with or without them and they have to
continually adapt to the pace of modern technology and all its implications. Besides,
repro companies have been getting into the supply of digital photography them-
selves and the boundaries between our industries are constantly blurring.
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40
Configuring Photoshop
Chapter Three
I
n order to get the best performance out of Photoshop, you need to ensure that your
computer system is well optimized for image editing work. When I first began
writing my Photoshop for Photographers series of books, it was very necessary
to guide readers on how to buy the most suitable computer for Photoshop work and
what hardware specifications to look for. These days I would suggest that almost any
computer you can buy is capable of at least running Photoshop at a basic level and
capable of being upgraded to run it faster.
As always, I try to avoid making distinctions between the superiority of the Macintosh
or PC systems. If you are an experienced computer user, you know what works best
for you and I see no reason to evangelize my preference for using a Mac. Throughout
my computer career, it’s what I have grown up with and it feels like home. The same
arguments apply if you’re a Windows PC user and apart from anything else, once
you have bought a bunch of programs, you are locked into that particular system. If
you switch, it means facing the prospect of buying your favorite software packages
all over again. And apart from anything else, the battle of the operating systems is
such a bore. Comparing like for like between the two systems may reveal marginal
speed benefits one way or the other as one system leapfrogs another, but the cost of
buying all the hardware for a Macintosh or PC system is going to be about the same
these days, especially since many computer peripherals share the same interface
connections. One of the key features of Photoshop 7.0 is that it has been adapted to
run on Windows XP and Mac OS X systems (more of which later). But first let’s
look at the basic hardware components of a computer system, what they do and how
they can be customized or upgraded to provide improved Photoshop performance.
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Configuring Photoshop
41
Buying a system
As I say, almost any new computer system you buy will be capable of allowing you
to run Photoshop. If you require state-of-the-art performance, then you will still have
to fork out big bucks. My main buying advice for beginners remains the same. If you
are new to computing and Photoshop, don’t splash out on a top of the range system
just yet. If you later decide image editing is not for you, then at least you can make
use of your computer for general purpose office use, linking to the Internet or shooting
down rogue asteroids. In a year or two you can either upgrade your current system or
purchase a machine that will probably be at least twice as fast as the most powerful
computers around today. And besides, even a basic system can include a pretty good-
sized monitor and plenty of opportunities for expansion. If you purchase a new
machine in a year or two, it will probably be at least twice as fast as the most power-
ful computers that are around now.
Today’s entry level computer will contain everything you need. For example, take
the Apple 500 MHz iMac. At the time of writing, this entry level iMac features a fast
G4 processor, has the CRT equivalent of a 17" resolution monitor, runs the Radeon
video card and has 128 MB of on-board RAM which can be upgraded to a maximum
of 512 MB. It’s got a fast 20 GB hard drive and the video performance is provided by
an ATI Rage 128 graphics card. Personally, I would probably want to add another
128 MB of RAM at the time of purchase and I would prefer working with a larger
screen, but otherwise it’s got quite enough to get you started. If you purchased the
basic 733 MHz Quicksilver G4 Macintosh, then this too has excellent specifications
for Photoshop work and its processor can be upgraded. Again, I would want to add at
least another 128 MB of RAM to take the memory up to 256 MB total. On the PC
side there are many more choices and I would say that without being able to pinpoint
any particular model, nearly all the basic packages will (like the iMac and the G4) be
able to satisfy all your basic Photoshop requirements. I shall be dealing with the
specifics shortly but I would assume that at the very least your entry level computer
should have the following: a fast Pentium III processor, 10 GB hard drive and 128
MB of RAM that can be expanded to at least 256 MB. If you are able to get all of this
and more, then you have yourself the beginnings of a powerful image editing system.
If you have acquired an old computer system (which in computer terms means more
than four years old!) you may encounter various problems such as a lack of
compatibility with the latest peripherals and find yourself with limited expansion
opportunities. Even so, converter devices are available to connect USB devices via
older SCSI or SDB ports. And you will also need a later version of the operating
system software. For example, Photoshop 7.0 will only run on Mac OS 9.04/9.1, Mac
OS X, or Windows 98, NT, ME, or Windows XP.
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Adobe Photoshop 7.0 for Photographers
42
Monitor display
The monitor is the next most important part of your kit. For Photoshop work, a
multiscan Trinitron or Diamondtron cathode ray tube (CRT) is best. I would advise
getting a 20"–22" sized screen, but there are also plenty of affordable 17" monitors
of this type on the market. I would not recommend you get anything smaller than this.
I am currently working with a 22" LaCie Blue screen monitor. This has a good sized
screen display and is supplied with a dark hood to help shield the surface of the
screen from extraneous light hitting the surface of the screen. The Barco Calibrator
is an expensive display screen, but it does feature sophisticated self-calibrating fea-
tures that ensure impeccable, consistent viewing conditions, which is very important
for good color management. This will be explained more thoroughly in the follow-
ing chapter.
Flat panel TFT type screens are also becoming more popular. The latest flat screen
displays are extremely comfortable to work with and the cost of these has come
down considerably in recent years. A major benefit of these is that they are physically
smaller in size and therefore occupy less desk space. But the problem with TFT
screens is they are mostly nigh on impossible to calibrate for consistent color output.
The color and brightness of the display can vary enormously as you adjust your
angle of view relative to the screen. Someone jokingly suggested that monitor
calibration of a TFT screen could be possible, so long as you were prepared to wear
a head brace that locked your head position relative to the screen! There are exceptions
though. The Apple 22" Cinema display does have a fairly consistent screen output at
a range of viewing angles. Silicon Graphics have also had a similar type of TFT
screen, designed for prepress work, on the market for a few years now. You cannot
attach a normal calibrator device with suckers to the delicate surface of a TFT screen
but it is possible to get special TFT screen calibrators that use a simple cantilever
device to allow gravity to gently press the calibrator against the angled surface of the
display.
If you are able to run two monitors from your computer, then you might want to
invest in a second, smaller screen and have this located beside the main monitor and
use it to display the Photoshop palette windows and keep the main screen area clear
of palette clutter. To run a second monitor screen you will need to buy an additional
PCI card that can provide a second video port. The drawback of second monitors is
one of calibration. Since both monitors will share a single monitor profile, the profile
used can only be correct for one monitor only.
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Configuring Photoshop
43
Video cards
If Photoshop is accused of being slow, in comparison to dedicated high-end image
editing systems that is not so much a fault of the software, but rather the architecture
of the computer used to run Photoshop. You have to realize that desktop computers
are designed to perform all types of tasks. This jack-of-all-trades compromise is one
thing which separates the desktop computer from other dedicated high-end systems.
However, most modern desktop computers have PCI expansion slots on the
motherboard. These allow you to add dedicated cards to the basic computer, and
these allow you to convert it to a customized workstation for broadcast video edit-
ing, 3D modeling or professional image editing.
The view output on your monitor display is processed by a graphics card in your
computer. An accelerated graphics card will enable your screen to do several things.
It will allow you to run your monitor at higher screen resolutions, it will allow you to
view your display in millions of colors and it will also hold more image screen view
data in memory. When more of the off-screen image data remains in memory the
image scrolling is enhanced and provides generally faster screen refreshes. In the old
days, computers were sold with a limited amount of video memory. If you were
lucky you could just about manage to run a small monitor screen in millions of
colors. If you buy a computer today the chances are that it will already be equipped
with a good, high performance graphics card, easily capable of doing all of the above.
These cards will contain 32 MB (or more) of dedicated memory. If you need added
video performance, a PCI graphics card will fit in an empty PCI slot on a Mac or PC
computer. The Matrox Millennium, ATI Rage and the Formac ProFormance cards
are recommended good buys.
Extras
An internal 24× or faster CD-ROM drive is standard issue these days. Other things to
buy could include a second hard drive to use as a scratch disk plus a removable
media storage device such as the Iomega Zip drive or a CD writer. You need these to
back up your main hard disk and store all your image documents (the hard disk
should be kept as empty as possible). Removable media disks are ideal for transfer-
ring documents to a bureau for printing. Bureaux should be able to satisfactorily read
Mac and PC format files. If you are going to continue using any SCSI devices, check
to see if you need to install a SCSI card interface. If you are buying from scratch then
you need not worry about SCSI, as it is not going to be supported any more as
standard. USB and FireWire™ (IEEE 1394) are the latest connection standards
for peripheral devices. You can have up to 127 USB devices linked to a single com-
puter and you can plug and unplug USB devices while the machine is switched on,
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