Graphics Plus/Graphics Plus.iso/general/procssng/compstol/cmpsttl1.lha/CompositeTool/v1.1.adoc/CompositeTool.ch.3.a

Text File | 1990-05-08 | 31.8 KB | 880 lines

3.1    CompostieTool Frames


NCSA CompositeTool    3.1


National Center for Supercomputing Applications

April 1990






3.1    NCSA CompositeTool

CompositeTool Frames    3.1

National Center for Supercomputing Applications

April 1990




5/2/90




Chapter 3    CompositeTool Frames



Chapter Overview
Base Frame
Canvas Frame
Frame Manipulation
Grid Frame
Palette Frame
Colorbar Frame
Text Frame
Image Frame
Contour Frame
Vector Frame
Features Frame
File Utility Frame
Display Photographs

Chapter Overview

This chapter discusses the options available in the CompositeTool
frames: Base, Canvas, Grid, Palette, Colorbar, Text, Images,
Contours, Vectors, Features, and Utilities.


Base Frame

The Base frame (Figure 3.1) appears on the screen when
CompositeTool is invoked, and remains up for as long as you run
the program. The frame includes 13 options as displayed below:
Canvas, FinalPic, Clear Palette, Grid, ColorBar, Text, Image,
Contour, Vector, Feature, FileUtil, and Quit. Notice that when you
choose a Base frame button option that displays new windows, the
selected button disappears from the Base frame. This feature
prevents you from opening more than one window of the same type.
The buttons reappear on the Base frame when their corresponding
windows are closed.

Figure 3.1  Base Frame


Canvas
The canvas button opens up a new canvas. (See Chapter 1,
"CompositeTool Basics.")


Final Pic
The Final Pic button erases the canvas and draws everything that
has a FinalPic toggle setting of ON. This button applies to stored
data, not to the currently displayed data.


Clear
The Clear button erases the displayed contents of the canvas, but
not the canvas itself.


Palette
The Palette button opens the palette frame.
Grid
The Grid button opens the grid frame.


ColorBar
The ColorBar button opens the colorbar frame.


Text
The Text button opens the text frame.


Image
The Image button opens the image frame.


Contour
The Contour button opens the contour frame.


Vector
The Vector button opens the vector frame.


Feature
The Feature button opens the image, contour, and vector features
frame.


FileUtil
The FileUtil button opens the file utility frame.


Quit
The Quit button closes the CompositeTool application.


Canvas

Before you can load any images, contours, or vectors into
CompositeTool, you must first open a canvas frame. To do so, click
the Canvas button on the Base frame.

NOTE:  When CompositeTool reads program setting files from the
FileUtil frame, you do not have to have the Canvas frame opened.
However, you do have to open the canvas and click the FinalPic
button before the setting file composite will appear on the canvas.`

When the canvas opens (Figure 3.2), it is considerably smaller
than full screen size, since you are actually only viewing the top
section of the complete canvas frame.

Figure 3.2  Canvas Frame



You may load in data, manipulate text, and perform all
CompositeTool functions regardless of the size of the canvas,
although you may not be able to fully view the results until the
canvas is enlarged. To do so, use the right mouse button as
explained in the section "Mouse Buttons" in Chapter 1. When
selecting an option from the SunView Frame Selection menu in
this manner, use the Fullscreen option rather than the Zoom option
in order to ensure both vertical and horizontal expansion. At any
time, you can return the canvas to its original, smaller size by
selecting the Unzoom option on the SunView Frame Selection
menu.

NOTE:   In order to remain oriented to the absolute nature of the
canvas size, use the grid (refer to this chapter's section "Grid
Frame") while laying out a display.

In its entirety, the Canvas frame  is 1152 horizontal pixels by 900
vertical pixels. The canvas frame border is 5 pixels wide on every
side, leaving a canvas of 1142 horizontal pixels by 890 vertical
pixels available for your use.

Finally, note that the origin of the canvas is always in the upper
left corner, and this origin is absolute (that is, the canvas cannot be
scrolled up and down or from side to side).

To take a photographs of the canvas and its contents of it, using the
negative to make 35mm slides see this chapter's section
"Photographing Your Display." In order not to detract from the
final presentation-quality screen display, the Canvas frame does
not contain a title bar.


Frame Manipulation

Most CompositeTool frames are set up so that you work through
their options as outlined below; however, you do not have to strictly
adhere to these steps.

1.    Select the desired frame from the Base frame.

2.    Enter the specifications for your image in the frame (e.g. pixel
size, pixel color range, palette, tag, and filenames, etc.) by
positioning the mouse beside the available options. Click the
mouse to move the prompt to that point, and type the values in.

3.    Click the DRAW it or ERASE it buttons to view the image with
the specifications you have just entered.

4.    Click STORE displayed values or DISCARD displayed values to
store or discard the most recently entered values.

5.    Click FinalPic toggle to ON in order to permanently save the
most recently entered values and to view them when you press
the FinalPic button in the Base frame. Click FinalPic toggle to
OFF to not save values.

6.    Click Done in the opened frame to close it.

7.    Click FinalPic in the Base frame to display the new image.


Grid Frame

The Grid (Figure 3.3) frame is intended as an aid in layout while
developing the canvas image. You can turn on the grid (via a
toggle) during development, and once you are satisfied with the
layout, turn it off before drawing the final picture.

Figure 3.3  Grid Frame

Defining Grid Color
The Color variable defines the color of the drawn grid. The Color
number is a palette entry index into the current palette and must be
in the range (0-255). See this chapter's section "Palette Frame"
and Chapter 2's "Raw Palette Files."


Defining Grid Spacing
The Pix/x-grid and Pix/y-grid variables refer to the pixel spacing
between x and y grid lines. In addition to the x (horizontal) and y
(vertical) lines, an "x" is drawn on the canvas in such a way that
the diagonal lines meet at the exact center of the canvas. During
development of the canvas picture, you may have only a part of the
canvas visible. The "x" serves to orient the center of the canvas
when you open the screen to full-size.


FinalPic toggle
This ON/OFF toggle applies to the FinalPic button on the Base
frame. The current setting is shown on the button. If OFF, the
newly entered values for the grid will not be drawn when the
FinalPic button is pressed. If ON, the new grid will be drawn when
the FinalPic button is pressed.


STORE displayed values
The numerical values shown for grid color and spacing (in pixels)
are stored, replacing the previously stored values.

NOTE:  Just because you enter values in a frame or have
CompositeTool draw your image specifications by pressing the
DRAW it button, numerical values ARE NOT SAVED. Once the
frame is closed, the most recently entered values are lost and the
last stored values are restored. Thus, you MUST press the STORE
displayed values button before pressing FinalPic in the Base
frame for CompositeTool to save and display the new values.


DISCARD displayed values
DISCARD displayed values discards the numerical values shown
for grid color and spacing (in pixels) and replaces them by the
most recently stored numerical values.


DRAW it
DRAW it draws the grid using the numerical values shown for
color and spacing (not the currently stored numerical values).
Only one grid can be drawn at a time. This means that the current
grid is always erased before a new one is drawn.


ERASE it
ERASE it erases the grid by filling it in using the current canvas
background pixel value which you've specified in the Palette
frame.


Done
The Done button closes the Grid frame. If you've entered any
values without pressing the Stored Displyed values button to store
the data, a message appears on the screen asking you to confirm
this decision. This feature helps prevent accidental loss of newly
entered data.


Palette Frame

The Sun Workstation uses the RGB (red, green, blue) color model,
where each of the three primary colors can take 256 distinct
gradations, ranging from no color to full color. A single byte,
consisting of 8 bits, is used to distinguish the 256 possible values of
gradation. These gradations are stored in arrays (one for each
primary color), and when a color is displayed on the screen, the
Sun combines the gradations for the three primary colors to form
the color displayed. For example, a high gradation of red and
green plus a low gradation of blue will produce a shade of yellow.

Each array that stores the gradations of the three primary colors is
256 bytes long, and the elements of each array are completely
arbitrary. That is, the levels of color gradation (the elements of the
arrays) may be in any order, with duplicates and omissions
allowed.

The three arrays used to store the gradations of the three primary
colors are collectively referred to as the palette. Once a palette has
been defined (that is, once the three arrays have been loaded), the
colors that are displayed on the screen are referred to by number (0
through 255), representing the element number of each of the red,
green, and blue arrays. For example, referring to pixel value 8
means that element number 8 of the red array plus element
number 8 of the green array plus element number 8 of the green
array are to be combined to form the color displayed on the screen.

CompositeTool provides on startup an initial palette, which you
may change at any later time. When loading your own palette,
note that elements 0, 253, 254, and 255 are reserved. Element 0
(canvas background color) is set to white. Element 255 (canvas
foreground color) is set to black. Element 253 (set to black) and
element 254 (set to white) are used for other purposes. When a
palette is loaded, CompositeTool will change these elements
accordingly, no matter what values you assign. Refer to Chapter 2,
section "Raw Palette Files," for more information on palettes.

NOTE:  You are advised not to use the color definitions in the
.sunview file in the home directory. If colors are defined, then
moving the cursor into and out of CompositeTool windows will
cause an irritating flash on the screen, and the CompositeTool
canvas will not be viewable unless the cursor is inside the canvas.

Figure 3.4  Palette Frame

Load palette
Load palette allows you to enter a filename which CompositeTool
finds when you press the option's button. If the file is a "raw"
palette then it must be a stream of 768 bytes. The first 256 bytes
represent the gradations of red, the next 256 bytes represent the
gradations of green, and the final 256 bytes represent the
gradations of blue. Otherwise, it must be an HDF file with a palette
in it and the equivalent data is extracted from the first palette in the
file. Note that the palette data is actually stored "interleaved," that
is red byte, green byte, blue byte, etc. in an HDF file.

Load background color
Load background color allows you to specify the canvas color when
you enter a number between 0 and 255 and press the button. A blank
field is interpreted as 0. The color chosen is based on the current
palette. Note that you must click the FinalPic button before
CompositeTool changes the canvas' background color.


Done
The Done button closes the frame. If you have entered any
information without pressing the button to store the data, you are
required to confirm the choice by pressing the button again. This
feature helps prevent accidental loss of data.


Colorbar Frame

The Colorbar visually displays the range of colors in the palette.
The appearance of 2D images can vary substantially depending on
the palette currently being used, and the colorbar allows you to have
some basis for palette comparison. (See this chapter's section
"Palette Frame" for more information on palettes.)

Figure 3.5  Colorbar Frame

X/Y points and X/Y origins
X/Y point options allow you to designate the width and length size
of the colorbar while the x/y origins options determine the
horizontal and vertical screen position of the bar. The number of
x-points (i.e., the width) is arbitrary, and should be based on
visibility. Since the colorbar is displayed vertically, 256 y-points
will display every allowable color. If the number of y-points does
not equal 256, linear scaling of the colorbar is performed. This
scaling has no effect on the palette. The colorbar origin is in pixels
from the upper left of the canvas.


Show color
Show color displays the numerical value of a particular color.
Specify the color value, which corresponds to a palette entry in the
current palette, and click the button. A "<" symbol appears on the
right edge of the displayed colorbar. The arrow points directly at
the color representation of the value you've entered. For example,
suppose you enter 100, which in this example will represent a
certain shade of red, in the Show color option. An arrow will appear
on the colorbar, pointing directly at the associated color of red.


Standard Buttons
Refer to this chapter's section "Grid Frame" for a description of the
FinalPic toggle, and the STORE displayed values, DISCARD
displayed values, DRAW it, and ERASE it buttons.


mouse mv
The mouse mv (mouse move) allows you to move a drawn colorbar
by using the mouse (instructions appear as a message on the base
frame when the button is pressed). When you move a colorbar, the
move is based on the currently shown numerical values (not the
stored values), and the currently shown numerical values are
updated to correctly indicate the new colorbar location on the
canvas. To deactivate the move capability, select the button again.

NOTE:  The arrows ("<") that point to specific colors on the
colorbar (see explanation in the section "Show color" above) do not
move from their original position on the screen. Thus, when you
move the colorbar, the arrows remain stationary.


Done
The Done button closes the Colorbar frame.


Text Frame

The Text frame gives you the ability to add text to a screen display.
By doing so, you can easily differentiate between several images
that have been simultaneously displayed or label a display for a
presentation-quality slide.

Figure 3.6  Text Frame


Tag Selector
Tag Selector allows you to alter the text number. CompositeTool is
capable of displaying a number of texts simultaneously, and these
texts are distinguished by attaching a tag to each one. The current
tag is shown in the frame label, and when the text frame is brought
up from the base frame, tag 't0' is always displayed. You can
increment or decrement the currently shown tag by either one or
five, with the text frame label always showing the currently
displayed tag. When you increment or decrement the tag number,
the effect on the displayed information is the same as if you pressed
the Done button; i.e., you are warned that the previous information
will be lost. (For additional information, see Chapter 1
"CompositeTool Basics.")


Copy data
The Copy data option saves you the trouble of re-entering repetitious
information (especially color and font). By selecting a tag and
pressing the Copy data from text tag button, you copy the
characteristics from this previously defined tag, leaving only the
new text body and origin to be entered. Press STORE displayed
values and then the DRAW it button. The copy process is now
completed.


X/Y Color and Origin of Text
Ñ    Color
    The Color entry refers to the pixel value of the drawn text. This
number is a palette entry index into the current palette and must
be in the range (0-255).

Ñ    X/Y Origin
    These variables define the origin, in pixels, of the lower left-
hand corner of the text string.


Standard Buttons
Refer to this chapter's section "Grid Frame" for a description of the
FinalPic toggle, and the STORE displayed values, DISCARD
displayed values, DRAW it, and ERASE it buttons. Refer to this
chapter's section "Text Frame" for a discussion on the buttons Tag
Selection and Copy data from text tag.


Text and Fonts
Text and Font variables define the body of the text and the font to be
used, respectively. A default font is supplied by CompositeTool. It
is in the User Defaults Database for CompositeTool and can be
changed by running defaultsedit  in SunView or editing
$HOME/.defaults. To activate the new default font, you must
restart CompositeTool.

You may find out what fonts are available by listing all the
elements in the given font directory (these elements are the fonts
available).


mouse mv
The mouse mv (mouse move) button allows you to move text by
using the mouse. (Follow the messages that appear on the Base
frame after you've pressed the mouse mv button.) When you
depress the left mouse button, a small box, which you can move with
the mouse, appears on the screen. Drag the square to the desired
location on the canvas, being aware that the lower left-hand corner
of the box will define the position of the lower left-hand corner of the
text. When you release the left mouse button, the text moves to the
new location and the box disappears. The move, as reflected in the
Base frame, is based on the currently shown numerical values (not
the stored values). The current values are updated to correctly
indicate the new text location on the canvas. To deactivate the
mouse move capability, select the button again.


Done
The Done button closes the Text frame.

Image Frame
CompositeTool determines the characteristics of your data from the
entries you've made in the Image frame (Figure 3.7). Refer to
Chapter 2, "Formatting Your Data Files" for a discussion of data
file formats for input data.

Figure 3.7  Image Frame

Standard Buttons
Refer to this chapter's section "Grid Frame" for a discussion of the
FinalPic toggle, and the STORE displayed values, DISCARD
displayed values, DRAW it, and ERASE it buttons. Refer to this
chapter's section "Text Frame" for a discussion on the buttons Tag
Selection and Copy data from image tag. Refer to the section
"Colorbar Frame" for a discussion of the mouse mv button.


X/Y points and origins
The X/Y points and X/Y origins define, in pixels, the dimensions
of the two-dimensional data and its origin on the canvas,
respectively.

The X/Y points are never used for an HDF file. The dimensions in
the file are always displayed and replace any entered dimensions.


File
The File entry requires that you enter the name of the data file to be
displayed.


Done
The Done button closes the Image frame.


Contour Frame

The Contour frame (Figure 3.8) resembles the Image frame, except
that the contour algorithm plots in the former are user-specified
contour intervals in your data, rather than individually plotted
data points as in the latter.

Figure 3.8  Contour Frame


Standard Buttons
Refer to this chapter's section "Image Frame" for a discussion of
features not outlined below.


Contour levels
Ñ    Start/End color
    Allows you to designate the start and end contour colors [pixel
values in the range (0-255)] for the input data .

Ñ    Contour interval
    Allows you to designate the interval between the contour levels.
Note that large files (for example, of dimension 256 x 256) with
contour intervals close together (for example, intervals of 4)
may take a long time to plot.


Color
The Color entry (a pixel value) allows you to define the color of the
lines drawn within the contour plot. The pixel value is a palette
entry index into the current palette and must be in the range
(0-255). See this chapter's section "Palette Frame" for more
information on palettes.


Done
The Done button closes the Contour frame.

Vector Frame

The Vector frame (Figure 3.9) allows you to plot 2D data in a vector
format, using two files as input. One file contains x-component
data, the other, y-component data. These files are displayed by
CompositeTool as the vector magnitude sqrt(x*x + y*y) with
angle arctan(y/x). This feature is useful when displaying data
with real and imaginary components.

Figure 3.9  Vector Frame


Standard Buttons
Refer to this chapter's section "Image Frame" for information on
the features not discussed below.

NOTE:  Two data files (one for the x-component and one for the y-
component)are required, rather than just a single file, as for
image data. If the x-component is stored in the first image set and
the y-component is stored in the second image set in an HDF file,
only the x-component filename is required. Any combination of
raw and HDF files are possible for the data files.


Color/Scale data
Ñ    X/Y color value
    Color=0 refers to an image data value (from 0 through 255) that
is defined as zero. All numbers less than this value are
negative, and all numbers greater than this value are positive.
You must define these values for both the x-component file and
the y-component file.

Ñ    X/Y Scale
    Allows you to define the x-component and y-component
magnitudes relative to each other. This is the only place in
CompositeTool where floating point numbers are used. When
entering the scales, you must use fixed decimal notation
(e format is not accepted).
Ñ    Vector color
    Defines the color of the lines drawn in the vector plot. The color
value is a palette entry represented in the current palette which
is defined in the range (0-255). (For more information on
palettes, see the section "Palette Frame").

Ñ    Max length
    Refers to the maximum pixel length of the longest vector in the
data; all other vectors are scaled down in magnitude with
respect to this maximum.


Points on image
The Points on image feature refers to the location of data within the
x-file and the y-file that are to be displayed. For example, if X-start
is 10, X-end is 200, and X-interval is 60, then vectors will be
displayed for image data points 10, 70, 130, and 190 in the
horizontal direction, applying to every row for which Y-start, Y-
end, and Y-interval are defined.

If Y-start is 20, Y-end is 30, and Y-interval is 10, then vectors will
be displayed for ordered data pairs:  (10, 20), (70, 20), (130, 20),
(190, 20), (10, 30), (70, 30), (130, 30), and (190, 30). Vectors will not be
displayed for any other points in the image files. The vector
magnitudes, angles, and color are as defined in the Color/Scale
data.


Done
The Done button closes the Vector frame.


Features Frame

The Features frame (Figure 3.10) allows you to copy features from
other tags and apply them to a current tag, as well as annotate 2D
data with several commonly used visual features:  axes, grid
lines, and major and minor tick marks.

Figure 3.10  Features Frame



Select
The Select button applies to any image, contour, or vector tag. You
must explicitly enter the appropriate tag to which this feature will
apply and then press the Select button. Specifications for image,
contour, and vector tags are shown in their respective frames.


Copy
The Copy button allows you to copy the features of any image,
contour, or vector data, once you have defined those features (fonts,
color, etc.). You can copy image features from contour features,
other image features, or vector features.


Features ON/Features OFF
The Features ON/Features OFF toggle turn axes, grids, and tick
marks on or off en masse.


DRAW it/ERASE it
DRAW it and ERASE it draw and erase the current features in the
usual manner. For a discussion of how these buttons work, refer to
this chapter's section "Grid Frame." These buttons draw or erase
only the features (specifications of the image, contour, or vector),
not the actual data image, contour, or vector that is being
annotated.


Axes, Grids, and Tick Marks
Axes, grids, and tick marks may be set on or off individually. To
change the current settings for any of these, press the ON/OFF
button located next to the desired option. The chosen feature will
change from lower case to upper case, and information on the
feature appears in the lower part of the frame. You can now change
the selected item's characteristics. For example, after selecting the
x-axis button, you would position the mouse in either the Thickness
or Color slider bar, and click at the desired location. The bar will
adjust itself by extending only to the point you've clicked. Notice
that the Thickness and Color values, located to the left of the bars,
also reflect the value of the area you have chosen.

Ñ    Axes
    Allows you to adjust the thickness and color of axes using
sliders. The buttons allow you to set the top and/or bottom axis
on/off (for the x-axis), and the left and/or right axis on/off (for
the y-axis). When you click x-axis or y-axis, sliders appear at
the bottom of the Features frame.

Ñ    Grids
    Allows you to adjust the thickness, color, and spacing of grids
using sliders. Figure 3.11 shows the sliders that appear at the
bottom of the Features frame when you click x-grid. (The
Features frame appears similarly when y-grid is chosen.)

Figure 3.11    Feature Frame with
X-Grid Selected


Ñ    Tick Marks
    Allows you to adjust the thickness, color, spacing, and length of
major and minor tick marks using sliders. x-tic1/y-tic1
specify the x/y major tic marks while x-tic2/y-tic2 specify the
x/y minor tic marks. Figure 3.12 shows the sliders and buttons
that appear at the bottom of the Features frame when you click x-
tic1. (The Features frame appears similarly when y-tic1, x-tic2,
and y-tic2 are chosen.)

Figure 3.12    Feature Frame with
X-Tic Selected


    The bot side ON and top side ON buttons allow you to set the top
and/or bottom tick marks on/off (for x-ticks) and the left and/or
right tick marks on/off (for y-ticks), respectively. The now IN
button, which toggles to now OFF, allows you to draw tick marks
into or out of the data region.


Done
The Done button closes the Features frame.


File Utility Frame

The File Utility frame (Figure 3.13) allows you to store
CompositeTool sessions for later use, retrieve sessions previously
saved, and saves all or part of the Canvas frame (screen dumps) in
a file in one of three ways: (1) as an image and its palette as an
HDF 8 bit Raster Image Set, (2) as a compressed image and its
palette as an HDF 8 bit Raster Image Set, and (3) as an image
without a palette as a raw raster image.

Figure 3.13  File Utility Frame


File
The File button names the output file (for the WRITE, SAVE ALL,
and SAVE PART buttons), or the input file (for the READ button).


Write
The WRITE button stores the current CompositeTool session to a
file. Only the CompositeTool session variables are written (not the
actual data files themselves), so the file requires very little space.

NOTE:  The file is stored with all filenames specified by full
pathnames. Composites may be moved around as long as all files
referred to in the session file have been copied to the directory and
are at the same level as the session file.


READ
The READ button loads a CompositeTool session from a file.

NOTE:  If the reading of a session file fails and this is due to a
wrong absolute path of one or more files, copy those files to the
directory at the same level as the session file. You may find all the
filenames used in the composite by searching the session file with
a text editor.


SAVE ALL
The SAVE ALL button initiates and completes a screen dump of the
whole Canvas frame using the file format you've specified from
the File Format options. (See "File Formats" below.)


SAVE  PART
The SAVE PART button initiates and completes a screen dump,
based on the start and end points shown and the file format you've
specified from the File Format options. (See "File Format" below.)


X and Y Pixel Ranges
This option allows you to chose the pixel range representation of the
x and y values. You may either enter the x and y start and end
points explicitly, or load the points using the mouse. To use the
mouse, press the button labeled "Load start and end points by
mouse", and follow the instructions given in the message on the
Base frame.


File Format
Select the file format for a screen dump by clicking the circular
arrows at the bottom of the File Utility frame. In Figure 3.13, the
circle is labeled with the default format "Save palette and image as
HDF 8-bit Raster Image set." This label changes as you repeatedly
click the circular arrows using the left mouse button. Eventually,
the name of the file format in which you want to save your image
appears. The selections available include the following:  (1) Save
palette and image as HDF 8 bit Raster Image Set, (2) Save palette
and compressed image as HDF 8 bit Raster Image Set, and (3) Save
image only as raw raster. (Refer to Chapter 2, "Formatting Your
Data Files" for more detailed information on saving files.)


Done
The Done button closes the File Utility frame.


Display Photographs

Like NCSA Layout for the Macintosh, CompositeTool makes it
easy for you to take presentation quality photographs of your
display. You can use a film recorder directly interfaced into the
computer, such as a Dunn or Mirus, or a 35mm camera to
photograph your displays. This section contains some suggestions
to help you take quality photographs of your display using your own
camera.

1.    Select a film with a speed of 100 ASA. NCSA photographers have
had good results with Kodak Ektachrome 100 (daylight
balanced) film.

2.    Set up the camera on a tripod directly in front of the screen. If
possible, use a cable release with the camera to minimize
shaking.

3.    Make sure the camera is aligned squarely in front of the
monitor (see Figure 3.14).

4.    If possible, use a narrow, or telephoto, lens. Wide angle lenses
tend to distort the image, whereas telephoto lenses actually
flatten it. The distance at which you set the camera will depend
on the focal length of the lens.

5.    Photograph in the darkest environment possible, to reduce
reflection from the monitor.

    NOTE: Since the dimensions of a Sun screen (see this chpater's
section "Canvas") are not proportional to those of a 35mm slide,
a small area of the monitor will probably be included in full-
screen slides. However, if the film is shot in a room-darkened
environment, this area will appear as black on the slide.

6.    Focus on a slightly larger area than what you want for the final
display, since the slide holder will probably obscure the
periphery of the slide.

7.    Select a slow shooting speed. Speeds of 1/60 of a second and
faster are too fast for the refresh rates of most screens, and often
capture a refresh line on film. A typical exposure setting for
most computer screens, using ASA 100 film, is about f2.8 at 1/4
second.

8.    If you have an exposure meter on your camera, use it in the
following manner: Put a large mid-gray image on your screen;
that is, a gray which is roughly half way between the white and
black of your screen. (You can use a solid color, or even an
image, if you can safely say that the overall brightness is mid-
gray╤not always an easy judgment.) Take an exposure
reading from this screen.

9.    Photograph the same display at different exposures to ensure
that a properly exposed image is captured. This method of
shooting, called bracketing, is especially important when you
are using slide film, which is very sensitive to light changes.

Figure 3.14    Side and Top
Views of Photo
Display Setup