TIFF Questions and Answers


What is TIFF?

The tag image file format, or TIFF, is a way of storing and 
exchanging digital image data.  The image data typically comes 
from a desktop scanner, video digitizer, or paint program.  TIFF 
is not used for storing text or draw-type (object-oriented) 
graphics.


Why was TIFF created?

Aldus began meeting with leading scanner vendors (Datacopy, DEST, 
Hewlett-Packard, Microtek, and New Image Technology) in the fall 
of 1985 to discuss strategies for incorporating scanned images 
more effectively into desktop publishing.  The vendors were 
interested in a common file format for data exchange and 
encouraged Aldus to define such a format.  With the help of 
Microsoft, TIFF was developed.


Is the TIFF specification continuing to evolve or is it complete?

So long as scanner hardware continues to evolve, TIFF too will 
evolve.  The specification was designed to be dynamic, permitting 
incorporation of new features while minimizing the impact on 
existing hardware and software.  In keeping with TIFF philosophy, 
future changes will be compatible with existing software.


Is TIFF being interpreted differently by different developers?

As an option within the TIFF specification, developers (those who 
write TIFF and those who read TIFF) can choose to support some or 
all of the features within the TIFF format.  Therefore, if a 
product that reads TIFF files doesn't support all the features of 
TIFF, it will not be able to import files that include those 
unsupported features.  If a product that writes TIFF files 
supports, say, only one TIFF feature, those files can be placed 
into software applications that read either that single TIFF 
feature or all its features.


Can you transfer TIFF images from the PC environment to the 
Macintosh and vice versa?

Yes, TIFF was designed to travel across any machine architecture.


Are TIFF and gray scale the same thing?

No.  TIFF is a file format capable of representing several kinds 
of scanned data.  Currently, there are two kinds of TIFF data that 
PageMaker accepts.  One type is bi-level, or black and white, 
data, and the second type is gray-scale data.


Exactly what are gray-scale images?

Gray-scale images consist of a rectangular array of pixels.  Each 
of these pixels can represent one or more shades of gray.  The 
pixels of a gray image are usually 4, 6, or 8 bits deep, 
representing 16, 64, or 256 different shades of gray.  This makes 
gray-scale images particularly useful for storing photographs, 
which are made up of various shades of gray.


But even PageMaker 1.2 for the Macintosh placed scanned 
photographs.

Yes,. but there were disadvantages if the scanned image hadn't 
been saved in the gray-scale TIFF format.  First, unless you stuck 
to certain sizes, the image didn't print well.  Second, the image 
was often distorted on the screen, especially in the "Fit in 
Window" view, which made cropping difficult.  And third, the image 
didn't look any better printed on a high-resolution device than it 
did on a 300 dot-per-inch (dpi) laser printer.


Is there anything you can do to improve the image quality if you 
scanner doesn't save in gray-scale TIFF format?

Yes.  PageMaker has a feature called "magic stretch" that allows 
you to tailor the size of an image to the resolution of your 
printer.  By holding down the Control key on the PC or the Command 
key on the Macintosh while you resize an image, PageMaker 
automatically calculates the ideal image size in multiples of the 
resolution of your printer.


So what does gray-scale do for you?

Quite a number of things.  You can stretch the image to any size 
and it will look good when it's printed.  You can choose any page 
view in PageMaker and the image will look good on the screen - 
even without one of the new gray-scale monitors.  You get smaller 
file sizes and faster print times.  And on high-resolution 
typesetters like the Linotronic 100 you get top-quality images.


So, the gray-scale format works particularly well for high-
resolution output devices like the Linotronic, but does it really 
make a difference on a 300 dpi laser printer?

In general, the image quality of a photograph scanned at 75 dpi 
resolution and saved in the gray-scale TIFF format will be equal 
to, and sometimes greater than, the same photograph scanned at 300 
dpi and saved in the bi-level TIFF format.  Again, if you're 
working with a gray-scale image, you'll be able to size it more 
easily in PageMaker, keep your file sizes smaller, and print 
faster on a 300 dpi laser printer.


Does the printer have to be PostScript-compatible?

No.  Any printer that PageMaker supports can be used.


How long does it take a gray-scale TIFF image to print?

It depends on which printer you're using, how much data is 
transmitted to the printer, and the size of the area to be 
halftoned.  The time can range anywhere from one minute to an 
hour.


What resolution should I use to scan gray-scale images?

Gray-scale images can be scanned at a lower resolution than bi-
level images and still produce very good results.  If you are 
printing to a 300 dpi laser printer, scan the image 75 dpi, and at 
150 dpi for higher-resolution printers.  If you plan on 
substantially increasing the size of the image in PageMaker, you 
may have to scan at a higher resolution to avoid loss of detail.