Printing
high quality digital photos.
January 2002.
All tradenames acknowledged.
Preface:
Digital photography is a
reality today. We can print
photos sitting at home without a
darkroom and without any
chemicals. Thanks to photoquality
2400 / 2880 dpi inkjet printers
and today's higher end megapixel
cameras which give us enough
resolution to make a life size
enlargement of a photo. The key
to enable all this happen is
really the software which we
would use to work with the
digital photo file on a computer.
We need to understand the
difficult concepts of a pixel,
dpi (dots per inch) etc. at least
to a working level. We also need
to understand that there is a
close relation between pixels,
dpi, file size and the final
printed size.
Basic concepts :
Pixel : A pixel
is the smallest well defined
piece of information in a photo
file. A pixel carries the
information of colour for a given
area. A pixel, square in size,
can be seen by a human eye on a
final printed output if the dpi
of that file is lower than say
100. Smaller the pixel in a
print, the higher or finer the
quality we get. Optimally the
pixels(dots) per inch should be
one fourth of the photo quality
dpi of the printer, i.e. if your
printer's dpi is 2400 then your
picture should have 600 pixels
per inch and so on.
DPI : The full
form of dpi is (1) dots per inch
if we are talking about a printer
and (2) pixels per inch if we are
talking about a photo file. The
printer always prints, say, 2400
dots per inch in photoquality
mode irrespective of the photo
file dpi. The photo file dpi is
only to let the printer know to
which size the photo is to be
printed. This means that if a
photo of 1200 pixels height X 900
pixels width has a dpi of 300,
then the printer will print 300
pixels of this photo per linear
inch (90,000 pixels per square
inch) with its 2400 dots per inch
resolution (roughly 2400/300 = 8
dots per pixels) and the final
size after printing will be
1200/300=4 inches height and
900/300=3 inches width.
File Size : This
is the memory space required on a
storage device. For a photo file
this varies with the colour
depth, dpi, file type etc. For
example a photo file of 3 inches
by 4 inches with 300 dpi will be
smaller than a photo file of the
same dimensions but with a dpi of
600. Similarly the file size will
increase with more colour depth
per pixel. A pure black &
which picture without any gray in
between can be saved with a
colour depth of just 1bit. For a
photo with all its continuous
colour tonal range the colour
depth has to be 24 bits i.e. 8
bits per colour (Red, Green,
Blue) per pixel. Considering this
a photo file of 1200 x 900 pixels
will have a size of 139 KB at 1
bit colour depth, whereas the
same file will have a file size
of 3,240 KB at 24 bit colour
depth.
File Type : The
information of each pixel in a
photo file is organised in
different ways in each file type
(format). There are many formats
like .bmp, .jpg, .pcx, .tif etc.
The .bmp format is Microsoft
Windows own format. This file
format can store photo
information at 24 bit colour
depth which is a must for the
true to life reproduction of a
photo. But this format at 24 bit
colour depth does not support
compression of information
(data). The file format of .jpg
also stores photo information at
a colour depth of 24 bit and it
also supports compression of
information although with a loss
of information depending on the
percentage of compression. The
compression algorithms used in
.jpg file are very complex. User
can decide between higher quality
- large file size and lower
quality - small file size. The
above mentioned photo file of
1200 x 900 pixels would be
approximately 247 KB at a
compression of 95% for .jpg after
loosing a little bit of quality.
Getting
better quality photos:
From the above information we can
assume that for a photo to look
like a photo, we need higher
pixels per inch printed with
higher dots per inch. But we
cannot know how to do that for
each and every photograph we need
to print. Many questions still
remain unanswered, like :
1. How to know the exact dpi of a
photo file?
2. How to calculate dpi with the
size of the photo I want to
print?
3. How do I relate pixels to
inches, millimeters etc.?
4. I want to print a photo in 5
inches x 7 inches but there is no
information available which can
tell me firmly that a given photo
file will print nicely at that
size?
5. What happens to a photo file
if I reduce the photo in size in
my photo editing software?
6. The photo becomes elongated
either horizontally or vertically
if I resize the photo using my
photo editing software. Why?
7. My photo looses sharpness
after reducing in size in my
photo editing software. Why?
8. What will happen if I want to
print a photo to a larger size
than my printer can print?
9. How do I protect the original
photo file from accidental saving
of changes?
And so on....
Along with the development of
inkjet printers and cameras,
there is also development in
software engineering for digital
image processing. With the proper
understanding of photographic
process and the needs of
photographers a new breed of
software for proper printing of
photos has come up. There is a
distinct difference between this
breed and all other photo editing
software. That is because those
photo editing software were
developed for printing and
publishing industry and not for
the photographer. Their
development started when there
were no inkjet printers or
digital cameras. That is why
'resizing' a photo is not an easy
task with them as also printing
multiple copies of a photo in a
row. There is always a chance
that if you resize a photo and
save it you almost always resize
the original photo file loosing
all its original details!!! Then,
you cannot open many photos at a
time and print them side by side.
Now let's have a look at that new
breed of photo printing software
- FotoReplica.
The main screen of FotoReplica
shows you the full final paper
preview with your selection of
photos arranged on it as they
will be finally printed. You also
see the full photo with its
cropped area for you to compose
the photo on-the-fly on one side.
You can also set the white margin
around photo with a slider. Flip,
rotate, zoom, compose etc. are
available at a single mouse
click.
FotoReplica uses all the pixel
information that is available
(Figure: 1) in the given photo
file. Typically a high quality
photo taken through a 3.1
megapixel camera contains
2160X1440 pixels. The internal
bitmap size of this image will be
9.3 MB. FotoReplica has the
capacity to print five such
images of passport size at a
time. This gives the photo
quality printed at more than 1000
dpi (dots per inch) because all
the 1440 pixels of the width will
be fit into the final photo width
of 1.377 inches (1440 / 1.377 =
1045 pixels per inch) and of all
the pixels in the height of 2160
pixels only 1852 pixels will be
printed within the height of the
final photo size of 1.771 inches
(this is because the photo is
automatically cropped to keep the
aspect ratio of 3.5 : 4.5 of a
passport size photo).
From this example we can see that
fotoreplica does the
"resizing" without
"resampling" the
original information contained in
a file.
Now consider the following - If
we try to print multiple copies
with all the above parameters
intact through a photo editing
software we will have to create a
file of 1045 dpi with 1852 pixels
height and 7530 pixels of width,
in which we will have to somehow
copy paste five copies of the
original picture (1) without
resampling (to make available all
the original pixel information
for the printer ) and (2) with
cropping to an aspect ratio of
3.5:4.5 (to print in the exact
passport size). The size of such
a file at 24bit true colour will
be 41.836 MB which cannot even be
opened by any software on a
standard desktop configuration.
Resizing and resampling
On the other hand, any photo/
picture has its own width by
height aspect ratio. If you want
to print that photo in some other
size of a given proportion
through a photo editing software,
then you will have to go through
many steps to finally print that
photo. First, you have to
resample the photo to fit to
either the height or the width
with your own choice of dpi for
optimum quality and working size.
Secondly, you will have to change
its paper size with "keep
aspect ratio" unchecked to
crop the photo to the exact size
that you require. Thirdly, For
all this you have to have a
working knowledge and know the
meaning of the terms like -
pixel, inch, millimeter, aspect
ratio, resizing, resampling, file
dpi, printer dpi etc. Finally,
the print you will get through
all this exercise will not carry
all the pixels that you captured
in your digital camera.
Working of FotoReplica
Aspect ratio: FotoReplica does
many tasks automatically without
user intervention. The cropping
to a given aspect ratio with
facility to compose the picture
within that size is the basic
thing required for photography.
In FotoReplica this is done
automatically without loosing
aspect ratio because you can zoom
in or compose the picture anyhow
without worrying about distorting
the photo, as the cropping
marquee expand or reduces only
diagonally.
Printing small size :
For small size printing
FotoReplica does not resample the
file information but actually
uses every pixel available within
the height or width depending on
the final print size aspect
ratio. This gives full justice to
the digital cameras / printers to
display their full potential.
Printing large sizes :
For larger size printing
FotoReplica uses interpolation
method so that no information is
lost as well as no big patchy
square pixels are seen to any
size of enlargement.
Printing large photos in
tiles : For enlargements
larger than the printer's maximum
paper size, FotoReplica
automatically tiles the photo
into several prints on the
selected paper size. You have the
choice to print any given tile at
a time or of printing all tiles
at a time. FotoReplica uses very
small amount of information at a
time for interpolation to enlarge
the image so that there is
virtually no limit for the size
of the enlargement. FotoReplica
also does not create big square
pixels on enlargement because it
interpolates the information to
make a 180 dpi file for printing.
Where as, in photo editing
software one can print an
enlargement to a certain size in
tiles, but he has to (1) print
all the tiles at a time. (2) If
there is any paper jam or with
some other problem you loose one
of the tiles, you have no other
choice than to print all the
tiles again, incurring a huge
expense of costly paper and ink
cartridges. (3) There is no
interpolation of information so
if your enlargement is really big
you are going to see big square
pixels in the photo. (4) There is
a size limitation with respect to
the working memory available on
the computer beyond which you
cannot enlarge the photo.
Preset Sizes :
FotoReplica has a list of preset
sizes which are commonly used for
printing of photos. So that you
don't have to resize photos every
time to a particular size.
FotoReplica takes care of putting
all the information available
through the camera into the
proportion of that selected size
filtering only the cropped
information
Auto load photo feature:
FotoReplica has a unique feature
of auto loading the latest photo
from the last opened directory.
This feature is very useful for
photo studios. In the
professional photo studio, where
I.D. card photos are taken often,
you do not have to select the
photo each time for printing. As
soon as the camera is connected
to the computer or the floppy
containing the photo is inserted,
FotoReplica detects (within ten
seconds) the latest photo taken,
and automatically loads it in the
passport size for four copies. As
soon as you click on any button
on the front screen or double
click on the photo for selection,
the auto load is disabled.
Clicking on Select size button
enables the auto load feature
again.
FotoReplica is a software which
retains all the pixels captured
by your digital camera even if
you want to print a small size
photo such as stamp or passport.
In conventional photo editing
software, if you resize the
original photo of say 1440 X 2160
pixels (3.1 mega pixel camera
output), to 35mm X 45mm passport
size, many pixels will be deleted
to accommodate the photo in the
smaller size. This will eat up
many details in the photo such as
a small highlight in the eye of
the subject.
FotoReplica has a built-in
feature, which retains all the
pixels and sends them to the
printer when printing, as the
printers are capable of printing
even 2400 pixels in one inch.
With this feature enabled,
FotoReplica seems to work a
little slower even for small size
photos but gives justice to your
camera and printer.
Conclusion :
The environment of a publishing
house and that of photo studio
completely differ from each
other. Though they both use or
work with photos, the role of a
photo vastly differs in both
these environments. Photos are
actually clicked in a photo
studio. The make ready of the
subject (e.g. a person) for a
photo takes its own time. The
photographer has to concentrate
more on proper artistic lighting,
exposure, aperture, shutter
speed, pose, composition etc. He
should require minimum time,
effort and learning when it comes
to printing of the photo.
Moreover the pains he has taken
to capture a fine picture in his
camera have to be justified by
the software and the printing
system he uses. He should require
minimum time for any printing
options and should save maximum
time to take photos to generate
more revenues.
Lastly, we can confidently
conclude that photo editing
software have no role to play in
a digital photo studio. Only
software like FotoReplica is
suitable for a digital photo
studio.
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