Advanced Photo Enlargement Processing
for Digital Photos
By: Mike Kruske
 I
have specialized in the processing and printing of
digital photographs since 1997, and since 1999, have
fine tuned that specialty to wide format digital
photo printing. I must say, the technical
advancements in digital cameras, digital image
processing software and digital photo printing
systems is absolutely amazing. In the past couple
years, these technical advancements have taken leaps
and bounds in print output capabilities.
Most individuals who have ventured into the world of
digital photography in recent years, have a somewhat
working knowledge of computers. They usually know
how to get their latest photos from the storage card
to their computer's hard drive, and printed out on
their desktop printer. Beyond that, well who cares
as long as the photo prints look OK.
Many of these individuals have even gone so far as
to delve into the subject a little deeper, and have
read or heard about the resolution needed for good
quality prints, a bit about file types, and even
touched base with a version of Adobe Photoshop to
process and enhance their works of art. This is all
fine and dandy, but the problem that arises is that
most of the knowledge they seem to collect in their
search, is either outdated or dished out by those
who sound like they know more than they actually do.
While it is true that you need a certain level of
image file resolution to produce a fine quality
photo print, how that level of resolution is
achieved is another matter. Digital photo printing
should be done with an image file that is at 200 to
300 dpi minimum, (actual term would be ppi for an
input file, or pixels per inch). As important as the
digital photo's resolution is to achieve this
resolution and print output size without resampling
the original digital photo file to produce this
resolution and print size. The absolute finest
quality photo prints will be produced with the
unresampled, original photo file.
To produce the larger print sizes now available on
the affordable medium format digital photo printers,
requires photo enlargement techniques. Most people
simply open the original photo file in their version
of Photoshop, and resize the file by entering the
width and height dimensions, resolution dpi they
want, leave the resample option checked and click
the OK thinking all is just great. This will
resample the photo file and degrade the original
image quality. Photoshop uses a simple bicubic
resampling method to resize the file. This method
actually recreates and artificially produces new
pixels for a higher image resolution and larger
print size. This is the action that degrades the
original image.
The Photoshop resampling will have to work if that's
all you've got. If your photo enlargement is not too
big, the degrading of the image may not be too
noticeable. If you require photo enlargements much
larger, or prints in the range of 16x20 and larger,
simple file resampling will not produce quality
results. That is why you hear all over the Web that
very large print sizes are just not possible, even
from the newer high resolution digital cameras. NOT
SO! I print and ship photo enlargements as large as
40x60 from 6 megapixel cameras and guarantee
customer's satisfaction. Have never had one
returned!
To achieve high quality photo enlargement of digital
photos requires a slight shift in processing
thinking and a certain file handling methodology.
You will also need to purchase additional digital
processing software, besides your image editing
application such as Photoshop. One application is a
Photoshop plug-in utilizing fractal technology for
image resolution boosting called Genuine Fractals.
The second application, and most important, is a
very high quality RIP software, or "Raster Image
Processing" program that will reprocess input files
before printing. RIP software is available, and
highly recommended, for use with all medium format
and large format digital printers where photo
enlargement is the rule of thumb. Most quality RIP
software applications today also include complete
color management features, along with many other
amazing editing and enhancement features.
Instead of preparing your digital photo for printing
using Photoshop, you will only use this program to
set up the file for photo enlargement and perform
some sizing and cropping functions, and any image
enhancements. Any required photo enlargement and
image resolution building will be performed with
Genuine Fractals. Digital processing to a proper
output resolution will be done with the RIP
software, which does a much, much better job of
resampling the photo file than Photoshop. There are
some enhancing functions that should not be
performed on the image file until after the photo
enlargement is at target print size. Read more photo
enlargement tips here.
The best way to describe this advanced photo
enlargement methodology is to walk through an
example photo enlargement using a standard high
resolution digital camera with a set large format
target print size. For this example I will use a
Canon 6.3 megapixel digital camera format with a
3072x2048 pixel dimension and a target print size of
30x40. This target print size will require photo
enlargement and photo cropping.
Please note that the RIP software I will be using in
this example will reprocess the final set up file to
a resolution of 360 dpi before sending to the
printer. It is best to use a set up dpi that is an
even variable of the final reprocessed dpi. The
lowest set up resolution I use for large format
photo enlargement is 90 dpi. The key to the finest
quality photo enlargements is to never resample the
file in Photoshop.
Using Photoshop CS and photo in landscape
orientation:
Start by opening the original photo file in
Photoshop CS then:
Click image > image size
uncheck resample and enter "90" in the resolution
field.
Produces an image: width 34.133 in. x height 22.756
in. at 90 ppi.- OK
Save in Genuine Fractals file format - encoding
lossless.
Open the same file in the Genuine Fractals format.
You will note the same image specifics from the
Photoshop sizing.
For the width and height fields select "inches" and
enter: height- 30 and width- will automatically be
45. For width and height fields re-select
"percentage" and you will see a photo enlargement of
131.836 % is required for this print size at 90 ppi.
- Click OK
Please note that Genuine Fractals states photo
enlargements up to 400% are possible, but experience
has taught me that to maintain original image
quality, it is usually best to keep this photo
enlargement percentage within a maximum of about
225%. The quality of the photo enlargement depends
on the pixel density of the original file.
Resave this processed file in a Photoshop format (.psd)
or .tif format.
Re-open .psd file in Photoshop CS. To crop for the
30x40 print size without resampling this file:
Select crop tool > enter in the crop tool
parameters:
Width - 40 in height - 30 in, and resolution 90.
Drag the crop tool over the entire image and click
view > snap to > document bounds, to keep the crop
lines within the edges of the image. Click crop
check mark to set crop.
You now have an image that is 40"w x 30"h at 90 ppi.
Now is time you would want to apply any image
enhancements to the photo enlargement, and the very
last function would be to sharpen the image using
the unsharp mask filter.
Send the photo enlargement to the printer through
the RIP software and the image will be re-processed
to 360 ppi, and print with amazing original image
quality. We provide a chart of photo enlargement
capabilities by digital photo megapixel resolution
for an easy reference. All the photo enlargement
sizes are figured utilizing the processing
methodology described in this article.
Wide format photo enlargements yielding original
image quality are absolutely possible if the
original file is processed correctly and you avoid
resampling the image pixels in your image editing
software. Of course, high quality results require
the use of these advanced software applications and
this will also require reaching a bit deeper in your
pockets.
About the Author
Mike Kruske established PhotoArt Imaging Digital
Arts Center in 1997 specializing in Photo
Enlargement, Digital Photo Enlargement and Wide
Format Digital Photo Printing of Digital Images.
This targeted experience provides a unique insight
into digital photo processing for large format print
output. More info here:
PhotoArt Photo Enlargement and Digital Photo
Printing
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