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One of the biggest challenges facing many
Photoshop users is maximizing compression while minimizing file
size. This is an especially tough balancing act when working
with photographs for the Web. Selective blurring can help.
Jpeg is still the file format of choice for
continuous tone Web images, such as the vast majority of photos.
However, jpeg is a lossy compression system -- it throws away
some of the image's data to reduce file size. The smaller the
file, the more lost data. (Gif and png are lossless compression
systems. They save all the data, but png files can't come close
to jpeg for size reduction.)
Because of the way jpeg looks at image data,
blurring an image can assist it in compressing the file. In
fact, Photoshop's Save for Web even has a blur feature built in.
(The slider allows for compression from zero to two pixels.)
Let's take a look at how blurring with Save for
Web affects file size. We took the same image and, using
otherwise the same jpeg settings, tried different amounts of
blur to check their effect on compression. The base image is a
photo 512 pixels by 341 pixels, with a size of 512 KB as a
Photoshop file. Jpeg's High Quality setting (60%) was used.
Under 30 KB is a good compressed size for this
image, but the price to pay to get there is high. The composite
image below shows the result of the various Save for Web blurs
on the two doggies' heads.
(The four images show the four levels of compression tested.)
There is, certainly, another way to drop the
file size below 30 KB. By increasing the amount of jpeg
compression we can continue to shrink the file. To break the
30-K barrier, this particular image needs a jpeg setting of 22%
in Save for Web.
(The poor doggies!)
So we know blurring is good for file
compression, but bad for poor Madison and Hugo. Why not have the
best of both worlds? We're Photoshop people, we know how to make
masks and selections and stuff! There's no reason why the grassy
background can't be blurred while the dogs stay in focus.
Making a mask of the dogs isn't too difficult
using Select> Color Range, since the green of the grass does not
appear in our subjects. The mask doesn't need to be too precise
either, because this will be a Web-based image, viewed only on
screen at 100% magnification.
Once we've isolated the dogs, we can blur the
background with a Gaussian Blur of 1.5 pixels. The effect is
visually-pleasing and, with the same 60% jpeg quality, reduces
the file size from 67.57 KB to a tidy 32.84 KB, less than half
as large. But not quite our target size of under 30 KB.
But wait! There's more! We can sneak this image
down even further by combining our blurs. After we've blurred
the original image 1.5 pixels in Photoshop with Gaussian Blur,
we can use the blur feature in Save for Web to take it down
another 0.5 pixel. That gives us a minor savings to 29.54 KB
without any noticeable change to the image quality.
As can be imagined, this technique works most
effectively with detailed backgrounds. The more large color
variations in small areas, the more trouble jpeg compression can
cause you. A bit of blur can also head off those tell-tale 8
pixel by 8 pixel blocks that jpeg creates. (What I call,
none-too-fondly, "the blockies.") *****
SIX SHOOTERS:
--Perhaps the most important addition to Photoshop 6 for most
users will be the improved typographic capabilities. In addition
to the Options Bar, your text-creation interface will include
the Character palette, the Paragraph palette, and dialog boxes
for advanced justification and hyphenation.
(Yes, Dorothy, you're not in Kansas anymore. But you are still
in Photoshop!)
--Another of the text-related features that's
sure to get some applause is the Warp text capability.
Yeah, it's fun! --Photoshop 6 has a few minor
cosmetic changes that will take a little getting used to. The
Pencil tool and the Paint Bucket both got demoted in the
Toolbox. They're now under the Paintbrush and the Gradient tool,
respectively. The old Line tool is no more. It's been added to
the Shape tools. (Photoshop 5 users: did you know the Line tool
could do arrowheads? Check the Options palette.) And, for the
record, it will no longer be the Rubber Stamp tool, but the
Clone Stamp tool. (Yeah. Sure. Whatever.) |