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Reduce the number of History states
In Photoshop CS3, each history state that includes an operation
that affects the entire image (for example, when you apply Gaussian
blur or unsharp mask to the entire image) creates a full copy of
your image at its original size. If your initial image is 500 KB,
and you apply Gaussian blur to it, your image will need 1 MB of
scratch space. If your history states consist of operations that
affect only part of the image, such as paint strokes, only the size
of the tiles touched by the strokes are added to the image size. If
you count up the number of histories you have where operations have
affected the entire image, and multiply your original image size by
that number, you'll have an approximate amount of scratch disk
space needed by the image. If you have applied levels, a reduce
noise filter, and an unsharp mask filter to your entire image 5 MB
in size, the image will need 20 MB of scratch space. When you
reduce the number of History states available, you potentially
reduce the number of copies of your image using scratch space.
Reduce patterns and brush tips
If you need to reduce your scratch disk overhead, you can
minimize the number of patterns and brush tips you use in each of
your presets, and you can reduce the number of patterns you use in
your image's Layer Styles (as applied with the Bevel and Emboss
Texture or in the Pattern Overlay). Each small pattern and sampled
brush in the presets uses at least one tile for storage. Patterns
used in Layer Styles use extra RAM as well.
Minimizing the number of layers
Layers are fundamental to working in Photoshop, but they also
increase file sizes and redraw time because Photoshop recomposes
each layer after each change in the image. After you have completed
changes to layers, you can flatten (merge) them to reduce the size
of a file. You should also make sure to remove blank layers from
the file since they too increase its size. It is important to
remember that Photoshop does not let you separate layers after
merging them. Instead, you can either use the Undo command or you
can use the History palette to reverse a merge.
- To flatten all layers in a file, choose Layer > Flatten
Image.
- To merge a layer with the layer below it:
- In the Layers palette, select the layer above the layer with
which you want to merge it.
- Choose Layer > Merge Down.
Flattening TIFF files
Photoshop allows layers to be saved in TIFF files. Layered TIFF
files are larger than flattened TIFF files and require more
resources for processing and printing. If you work with a layered
TIFF file, save the original layered file as an Adobe Photoshop
(.psd) file; then, when you are ready to save the file in TIFF
format, save a copy without layers.
Using image compression
Although compressed files generally have small file sizes,
Photoshop may take longer to open or save them. With the exception
of images saved in Photoshop format, Photoshop must decompress a
file to open it and then recompress the file to save it. The BMP,
CompuServe GIF, JPEG, Photoshop, Photoshop EPS, Photoshop PDF, and
TIFF formats all can be saved with compression. In addition,
Photoshop enables you to specify a compression method for TIFF
layers in the TIFF Options window. You can improve performance by
saving your file in compressed Photoshop format (a compression
format in which there is no data loss) as you work, and then save
your file in the format you want when you are finished editing the
image.
To save an image without compression from Photoshop, choose File
> Save As, select the format you want, and then select the No
Compression option in the format Options dialog box. For example,
select the TIFF format, and in the TIFF Options dialog box, select
None for Image Compression.
Editing individual channels
Photoshop requires less memory to apply a filter to a single
channel than it does to apply a filter to multiple channels or to
an entire image (composite channel). In a flattened image, each RGB
channel is about one-third the size of the file; each CMYK channel
is about one-fourth the size. To edit a single channel, select the
channel you want to edit in the Channels palette.
Using the Filter Gallery and applying filters to
individual channels
The Filter Gallery in Photoshop CS3 allows you to test one or
more filters on an image before applying the effect(s), which can
save considerable time.
Dragging and dropping between files
Dragging and dropping layers or files is more efficient than
copying and pasting them. Dragging bypasses the clipboard and
transfers data directly. Copying and pasting can potentially
involve more data transfer and is much less efficient.
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