Intro Digital Imaging

Intro to

Photoshop

Michael E. Stern
PHOTOGRAPHY EDUCATION CONSULTING
CyberStern.com

Photoshop
is a math program that allows any practitioner create art.

A bit-map image is made up of tiny picture elements aligned
vertically and horizontally along a raster grid. These picture
elements are often referred to as pixels. There can be hundreds,
thousands or millions of pixels in a bit-mapped image. Continuous
tone images like photographs are better served using pixels.

The number of pixels present in an image is determined at the
moment of creation (scanning or photography) and limits the size
and quality of the output. The more pixels in an image the better the
quality. A bit-map image is resolution dependent.

Each pixel is actually computer code, ones and zeros. In the Info
Palette we see it represented as a number. This number controls the
brightness value (luminosity) and color value (chrominance) of each
and every pixel at its location on the grid

Editing pixels affects output quality and therefore must be done with
great care by using specific tools.

Michael E. Stern
CyberStern.com

Photoshop

Grain Dot Pixel

Michael E. Stern
CyberStern.com

Photoshop

A vector image is described by math coordinates and can be scaled up or down
many times without affecting its’ quality. A vector is not resolution dependent.

Vectors are usually logos and text, things that are used many times in various
sizes and shapes. Vectors are very flexible this way. Pixels are not.

Michael E. Stern
CyberStern.com

Photoshop

By activating its Tools, Filters, Adjustment Layers, Smart Objects,
Blend Modes, etc., Photoshop multiplies, divides, adds or subtracts a
pixels’ original number. The net result is this pixel becomes darker,
lighter, has color added, has color subtracted, has increased contrast,
has decreased contrast, disappears permanently, temporarily, partially
or completely. There are of course other changes as well.

Of course it is impractical to work on a digital image containing millions
of pixels one by one. And therein lies the rub....

Michael E. Stern
CyberStern.com

Photoshop Image Adjustments:
B&W

Accessed from the bottom of
the Layers palette.......

Michael E. Stern
CyberStern.com

B&W

Accessed from the bottom of
the Layers palette as an
“Adjustment Layer”.

An adjustment layer is a filter
through which one can view
edits to an image without
making actual changes to the
data. The purity of the file
remains intact while
variations to the image are
evaluated.

Adjust the tones by moving the
triangle sliders or simply drag
across the image itself and see
Michael E. Stern what happens.
CyberStern.com

B&W

Michael E. Stern
CyberStern.com

Photoshop

Photoshop is a dumb program. We have to point it in the right
direction so it performs where we want and what we want it to do.

Generally speaking if the work being performed is local, then one
works with hundreds or thousands of pixels at a time. If the work
involves a global correction then working with millions of pixels at a
time is normal.

The key to working locally (on a specific area of a file) is to select
those specific pixels first before performing any task. This selection
process not only identifies the area we want Photoshop to affect
change to but it simultaneously protects the rest of the pixels from
being changed.

Michael E. Stern
CyberStern.com

Photoshop

Global Toning: Select the luminosity of an image and use this
data to brighten or darken the image globally.

Keyboard MAC: option + command + tildé. Keyboard PC: alt + control + tildé.

Selects the luminosity values in a file.

The marching ants identify the brightest areas of the image.

Michael E. Stern
CyberStern.com



“Jump” this selection to its’ own layer. Command or control “j” does the trick.

Michael E. Stern
CyberStern.com



Select a darkening “Blend Mode” to darken and a lightening “Blend Mode” to lighten. Adjust
opacity to taste.

Make Darker

Make Lighter

Add Contrast

Michael E. Stern
CyberStern.com



Color Burn blend mode with a 70% layer opacity adjustment.

Michael E. Stern
CyberStern.com

Original

Adjusted

Michael E. Stern
CyberStern.com

Photoshop

Camera Original Smart Sharpen

Michael E. Stern
CyberStern.com

Photoshop

The original numbers populating the raster grid are easy to change.
One must however understand and appreciate if care is not taken great
damage will be done. This damage may not be apparent on screen but
the damage will show up in a print.

This damage takes the form of posterization, pixelation or banding.

The work around to this inherent problem is working in layers, masks
and adjustment layers.

Michael E. Stern
CyberStern.com

Photoshop

Quality in a digital image is determined by how many pixels per inch
there are. We refer to this as ppi.

The higher the ppi the better the quality.

The higher the ppi the larger the file.

The larger the file the longer it takes to perform any task.

The larger the file the more space required on a hard drive.

It is necessary to have as fast a computer as possible, as much RAM as
possible and the largest capacity hard drive one can afford.

Without these best practices, Photoshop will make you cry.

Michael E. Stern
CyberStern.com

Photoshop
set the correct file resolution first

ppi = pixels per inch, the marker for quality in a given file

ppi should reflect your image requirements; higher ppi for small prints, lower ppi for large prints

for hard paper surfaces use a high ppi

for soft paper surfaces use a low ppi

if a print can be comfortably viewed at arms length or closer, use 480 ppi

if a print is best viewed no closer than arms length, use 360 ppi.

Michael E. Stern
CyberStern.com

Photoshop

This is the “Image Size” dialog box
inside Photoshop. A camera file will open up at the
default resolution of 72 ppi. This is from the days
when digital cameras were not high enough
resolution and were used mainly for web imagery
and email attachments.

Look closely and you’ll see the 72 ppi resolution
will produce a document size of 56X37. Large
indeed but not nearly enough quality. Take note of
the file size: 31.4 megabytes.

Michael E. Stern
CyberStern.com

Photoshop

The “Resample Image” box is unchecked. When
the ppi is increased for a small print size notice
the document size changes. The image is still
31.4 megabytes, all we have done is
redistribute the information in the grid.

As the resolution changes so does the
document size. If you select a document size
but the resolution is not enough then you have
to.....

Michael E. Stern
CyberStern.com

Photoshop

recheck the “Resample Image” box and plug in
your preferred number. Notice how the file size
grows from 31.4 to almost 350 megabytes.

Be sure to check one of the bottom two resample
options when working with the “Resample Image”
box checked.

Bicubic Smoother is designed for retaining edge
detail when upsampling but it can decrease
contrast. Experimentation and personal taste will
drive the settings for this command.

Michael E. Stern
CyberStern.com

Photoshop

dpi = dots per inch, sometimes named econmoy/draft (360), fine (720), photo (1440),
best photo (2880) and super best photo (5760)

for glossy surfaces use 1440 or 2880 dpi

for matte surfaces use 1440 or 2880 dpi

for semi-gloss surfaces use 1440 or 2880 dpi

for proofing and plain paper, use economy/draft or 360 dpi

Michael E. Stern
CyberStern.com

Photoshop

See ya!

Michael E. Stern
CyberStern.com

Intro Digital Imaging

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (15)

Similaire à Intro Digital Imaging

Similaire à Intro Digital Imaging (20)

Plus de Michael e. Stern Photography

Plus de Michael e. Stern Photography (20)

Dernier

Dernier (20)

Intro Digital Imaging