46
ZOOMING PAST POINT AND SHOOT!
M AT C H B O X ™ I S A T R A D E M A R K O F M AT T E L , I N C .
GUIDE TO DIGITAL PHOTOGRAPHY, PART I
REVIEWS AND RESOURCES
LENS
There are a number of informative web sites, books, and
magazines that can help you make a good decision when you
are ready to buy. Each is updated frequently, which is critical
with the pace of change in the digital camera industry.
APERTURE. The circular area behind the lens that opens to
allow light in and expose the film or digital CCD. Most cameras can vary the aperture’s diameter to control the amount of
light reaching the exposure plane.
ON-LINE
DEPTH OF FIELD. The difference between the nearest and furthest in-focus objects. The smaller the aperture, the larger the
fstop value, and the more background will be in focus.
• WWW.DPREVIEW.COM, it’s by far the most informative and
comprehensive site on digital cameras, with in-depth
reviews of most camera models by a very experienced photographer. Bookmark this one site if no where else.
• WWW.AMAZON.COM, can’t beat the selection.
• WWW.MYSIMON.COM, to search for the best available
price; read the small print for shipping, make sure the
camera isn’t “gray market” from offshore—it voids the warranty.
NEWS STAND
• DIGITAL PHOTO, also on the web at www.pcphotomag.com
FSTOP. A measurement of the diameter of the aperture’s
opening during exposure. The lower the fstop, the larger the
aperture will open and the more light will be sent to the sensor.
For example, if you set the aperture to f/2.8, it is larger than f/8.
FILM SPEED/ISO. The sensitivity of a given film to light, indicated by the ISO [International Standards Organization]
number. The higher the number, the more sensitive or faster
the film becomes. Some digital cameras have an ISO setting
that emulates film ISO by varying the CCD’s light sensitivity.
The digital image can be made to appear like a print from film
with the corresponding ISO level.
• DIGITAL PHOTOGRAPHY MADE EASY, one of several outstanding publications from the U.K. You can find it and
others at larger bookstores or news stands.
FOCAL LENGTH. The distance between the film and the optical
center of the lens when the lens’ focus is set to infinity.
BOOK STORE
OPTICAL VS. DIGITAL ZOOM. Optical zoom cameras
rearrange and move internal lenses to achieve magnification.
Digital zoom enlarges the image via pixel interpolation, like
Photoshop, resulting in a lower-quality image. Because digital
zoom doesn’t generate any new image data, you don’t see extra
detail when compared to optical zoom.
There are hundreds of books on photography and easily
dozens on digital photography. Two that we’ve found useful are
on filters and their use.
• HOW TO DO EVERYTHING WITH YOUR DIGITAL
CAMERA, by Dave Johnson
• THE PHOTOGRAPHER’S GUIDE TO FILTERS, by Lee Frost
• USING FILTERS, published by Kodak Books
INFINITY. The farthest-away position of focus.
OVER- AND UNDEREXPOSURE. Too much or too little light
reaches the exposure plane. Overexposure results in a light
image with lost highlight detail, and underexposure results in a
dark or muddy-looking image with lost shadow detail.
SHUTTER SPEED. The length of time the camera’s aperture
remains open during the exposure of the photograph. The
slower the shutter speed, the longer the exposure time. The
shutter speed and the aperture together control the total
amount of light reaching the sensor.
GLOSSARY AND RESOURCES
LIGHTING
ACETATE. Clear plastic-like sheet often color tinted and fitted
over studio lights.
AMBIENT LIGHT. Natural, outdoor light.
SOFT BOX. Popular lighting accessory that produces extremely
soft light. Various sizes and shapes are available; the larger they
are, the more diffuse the light.
SPOT. A directional light source.
BARN DOORS. Set of four flaps that fit over the front of a
studio light to control the direction of the light.
SWIMMING POOL. Large soft box giving soft lighting.
BOOM. Long arm fitted with a counterweight which allows
studio lights or reflectors to be positioned above the subject
UMBRELLA. Lighting accessory used to bounce a light source
from and onto a subject. They come in a range of colors. The
larger the umbrella, the softer the light.
CONTINUOUS LIGHTING. Sources that provide steady
illumination, in contrast to flash which fires briefly.
DIFFUSER. Any kind of accessory which softens the output
from a light source.
EFFECTS LIGHT. Studio light used to illuminate a specific part
of the subject.
FILL LIGHT. Studio light for reducing shadows.
FLASH HEAD. Studio lighting unit which emits a quick and
powerful burst of light.
INCIDENT READING. Exposure reading of the light falling
onto the subject.
KELVIN. Scale used for measuring the color of light. Daylight
and electronic flash is balanced to 5500K.
DIGITAL FILE
8-BIT VS. 16-BIT. The amount of data (2 vs. 2 ) that can be
used to describe the grayscale tone gradation for red, green or
blue, for each pixel. An 8-bit image has 256 levels of tone
description of each color for every pixel in the image.
8
16
CCD. [Charge Coupled Device] The light-sensitive instrument
that records the image. Made up of thousands of pixel-sized
sensors, each of which typically read only red, green or blue.
The camera’s “megabits” represent an approximate rounding of
the size of the CCD array, which is determined by multiplying
its horizontal pixel-sensors by its vertical ones. The camera we
used is a 4-megabit camera, since its CCD measures 1,722 x
2,274 pixels, which totals roughly 4 million.
KEY LIGHT. The main lighting source.
PIXEL. [Picture Element] The building blocks of a digital
photo, and single unit of light capture.
LIGHT METER. A light-sensitive tool built into most digital
cameras that determines the light level(s) of the image. A
camera uses these readings to determine the exposure length.
RAW FORMAT. The uncompressed data as it comes from the
CCD. This may contain additional detail that can improve
image quality when compared to saving in the JPEG format.
MULTIPLE FLASH. Firing a flash head several times to give the
amount of light required.
RESOLUTION. The density of pixels per measurement unit,
expressed as a number of horizontal pixels by a number of
vertical pixels. “300 DPI” scans measure 300 horizontal x 300
vertical pixels for a total of 90,000 pixels per square inch.
REFLECTOR. Metal shade around a light source to control and
direct it, or a white or silvered surface used to redirect light.
RINGFLASH. Circular flash tube which fits around the lens and
produces a characteristic shadowless lighting.
SCRIM. Any kind of material placed in front of a light to
reduce its intensity.
SNOOT. Black cone which tapers to concentrate the light into a
circular beam.
Guide
To Digital Photography
© 2004 All rights reserved.
3
FSTOP
FSTOP 2.5
GREATER EMPHASIS ON THE
POINT OF FOCUS. We captured
this image with the fstop set to
2.5. The low fstop results in
lessened depth of field and
heightens emphasis on the point
of focus (the rear tire). We relied
on the camera to determine
the right exposure time based on
the manual fstop setting. This
shot required an exposure of
1/10 second, much less time (and
light) required to capture an
image with a lower fstop. This is
specially relevant if you are
shooting without a tripod. The
longer the exposure, the steadier
the hand must be!
FSTOP/APERTURE (MANUAL): 2.5
SHUTTER SPEED (AUTO): 1 /10 SECOND
WHAT IS THE FSTOP?
The fstop setting controls the diameter of
the aperture, the temporary opening that
allows light to enter and expose the image
media as you take a picture.
WHAT DOES IT MEASURE?
The higher the fstop, the smaller the diameter of the aperture during exposure.
WHAT IS THE IMPACT?
A lower fstop results in a shorter depth of
field, which is the area of foreground and
background relative to the focal point that
remains in focus. Notice that the El Camino
behind the Corvette, as well as the
Corvette’s shadow, are out of focus at this
camera’s lowest supported fstop setting
(2.5), whereas they are crisper at its highest
fstop setting (8.0).
WHAT ABOUT EXPOSURE?
FSTOP 8.0
FSTOP/APERTURE (MANUAL): 8.0
SHUTTER SPEED (AUTO): 1 SECOND
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Guide To Digital Photography
© 2004 All rights reserved.
GREATER DEPTH OF FIELD.
We captured this image with the
fstop set to 8.0, the camera's
maximum. Notice the increased
detail in both the foreground and
the background, as the higher
fstop results in a deeper depth of
field. The resulting image benefits
from increased clarity (more
seems in focus), while reducing
the emphasis and impact of the
point of focus. Note that the
exposure time required, which
the camera set based on our
fstop setting, increased to one
full second, which requires a
tripod to maintain a steady
camera through the exposure
and avoid a blurry photograph.
To compensate for the decrease in volume
of light, exposure time (shutter speed) must
increase as the fstop increases.
During the capture of these images, we
used the camera’s built-in light meter to
keep the light an approximate constant. The
exposure time had to be 10 times longer to
maintain the same brightness at an fstop of
8.0 vs. 2.5.
Note that all of these exposures were
made at a very low film speed (ISO setting
of 50), which resulted in a long exposure
requirement across the board. Also note
that it would take an extraordinarily-steady
hand to shoot these images without a
tripod. The exposure times are just too
long, and even a little bit of movement will
result in a blurry shot.
ISO VALUE
WHAT DOES ISO MEASURE?
ISO 50
ISO, which stands for International Standards
Organization, is a measure of the relative light
sensitivity of photographic film. The higher the
number, the more sensitive or faster the film
becomes, creating a correctly-exposed image in
less time. Higher-speed film is typically used to
capture sports and other action shots.
DOES IT APPLY TO DIGITAL?
As with other mid-range to high-end digital
cameras, the Canon Powershot G2 we used has
an ISO setting that controls the sensitivity of the
light sensor (referred to as the charge-coupled
device or CCD). Use this to impose a specific
exposure or look-and-feel to your image.
WHAT IS THE IMPACT?
As the ISO value increases, film’s sensitivity to
light increases, allowing you to capture images at
lower light levels and/or faster exposure times
(that’s why ISO is also referred to as film speed).
This is especially helpful for both low-light
conditions and subjects with motion.
FSTOP/APERTURE (MANUAL): 8.0
ISO SPEED (MANUAL): 50
SHUTTER SPEED (AUTO): 1/2 SECOND
ISO 400
WHAT ABOUT QUALITY?
The higher the ISO setting, the more grainy
the image becomes. In the examples to the right,
the digital camera’s minimum-supported ISO
setting, a value of 50, resulted in a very long
exposure requirement (1/2 second), but also
resulted in a very smooth texture. The highest
supported ISO value, 400, reduced the exposure
time required by a factor of 10 (1/20 second), but
resulted in a grainy overall texture.
CAN I MAKE IT GRAINY?
If your camera supports it, setting the ISO
value to 400 or more will give you a grainy look
that is typically associated with faster films. You
can emulate this look by experimenting with
Photoshop’s ADD NOISE filter under EFFECTS.
FSTOP/APERTURE (MANUAL): 8.0
ISO SPEED (MANUAL): 400
SHUTTER SPEED (AUTO): 1 /20 SECOND
Guide
To Digital Photography
© 2004 All rights reserved.
5
JPEG MEDIUM
MEDIUM
JPEG
JPEG SMALL
SMALL
JPEG
FILE SIZE: 0.4 MB
IMAGES PER 64 MB CARD: 160
FILE SIZE: 0.9 MB
IMAGES PER 64 MB CARD: 70
This image was saved from the camera with maximum JPEG compression.
It looks ok until you see what you are missing. while subtle, there is clear
loss of detail when working with jpeg originals.
High levels of compression, as evidenced by the first two sets of JPEG
images above, result in loss of detail and degradation in tone. These
images are only suitable for use on the World Wide Web, where file size
typically takes precedence over image quality and fidelity.
SHOULD I USE JPEG OR 16-BIT RAW?
WHY NOT ALWAYS WORK IN 16-BIT?
There’s simply no question that you should capture your digital
photography images in an uncompressed RAW format, if your
camera supports it. This will have a significant impact on image
quality, as demonstrated above.
Many Photoshop features and filters only work on 8-bit-perchannel images. Photoshop 7.0 can only apply the following
features to 16-bit images, typically for selection and correction:
DUPLICATE, FEATHER, MODIFY, LEVELS, AUTO LEVELS, AUTO CONTRAST, AUTO COLOR, CURVES, COLOR BALANCE, HISTOGRAM, HUE
HOW DO I OPEN IT?
The new version of Adobe Photoshop, CS/8.0, can now open raw
images directly, giving you complete control over a wide range of
camera settings (meta data) during the conversion process.
Alternatively, your camera’s manufacturer may supply software to
browse, convert, and even correct images in RAW format. Note
that the files are twice the size of standard 8-bit TIFFs.
6
Guide To Digital Photography
© 2004 All rights reserved.
/SATURATION, BRIGHTNESS/CONTRAST, EQUALIZE, INVERT, CHANNEL
MIXER, GRADIENT MAP, IMAGE SIZE, CANVAS SIZE, TRANSFORM
SELECTION, ROTATE CANVAS, MARQUEE, LASSO, CROP, MEASURE, ZOOM,
HAND, HISTORY BRUSH, EYEDROPPER, SLICE, COLOR SAMPLER, CLONE
STAMP, HEALING BRUSH, PATCH; PEN, SHAPE TOOLS (WHEN DRAWING
WORK PATHS ONLY) AND A HANDFUL OF FILTERS.
If you’ve upgraded to Photoshop CS, you have more tools that
can edit a 16-bit image, but most filters still do not work in 16bit mode. SOURCE: ADOBE
FILE FORMAT
JPEG LARGE
LARGE
JPEG
RAW 16-BIT
16-BIT
RAW
FILE SIZE: 1.5 MB
IMAGES PER 64 MB CARD: 41
FILE SIZE: 3.3 MB
IMAGES PER 64 MB CARD: 19
JPEG compression sacrifices fine detail and subtle tone shifts. Notice the
difficulty the JPEG images have in maintaining the pattern of the El
Camino’s grill. Other problematic areas are subtle tones, as evidenced by
the shadow shifts from the car’s fender to hood. Even the best JPEG
compression setting has loss of detail and tone.
The RAW 16-bit format is THE uncompressed data captured by the
camera’s CCD. Notice the detail in the grilL and the smooth transitions in
the paint. The tone improvement is a result of the immense difference in
gray levels per color: 256 (28) levels per color channel in a JPEG or other
standard desktop file, vs. 65,536 (216) for the RAW format.
WHY WORK IN 16-BIT?
WHEN SHOULD YOU CONVERT TO 8-BIT?
When applying a Levels or Curve correction on an 8-bit image, a
smooth histogram (the range of tone from shadow thru highlight) can develop gaps, making it look like a comb. 256 levels of
gray are barely enough to create a smooth gradation, as anyone
working with desktop blends can attest. As the number of
distinct levels are further reduced, visual banding occurs where
you can see the steps as tones change, diminishing the overall
quality of the image. These gaps create uneven gradation changes
and introduce banding into your image. By applying Level and
Curve corrections to a 16-bit image, you are working with over
65,000 levels of gray per channel, not just 256. That’s far more
than needed to maintain a smooth blend or gradual tone change.
During the creative process, you should only convert to 8-bit if
you need to take advantage of an image editing feature that
requires it. Even so, on a color-critical image you should perform
all of your color correction and proofing adjustments (levels and
curves, for example), as well as proof your image, before conversion. If you don’t need to apply a specialty filter, leave your
images as 16-bit RGB until you are ready to print a proof or
release your project. You can convert to CMYK while still in 16bit, and then finally convert to 8-bit right before collect-foroutput. Note that you will need to update the images, since the
file will have been modified from the RGB.
Guide
To Digital Photography
© 2004 All rights reserved.
7
How to Do Everything
with Your Digital
Camera!
HOW TO DO EVERYTHING WITH
YOUR DIGITAL CAMERA
This book, How to Do Everything with Your Digital
Camera, offers a comprehensive introduction to
digital photography. The book’s author, Dave
Johnson, is a photographer and a best-selling author
of 15 books on portable technology and digital
photography. This book divides the topic of digital
photography into small, focused sections to help the
novice to intermediate user gain practical insight into
improving the quality of digital camera images.
One of the book’s best features is its strong
coverage of image composition topics. Johnson does
a good job teaching the essential basics of what it
really takes to make a good photo, in contrast to
similar titles that often feature nothing more than a
disjointed collection of tips and tricks.
Image transfer is another topic that Johnson
explains thoroughly. Topics include how to transfer
photos to a PC, resolution options and different file
formats for saving images, and understanding scanners and how to use them. Johnson also gives his
recommendations on which types of scanners to buy.
You will also pick-up a few tips on how to choose
the image-editing program that is right for you.
Johnson uses Jasc's PaintShop Pro to illustrate most
of his image-manipulation examples. This program
shares a lot of the same functionality as Photoshop,
and you shouldn’t have trouble understanding the
principles and applying them to your application of
choice. This book provides a solid foundation in
digital photography, hardware and software. It is a
great choice for the studio or department that is
expanding into digital photography.