Professional Information Technology-Programming Book part 7 ppt

2.5. Light Metering Tricks
There are all sorts of ways to measure exposure.
You can use one of your camera's metering modes in P shooting mode or (better
yet) bracket a sequence of shots in half stop increments. You can look at the actual
photo on your preview monitor after you shoot the test. Most cameras will also
show you the exposure if you tell them to "show info." So, just pick the shot in
your sequence that has the best exposure, get the info, switch to M mode, and set
the exposure accordingly.
Or you can shoot a gray card in spot metering mode. This ensures that you're only
metering the image's midtones, so you should get the best compromise in exposure
for all the prevailing levels of brightness. Your camera's color balance is calibrated
at the same time, so you can set the white balance for all these exposures with one
of the White Balance droppers that are available in both Photoshop and Camera
Raw. In Photoshop Elements 4, you can only use an eyedropper to set white
balance by choosing a Levels Adjustment Layer from the Layers palette. If the
result is too much or too little brightness, you'll have to correct it by adjusting the
midtone slider in the RGB channel (see Chapter 5).
2.5.1. Types and Uses for External Meters
Although you can preview a shot and adjust your exposure according to the
exposure information for that shot, there are times when an external meter can save
time. That's because you can read for proper exposure before you start taking
pictures. Also, most meters read exposure in such a way that you see a variety of
aperture and shutter speed combinations that allow the transmission of equal
amounts of light to be recorded by your sensor. That way, you don't have to do
calculations each time you switch to manual mode but want to use a different
shutter speed and aperture combination (see Table 2-1).
Table 2-1. A chart of equivalent f-stop and shutter speeds at ISO 100 in average
daylight. For each doubling of ISO speed, decrease the f-stop by raising it to the
next highest number in the chart. Most digital cameras allow you to adjust both
shutter and f-stop in half-stop increments.
1/8 sec 1/15 1/30 1/60 1/125 1/250 1/500

f-16 f-11 f-8 f-5.6 f-4.0 f-2.8 f-2

There are two types of meters that might come in handy: Incident and Spot.

Incident light meters
These meters are held in the area that is the center of interest and are pointed
toward the camera. You set the ISO on the meter that will be the same ISO
for your camera. You then press a button and the range of alternative
exposures in Table 2-1 suddenly appears. Gossen makes an incident light
meter that can measure either available light or strobe. You can see an
incident light meter in Figure 2-9.
Figure 2-9. An incident light meter being held as it is used to measure
exposure.

Spot meters
Spot meters that aren't built-in generally look a bit like miniature telescopes
and can be used to measure a small portion of the subject, even if it's too far
away to get close to. If you frequently use long telephoto lenses, you might
want to consider an external spot meter. However, if you shoot with a
camera back or a DSLR, your built-in meter is measuring an area that is
always within the angle of view for that particular lens. So there's far less
need for a spot meter. Table 2-2 shows the ISO ranges of several popular
DSLR camera models.
Table 2-2. A chart showing the actual ISO ranges of several DSLR cameras.
Canon 350D


100

200

400

800 1600


Canon 20D


100

200

400

800 1600 3200 option

Canon 5D 50 option

100

200

400

800 1600 3200 option

Canon 1DS Mk II

50 option

100

200

400

800 1600 3200 option

Nikon D2X


100

200

400

800 1600 option

3200 option

Nikon D200


100

200

400

800 1600 3200 option

Nikon D70 Auto


200

400

800 1600


Nikon D50 Auto


200

400

800 1600


Olympus E-500 Auto 100

200

400

800 option

1600 option



Olympus Auto 100

200

400

800 option

1600 option



Pentax DL Auto


200

400

800 option

1600 3200
Pentax DS2

200

400

800 option

1600 3200
Fuji S3 Pro


100

200

400

800 1600


Minolta 7D Auto 100

200

400

800 1600 3200
Minolta 5D Auto 100

200

400

800 1600 3200
Contax


100

200

400

800 1600







2.6. Tricks for Steady Shooting
Unintentionally blurry pictures are almost always the first to the trash. Most of the
time, it has nothing to do with the movement of the subject, but with the fact that
you haven't been careful enough to keep the camera steady. So it pays to practice
avoiding blurry shots that happen because a camera is too unsteady for the shutter
speed called for by the conditions of lighting and subject motion. Of course, there
are ways to minimize or even ensure that the camera won't move when the shutter
fires.

2.6.1. Antishake Mechanisms
There's at least one DSLR manufacturer, Sony (Alpha 100 DSLR), that has an
antishake mechanism built into its sensor. It's a feature I wish all DSLR makers
would offer, especially those that have higher-resolution (8+ MP) sensors. The
advantage is that the antishake mechanism works for up to a three-f-stop diff
erence
in exposure. So a nightclub shot that had to be taken at ISO 400 at 1/80th of a
second can now be taken at 1/20th of a second. If you shoot a lot of news, parties,
and events, it's worth having one of these camerasyou'll hardly ever have to shoot
with flash. Heck, even when you do shoot with flash, you could use a slow enough
shutter speed to get a lot more detail in the background that isn't motion blurred.
If you have a DSLR that doesn't have built-in anti-shake (aka image
stabilization)particularly a higher-resolution, lower-noise oneall is not lost. Most
lens vendors make antishake lenses. The bad news is that you will pay significantly
more for the lens. Furthermore, you have to buy one in every focal length you need
the feature for. Heaven forbid you have to shoot both wildlife and weddings.
2.6.2. Bracing and Breathing
By far, the most common situation you will find yourself in is simply holding the
camera in your hands while you grab a shot before the opportunity flits away. So
you want to keep your shutter speed at around 100th of a second, just to ensure a
reasonable chance of sharpness. Wide-angle shots are less likely to appear blurry
than telephoto shots. Telephoto lenses much more than 150mm in effective length
require either a rock-steady camera or some image stabilization mechanism in the
camera.
If you don't have a tripod, or the time to set one up, brace yourself by leaning
against something solid. If you're near a flat surface like a table top or guard rail,
brace your elbows on it. If you're not, press your elbows tight against your torso.
Take a deep breath. Just before your lungs are filled and you have to let your
breath out, squeeze the shutter button so smoothly that you're surprised when you
hear the shutter (or mirror) click.

You can also use your camera strap to make sure the camera is steady. Put your
elbows inside the strap and then spread your arms so that there is tension between
your body and the camera.
Once you've done all the above, reduce the shutter speed to about one-fifth of a
second and make a test shot of a motionless subject. Press the Preview button and
then do what your camera requires to enlarge the preview image to 100 percent (or
more). If the edges of the subject are sharp, you've either got it down or got lucky.
Try this a few more times until you know you've got it down.
Repeat this exercise every time you get a chance until you are so good at it that you
can shoot at even slower shutter speeds. I have a friend is so good at it that she can
hand-hold for a full second. Figure 2-10 shows a photographer practicing all of the
above.
Figure 2-10. A photographer taking all the steps to keeping the camera steady
when there's no chance of setting up a tripod.
2.6.3. Tripods and Monopods
Surely nobody who is reading this book doesn't know what a tripod is. Just in case
you don't, though, it's a three-legged stand with variable length legs and a
swiveling head that screws tightly to the bottom of your camera. The bigger and
tougher the tripod, the steadier it's likely to be. However, the trick is to get one
that's just big, steady, and precise enough to keep your camera motion-free. After
all, if it's too heavy, you'll never take it with you. The tripod you need for a point-
and-shoot could be about half the weight of the one you need for an entry-level
DSLR, for example, as cameras grow in size and price. One big caution: don't use
a tripod that doesn't stay adjusted while you're working. A funky tripod head or leg
tightener just isn't worth having. Furthermore, they become looser and more
useless over time. The more you tighten them up, the looser they get.
Tripods are expensive, but look for one that is unusually steady for its
lightweightness. If you see the words magnesium alloy or carbon fiber, you're
probably in good shape. Figure 2-11 shows you a reasonably priced tripod.
Figure 2-11. Popularly priced but sturdy tripod with a ball head.

Let's face it; sometimes tripods are just too much of a pain to lug around. A
monopod can do very nearly as good a job, as long as you brace it. A monopod is,
essentially, one tripod leg with four, rather than three, sections so you can collapse
it to about a couple of feet in length. For hikers, monopods can also double as
walking sticks.
NOTE

It is much harder to keep the camera in exactly the same spot between shots when
using a monopod. Therefore, they're rarely suitable for making multiple exposures
for use in a panorama, stitched mosaic, or HDR image. (See Chapter 11 for more
on HDR.)
2.6.4. Shoot, but Don't Touch
One of the most common causes of unintentional camera shake is the act of
punching the shutter release. The remedy? Squeezedon't push. You want to be so
gentle with your depression of the shutter release that you are a bit surprised when
you hear the shutter click.
An even better solution is a device that makes it possible to fire the shutter without
touching the camera at all. The devices used for touchless shutter release are even
more valuable when the camera is just placed on a flat surface for bracing, rather
than on a tripod or clamp.
The best, cheapest, and most old-fashioned of all touch-free shutter releases is
something called a cable release (see Figure 2-12). You can buy one for next to
nothing, and it is always reliable.
Figure 2-12. A cable release.
Making a camera that has a cable release socket doesn't cost a single penny more,
either. It's just that crafty camera makers have found a way to boost their profit
margins by not drilling a threaded hole in the shutter release button. You then have
to buy an electronic device known as a remote control. Really reliable remote
controls are wired to the camera because they go off the instant you push the
button. The more common type is infrared. The disadvantage here is that there has

to be a clear line-of-sight between the remote control device and the infrared
receptor on the front of the camera. Of course, if you're not careful, holding it in
front of the camera can be difficult without including it in the picture. Once again,
practice to the rescue. Before you have to use the remote, practice your holding
position when you're shooting with it until you don't see anything in front of the
lens that shouldn't be there.