What controls exposure?
ISO ratings determine the image sensor’s sensitivity to light,
each value of the rating represents a “stop” of light, and each
incremental ISO number (up or down) represents a doubling
or halving of the sensor’s sensitivity to light.The Aperture
controls the lens’ diaphragm, which controls the amount of
light traveling through the lens to the film plane. The aperture
setting is indicated by the f-number, whereas each f-number
represents a “stop” of light.The Shutter Speed indicates the
speed in which the curtain opens then closes, and each shutter
speed value also represents a “stop” of light. The shutter speed
is measured in fractions of a second.
each value of the rating represents a “stop” of light, and each
incremental ISO number (up or down) represents a doubling
or halving of the sensor’s sensitivity to light.The Aperture
controls the lens’ diaphragm, which controls the amount of
light traveling through the lens to the film plane. The aperture
setting is indicated by the f-number, whereas each f-number
represents a “stop” of light.The Shutter Speed indicates the
speed in which the curtain opens then closes, and each shutter
speed value also represents a “stop” of light. The shutter speed
is measured in fractions of a second.
When these three elements are combined, they represent a given
exposure value (EV) for a given setting. Any change in any one
of the three elements will have a measurable and specific impact
on how the remaining two elements react to expose the film frame
or image sensor and how the image ultimately looks. For example,
if you increase the f-stop, you decrease the size of the lens’
diaphragm thus reducing the amount of light hitting the image sensor,
but also increasing theDOF (depth of field) in the final image.
Reducing the shutter speed affects howmotion is captured, in that this
can cause the background or subject to become blurry. However,
reducing shutter speed (keeping the shutter open longer) also
increases the amount of light hitting the image sensor, so everything
is brighter. Increasing the ISO, allows for shooting in lower light
situations, but you increase the amount of digital noise inherent in
the photo. It is impossible to make an independent change in one
of the elements and not obtain an opposite effect in how the other
elements affect the image, and ultimately change the EV.
exposure value (EV) for a given setting. Any change in any one
of the three elements will have a measurable and specific impact
on how the remaining two elements react to expose the film frame
or image sensor and how the image ultimately looks. For example,
if you increase the f-stop, you decrease the size of the lens’
diaphragm thus reducing the amount of light hitting the image sensor,
but also increasing theDOF (depth of field) in the final image.
Reducing the shutter speed affects howmotion is captured, in that this
can cause the background or subject to become blurry. However,
reducing shutter speed (keeping the shutter open longer) also
increases the amount of light hitting the image sensor, so everything
is brighter. Increasing the ISO, allows for shooting in lower light
situations, but you increase the amount of digital noise inherent in
the photo. It is impossible to make an independent change in one
of the elements and not obtain an opposite effect in how the other
elements affect the image, and ultimately change the EV.
I
ISO Speed
ISO is actually an acronym, which stands for International Standards
Organization. The ISO rating, which ranges in value from 25 to 3200
(or beyond), indicates the specific light sensitivity. The lower the ISO
rating, the less sensitive the image sensor is and therefore the smoother
the image, because there is less digital noise in the image. The higher
the ISO rating (more sensitive) the stronger the image sensor has to
work to establish an effective image, which thereby produces more
digital noise (those multi-colored speckles in the shadows and in the
midtones). So what is digital noise? It is any light signal that does not
originate from the subject, and therefore creates random color in an
image. The digital camera engineers have designed the image sensor
to perform best at the lowest ISO (just like with film). On most digital
cameras this is ISO 100, although some high end DSLRs have a mode
that brings the ISO down to 50 or even 25.
Organization. The ISO rating, which ranges in value from 25 to 3200
(or beyond), indicates the specific light sensitivity. The lower the ISO
rating, the less sensitive the image sensor is and therefore the smoother
the image, because there is less digital noise in the image. The higher
the ISO rating (more sensitive) the stronger the image sensor has to
work to establish an effective image, which thereby produces more
digital noise (those multi-colored speckles in the shadows and in the
midtones). So what is digital noise? It is any light signal that does not
originate from the subject, and therefore creates random color in an
image. The digital camera engineers have designed the image sensor
to perform best at the lowest ISO (just like with film). On most digital
cameras this is ISO 100, although some high end DSLRs have a mode
that brings the ISO down to 50 or even 25.
A
Aperture
A lens’s aperture is the opening in the diaphragm that determines
the amount of focused light passing through the lens. At a small
f-stop, say f/2, a tremendous amount of light passes through, even
at a fraction of a second; but at f/22, when the diaphragm is perhaps
at its smallest, only a tiny amount of light is let in (even at longer
shutter speeds). An interesting thing about the aperture and the
f-numbers is that it doesn’t matter the focal length of the lens as long
as the f-number is held constant. This is because the arithmetical
equation that determines the f-number indicates that the same amount
of light passes through the lens on a 35mm lens as on a 100mm lens,
with a shutter speed of 1/125s. The size of the diaphragm is
unquestionably different, but the amount of light passing through
is the same.
the amount of focused light passing through the lens. At a small
f-stop, say f/2, a tremendous amount of light passes through, even
at a fraction of a second; but at f/22, when the diaphragm is perhaps
at its smallest, only a tiny amount of light is let in (even at longer
shutter speeds). An interesting thing about the aperture and the
f-numbers is that it doesn’t matter the focal length of the lens as long
as the f-number is held constant. This is because the arithmetical
equation that determines the f-number indicates that the same amount
of light passes through the lens on a 35mm lens as on a 100mm lens,
with a shutter speed of 1/125s. The size of the diaphragm is
unquestionably different, but the amount of light passing through
is the same.
S
Shutter Speed
Shutter speed is measured in fractions of a second, and indicates
how fast the curtains at the film plane open and close. The shutter
speed controls how long light enters the lens and hits the image sensor
or film plane. The shutter speed enables you to capture the world in
split seconds, but it can also absorb the world at speeds upwards of
three and four seconds (or remain continually open up until the
photographer wants to close the curtain). Snapping the shutter in
a fraction of a second, also gives you control on how motion is recorded.
If the shutter speed is faster than the object or background, then the
image will be tack sharp. If the shutter speed is slower, then you’ll get
blurred objects. Think about the rain in a rainstorm, how fast is that water
falling? Well, at 1/30th the raindrops are streaks of undistinguishable
white. But at 1/250th, the raindrops hover in mid air and you can see
the full swell of each water drop.
how fast the curtains at the film plane open and close. The shutter
speed controls how long light enters the lens and hits the image sensor
or film plane. The shutter speed enables you to capture the world in
split seconds, but it can also absorb the world at speeds upwards of
three and four seconds (or remain continually open up until the
photographer wants to close the curtain). Snapping the shutter in
a fraction of a second, also gives you control on how motion is recorded.
If the shutter speed is faster than the object or background, then the
image will be tack sharp. If the shutter speed is slower, then you’ll get
blurred objects. Think about the rain in a rainstorm, how fast is that water
falling? Well, at 1/30th the raindrops are streaks of undistinguishable
white. But at 1/250th, the raindrops hover in mid air and you can see
the full swell of each water drop.
2
What is "Auto Bracketing"?
Auto Bracketing is an exposure technique whereby you can ensure
that you have the optimal exposure by taking at least three (3)
exposures of the exact same composition with one at the metered
EV, one at 1/3 of a stop below the metered EV and one at 1/3 of
a stop above the metered EV. So “Auto Bracketing” is a function
in which you set the EV value then release the shutter and the
camera automatically makes the necessary up and down adjustments
to the EV to give you the bracketed exposures. Then you can review
the three (or more) exposures, see the subtle but critical differences
in the images, and decide which one is the best image for your
purposes. In the three images on the right, you might prefer the
overexposed (by 2 stops) image because the setting sun is most
brilliant. Bracketing was a technique that was popularized from
shooting slide film, due to the limited ability to correct the image
in the darkroom. Many photographers still use the technique today,
so they have the exposure that they want. Having the three bracketed
images lowers the amount of post-processing time that they might
have to spend.
that you have the optimal exposure by taking at least three (3)
exposures of the exact same composition with one at the metered
EV, one at 1/3 of a stop below the metered EV and one at 1/3 of
a stop above the metered EV. So “Auto Bracketing” is a function
in which you set the EV value then release the shutter and the
camera automatically makes the necessary up and down adjustments
to the EV to give you the bracketed exposures. Then you can review
the three (or more) exposures, see the subtle but critical differences
in the images, and decide which one is the best image for your
purposes. In the three images on the right, you might prefer the
overexposed (by 2 stops) image because the setting sun is most
brilliant. Bracketing was a technique that was popularized from
shooting slide film, due to the limited ability to correct the image
in the darkroom. Many photographers still use the technique today,
so they have the exposure that they want. Having the three bracketed
images lowers the amount of post-processing time that they might
have to spend.
3
Overexposure & Underexposure
How do you define overexposure and underexposure, since
we said that “correct” exposure is subjective? Simply put,
overexposure is when the information in the highlights is effectively
unreadable. When there is this type of excessive loss of image
information there is no way to “retrieve” that missing information
in the digital dark room. Underexposure is pretty much the same
concept; except in this case there is no image information
contained within the shadows. This non-existant information
cannot be retrieved through post processing either. In digital
photography, once that image information is gone, there’s no
way to retrieve it. This is not always the case in the photochemical
world of film photography. With film (as opposed to digital) processing,
it is possible to “find” image information in an excessively underexposed
frame, and perhaps “find” image information during the printing
process for seriously overexposed images as well.
we said that “correct” exposure is subjective? Simply put,
overexposure is when the information in the highlights is effectively
unreadable. When there is this type of excessive loss of image
information there is no way to “retrieve” that missing information
in the digital dark room. Underexposure is pretty much the same
concept; except in this case there is no image information
contained within the shadows. This non-existant information
cannot be retrieved through post processing either. In digital
photography, once that image information is gone, there’s no
way to retrieve it. This is not always the case in the photochemical
world of film photography. With film (as opposed to digital) processing,
it is possible to “find” image information in an excessively underexposed
frame, and perhaps “find” image information during the printing
process for seriously overexposed images as well.
4
AE LOCK (AEL)
Auto Exposure Lock is a camera setting in which the EV is locked
in (when you’re shooting one of the semi-automatic or fully automatic
modes, i.e. Shutter-priority), so that now matter what changes there
are to the lighting in the scene, the camera locks in the ISO, Shutter
and/or Aperture settings, so you can continually achieve the same EV
without having to re-meter the scene.
in (when you’re shooting one of the semi-automatic or fully automatic
modes, i.e. Shutter-priority), so that now matter what changes there
are to the lighting in the scene, the camera locks in the ISO, Shutter
and/or Aperture settings, so you can continually achieve the same EV
without having to re-meter the scene.
C
Conclusion
One highly practical advantage to digital photography is that it
costs next to nothing to experiment with the camera’s controls,
so go out there and shoot away. You want to become increasingly
proficient with all three elements of the exposure triangle, so that
you can make adjustments on the fly and know exactly what the
resulting effect is going to be.
sumber by: Exposure Guide
costs next to nothing to experiment with the camera’s controls,
so go out there and shoot away. You want to become increasingly
proficient with all three elements of the exposure triangle, so that
you can make adjustments on the fly and know exactly what the
resulting effect is going to be.
sumber by: Exposure Guide
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