Digital sensor array- does size matter???
Yes and no
Larger size=more photosites=more resolution
Smaller size=more compact=cheaper
1.35mm film size
Film is 35mm wide
Image area=24mm x 36mm
Half frame compact cameras=24mm x 18mm (circa 1913)
Sensor array size
Full frame sensor=24mm x 36mm
Smaller sensors defined with a crop factor
Eg: 1.5x
1.6x
crop factor relates to the cropping of the angle of view as a result of the sensor.
Effective focal length of lens is magnified by crop factor
Eg: 200mm lens x 1.5=300mm(effectively)
Photosite size and noise
SLR= Subject Luminance range
Film: known as “density range”
If photsite overflows it called “blooming”
Ability of sensor to record low to high luminance’s
Tungsten lighting
Electricity passes through tungsten filament causing it to glow, more electricity=more light
Tungsten filament lamps
Tungsten discharge lamps
Friday, April 9, 2010
Thursday, April 8, 2010
Week 6
Hyperfocal distance
Lens focused at infinity d1 for any given aperture is known as H.P
Lose half of your d.o.f if lens is on infinity
Sensor array type- differences
CCD
-separate off sensor signal amplifies, often just one result in: less noise, more uniform output, slower to analyse and amplify signal
-more “photosites” in a given area
-uses more power
-more expensive to manufacture.
CMOS
-signal amplifier at each “photosite” results in- more noise, less uniform output, faster to analyse and amplify signal
- fewer “photosites” in a given area
-uses less power
less expensive to manufacture
advances have preferred sensor type
Lens focused at infinity d1 for any given aperture is known as H.P
Lose half of your d.o.f if lens is on infinity
Sensor array type- differences
CCD
-separate off sensor signal amplifies, often just one result in: less noise, more uniform output, slower to analyse and amplify signal
-more “photosites” in a given area
-uses more power
-more expensive to manufacture.
CMOS
-signal amplifier at each “photosite” results in- more noise, less uniform output, faster to analyse and amplify signal
- fewer “photosites” in a given area
-uses less power
less expensive to manufacture
advances have preferred sensor type
Week 5
The ideal shutter should
Expose each part of the film/sensor equally and simutanlesly
Be silent inopertaion
Be vibration free
Little effort to set in motion
Take minimal time to open and close
Effective exposure should be repeatable
Focal plane (FP) shutter
Flash should only operate when shutter is fully open
Flash synchronisation is therefore limited
In order to achieve very fast speed the 2nd curtain is released soon after the first to follow it across the shutter window or “gate” as a “slit”
Between the lens or leaf shutter
Operates between lens elements
Must be “cocked” during lens attachment/removal
Maximum speed of 500th sec due to mechanical limitations.
Synchronises with electronic flash at all speeds
Most medium format cameras
Accuracy is affected at high shutter speeds and when wide aperture are combined with high shutter speeds eg: 1/500th sec
At 500 a greater proportion of the time is used to open and close the shutter so exposure is actually less than expected.
Often 400 is used, inefficiency reduces exposure closer to that ideal 500th sec
Shutter opens and closes at the same rate regardless of shutter speed chosen
Shorter time to uncover a small aperture
Motion and shutter speed
Depth of field
The region of acceptably sharp focus around a subject position, extending toward the camera and away from it, from the plane of sharpest focus
The boundaries of dof are referred to as the near limit (d1) and the far (d2).
Subject distance(u)
Controlling- aperture, lens, shutter speed
Increased- smaller apertures, using larger subject distances, using wider angle lenses
Expose each part of the film/sensor equally and simutanlesly
Be silent inopertaion
Be vibration free
Little effort to set in motion
Take minimal time to open and close
Effective exposure should be repeatable
Focal plane (FP) shutter
Flash should only operate when shutter is fully open
Flash synchronisation is therefore limited
In order to achieve very fast speed the 2nd curtain is released soon after the first to follow it across the shutter window or “gate” as a “slit”
Between the lens or leaf shutter
Operates between lens elements
Must be “cocked” during lens attachment/removal
Maximum speed of 500th sec due to mechanical limitations.
Synchronises with electronic flash at all speeds
Most medium format cameras
Accuracy is affected at high shutter speeds and when wide aperture are combined with high shutter speeds eg: 1/500th sec
At 500 a greater proportion of the time is used to open and close the shutter so exposure is actually less than expected.
Often 400 is used, inefficiency reduces exposure closer to that ideal 500th sec
Shutter opens and closes at the same rate regardless of shutter speed chosen
Shorter time to uncover a small aperture
Motion and shutter speed
Depth of field
The region of acceptably sharp focus around a subject position, extending toward the camera and away from it, from the plane of sharpest focus
The boundaries of dof are referred to as the near limit (d1) and the far (d2).
Subject distance(u)
Controlling- aperture, lens, shutter speed
Increased- smaller apertures, using larger subject distances, using wider angle lenses
Week 4
Film, shutter speed, lens aperture
ISO400, 500, F8
ISO200, 250, F8
ISO100, 125, F8
ISO50, 60, F8
ISO25, 30, F8
Film, lens aperture, shutter speed
ISO400, F16, 125
ISO200, F11, 125
ISO100, F8 , 125
ISO50, F5.6, 125
ISO25, F4, 125
Achieve “correct exposure”.
High ISO= image degredation
Rule of thumb: use lowest ISO in a given situation
Film: increases in image grain
Sensor: increases in image “noise”
Film= fixed sensitivity
Sensors sensitivity can be manipulated
High ISO= high grain
Low ISO= finer grain- portraits
ISO100- finer
ISO3200-grain
Exposure- level of illumination
High- faster shutter speed, smaller lens aperture
Low- slower shutter speed, wider lens apertures
- use of a tripod
hand held work (without vibrant reduction technology)
- use a shutter speed at least twice the value of the lens focal length
eg: lens focal length is 50mm, use at least 100thsec shutter speed
Level of subject reflectance:
-camera uses a reflected exposure meter
-measures light reflected from subject calibrated to always render the subject as a mid tone
-auto or manual results in same rendering
-white subject=mid tone rendering
-mid tone subject=mid tone rendering
-black subject= mid tone rendering
Exposure modes:
-average- entire field of view is averaged
-evaluative- interprets scene based on data base
-centre weighted- majority of measurement in centre
-spot- majority measurement in small area
White wall- 125sec @f9 not 125sec @f22
ISO400, 500, F8
ISO200, 250, F8
ISO100, 125, F8
ISO50, 60, F8
ISO25, 30, F8
Film, lens aperture, shutter speed
ISO400, F16, 125
ISO200, F11, 125
ISO100, F8 , 125
ISO50, F5.6, 125
ISO25, F4, 125
Achieve “correct exposure”.
High ISO= image degredation
Rule of thumb: use lowest ISO in a given situation
Film: increases in image grain
Sensor: increases in image “noise”
Film= fixed sensitivity
Sensors sensitivity can be manipulated
High ISO= high grain
Low ISO= finer grain- portraits
ISO100- finer
ISO3200-grain
Exposure- level of illumination
High- faster shutter speed, smaller lens aperture
Low- slower shutter speed, wider lens apertures
- use of a tripod
hand held work (without vibrant reduction technology)
- use a shutter speed at least twice the value of the lens focal length
eg: lens focal length is 50mm, use at least 100thsec shutter speed
Level of subject reflectance:
-camera uses a reflected exposure meter
-measures light reflected from subject calibrated to always render the subject as a mid tone
-auto or manual results in same rendering
-white subject=mid tone rendering
-mid tone subject=mid tone rendering
-black subject= mid tone rendering
Exposure modes:
-average- entire field of view is averaged
-evaluative- interprets scene based on data base
-centre weighted- majority of measurement in centre
-spot- majority measurement in small area
White wall- 125sec @f9 not 125sec @f22
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