LENS:
Lens aperture is relative.
The bigger the aperture the longer the lens needs to be to compensate.
We can liken this to the torch analysis. If you hold it close to a wall the light will be small and intensely bright.. as you move further away from the wall the light becomes bigger and therefore less intense.
We learnt each F-Number is related to the focal length of the lens......
However the same F-number of any lens passes the same amount of light despite being a different diameter. So an F8 is always going to be an F8 no matter what the lens.
Lenses come with LENS ABERRATION.
WHAT?
Aberration of the lens is basically an optical error.
All lenses suffer aberration because there is no such thing as a perfect lens.
Not all aberrations are negative, some are welcomed such as soft focus.
Although there is no 'cure' for lens aberration, many of them can be corrected by using alternate errors in the lens, counteracting in a sense.
WHY?
Because of light refraction when the light is passed through glass.
The amount of refraction depends on the wavelength of light, IE some colours of light will bend more than others.
Hence different wavelengths don't focus at the same point.
SPHERICAL SURFACES FAIL TO BRING LIGHT TO A FOCUS. And most lenses uses spherical surfaces.
Sphyrical Aberration:
*Loss of contrast
*Can't bring marginal and axial rays to the same point
*Stopping down can reduce.
Chromatic Aberration:
*Has to do with colours
*Affects where/how/whether colour focuses
*causes magnification of certain colours
LONGITUDINAL & LATITUDINAL
Achromatic : corrected for 2 colours (B/G)
Apochromatic: corrected for 3 colours (R/G/B)
Superchromatice: corrected for 4 (Infared/R/G/B)
COMA aberration:
Off axis, spherical aberration...
*Creates cone shaped points
*Stopping down can reduce
Barrel and Pincushion distortion.
DOES NOT EFFECT IMAGE SHARPNESS
Geometric distortion.
Stretched to fit a film plane.
Wednesday, May 5, 2010
Saturday, April 24, 2010
LENSES
Today was focused a lot on light and it's coexistence with the lense.
We know that the speed of light is medium dependant, if it has to pass through a medium it slows down the light.
Hence we know the denser the medium the slower the speed of light.
Refraction happens when light is bent.
We also know that a lens is highly dependant on light as it is a series of prisms designed to bring the light to a single point, which is where we achieve focus.
There are 2 main types of lenses : CONVERGENT (Positive double convex > Looks like an oval)
and DIVERGENT (Negative> Double concave > looks like an apple core)
We also learnt about a thing called circle of confusion which is where the image is soft and out of focus.
FUNDAMENTALS OF THE FOLLOWING LENSES:
*Wide Angle : Allows you to fit a lot of things into the image. Distance between objects is stretched.
* Zoom : Makes objects that are far away appear closer. Can change focal length quickly.
*Long Focus : Takes long distance shots with more in focus.
*Telephoto : Allows you to zoom in more. Making distance objects appear closer and magnified.
*Retro Focus : Opposite and inverted version of a telephoto lens.
*Quasi Fish Eye : Covers the entire frame (Not circular)
*Fish Eye (Circular) : Produces a circular image of a wide frame
*Catadioptric : Uses a mirror to shift focus by reflecting and retracting
*Macro : Used to make macro objects appear bigger. Used close up.
*Teleconverter : Similar to a telephoto lens. Enlarges the centre part of an image by being placed between the camera and the lens.
*Supplementry : Placed in front of the lens to enhance close ups.
*PC/Tilt-shift lense: PC stands for perspective control, hence is a lense that allows the photographer to change the perspective of the image by shifting tilt.
We know that the speed of light is medium dependant, if it has to pass through a medium it slows down the light.
Hence we know the denser the medium the slower the speed of light.
Refraction happens when light is bent.
We also know that a lens is highly dependant on light as it is a series of prisms designed to bring the light to a single point, which is where we achieve focus.
There are 2 main types of lenses : CONVERGENT (Positive double convex > Looks like an oval)
and DIVERGENT (Negative> Double concave > looks like an apple core)
We also learnt about a thing called circle of confusion which is where the image is soft and out of focus.
FUNDAMENTALS OF THE FOLLOWING LENSES:
*Wide Angle : Allows you to fit a lot of things into the image. Distance between objects is stretched.
* Zoom : Makes objects that are far away appear closer. Can change focal length quickly.
*Long Focus : Takes long distance shots with more in focus.
*Telephoto : Allows you to zoom in more. Making distance objects appear closer and magnified.
*Retro Focus : Opposite and inverted version of a telephoto lens.
*Quasi Fish Eye : Covers the entire frame (Not circular)
*Fish Eye (Circular) : Produces a circular image of a wide frame
*Catadioptric : Uses a mirror to shift focus by reflecting and retracting
*Macro : Used to make macro objects appear bigger. Used close up.
*Teleconverter : Similar to a telephoto lens. Enlarges the centre part of an image by being placed between the camera and the lens.
*Supplementry : Placed in front of the lens to enhance close ups.
*PC/Tilt-shift lense: PC stands for perspective control, hence is a lense that allows the photographer to change the perspective of the image by shifting tilt.
DIGITAL SENSOR ARRAY
Basically today's lesson was about digital sensors array...
We learnt that LARGER = more photosites > more resolution
and SMALLER = more compact > cheaper
A full frame sensor: 24mm x 36mm
And smaller sensors: Defined with a crop factor (cropping of the angular view as a result of smaller sensor; effective focal lengh of lens is magnified by crop factor) cropping angular view.
If noise is constant we know that a smaller site will have a lower signal to noise ratio but image quality and ISO is affected.
We also learnt about blooming which is the loss of subtleties of different readings, so photosites spill over to other areas of the image and the image is affected. You lose highlights.
SLR = Subject luminance range
FILM = Known as density range
We learnt that LARGER = more photosites > more resolution
and SMALLER = more compact > cheaper
A full frame sensor: 24mm x 36mm
And smaller sensors: Defined with a crop factor (cropping of the angular view as a result of smaller sensor; effective focal lengh of lens is magnified by crop factor) cropping angular view.
If noise is constant we know that a smaller site will have a lower signal to noise ratio but image quality and ISO is affected.
We also learnt about blooming which is the loss of subtleties of different readings, so photosites spill over to other areas of the image and the image is affected. You lose highlights.
SLR = Subject luminance range
FILM = Known as density range
Digital Capture
This lesson we learnt about digital sensor arrays
"A digital sensor is a device that responds to different levels of light by producing an electronic signal in proportion to the amount of light"
There are two main types:
CCD (Being Charged Couple Device) and CMOS (Being Complementary Metal Oxide Semiconductor)
The have many differences and can be contrasted and compared in many different ways.
CCD:
* Creates less noise
* Has more uniform output
* Is slower
* Uses more power
CMOS:
* Creates more noise
* Has less uniform output
* Is Faster
* Uses less power
Advances in technology have seen that the CMOS sensor array type has become the preferred type.
We also learnt about RGB (Red Green Blue) and CMY (Cyanne Magenta Yellow)
CY=G
MY = R
CM = B
We also learnt that photosites are the pixel opportunities within an image.
"A digital sensor is a device that responds to different levels of light by producing an electronic signal in proportion to the amount of light"
There are two main types:
CCD (Being Charged Couple Device) and CMOS (Being Complementary Metal Oxide Semiconductor)
The have many differences and can be contrasted and compared in many different ways.
CCD:
* Creates less noise
* Has more uniform output
* Is slower
* Uses more power
CMOS:
* Creates more noise
* Has less uniform output
* Is Faster
* Uses less power
Advances in technology have seen that the CMOS sensor array type has become the preferred type.
We also learnt about RGB (Red Green Blue) and CMY (Cyanne Magenta Yellow)
CY=G
MY = R
CM = B
We also learnt that photosites are the pixel opportunities within an image.
Friday, April 16, 2010
15/3
This lesson we learnt that the ideal shutter is not technically possible.
In a focal shutter plane the flash should only operate when the shutter is fully open hence the flash synch is limited.
We also learnt about depth of field.
Boundaries of depth of field are referred to as D1 (For the near limit) and D2 (for the far limit)
Subject distance (u) refers to the distance from the camera to the subject...
We need to remember that the larger the aperture = the shallower the depth of field.
To INCREASE your D.O.F you need to *Use a smaller aperture
* Use larger subject distances
or * Use a wider angle lense
F4 = Shallow F32 = Deep.
In a focal shutter plane the flash should only operate when the shutter is fully open hence the flash synch is limited.
We also learnt about depth of field.
Boundaries of depth of field are referred to as D1 (For the near limit) and D2 (for the far limit)
Subject distance (u) refers to the distance from the camera to the subject...
We need to remember that the larger the aperture = the shallower the depth of field.
To INCREASE your D.O.F you need to *Use a smaller aperture
* Use larger subject distances
or * Use a wider angle lense
F4 = Shallow F32 = Deep.
Monday, March 8, 2010
E X P O S U R E
This weeks class was heavily based on exposure, and the tools used to achieve the correct exposure of an image.
Exposure depends on:
*ISO rating
*Subject lighting (The level of illumination)
*Subject reflectance
*Your personal preference
Because of these variables an image can either turn out over exposed, under exposed or 'correctly' exposed.
As an ISO standard we can see that a doubling of the rating = a doubling of the sensitivity
So an ISO of 400 requires half the exposure of an ISO of 200!
Setting a high ISO = Image degradation so therefore we know we should use the lowest ISO in any given situation to avoid image quality being disrupted.
We also know that digital cameras use a sensor to convert light to an electronic signal, which can then be manipulated by amplifying the signal.
We can also gather that the higher the illumination the faster the shutter speed needs to be, with a small aperture for the image to be correctly exposed, likewise when the illumination is low, the shutter speed used can be lower with a wider aperture. This sort of slow shutter and aperture width may require the use of a tri pod to avoid camera shake.
We also discussed meter reading types such as;
* AVERAGE - the entire field of view is averaged.
* EVALUATIVE - interprets scene based on data base
* CENTRE WEIGHTED - the majority of the measurement comes from the center
* SPOT - majority of light measured in a small area
Exposure depends on:
*ISO rating
*Subject lighting (The level of illumination)
*Subject reflectance
*Your personal preference
Because of these variables an image can either turn out over exposed, under exposed or 'correctly' exposed.
As an ISO standard we can see that a doubling of the rating = a doubling of the sensitivity
So an ISO of 400 requires half the exposure of an ISO of 200!
Setting a high ISO = Image degradation so therefore we know we should use the lowest ISO in any given situation to avoid image quality being disrupted.
We also know that digital cameras use a sensor to convert light to an electronic signal, which can then be manipulated by amplifying the signal.
We can also gather that the higher the illumination the faster the shutter speed needs to be, with a small aperture for the image to be correctly exposed, likewise when the illumination is low, the shutter speed used can be lower with a wider aperture. This sort of slow shutter and aperture width may require the use of a tri pod to avoid camera shake.
We also discussed meter reading types such as;
* AVERAGE - the entire field of view is averaged.
* EVALUATIVE - interprets scene based on data base
* CENTRE WEIGHTED - the majority of the measurement comes from the center
* SPOT - majority of light measured in a small area
Monday, February 22, 2010
F to the IRST REAL PHOTOG TECH CLASS
Clearly there are a lot of hard core technical properties that go into creating an image with a camera.
Our first real photography technology class today touched on this and was concerned mainly on basic camera controls and history with a heavy focus on exposure, shutter and aperture.
We sort of looked at camera technology in a chronological order, touching on camera history such as pin hole cameras and camera obscura (Latin words literally translation of 'dark room') We know the camera needs a few fundamentals to function:
* A Light tight body
* Lens to focus the image
* Means of capturing the image (Aka film/sensor)
* Aperture through which the light passes (A hole such as the pin hole in a pin hole camera)
* And a shutter to begin and end the exposure.
but today we moved on to look in greater detail at some of these fundamentals and the variables that can incur in them such as aperture sizes, shutter types and shutter speeds.
APERTURE: Basically a hole or opening that can be set to different sizes, hence allowing varied exposures. Basically for low light you're going to want to use a large aperture and vice versa. We were taught about Iris diaphragm (mechanism) which allow more control as it is adjustable like the iris in your eye, in comparison to apertures used in earlier cameras which were made of brass and usually had to be slotted in the camera and adjusted manually. The aperture size is associated with an F-stop which refers to a particular sized opening and an F-number which represents the F-stop. The F-numbers are kind of contradictory in a sense that the larger the number, the smaller the aperture size and the less light passed through.
We were also taught about the typical range of F-numbers with each step either doubling or halving the exposure... These were 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32
Shutter: The control that begins and ends the exposure, different lights require different shutter speeds. The lower the light, the longer the exposure, hence the longer the shutter needs to be opened.
There are two main types of shutters
* Focal plane and
* BTL/leaf
The shutter speed is described by numbers usually which are measured by fractions of seconds however can be measured by bigger rates than that. The larger the number the shorter the time the shutter is open for, again a little contradictory.
Again Shutter speed has a typical range of numbers which either double or halve the amount of light passed.
and last of all EXPOSURE which is the total amount of light which is captured, an image can either be over exposed or under exposed...
Basically we learnt a lot, still a long way to go but. The more I learn the more I realise I don't know!
Our first real photography technology class today touched on this and was concerned mainly on basic camera controls and history with a heavy focus on exposure, shutter and aperture.
We sort of looked at camera technology in a chronological order, touching on camera history such as pin hole cameras and camera obscura (Latin words literally translation of 'dark room') We know the camera needs a few fundamentals to function:
* A Light tight body
* Lens to focus the image
* Means of capturing the image (Aka film/sensor)
* Aperture through which the light passes (A hole such as the pin hole in a pin hole camera)
* And a shutter to begin and end the exposure.
but today we moved on to look in greater detail at some of these fundamentals and the variables that can incur in them such as aperture sizes, shutter types and shutter speeds.
APERTURE: Basically a hole or opening that can be set to different sizes, hence allowing varied exposures. Basically for low light you're going to want to use a large aperture and vice versa. We were taught about Iris diaphragm (mechanism) which allow more control as it is adjustable like the iris in your eye, in comparison to apertures used in earlier cameras which were made of brass and usually had to be slotted in the camera and adjusted manually. The aperture size is associated with an F-stop which refers to a particular sized opening and an F-number which represents the F-stop. The F-numbers are kind of contradictory in a sense that the larger the number, the smaller the aperture size and the less light passed through.
We were also taught about the typical range of F-numbers with each step either doubling or halving the exposure... These were 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32
Shutter: The control that begins and ends the exposure, different lights require different shutter speeds. The lower the light, the longer the exposure, hence the longer the shutter needs to be opened.
There are two main types of shutters
* Focal plane and
* BTL/leaf
The shutter speed is described by numbers usually which are measured by fractions of seconds however can be measured by bigger rates than that. The larger the number the shorter the time the shutter is open for, again a little contradictory.
Again Shutter speed has a typical range of numbers which either double or halve the amount of light passed.
and last of all EXPOSURE which is the total amount of light which is captured, an image can either be over exposed or under exposed...
Basically we learnt a lot, still a long way to go but. The more I learn the more I realise I don't know!
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