MT1 Flashcards
What is a camera? (2)
optical instrument to capture still images or to record moving images, which are stored in a digital system or on film.
A camera consists of a lens and a camera body which holds the image capture mechanism.
What is the camera obscura? (3)
Leonardo da Vinci used the Camera Obscura to figure out how the human eye works.
It consists of a darkened room or box with a small hole or aperture on one side. Light from outside passes through the aperture and projects an inverted image of the external scene onto the opposite surface inside the darkened space.
The camera obscura operates on the principle of light rays traveling in straight lines. When light passes through the small aperture, it projects an inverted and reversed image of the external scene onto the surface opposite the aperture.
What parts does a DSLR Camera have? (6)
What is the difference between a DSLR and a mirrorless System?
Apetenture, Lenses, Flip up mirror, a viewing system, a shutter, a sensor
a DSLR uses a mirror to reflect light onto the image sensor, while a mirrorless camera lets light directly hit the sensor, resulting in a quieter and quicker process.
What is Exposure?
the amount of light that reaches your camera’s sensor, creating visual data over a period of time.
Which camera settings change the exposure? (3 long)
Shutter speed
* defines the time between opening and closing the shutter
* measured in 1/x seconds (parts of seconds): i.e 1/100s, 1/500s, 1/4000s or 2’’, 10’’ for 2 / 10 seconds
* longer exposure time = more light exposes the sensor = brighter image
Iris/Apeture/F-Stop
* setting for opening of the lense
* measured in F-Stops (i.e. f1.4 / f/1.4 or simply 1.4)
* from one full F-Stop to the next means twice or half the amount of light
* focal lenght ÷ diameter of aperture opening = F-stop
→ (40mm focal length/20mm aperture = F2.0)
* standardised F-Stops (only full F-Stops) → F1.8 = most open, F11 = smallest opening
ISO/gain
* in this case: measurement for the light sensitivity of the sensor or film
* ISO 50, 100, 200, 400, 800,..
* video cameras: Gain, measured in Decibel + / - 6db = double / half light sensitivity
* twice the ISO value = twice the sensitivity = image is twice as bright
-> shutter speed can be reduced and / or aperture can be closed further reduce sensitivity
* Disadvantage: the higher the ISO setting differs from the sensor’s native ISO value, the more the quality of the recording suffers (grain increases, loss of contrast, loss of colors, loss of sharpness)
What is the dynamic range of the sensor or film? (5)
-quotient of maximum and minimum exposure of the sensor or film → big impact on the way the images will look
-measured in F-Stops or EV (Exposure Value)
-Scenes with high contrast can only be properly recorded without further adjustments with a sensor with an equally high dynamic range.
-Recording with a sensor with lower dynamic range results in over- and / or underexposed parts of the image
-If the scene has a high contrast which can not be met by the sensor, you need to adjust your camera settings in a way, that the parts of the image that are important to you are properly exposed
What is HDRI?
-Multiple recordings with two or more different exposure settings (highlights, low lights, average) are combined.
What is the camera doing when you set it to fully automatic mode? Does the camera know what you are trying to record?
-Fully automatic mode: camera adjusts ISO, Shutter Speed and Aperture in a way, that the average of the measured area of the frame matches the reference value and avoids also motion blur with relatively short exposure time
What is a reference value? (2)
-the camera compares the incoming light with the reference value of 18% neutral gray
-Result: scenes that you want to look dark will be recorded too bright and the other way around.
How do I get the perfect exposure settings?
-Metering of reflected light (objects metering)
-Metering of the light source (direct light metering)
Example DSLR: metering refrelected light
* 0 = reference value 18% neutral gray is matched
* -1 = 1 EV under exposed in comparison the reference
* +1= 1 EV over exposed in comparison the reference
* Point means 1/3 EV.
How to meter a light source
* you need an exposure meter with calotte (spherical diffusor cap) * the light meter is turned towards the light source directly in front of the objects / persons * feed the light meter an ISO value and shutter speed (video or film, usually 1/50 s) and receive an F-Stop value * refrence value 18% neutral gray
What is EV (Exposure value)? (2)
-the amount of light obtained from the combination of “aperture value” and “shutter speed’’ to match the refrence value of 18% gray
-one EV- step +/- is relative to one F-Stop or twice / half shutter speed
What is white balance? what is color meter? (2)
white balance
* measures colors and compares them with the neutral reference value or a set reference value
→ colors will then be adjusted according to the reference
* for neutral color representation a white balance is necessary but automatic white balance can lead to unwanted color representation
* enables a consequent color impression
color meter
-enables the exact metering of light sources (direct light metering)
-absolutely necessary in situations that involve studio lights with different color temperatures
-doesn‘t work with all LEDs
what is color temperatur? (3)
-measured in kelvin → Kelvin is a unit to define the light color impression
-when something is orange it is not as hot as something glowing blue
-Kelvin scale is a reference to the light emission of a glowing „black body“ heated to different high temperatures
-Color temperature varies during different times of the day, weather conditions, light sources and situations
What are Additive vs. Subtractive Colours?
additive: red, blue and green combined and become white/ grey (light colors)
substractive colors: colors we see, together they become brown -> subtract from one another
What lense types are there? what are their differences? (5)
- convex (thicker at the centre and thinner at the edges, can converge a beam of light coming from outside and focus it to a point on the other side)
- concave (have at least one face that is curved inward and spreads out light rays that have been refracted through it
Convex
* Bi-Convex: both sides bent outward, has shorter focal length
* Plano-Convex: one flat surface and one spherical surface
Concave
* Bi-Concave Lenses: Both sides have equal radius curvature and can deviate from incident light (bothcurved inward) * Plano-Concave Lenses: Both sides have equal radius curvature and can deviate from incident light but the lenses have one flat face and one concave and a negative focal length.
→ Convexo-Concave Lenses: one convex surface and one concave surface
What is an aberration? what are the different types and fixes each? (4)
difference from the ideal behavior of an optical system, such as a lens or a mirror.
* chromatic aberrations: Light frequencies refract in different ways (break up into different colors). → fix: use achromatic lense system: corrected to bring two wavelengths into focus on the same plane. * Spherical Aberration: Parallel light rays refract differently depending on the angle they meet the lens
** → fix: Aspherical Lens: light rays all meet at one point after existing lenseand don’t continue on
combi of more aberrations: Astigmatism: Bundles of light rays meeting the lens in an angle, refract differently depending on the angle. This results in varied focal lengths for the same bundle and an oval instead of a round image. At the edges the image becomes distorted
→ coma: Combination of Astigmatism and Spherical Aberration that appears with badly manufactured lenses : light rays incides on a lens not in parallel but at an angle to the optical axis, the ray will pass through the optic system in an unsymmetrical way due to different surface curvatures and rays are not bundled again in one image point
lower aperture to get rid of abberations
what is focal lenght? (4)
-distance between the center of the lens and the focal points
-changes the angle of view
* The smaller the sensor/film = the smaller the frame of the image * To get a bigger view of the image with small sensors even shorter focal lengths are required
what is crop factor? (3)
Crop Factor is the factor of how much of the image is cropped away with sensors smaller than 35mm format.
-full frame sensor: 35mm format
-24 (lenght) x 35 (width) mm
What is a so-called crop sensor and the crop factor?
Result: Smaller sensors require shorter focal lengths in order to show the same frame as longer focal lengths with bigger sensors.
what does a wide-angle lense do? what does a tele lens do? (3 each)
wideangle
* gives you a wide field of view → see more in one frame * short focal lenght * stretching and distortion of frame
Telelens
* brings distant subjects closer with the use of long focal lengths * use focal lenght that is shorter than the lenses lenght * extremely shallow depth of field
What does a CCD sensor do? (4)
CCD (Charged Coupled Device)
* consists of millions of tiny photo diodes * once light hits the photo diodes get charged → the charge gets transmitted simultaneously via semi conductors for further computation * advantages: very light sensitive, no rolling shutter effect -> lines get distorted at edges bc it reads out lines from top to bottom, temperal difference * disadvantages: expensive manufacturing, in comparison to CMOS slow, possible blooming
What does a CMOS sensor do?
What is the difference to CCD? (4 and 2)
CMOS (Complementary Metal Oxide Semiconductor)
* consists of millions of tiny photo diodes * once light hits the photo diodes they get charged → the charge is then transmitted row by row for further computing * advantages: reduced blooming, the signal of each diode is combined with an amplifyer * disadvantages: the amplifyer also amplifies the static noise, rolling shutter effect, less light sensitive than CCD
→ difference:
* ccd: simotanious reading of chart, all at once
* cmos: bottom read out first and top later, row by row reading → effect of picture
What is RGB and the Bayer Filter Array? What is interpolasition?
-RGB: Each color has its seperate but same image and all the promary colors are added together to produce the fnished picture with all colors (?)
-Bayer Filter Array: uses a mosaic pattern of raw data to interpret the color information arriving at the sensor, the digital algorithms are applied to interpolate the resulting Bayer pattern and turn it into full-fledged color data for the image.
-interpolation: use two values to calculate a missing value → fill up to get RGB images as result
What do we know about Light? (5)
- part of electromacnetic spectrum: waves, in different lenghts, made of photon particles
- can be reflected, absorbed, refracted, bent as a whole or in parts
- refraction amount changes on density of the transition between different mediums
- 400-700 light spectrum
- different wavelengths have different energy: shorter wavelengths have higher amount of energy
What is Young‘s double slit experiment? (3)
-proof of different wavelengths, bending, interference: light has the characteristics of waves
-proof of particles (photons): light has the characteristics of particles
shows us light interference,
shows us that that light bends and is made of waves and thus the pattern is waves
