Lesson 4 : 15.3.2010 - Shutter Speed, Aperture and D.O.F

Lesson 4 : 15.3.2010

Shutter Speed, Aperture and D.O.F

The Ideal Shutter Should
- expose each part of the film/sensor equally and simultaneously
- be silent in operation
- be vibration free
- little effort to set in motion
- effective exposure should be repeatable

Focal Plane Shutter
- flash should only operate when shutter is fully open
- flash synchronisation is therefore limited
- In order to achieve very fast speeds the second 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
- 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 speeds and when particular apertures are chosen
- shutter opens and closes at the same rate regardless of shutter speed chosen
- shorter time to uncover a small aperture
- longer time to uncover a large aperture

Depth of Field Definition
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 depth-of-field are referred to as the near limit (d1) and the far limit (d2).

Controlling D.O.F
Depth of field is increased by:
- using smaller apertures
- using larger subject distances
- using wider angle lenses

Lesson 3 : 1.3.2010 - Exposures

Lesson 3 : 1.3.2010 - Exposures

Today's lesson taught as a more indepth understanding of exposure as well as how to calculate different apertures and shutter speedsin certain situations.

In-camera exposure calculation

Exposure = Total amount of light used to create an image. This is controlled by shutter speed and lens aperture . The same amount of exposure can be achieved using a variety of combinations

Exposure
The exposure used in any given situations is dependant on the following major factors.

- The ISO setting (film/sensor sensitivity)
- The lighting (level of subject illumination)
- The subject (level of subject reflectance)
- Personal preference

Origins in film sensitivity ratings

film with high sensitivity to light has a high rating
film with low sensitivity to light has a low rating

DIN (Deutsches Institut für Normung)
ASA (American Standards Association)
ISO (International Standards Organisation)

- High level of illumination allows the use of faster shutter speeds and smaller lens apertures

- Low level of illumination allows the use of slower shutter speeds and wider lens apertures and may also require the use of a tripod.

Camera uses a reflected exposure meter

measures light reflected from the 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
MANUAL exposure measurement allows you to adjust this rendering.

In Camera Exposure Modes
Average - entire field of view is averaged
Evaluative - interprets scene based on data base
Centre Wweighted - majority of measurement in centre
Spot - majority of measurement in small area

Lesson 2 : 22.2.2010 - History of the Camera

Lesson 2 : 22.2.2010 - History of the Camera

Today's lesson took us through a basic history of the camera. Camera is a latinword meaning vault and obscura means darkness. The camera obscura was originally designed and used as a drawing aid. It has then developed into the camera that we all know and use today.

Brief History
1267 - Roger Bacon writes about the camera obscura from 10th century Arab scholars writings.
1490 - Leonardo Da Vinci describes one in detail
1558 - Giovanni Battista della Porta, suggests it be used as a drawing aid and then went onto install mirrors and a lens to revert the image and make it sharper and brighter.
1557 - First moveable camera obscuras appeared.
1676 - First reflex camera produced.
1685 - First telephoto lens

Light Sensative Materials
There were many significant discoveries from the early 1700’s to the early 1800’s but history records Joseph Niépce as the person responsible for the first permanent camera image, a view from his window in 1826.

This was an 8 hour exposure. - Bitumen of Judea on Pewter


Camera Basics
- light-tight body
- lens to focus the image
- means of capturing the image (film/sensor)
- aperture through which the light passes
- shutter to begin and end the exposure/capture

Aperture
- aperture means hole or opening
- different sized apertures allow exposure to be varied
- when light level is low, a large aperture can be used
- when light level is high, a small aperture can be used

Shutter
- mechanism to begin and end the exposure/capture
- early versions were simply a lens cap
- low light level requires a long exposure
- high light level requires a short exposure
- focal plane or between the lens (BTL/Leaf) variety

Shutter Types
- Focal plane: operates in front of the film ‘at’ the focal plane -
BTL or Leaf: operates inside the lens much like a diaphragm


Blogwork:

Familiarise yourself with your camera.

Canon 40D

- Shutter Speed Range: 30 - 1/8000 sec

- Lens Aperture Range: F1.0 - F91 (dependant on lens)

- Exposure Modes:
• Auto
• Program AE (P)
• Shutter priority AE (Tv)
• Aperture priority AE (Av)
• Manual (M)
• Auto depth-of-field
• Portrait
• Landscape
• Close-up
• Sports
• Night portrait
• Flash off
• Camera user settings 1 *
• Camera user settings 2 *
• Camera user settings 3 *

- ISO Range: 100 - 1600

- The preset white/grey balance:
• Auto
• Daylight
• Shade
• Cloudy
• Tungsten
• Fluorescent
• Flash
• Custom
• Kelvin (2500 * - 10000 K in 100 K steps)

- File Types:
• RAW (.CR2; 14-bit *)
• JPEG (EXIF 2.21) - Fine / Normal
• RAW + JPEG (separate files)
• sRAW (2.5 MP) *