The Art And Physics Of Photography

The Art And Physics Of Photography - Transcript

Lesson 1 The Art and Physics of Photography
Digital Photography MITSAA IAP 2003 Rob Zehner

General Info
Instructor Rob Zehner zehner pobox com Meeting time 7 00 8 30 p m every Wednesday We will meet in front of the SAA office Please bring any borrowed equipment with you to class every week

Outline
How the camera works
lens shutter aperture film

How the digital camera works Some rules of thumb for good photos

The Camera
virtual image lens image

aperture

The Lens
Purpose to collect light from the sample and focus it on the film plane Focal length distance from the lens to the film plane for a single element lens when focused at infinity
Longer focal length more magnification

The Shutter
Prevents light from reaching the film Opens to allow light through In most cameras the shutter is actually two pieces of cloth or metal that move across the film plane one after the other Shutter speeds are usually reported as reciprocal seconds e g 1000 1 1000th sec

The Shutter continued
Shutter speed determines relative effects of motion
Slow shutter speeds blurry images Fast shutter speeds stopped motion Rule of thumb 1 60th or faster will eliminate the effects of shaky hands

Also determines film exposure
2X shutter speed 1 2 the light to the film 1 2 the shutter speed 2x the light to the film

The Aperture
Placed at the focal point of the lens Typically a circular opening Diameter of circle determines amount of light that gets to the film Reported as f number ratio of focal length to aperture
Larger f number smaller opening

The Aperture continued
Size affects depth of field distance in front of and behind the focal plane that is in focus
Small apertures large f number greater depth of field

Size also affects film exposure
Increase of 1 stop x 1 414 1 2 as much light Decrease of 1 stop 1 414 2x as much light

The Film
The film s job is to detect light
Photons hit the film and promote a reaction

Film speed is typically reported in ASA
Higher ASA faster film needs less light Doubling ASA 1 stop less light needed

Rule of thumb sunny f16 rule
Under bright sun use f16 and 1 ASA shutter

Generally film with a higher ASA is grainier

Digital differences
Film is replaced by an image sensor
Photons hit the sensor and create charge which is converted to voltage which is converted to bits All image sensors are actually analog

Shutter may be electronic not mechanical Image sensors are subject to thermal noise
Long exposures may not be possible

Digital differences continued
For now image sensors are smaller than film
Image size is a function of focal length vs sensor size Small sensor short focal length Short focal length means it s hard to get small apertures Short focal length means that depth of field is relatively larger at all apertures

The Rule of Thirds

Other tips for good photos
Use natural light
Avoid on camera flash as much as possible

Find new perspectives
Move around Take horizontal and vertical shots



Find converging lines Play with negative space Take candid portraits When in doubt bracket exposures