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

2. 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

3. Outline How the camera works –lens –shutter –aperture –film How the digital camera works Some rules of thumb for good photos

4. The Camera image lens aperture virtual image

5. 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

6. 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.

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. The Rule of Thirds

14. 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