Introduction To EngineeringCamera Lab #2 - 2

Agenda Open cameras, remove batteries, discharge

capacitors, and disassemble/reassemble ! Sketch critical elements of the shutter

mechanism Estimate Shutter speed from photos of bike

wheels

Important notes:

Each group must record data Make sure one person in each group

gets all the data!Make sure data is given to all group

members

Measuring Blur Angle

Measure the blur angle () with a protractor

Estimating Shutter Speed

Measure the blur angle () with a protractorThe radius of the wheel is rThe bicycle traveled at 15 mph. Convert this to in/sec.

v 15 mph 15

mileshr

5280ft

mile12

inft

3600

sechr

264

insec

The amount of travel per revolution is

c 2r

inrev

The angular speed is given by

If is the blur angle in degrees, the fraction (f) of a revolution is

f deg rev

360deg

360rev

v / c v

2rinsec

revin

2642r

revsec

42.0r

revsec

Estimating Shutter Speed

The time (t ) for the wheel to move the fraction (f ) of a revolution for a constant angular speed is related to f by:

f tThe time (t ) is expressed in the formula:

t f

360

rev

42r

revsec

r

360(42.0)sec r

15,100sec

Estimating Shutter Speed

• The speedometer actually measures the angular velocity of the wheel axis. It assumes a wheel diameter of 26” to convert to ground speed. Therefore, use r = 13 in and assume θ = 12 deg;

t12(13)

15,100sec0.010 sec = 10 milli sec

Estimating Shutter Speed

Making the Camera Safe

Pry open the five snap fits that hold the back cover: both ends, top, bottom, back.

Remove the back case, and take out the battery. Note battery orientation (+ down)!

If the front cover falls off, put it back on without touching any part of the circuit board

Making the Camera Safe

Wind the shutter release by rotating the blue wheel until it stops.

Press shutter release to trigger the flash. Take off the front case, and hand the camera

to the instructor. Don’t touch anything on the circuit board, especially the small black can!

The instructor will touch a screwdriver across capacitor leads to discharge the capacitor.

The camera is now safe to handle.

Front of CameraSnap to release lens assembly

Capacitor Capacitor leads

Older Type of Lens Assembly

Shutter Cocked for Picture

Pivot allows shutter to rotate open when arm moves to right.

Shutter Open

Brass bar connected to circuit board

Spring tab connected to circuit board

Contact between shutter and bar completes flash trigger circuit

Shutter in closed position

Summary of Lab Steps

Remove back of camera, remove battery, wind and release shutter/flash; have instructor discharge capacitor.

Measure blur angle, compute shutter speed, and record value.

Disassemble and reassemble camera with emphasis on shutter mechanism.

Sketch critical elements of shutter mechanism.

Assignment

Read Camera Lab 2 materials CAREFULLY!!