emissivity of white camera lenses vs black lenses landon hansen trey mortensen
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Emissivity of White Camera Lenses vs
Black LensesLandon Hansen Trey Mortensen
Background• Canon claims that the white paint keeps the
camera lens cooler than the black paint• Helps protect thermally sensitive components • Used on large lenses ($$$$$)
Objective• Observe if the white paint is actually effective in
heat reduction and determine by how much• Compare measured results to theoretical work
Experiment• Two lamps in a large room at constant temperature
• Lens sat under lamps for 4 hours
• Measured the initial and final temperature with an IR thermometer
Assumptions• Steady state is reached
• α and ε based off of similar paints
• Inside temp is constant
• Only Natural Convection
• T∞ is Constant
• Lamps are equivalent to the sun
• For qbulb, use the wattage of the bulb
ProcedureG (Irradiation)
E (Emmision)
qconv (Free Convection)
T∞
Results Experimental
Dataα ε Initial Temp
(°C)Final Temp (°C)
White Lens .3 .887 16.0 18.8
Black Lens .956 .86 16.0 18.9
Calculated Results
α ε Initial Temp (°C)
Final Temp (°C)
White Lens .3 .887 16.0 33
Black Lens .956 .86 16 21
Conclusion• The white paint does remain cooler
• Calculation - Approx. 10°C difference• Measurements - .1°C difference
Sources of Potential Error• Nusselt Number assumption
• Assumed vertical cylinder
• α and ε were not measured but assumed• Noise based off of small temperature change• Assumed all white/all black lenses (no rubber grips)• Unknown exact lens dimensions
Recommendations• Stronger light source • Actual measured α and ε • Better controlled Environment
AppendixEmissivity and Absorption Table
Wiki.naturalfrequency.com/wiki/Absorptance_and_Emittance
For properties, derivation of equations and details of solution, see scans
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