Hello dear readers. I would like to engage you in a little trivia challenge. If I get good responses I’ll continue with yet more challenges – and prizes! Share this with your buds (after you’ve taken a crack at it), and yes, there is a prize. Read on…
Trivia Question
This is a multi-part question. Answer both parts in a sentence or two to get in the game. Good luck.
- In Photo 1 below, what caused the starburst effect seen near the top of the lighthouse and the porch light in the lower right?
NOTE: The starbursts were not added or modified by photo editing. - Without resorting to photo editing is it possible to get a different number of spikes? If so, how?
Photo 1: What caused these starbursts at Pigeon Point Lighthouse, Pescadero, California?
Contest Rules
The winner will receive $50 in cash – provided the following rules are met:
The prize will go to the first entrant who has correctly answered the trivia challenge and also attends the November, 2011 Star Circle Academy workshop. It is not necessary to sign up for or attend a workshop to enter the contest. The order in which the correct and valid entries are received (as determined from the timestamps on the comments) shall determine eligibility for the prize.
The staff of Star Circle Academy shall at its sole discretion determine which of the entrants have correctly answered the trivia challenge. If no entries are received or no correct answers are submitted no prize will be awarded.
How to Enter
To become a contestant, you must provide your answer in the form of a comment here 0r by using the “leave a comment” link at the bottom of this article. Only one entry per contestant is allowed. You must include your complete, correct name with your entry and a valid email address. Your email address will not be shown or used in any way except to contact you regarding this contest.
The staff and immediate family of Star Circle Academy are not eligible to win though they may enter the contest.
Entries will be kept secret until the contest ends on April 15, 2011 at 11:00 PM Pacific Daylight Time. Thereafter the first 10 entries judged to be correct will be revealed, along with the answers to the trivia challenge.
Good luck!
1- Stop down f stop
2- yes; switch lenses 😉
{Editor’s response: 1 – yes, but you haven’t said what causes the effect; 2 – partial credit as this is correct unless the lens you switch to has the same blade configuration. Score: 60%}
Post your answer as a comment. Again, good luck.
PS … your answer will not be revealed until April 15th so that people with “almost correct answers” won’t give others a head start.
There are 7 submissions so far (as of April 6, 2011). Some pretty strong answers so far… some not so much.
(Reposted by Steven from email: Sent: Tuesday, March 29, 2011 8:15 AM)
1) The star burst effect is caused by the light passing over the
aperture leaf of a very “stopped down” lens setting. (f/16, f/22 or
smaller opening).
2) Yes, you can change the number of star burst rays by switching to
another lens with an aperture configuration that uses a different
number of leaves.
Brian
{Editor’s response: 1 – correct, though the answer doesn’t state the phenomenon as “diffraction”. 2 – exactly! Verdict: 90%}
The starburst refraction off the lens blades. if there are 8 blades there are 8 rays. The only way to change the number of rays is by changing the number of blades, i.e., a different lens.
The intensity of the burst can be changed by increasing by increasing the f stop. Lower focal lengths at the same F-Stop creates smaller openings, so you should see more starburst intensity at shorter lengths. The greater intensity may cause the appearance of more starbursts.
I answer only as nobody else has. Unfortunately, I will not be attending the November, 2011 Star Circle Academy workshop, as I will be attending the Bristlecone workshop. I just felt compelled to attempt an answer as no one else had.
{Editor’s comments: The cause (diffraction – not refraction) is close. The relationship between rays and blades is correct and thus full credit for the second question. Bonus points also for noting that increasing the f/stop increases the intensity of the spikes. Final Score: 90%}
1) photo taken with higher (f18) than lower (f2.8) f stop that causes the 2 bright lights to have starburst.
2)a) change lense – this different lense must have a different number of blades that create the aperature size than the first lense – more blades more rays – fewer blades fewer rays
2)b) one could put a starburst filter on lense
{Editors response: 1 – how to create starburts is correct, what causes them (diffraction) is not stated. 2 – in the right ball park, except that a 7 bladed lens creates 14 rays while an 8 bladed lens will create 8. Score: 65%}
Answer 1: a small aperature (f-stop) will produce the starburst effect on long exposures.
Answe 2: more spikes can be achieved using filters that range from 2 to 8 or more spikes.
Hopefully I am at least CLOSE!
{Editor’s comment: Close. Answer 1 is partially correct but it doesn’t explain what causes the star pattern (diffraction) and long exposures are not required. Answer 2: No filters are required, so partial credit only. Score: 35%}
1. Starbursts are caused by diffraction- light spreading over the blades.
2. The number of spikes is based on the number of blades in the lens.
Also there are filters available for starbursts I’ve seen with 2 points to 8 points.
{Editors comments: 1 – nearly right. Light doesn’t spread over, but around the edge of the blades this is a meaningless symantic triviality so no loss of points, stopping down was not mentioned, however and this is required to get noticeable spikes. 2 – correct, but the question was “how to get a different number of spikes” +10% for suggesting filters as that will work, but is not the simplest answer (swapping lenses) which we assumed was implied by the statement. Score 80%}
1. A starburst is created when using a small aperture. It’s caused by diffracting light.
2. The smaller the aperture the more diffraction and therefore more points.
Thanks,
T
{Editor response: 1 – exactly correct. 2 – incorrect. The number of rays do not change with a change in aperture. Score 50%}