# Hike Mission Peak and Catch Sunset

#### In this photo:

There are no tags for this photo

Added by A former member
on Apr 20, 2011.

6 of 6 pages

• very cool bob! is this with a long exposure?

or cancel

• A former member

I think I know where he got the idea (http://blog.starcircleacademy.com/2011/03/driven-to-abstraction/)! I like it Bob! Trivia question: Bob took this shot by moving his camera while the lens was open... why do the lights look "dotted" instead of continuous?

or cancel

• A former member

I actually hadn't seen that blog post. It's an excellent explaination of camera movement and focus adjustment during long exposures though. I really need to read the Star Circle Academy blog more often. May - Yes, it was about half a second exposure at f5 and iso 100. One of the tricks is trying to remember that the movement in the image will appear as the opposite of the camera motion. So in this one the camera moved in a U shaped motion. Steven - That is a powerful question.

or cancel

• A former member

Flickering lights and short exposure and fast movement? =)

or cancel

• A former member

@Alex - close. Why were all the lights apparently flickering at the same time and rate?

or cancel

• A former member

i don't know =) was making a semi-educated guess.

or cancel

• A former member

Here is the answer: Nearly every light source in this photo is fed by 60 hz AC current. Our eyes don't notice it, but all those lights are flickering at a rate of 60 cycles per second. The movement of the camera in this case reveals the 60 hz cycle and shows each of the lights as dashed lines. All the lines are similarly dashed because they are all fed by 60 hz electricity. If you take a photograph lit by indoor light without a flash at 1/200 of a second you are likely to notice that sometimes your subject is lit, sometimes not - due to the same flickering lights phenomenon. So, give these each a try and see what you get! PS, I *think* it's possible to use the dashes to measure the angular speed of the camera motion AND the length of the exposure. I think it's also possible to determine the relative distances of each of the lights by comparing the lengths of their dashes. Anybody feel enough geek coming on to take a stab at these?

or cancel

### Want to comment on this photo?

Sign in, if you're already a member of this group or Join The Bay Area Photography & Exploration Society

## Other photo albums

• #### Afrolicious Hair Expo

13 photos

Activity on May 13, 2018

• #### Weekly Photo Project: Flowers

13 photos

Activity on May 11, 2018

• #### Weekly Photo Project: Urban Against Nature

1 photo

Activity on Mar 29, 2018

• #### Weekly Photo Project: Graffiti

8 photos

Activity on Mar 12, 2018

### Move photo

Do you want to move this photo to “__ALBUM_NAME__”?

Yes, I'm Sure

Yes, I'm Sure

### San Francisco, CA

Founded Nov 11, 2007

#### People in this Meetup are also in:

• ##### Walking in San Francisco for Health and History

12,693 Recreational Walkers

• ##### Live Music San Francisco

12,478 Music Lovers

• ##### East Bay Photo Walkers

1,076 EastBayPhotoWalk

• ##### SF Arts + Culture

12,199 Art + Culture Lovers

• ##### The San Francisco Photography Meetup Group

4,068 Photographers

• ##### Marin Photo Club Meetup

660 Photographers