Approve the Cookies
This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies and our Privacy Policy.
OK
Index  •   • New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Guest
New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Register to forums    Log in

 
FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 20 Aug 2018 (Monday) 21:39
Search threadPrev/next
sponsored links
(this ad will go away when you log in as a registered member)

Stroboscopic Question

 
huntersdad
Goldmember
4,571 posts
Likes: 190
Joined Nov 2008
     
Aug 20, 2018 21:39 |  #1

I've tried to find something on Google, but haven't been successful.

If you're using the Multi-flash function, how do you determine the right flash power to use? I know it needs to be pretty dark, so I'm looking to hopefully be able to to fire at 1/2 second intervals and stop action.

Possible or not possible?


Facebook (external link)

http://WWW.BLENDEDLIGH​TPHOTOGRAPHY.COM (external link)
5D4 / 35 F2 / 50L / 85 1.8

  
  LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as a registered member)
monty28428
Cream of the Crop
Avatar
10,121 posts
Gallery: 1 photo
Likes: 248
Joined Jul 2007
Location: Carolina Beach
     
Aug 20, 2018 22:19 |  #2

Certainly possible

See some examples here -> https://photography-on-the.net …hread.php?t=383​186&page=1




  
  LOG IN TO REPLY
huntersdad
THREAD ­ STARTER
Goldmember
4,571 posts
Likes: 190
Joined Nov 2008
     
Aug 20, 2018 22:40 |  #3

monty28428 wrote in post #18688938 (external link)
Certainly possible

See some examples here -> https://photography-on-the.net …hread.php?t=383​186&page=1

How do you determine the flash power need to stop the action and get a full freezing of the action? I tested it today in my garage and got nothing but images that looked like ghosting. Nothing was frozen or sharp.


Facebook (external link)

http://WWW.BLENDEDLIGH​TPHOTOGRAPHY.COM (external link)
5D4 / 35 F2 / 50L / 85 1.8

  
  LOG IN TO REPLY
Wilt
Reader's Digest Condensed version of War and Peace [POTN Vol 1]
Avatar
41,354 posts
Gallery: 1 photo
Likes: 2385
Joined Aug 2005
Location: Belmont, CA
Post edited 6 months ago by Wilt. (2 edits in all)
     
Aug 20, 2018 23:03 |  #4

huntersdad wrote in post #18688958 (external link)
How do you determine the flash power need to stop the action and get a full freezing of the action? I tested it today in my garage and got nothing but images that looked like ghosting. Nothing was frozen or sharp.

Let us assume some things for the purposes of understanding, with a mythical flash unit...

  • At full power, 'full' exposure is 10' at f/22 (measured by flash meter), light output is 1/400
  • At half power, 'full' exposure is 10' at f/16 (measured by flash meter), light output is 1/800
  • At 1/4 power, 'full' exposure is 10' at f/11 (measured by flash meter), light output is 1/1600
  • At 1/8 power, 'full' exposure is 10' at f/8 (measured by flash meter), light output is 1/3200
  • At 1/16 power, 'full' exposure is 10' at f/5.6 (measured by flash meter), light output is 1/6400
  • At 1/32 power, 'full' exposure is 10' at f/4 (measured by flash meter), light output is 1/12800
  • At 1/64 power, 'full' exposure is 10' at f/2.8 (measured by flash meter), light output is 1/25600
  • At 1/128 power, 'full' exposure is 10' at f/2 (measured by flash meter), light output is 1/51200
  • At 1/256 power, 'full' exposure is 10' at f/1.4 (measured by flash meter), light output is 1/102400



In strobo mode, at 1/16 power, 'full' exposure would need to be f/5.6, and because the flash is firing 16 times per second, it only fires 16 times in one second before running out of power in the power capacitor.
If you change to strobo mode at 1/32 power, full exposure should be f/4, but you shoot at f/5.6 so the subject is faintly 'transparent' and underexposed due to underexposure against a black background.

If your movement is faster than can be frozen by the brief burst (1/12800) of light, the image of the subject will not be sharply defined but 'smeared' across the frame by the motion.

Does that help you understand the concept?

If your user manual gives you an ISO 100 Guide Number at the power setting you choose, simple compute using the general formula

Guide Number = Distance * f/stop

where distance is measured from light source to subject.

You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

  
  LOG IN TO REPLY
F2Bthere
Goldmember
Avatar
1,032 posts
Likes: 452
Joined Oct 2015
     
Aug 25, 2018 21:35 |  #5

It depends on your flash. If you have a manual, look at it. Or check on the web.

Generally speaking, the duration of the flash (how long it is on) is faster as you use a lower power setting.

So if you can't find documentation, set your flash to the lowest power, set your camera to get an exposure and try it.

Then you can adjust to see how far up you can go with the strobe you have and still arrest motion.


C&C always welcomed...
On my images, of course, and on my words as well--as long as it's constructive :).
https://www.instagram.​com/storyinpictures_co​m/ (external link)

  
  LOG IN TO REPLY
inkista
Senior Member
Avatar
612 posts
Likes: 69
Joined Oct 2007
Location: San Diego, CA, USA
     
Aug 28, 2018 14:58 |  #6

huntersdad wrote in post #18688958 (external link)
How do you determine the flash power need to stop the action and get a full freezing of the action? I tested it today in my garage and got nothing but images that looked like ghosting. Nothing was frozen or sharp.

You have to kill the ambient for flash to "freeze the action", and the flash should only hit the subject that's moving (not your background). If, say, you have three bursts, and the light is hitting the background, the background gets lit three times, but the subject only get lit once in each position as it moves.

Remember, every flash image combines light from the ambient (light that isn't from the flash) and the light from the flash. You can almost think of it like combining in layers in photoshop.

Start with killing the ambient. If, taking an image without the flash isn't giving you a black frame, you're not killing the ambient.

As for flash power, for me, it's generally a matter of how high can I set it so that the flash can still do the multiple bursts without having to wait for recycling (refilling the capacitor from the batteries). The higher the power, the slower the bursts have to be. My TT685 can only full-power recycle about once every two seconds. So, 1/2 power would be fine. But if I wanted bursts at 5Hz (1/5s), I'd probably have to be at 1/16 power or thereabouts.

Ambient exposure is controlled by iso, aperture, and shutter speed.

Flash exposure is controlled by iso, aperture, flash power, and flash-to-subject distance.

So, adjusting the iso or aperture to get more flash exposure will also run the risk of getting more ambient exposure as well. You can try moving the flash closer to your subject if you are forced by recycling time to lower the flash power.


I'm a woman. I shoot with a Fuji X100T, Panasonic GX-7, Canon 5DmkII, and 50D. flickr stream (external link)

  
  LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as a registered member)

1,772 views & 1 like for this thread
Stroboscopic Question
FORUMS General Gear Talk Flash and Studio Lighting 
AAA
x 1600
y 1600

Jump to forum...   •  Rules   •  Index   •  New posts   •  RTAT   •  'Best of'   •  Gallery   •  Gear   •  Reviews   •  Member list   •  Polls   •  Image rules   •  Search   •  Password reset

Not a member yet?
Register to forums
Registered members may log in to forums and access all the features: full search, image upload, follow forums, own gear list and ratings, likes, more forums, private messaging, thread follow, notifications, own gallery, all settings, view hosted photos, own reviews, see more and do more... and all is free. Don't be a stranger - register now and start posting!


COOKIES DISCLAIMER: This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies and to our privacy policy.
Privacy policy and cookie usage info.


POWERED BY AMASS forum software 2.1forum software
version 2.1 /
code and design
by Pekka Saarinen ©
for photography-on-the.net

Latest registered member is kitchentime
464 guests, 355 members online
Simultaneous users record so far is 15144, that happened on Nov 22, 2018

Photography-on-the.net Digital Photography Forums is the website for photographers and all who love great photos, camera and post processing techniques, gear talk, discussion and sharing. Professionals, hobbyists, newbies and those who don't even own a camera -- all are welcome regardless of skill, favourite brand, gear, gender or age. Registering and usage is free.