Freezing Action w/Speedlights

Icebear · February 8, 2012

There was a recent thread that inspired me to do some testing. Here's a first look at what I'm cobbling together.
This is just some newspaper sheets affixed to a bicycle wheel. I shot it with a Nikon SB-600 and SB-800. The 600 was set to 1/64th power, and the 800 at 1/128th power. The 600 was triggered by radio, and the 800 optically slaved off the flash from the 600. So, no preflashes. Got it? Pretty boring, eh? Oh, yeah, manual exposure f/8 1/250th.

Why's it worth a second look? The wheel was spinning. By my crude calculations, the 27" diameter rim was running at around 21mph. I intend to do some more rigorous testing, but I make no claim that any of it will be carefully controlled. I don't care about the numbers. I just want to get better at stopping action.

1. Full Frame

2. Here's about a 100% crop out at the rim.

pathfinder · February 8, 2012

Nice demonstration of how brief the flash is from a speedlite that is dialed way back, John.

Very cool!

johng · February 9, 2012

Icebear - flash duration is in the neighborhood of 1/200-1/8000 of a second. The key to stopping motion lies in how much contribution ambient light makes to the exposure. You generally want the camera's exposure set to at least 2 stops below "ambient" to freeze motion. Any closer and you see ghosting. Here are some samples of my son throwing his football. Image 1 is 1/60 f3.2 and ISO 800. Image 2 drops the ISO to 400.
Image 1:

Image 2:

See the ghosting in the ball/arm in shot 1 vs. shot 2? By the way, even shot 2 has SOME.
Also notice something else - shot 1 has 2 different color temperatures because of the directional light. In shot 2, the temperature is more consistent because the light source is dominated by the flash.

However, it's a balancing act. The more you rely on flash as the dominant source the more powerful that flash has to be. AND the more you get a stark difference between your subject and background. Sometimes that difference looks ood and sometimes it doesn't.

Here's the technique in a more real-world situation:

Some people like the stark difference between subject and background, others do not.
Here's a shot without flash:

Both have their pros/cons.

Icebear · February 9, 2012

Actually, the flash durations in my shot were about 1/30,000th (SB600) and 1/40,000th (SB800). These are NOT typos. Speedlight pulses are way shorter than studio strobe pulses. As for ambient, here's the shot with only ambient. Same ISO, same exposure setting. Not gonna get any ghosting from that.

REAL WORLD
Unless you're shooting very close to your subject, the power settings I used for this shot aren't particularly useful. Seriously, 1/128th power? But things are still pretty interesting at 1/8th with the Nikon speedlights. 1/8th power still gives you a flash duration of only 1/5900th on an SB800. Gang four of those puppies and you have a 1/2 power flash with a pulse that will stop any human generated motion. That is where I'm hoping to go with this project. I'm sure it's been done, but it's a new idea for me.

pathfinder · February 9, 2012

The gang of four speedlight holder does provide for interesting project contemplation, doesn't it?

I am surprised we haven't seen something like that used by some wildlife shooters at times.... With the higher ISOs available from Nikon, the very brief pulses of flash will hardly be noticed by many animals, I suspect.

I did use fill flash a few times in Africa, and the lion did not react at all; but one should only do that on their own recognizance, of course....

Icebear · February 9, 2012

pathfinder wrote: »

The gang of four speedlight holder does provide for interesting project contemplation, doesn't it?

I am surprised we haven't seen something like that used by some wildlife shooters at times.... With the higher ISOs available from Nikon, the very brief pulses of flash will hardly be noticed by many animals, I suspect.

I did use fill flash a few times in Africa, and the lion did not react at all; but one should only do that on their own recognizance, of course....

Or with a very different kind of "shooter" standing over one's shoulder.

Sam · February 9, 2012

There is a Strobist video out that goes into this subject. The basic thought process is the same as yours. Use multiple speed lights at low power for short duration to freeze motion.

Sam

Bryce Wilson · February 9, 2012

Neat test, thanks for sharing!

Now on to a stupid question...

How does one figure out what speedlight power setting will give you two stops below ambient, say in an ice arena?

I bet I slap my forehead when I read the answer.:D

pathfinder · February 9, 2012

You are wanting your subject lit by flash two stops brighter than ambient, aren't you? Or are you really wanting to shoot in ambient and use the flash for 2 stops under fill flash? Nah!!

Meter for ambient with ISO, shutter speed, and aperture in Manual mode. Now, without changing your aperture, set your shutter speed two stops faster than needed for ambient, and shoot with your flash in ETTL is one way.

A way some folks use, is to meter ambient exposure, and set that in your camera with the shutter speed two stops faster, to give you the darker ambient in Manual Mode. Now start adding flash power until you get the forground exposure you are wanting with your flash in Manual mode as well.

johng · February 10, 2012

for what it's worth - it isn't just shutter speed you can change - you can change shutter, aperture OR ISO or any combination of the 3. This is important because of the flash synch speed (usually 1/250 or so). In the two photos I posted above I used ISO to drop the camera's exposure settings and freeze action.

pathfinder · February 10, 2012

johng wrote: »

for what it's worth - it isn't just shutter speed you can change - you can change shutter, aperture OR ISO or any combination of the 3. This is important because of the flash synch speed (usually 1/250 or so). In the two photos I posted above I used ISO to drop the camera's exposure settings and freeze action.

Yes, I agree.

I did not suggest High Speed Synch either, and all of these may be used, or needed.

How about describing to Bryce , your techniques for setting exposure with ambient two stops down from your flash.

Icebear · February 10, 2012

pathfinder wrote: »

How about describing to Bryce , your techniques for setting exposure with ambient two stops down from your flash.

Yes, please. I don't see how changing the ISO affects the ratio of flash to ambient in the exposure.
I assume we're talking about manual exposure mode.

pathfinder · February 10, 2012

Or aperture, alone, either, John.

Changing ISO, without changing flash output power, WILL change the flash guide number if shooting with manual flash, of course.

johng · February 10, 2012

ISO affects exposure just like aperture and shutter speed. You'll see some articles discuss how that isn't the case and they'll show photos like the ones with people posed with city far in the background. That's completely different - when the ambient light is on your main subject (i,e. not two different lighting situations as depicted in these other photos) ISO absolutely has an effect. It's exactly a reason I took the photos I did of my son throwing the nerf. Here's the deal:
Whether you use ISO, aperture or shutter speed to adjust the exposure in manual WITHOUT flash/strobe and you adjust down, do you agree the photo is darker? When you have a camera exposure 2 stops below ambient light on your subject the resulting image is really dark. It's just as dark regardless of which of the 3 constraints you changed. So, when the flash burst goes off, there's only enough light recorded during the burst to record a successful image.

As for determining "two stops below" - meter the shot as you would without flash on - however you normally do that. Even take some test shots. Then adjust your exposure values. Typically I'll lower my ISO to 800 so I don't need noise reduction. AND I'll close down my aperture to f4-5.6 for football so I can get 2 players in good focus and get sharper results than my sigma 120-300 2.8 produces at 2.8. The light falloff takes care of my subject isolation. Shutter speed then stays around 1/300 to help with ghosting in case I'm a bit "over" the 2 stop situation.

Icebear · February 10, 2012

johng wrote: »

Here's the deal:
Whether you use ISO, aperture or shutter speed to adjust the exposure in manual WITHOUT flash/strobe and you adjust down, do you agree the photo is darker? When you have a camera exposure 2 stops below ambient light on your subject the resulting image is really dark. It's just as dark regardless of which of the 3 constraints you changed. So, when the flash burst goes off, there's only enough light recorded during the burst to record a successful image.

I'm not usually this dense, but I still can't see how ISO affects ambient any differently than flash?

johng · February 11, 2012

Icebear - turn the flash off. Set a manual exposure with ISO at 800 in your house so a subject is exposed properly. Good? Now change the ISO from 800 to 200. Take another photo. look at the photo. Does it look darker to you?

Icebear · February 11, 2012

johng wrote: »

Icebear - turn the flash off. Set a manual exposure with ISO at 800 in your house so a subject is exposed properly. Good? Now change the ISO from 800 to 200. Take another photo. look at the photo. Does it look darker to you?

Of course. That was never in doubt. It would be darker whether you shot with ambient OR flash.

johng · February 11, 2012

Icebear wrote: »

Of course. That was never in doubt. It would be darker whether you shot with ambient OR flash.

Without flash it is darker - correct. SOOO, the camera/flash needs to output more light to compensate. Exactly the same as if you left ISO alone and increased shutter speed. However you drop the exposure, the flash needs to produce more light to compensate.

Icebear · February 11, 2012

johng wrote: »

Without flash it is darker - correct. SOOO, the camera/flash needs to output more light to compensate. Exactly the same as if you left ISO alone and increased shutter speed. However you drop the exposure, the flash needs to produce more light to compensate.

Changing the ISO has NO effect on the flash:ambient contribution ratio. Yes, it affects the exposure, but it affects the flash and ambient identically.

The question was how to change them relative to each other. ISO will not do that.

johng · February 12, 2012

OK John - go ahead - let me know when you have an explanation for what you see in the two photos I posted - you can see that not only did changing the ISO affect the freezing of motion it also affected the contribution of the ambient light to the color of the photo.

Icebear · February 12, 2012

johng wrote: »

OK John - go ahead - let me know when you have an explanation for what you see in the two photos I posted - you can see that not only did changing the ISO affect the freezing of motion it also affected the contribution of the ambient light to the color of the photo.

Not enough information. There's no exif data in the image. And even if there were, I probably wouldn't know if you'd used TTL. See, that would have changed the whole equation, because you would not have kept the flash output the same. But seriously, John, all changing the ISO does is change the sensitivity of the sensor. How does that affect the ratio of flash to ambient in any image?

johng · February 12, 2012

John - of course I used TTL. If I change exposure values and keep flash output the same the photo would be too dark. Maybe that's where we are not connecting. Flash output has to go up as exposure goes down to keep your subject looking correct. Whether you drop the exposure by changing ISO, aperture or shutter speed - same thing. Instead of using TTL I could have used manual flash settings but I would have had to increase power between shot 1 and shot 2 - and why? Because the exposure went down. Less light recording on the sensor so flash output must be increased.

Icebear · February 12, 2012

That pretty much explains our disconnect, John. With TTL you have no direct control over the flash's power setting. It's all on autopilot. The whole idea of this thread was to use very low power settings on the speedlights in order to keep the pulses as short as possible, yet still have adequate light for exposure.

That's why we were discussing multiple speedlights on manual at low power settings.

I don't have any way to measure this stuff, but will try to do some results-oriented testing with as many as four speedlights in TTL. I gotta get that bicycle wheel spinning a bit faster. TTL, if it works in this scenario, will sure make sports shots easier. Manual flash power settings are tough when you can't control flash-subject distance. Seriously though, properly exposed athletes at say 1/6000th sec?? What's not to like?

rwells · February 13, 2012

John,

I think you may be missing the main point in stopping motion in a "sports world" scenario.

As johng has pointed out, if your flash output is within 2 stops of ambient, then your going to get ghosting, no matter how powerful or short your flash duration burst are.

Re-shoot your newspaper wheel. Make sure that your flash output and ambient are only 1 stop difference. Do you see any ghosting? Keep experimenting with the flash to ambient exposure ratios and you will clearly see what johng is trying to explain.

In the real world, you will start to encounter variables that tend to make it difficult for your camera and flash to stop action. Your sync speed is what, 1/250 sec? Now that you've hit that limit, you have to work with ISO, aperture and flash power, you open up your lens to say f/2.8, now you have ISO and flash power to work with. (it should be obvious that you can't control distance to flash on a lot of sporting events) You only have so much flash power, and to keep from ghosting your ambient needs to stay at least 2 stops under your flash output, that's where you hit the wall, so to speak.

No amount of input will be more valuable to you than your own experimentation. Were just trying to point your efforts in the right direction.

Hope that helps...

Icebear · February 13, 2012

rwells wrote: »

John,

I think you may be missing the main point in stopping motion in a "sports world" scenario.

No amount of input will be more valuable to you than your own experimentation. Were just trying to point your efforts in the right direction.

Hope that helps...

Thanks Randy. Still though, I'm not missing John's point. I fully understand that changing ISO changes the equation. That was never in question in my mind. I was discussing shooting in manual exposure and manual flash. John was thinking in TTL terms all along. We were having two separate and nearly unrelated conversations about the same subject. Clearly, unless you're shooting "sportraits" where you can control the flash-to-subject distance, shooting field sports calls for TTL. That or a brain and fingers way faster than mine.

vdotmatrix · May 10, 2015

Icebear wrote: »

Thanks Randy. Still though, I'm not missing John's point. I fully understand that changing ISO changes the equation. That was never in question in my mind. I was discussing shooting in manual exposure and manual flash. John was thinking in TTL terms all along. We were having two separate and nearly unrelated conversations about the same subject. Clearly, unless you're shooting "sportraits" where you can control the flash-to-subject distance, shooting field sports calls for TTL. That or a brain and fingers way faster than mine.

THAT's IT??? No more discussion? So, we are first starting in manual mode on camera. I take an ambient light reading. Sha-bang!!!! ball park is 2 stops below ambient.

what do I know? I know that for at around 8ft , 400ISO, 125th sec on 1/8th power in my exposure is around f8 (bright shade I can get an acceptable exposure with roughly 30% contribution from the flash.....)

So would I cut the flash power by 2 stops ( ooopps...beers...) I am going outside to stop the flights of honey bees in and out of the hive.

Gary752 · May 10, 2015

John, As you know, ISO, Shutter Speed, and F-Stop control ambient light. Only ISO and F-Stop controls flash power. Looking at the chart below that has been prepared by Scott Robert Lim, If you have a setting of SS=200, ISO=200, and an F-Stop of 4.0, to get a proper exposure you need a flash setting of 1/32. If you prefer more light from the flash, looking at the chart below, by changing the ISO to 400, and not changing the flash setting or the F-Stop, you would have the equivalent of 1/64 flash power. Same goes for only changing the F-Stop from the original settings to F 2.8. Also note that the chart below is for 6-8ft distance from subject. If you move the flash in to 3-4ft you would increase the amount of light by 2 stops, so using the orignal settings above, and moving the flash in to 3-4 ft, you would need a flash setting of 1/128. Hope this helps!

GaryB

vdotmatrix · May 11, 2015

Gary752 wrote: »

John, As you know, ISO, Shutter Speed, and F-Stop control ambient light. Only ISO and F-Stop controls flash power. Looking at the chart below that has been prepared by Scott Robert Lim, If you have a setting of SS=200, ISO=200, and an F-Stop of 4.0, to get a proper exposure you need a flash setting of 1/32. If you prefer more light from the flash, looking at the chart below, by changing the ISO to 400, and not changing the flash setting or the F-Stop, you would have the equivalent of 1/64 flash power. Same goes for only changing the F-Stop from the original settings to F 2.8. Also note that the chart below is for 6-8ft distance from subject. If you move the flash in to 3-4ft you would increase the amount of light by 2 stops, so using the orignal settings above, and moving the flash in to 3-4 ft, you would need a flash setting of 1/128. Hope this helps!

GaryB

OKAY....so is this chart specifically for stopping action by using flash? or a modified guide number system?

ziggy53 · May 11, 2015

vdotmatrix wrote: »

... I am going outside to stop the flights of honey bees in and out of the hive.

Action Stopping bees is very similar to Action Stopping hummingbirds:

STROBIST Winter Treat: Frozen Hummingbirds

The-Digital-Picture - Hummingbird Photography Tips

vdotmatrix · May 11, 2015

ziggy53 wrote: »

Action Stopping bees is very similar to Action Stopping hummingbirds:

STROBIST Winter Treat: Frozen Hummingbirds

The-Digital-Picture - Hummingbird Photography Tips

Very nice work but I have to come out and say it: how do I do this?

I am shooting manual right?
Are my flashes all dialed down on manual to some power based on the ambient light reading?

I can put 3 flashes on flexes and now what...I have read this post but I am missing something very small that isn't putting all together for me.

still getting ghosting

ziggy53 · May 12, 2015

Ambient is more enemy than friend. You want the primary exposure coming from the flashes. Control ambient on the subject as possible with large pieces of corrugated cardboard or similar.

I suggest practicing with a single leaf to start. Set the camera/tripod close to a bush with a protruding branch and focus on a single leaf at the end.

From the second link:

"5. Starting Settings:

Camera set on manual
ISO-200
Shutter @ highest sync speed i.e. 1/200 or 1/250th
f/16
White balance set to flash"

Skip the flash for now and get control of ambient light until subject is very dark. Do this by obstructing ambient light sources with cardboard or whatever you have available.

Once the subject is at least 5 stops below middle gray (very dark), start adding the flashes.

"Flash set to manual and 1/16th power"

You may also wish to use less flash power for an even shorter effective exposure, and add more flashes.

Use distance and number of flashes to adjust flash intensity on the subject. Once you achieve a balanced exposure for the subject, record all of the distances to subject (camera, and each flash) and translate your setup to the bee hive location.

Freezing Action w/Speedlights

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