Freezing a dancer jumping with flash and flash duration advice

[Manfred M]

+1 to Bill's comments.

The only thing that really pops out in your photocomposite is the mixed light issue you are facing there. The figure on the left has a far cooler tone than the moving dancer who is illuminated by both ambient and flash. I'd be tempted to warm that image up in post before working the dancer into the shot. Gelling your flash with 1/2 CTO to full CTO would give you a more neutral look to all the shots.

With regard to the light spilling past your model onto the curtain, there are two or three things to try to control this. In practice, because I do not know your location or equipment, I can only suggest in generalities. The two things that we try to do with spill light is to either prevent it or to mitigate its impact. This can be accomplished in several ways (I often use a combination of these techniques).

1. The inverse square law is you friend - if possible position the subject further away from the curtain so that light drop off means that little light is hitting the curtain. The percentage drop of decreases the further the light is away, so by positioning the light as close as possible to the subject the light level drops off more quickly and objects that are further away get less illumination.

2. Prevent the spill light from hitting the curtain you are shooting against in any meaningful way. The first step is by positioning your light (distance, angle and tilt) so that little or no light hits places it shouldn't.

On studio equipment, the light shaping tools prevent light spill. I have grids that let me narrow the beam from my soft boxes and reflectors.

Flagging the lights - by putting a "flag", i.e. a black object that does not reflect light close to my light source, I can prevent the light from the flash ending up in places I don't want it to go. I typically attach a piece of black foam core to a C-stand and position it in such a way that the light is blocked from hitting places that I don't want it too.


All of these techniques require trial and error to get them to work properly, which is why I suggested that shooting tethered for the type of work you are doing has many advantages.

[William W]

. . . The only thing that really pops out in your photocomposite is the mixed light issue you are facing there. The figure on the left has a far cooler tone than the moving dancer who is illuminated by both ambient and flash. I'd be tempted to warm that image up in post before working the dancer into the shot. Gelling your flash with 1/2 CTO to full CTO would give you a more neutral look to all the shots. . .

Yes I was thinking about this too. Previously I wanted to commend the improvement and I didn't have much time to write anything else, and certainly not enough time to go into detail.

I just had close look. Taking into account that the light DIRECTION is different and also it is an HARDER light for the image at camera left I also note that the left hand Subject’s Skin Tones are more EXPOSED than the right hand Subject. I concluded that as well as using a gel for the Flash for this type of composite image; ensuring that a CONSISTENT exposure for Skin Tones would also be a great benefit.

I then did an experiment, here are the results:



Viewing the image from left to right:

The left hand Subject is as per the original by teigas
The next is a facsimile of about 1½ to 2 Stop less exposure only
The next is a facsimile of the less exposure AND also a ½~ ¾ CTO Filter
The right hand Subject is as per the original by teigas

Looking at only the majority of the skin tone area on the midriff and face and the highlights of the hair, I note how close “about 1½ to 2 Stop less exposure only” is to the RH image.

Having done this test both certainly do have an effect, because the “less exposure AND also a ½~ ¾ CTO Filter” is really a very close fit to the RH Subject.

WW

[teigas]

Thanks for all the help last time. I made a new thread (link below) and hope some of you that helped me last time might help me a little again. Now this time some dancers have invited me to the same place but to shoot them im motion. They as always had limited time, so i think i will try to get some of them with me at a later point. They also had a guy that should run some stage lights for them.
So my questions is, if they crank up the stage lights will i manage do shoot them without any flash? I guess that deppends on a lot of things. But have anybody have any experience with that?

I now if i set the shutter time to 1/200 and use a strobe i would block out the most of the ambient light, and just use a flash, and if i use an einstein flash the duration of the flash will freeze them. Any experience what shutter speed i need to freeze a dancer in a jump?

But will the einstein still be able to freeze them if i lower the shutter speed? And let in more stage light ? Or will the stage light then overpower the einstein strobe?

The new post: Shooting dancers in stage light or use flash? Or mix?
.

[Manfred M]

Unfortunately, you are on your own here. We have given you the theory you need to accomplish what you are trying to do, but the specifics of your shooting situation are so highly variable, that we cannot give you any specifics. Let me recap a few concepts for you.

1. For flash (without shooting high speed synch), the fastest shutter speed you can use will be your camera's synch speed. The flash burst will be shorter than the length of time that the shutter is open.

2. The Einstein 640 and small flash have somewhat similar operating characteristics. The higher the power level, the longer the flash duration. When looking at stopping motion, always look at the t.1 time (i.e. the length of time that 90% of the flash). This behaviour unique to the Einstein units (other studio flash units may also perform this way, but I am not aware of any. Other types of studio lights tend to have the shortest flash at maximum power and the length of the flash increases as the power output decreases.

The Einsteins have two operating modes; Action Mode and Color Mode. The Color Mode is what I normally use as it provides the most consistent colour temperature between shots. You can sacrifice a bit of colour temperature repeatability for a faster flash by using Action Mode. The only time the two modes give you identical results are at full power.


http://www.paulcbuff.com/e640.php



3. Small flash (speedlights) tend to have a maximum output that is an order of magnitude lower than studio flash. This means that speedlights are going to give you a lot less light output than studio flash. Your Einsteins have a maximum output of arond 640 W-s whereas a high end small flash is going to be in the range of 70 W-s.

4. Changing the shutter speed to a setting that is lower than the synch speed for your lights will have no impact on the amount of light from the flash that affects the image, but the longer the exposure the more the ambient light will come into play. As has been mentioned in previous posts, the colour temperature of the studio flash will be different from the ambient light from the stage lighting.

Note: This published synch speed applies to small flash only. Studio lights tend to fire more slowly and you might have to use a slightly slower shutter speed.

5. High speed synch (HSS) will cost you around two stops of light. I know PocketWizards suggests that you can use the Einsteins in a HSS mode. I have tried to do this with my units, but have not had any success. As Bill has noted in his reply, you will lose 2 stops of light in HSS mode. This mode seems to work well with my Nikon Speedlights.

6. If you are shooting with Einsteins, the best way to freeze your subjects would be to shoot at the highest speed at or just below the published synch speed of your camera + use the lowest power setting you can get away with. This will tend to push you to a wide aperture setting, so you will be dealing with a narrow Depth of Field (DoF).

Bill has gone over this in the other thread you posted in: Shooting dancers in stage light or use flash? Or mix?

7. If you wish to check out the amount of impact that the ambient studio lighting has on your image, shoot the camera at the shutter speed / aperture setting / ISO that you plan to shoot at WITHOUT using any flash. That will show you the contribution that the ambient light makes on the image. If it is too much. either turn down the ambient lights or reduce the aperture until you get a black image.

8. Shooting mixed light can give you interesting images as the ambient light will give you a blurred image and the flash will freeze the dancer. Look at the front curtain / rear curtain (Nikon speak) or first curtain / second curtain (Canon speak, if I remember correctly), as this setting give you totally different looking results.

[teigas]

Unfortunately, you are on your own here. We have given you the theory you need to accomplish what you are trying to do, but the specifics of your shooting situation are so highly variable, that we cannot give you any specifics. Let me recap a few concepts for you.

1. For flash (without shooting high speed synch), the fastest shutter speed you can use will be your camera's synch speed. The flash burst will be shorter than the length of time that the shutter is open.

2. The Einstein 640 and small flash have somewhat similar operating characteristics. The higher the power level, the longer the flash duration. When looking at stopping motion, always look at the t.1 time (i.e. the length of time that 90% of the flash). This behaviour unique to the Einstein units (other studio flash units may also perform this way, but I am not aware of any. Other types of studio lights tend to have the shortest flash at maximum power and the length of the flash increases as the power output decreases.

The Einsteins have two operating modes; Action Mode and Color Mode. The Color Mode is what I normally use as it provides the most consistent colour temperature between shots. You can sacrifice a bit of colour temperature repeatability for a faster flash by using Action Mode. The only time the two modes give you identical results are at full power.


http://www.paulcbuff.com/e640.php



3. Small flash (speedlights) tend to have a maximum output that is an order of magnitude lower than studio flash. This means that speedlights are going to give you a lot less light output than studio flash. Your Einsteins have a maximum output of arond 640 W-s whereas a high end small flash is going to be in the range of 70 W-s.

4. Changing the shutter speed to a setting that is lower than the synch speed for your lights will have no impact on the amount of light from the flash that affects the image, but the longer the exposure the more the ambient light will come into play. As has been mentioned in previous posts, the colour temperature of the studio flash will be different from the ambient light from the stage lighting.

Note: This published synch speed applies to small flash only. Studio lights tend to fire more slowly and you might have to use a slightly slower shutter speed.

5. High speed synch (HSS) will cost you around two stops of light. I know PocketWizards suggests that you can use the Einsteins in a HSS mode. I have tried to do this with my units, but have not had any success. As Bill has noted in his reply, you will lose 2 stops of light in HSS mode. This mode seems to work well with my Nikon Speedlights.

6. If you are shooting with Einsteins, the best way to freeze your subjects would be to shoot at the highest speed at or just below the published synch speed of your camera + use the lowest power setting you can get away with. This will tend to push you to a wide aperture setting, so you will be dealing with a narrow Depth of Field (DoF).

Bill has gone over this in the other thread you posted in: Shooting dancers in stage light or use flash? Or mix?

7. If you wish to check out the amount of impact that the ambient studio lighting has on your image, shoot the camera at the shutter speed / aperture setting / ISO that you plan to shoot at WITHOUT using any flash. That will show you the contribution that the ambient light makes on the image. If it is too much. either turn down the ambient lights or reduce the aperture until you get a black image.

8. Shooting mixed light can give you interesting images as the ambient light will give you a blurred image and the flash will freeze the dancer. Look at the front curtain / rear curtain (Nikon speak) or first curtain / second curtain (Canon speak, if I remember correctly), as this setting give you totally different looking results.

Thank you for the great help and advice. I think i will try a few without any flash also.. Any suggestions what shutter time i should be at to be able to freeze the motion? 1/500 - 1/1000?