Flash and Bracketing?

[taygull]

I know I can test this but I'm curious if anyone knows the answer?

I'm wanting to bracket some shots using either studio lights or Speedlights in M Mode.

Somewhere I'm thinking I read that the bracket feature won't work while shooting flash.

I want the shutter speed to change in my sequence.

[Wilt]

Shutter speed will have absolutely no effect on studio flash exposures (unless you end up exceeding the X-synch speed limit)...you HAVE TO alter Aperture or the Intensity of the light! Of course, altering Aperture also alters your DOF as well.

[PacAce]

I know I can test this but I'm curious if anyone knows the answer?

I'm wanting to bracket some shots using either studio lights or Speedlights in M Mode.

Somewhere I'm thinking I read that the bracket feature won't work while shooting flash.

I want the shutter speed to change in my sequence.

What exactly are you trying to achieve by the bracketing? Some flash units, like the 580EX, allow you to bracket the flash exposure automatically. However, if you are using studio lights or a Speedlite off camera or connect via the PC terminal, then you won't be able to bracket the flash exposure automatically.

[taygull]

Shutter speed will have absolutely no effect on studio flash exposures (unless you end up exceeding the X-synch speed limit)...you HAVE TO alter Aperture or the Intensity of the light! Of course, altering Aperture also alters your DOF as well.

That is 100% incorrect.

Reducing shutter speed will introduce movement and ambient light.

[taygull]

What exactly are you trying to achieve by the bracketing? Some flash units, like the 580EX, allow you to bracket the flash exposure automatically. However, if you are using studio lights or a Speedlite off camera or connect via the PC terminal, then you won't be able to bracket the flash exposure automatically.

What I'm trying to accomplish is to determine if the camera will or will not allow bracketing when the flash is hooked up.

By reducing shutter speed I introduce partial movement into the sequence of shots. The faster the shutter speed the less movement the slower the shutter speed more movement/motion.

I have a subject where I will be freezing part of the image but want motion to shown in another part. So what I'd like to do is bracket the shutter so I can get 5-7 shots in the same "motion" with varying degrees of motion.

[Curtis N]

Only way to auto-bracket shutter speed is in Av mode as far as I know.
I don't think using flash, dedicated or otherwise, will prevent use of that feature.

[PacAce]

What I'm trying to accomplish is to determine if the camera will or will not allow bracketing when the flash is hooked up.

By reducing shutter speed I introduce partial movement into the sequence of shots. The faster the shutter speed the less movement the slower the shutter speed more movement/motion.

I have a subject where I will be freezing part of the image but want motion to shown in another part. So what I'd like to do is bracket the shutter so I can get 5-7 shots in the same "motion" with varying degrees of motion.
Since the flash will always freeze the motion, I'm assuming that the motion that you want to capture will be lit by ambient lighting, right? in that case, you don't need flash exposure bracketing, which is what most of us were assuming you wanted to do.

When a dedicated flash is attached, AEB is automatically cancelled so you would only be able to do AEB with flash or strobe if it is connected via the PC sync terminal. But it takes time for the flash or strobe to recycle after firing so you'd need to wait until thte flash or strobe is ready before firing the next frame. That means you probably won't be able to shoot in burst mode unless you set the power of the flash such that it can keep up. Not sure if the strobe works the same way, though, as far as recycle vs power is concerned.

[Curtis N]

When a dedicated flash is attached, AEB is automatically cancelled.Hmm.

More stupid Canon programming.

But my B1600 at 1/16 power will keep up with 5 fps burst so it could be feasible.

[taygull]

Hmm.

More stupid Canon programming.

But my B1600 at 1/16 power will keep up with 5 fps burst so it could be feasible.

That is what I was thinking....

So I'm guessing (I'll try it later today), using my pocket wizards with some AB's I'll be able to use AEB. Since I am wanting a mix of ambient light in the shot I'm sure I can still get the shot with an ISO around 800 and power down the flash. DOF is not a huge concern either so I'm sure I'll have enough flexibility to cut the power so they can recycle quick enough.

Thanks!

[PacAce]

That is what I was thinking....

So I'm guessing (I'll try it later today), using my pocket wizards with some AB's I'll be able to use AEB. Since I am wanting a mix of ambient light in the shot I'm sure I can still get the shot with an ISO around 800 and power down the flash. DOF is not a huge concern either so I'm sure I'll have enough flexibility to cut the power so they can recycle quick enough.

Thanks!
Just a word of warning. The strobes have a longer flash duration than the flash units do so, depending on how fast whatever it is you want to capture the motion of, the strobe may not be able to do a good job of freezing it as well as the flash would.

See this thread for more details: http://photography-on-the.net/forum/showthread.php?t=320826&highlight=freeze

[Curtis N]

Chris, I will be interested to see the results.

[taygull]

Chris, I will be interested to see the results.

So will I!:lol:

I've got a backup plan and I may not even need to shoot this way...I just want to have it in my back pocket.

I'd share more on the specific image but since it is for a publicaiton I'm bound to not share much of the idea.

[taygull]

Just a word of warning. The strobes have a longer flash duration than the flash units do so, depending on how fast whatever it is you want to capture the motion of, the strobe may not be able to do a good job of freezing it as well as the flash would.

See this thread for more details: http://photography-on-the.net/forum/showthread.php?t=320826&highlight=freeze


Thanks, I'll check that thread out later today.

[Wilt]

That is 100% incorrect.

Reducing shutter speed will introduce movement and ambient light.

It is true about motion capture under certain conditions, and my earlier statement was an oversimiplification to an extent (but I wasn't trying to be the encyclopedia of studio flash in one message!).

But it is not '100% incorrect'! if the flash is the ONLY significant source of lighting in the scene, and your shutter speed is up near the max speed for X-sync, and your aperture is some typical studio flash exposure of around f/5.6 or f/8, and your ISO is set for quality reasons down around ISO 100, changing the shutter speed indeed will not make a difference in the exposure because the flash is making the entire exposure!

You qualified your conditions five messages later, so I had no idea of the purpose of your question. It would have helped to state the conditions and the goal, at the opening.

[taygull]

Shutter speed will have absolutely no effect on studio flash exposures (unless you end up exceeding the X-synch speed limit)...you HAVE TO alter Aperture or the Intensity of the light! Of course, altering Aperture also alters your DOF as well.


Fair enough Wilt,

but for other readers when you ay "Shutter speed will have absolutely no effect on studio flash exposures" that is a 100% inaccurate statement.

If you had said in an environment where there is no ambient light then you are correct. I never said I was in a studio or that there was a lack of ambient light.

I agree I could have given more info but...saying something has "absolutely no effect" is still not accurate with or without all the info.

[martinsmith]

Well, shutter speed has no effect on FLASH EXPOSURE unless exceeding x-sync so wilt is correct. However, it will make a difference to ambient.

[Wilt]

Fair enough Wilt,

but for other readers when you ay "Shutter speed will have absolutely no effect on studio flash exposures" that is a 100% inaccurate statement.

If you had said in an environment where there is no ambient light then you are correct. I never said I was in a studio or that there was a lack of ambient light.

I agree I could have given more info but...saying something has "absolutely no effect" is still not accurate with or without all the info.

We're debating nits here. For all intents and purposes, when most (not 'all', but 'most') people use a flash meter to meter studio flash lighting during typical (not'all', but 'typical') portraiture sessions and even for product photography, there is not a meaningful impact on the OVERALL exposure for typical circumstances, unless resorting to extremes...like super high ISO, or quite slow shutter speeds, and quite bright ambient light -- and that affects the AMBIENT lighting exposure, not the flash portion of the exposure, as has been pointed out.

I have shot flash under fluorescent lighting in the past, for example, and under ISO 400 the ambient-only exposure is around 1/60 f/2. So if my fundamental flash exposure is at f/5.6, I already am -3EV in ambient light brightness, and light at that level still registers as black. If I slow my shutter speed to 1/30 (+1EV), the ambient level is still -2EV, bright enough to make a scarecly perceivable difference in the black, with some discernable detail (vs. absolute black) but not enough to really sufficint to register motion blur well enough.