shutter speed with flash

[delhi]

Hello,
When my built in flash pops up, the shutter speed should be faster right? So say in a dim environment where the camera register a Tv of say 1/10. But when the flash pops up it should register say 1/200 (hypothetical). The camera adjusts for the light that the flash will provide.
But it is not doing so with my 550ex? The camera's Tv still remained as if the flash was not activated. Am I missing something here?
Please help.

thanks.

[SimonG]

... But when the flash pops up it should register say 1/200 (hypothetical). The camera adjusts for the light that the flash will provide. ...
Nope, you're not missing anything. Your camera will always meter for ambient light... the flash will then try to determine how much power is necessary to illuminate the subject (I believe that the flash will operate as fill in Tv and Av modes). Remember, when shooting with flash you are really balancing two separate exposures at the same time.

[Jim G]

Try reading the EOS flash bible, I believe there's a link to it in the sticky here...

[Curtis N]

The camera adjusts for the light that the flash will provide.This is a common misconception. Camera can't know ahead of time how much light the flash will provide. It doesn't know the subject distance, angle of the flash head, what it's bouncing off, or if there is a diffuser attached. It can only make this determination after firing its preflash and measuring the light from it.

[delhi]

so what can I do? Shoot in M and force the shutter speed to be faster since I have the flash going?

[SimonG]

That really depends on what you are trying to do, but that's one approach that will work. You can set the shutter speed to max sync, pick your aperture, and then adjust ISO to ensure that you are getting a proper exposure. If you do this for indoor photography however you are going to completely overwhelm the ambient light, giving you harsh shadows from the flash.

If you give some sort of indication of the environment / type of shot that you want, you're apt to get some other suggestions on how to handle it.

[MrWills]

so what can I do? Shoot in M and force the shutter speed to be faster since I have the flash going?

Shutter speed really has no effect with the exposure using the flash. Shoot in M and set Shutter to maximum sync speed. 250 at the max not sure your camera. Then adjust aperture and ISO to get correct exposure, you can also adjust the flash. I use the histogram and use it to adjust my settings. I hope that helps you some or makes sense. :D

[delhi]

OK I should better qualify the question. This issue of shutter speed and Flash occured to me when I was shooting a portrait of my friend indoors. They turned out blurry and a quick check on the info it showed that my Tv was at 1/10. I was using Av at that time and the aperture was set for like 3.5 or something. I guess I should've used my tripod, but I was just horsing around 'showing off' my new flash. :)

[Wilt]

OK I should better qualify the question. This issue of shutter speed and Flash occured to me when I was shooting a portrait of my friend indoors. They turned out blurry and a quick check on the info it showed that my Tv was at 1/10. I was using Av at that time and the aperture was set for like 3.5 or something. I guess I should've used my tripod, but I was just horsing around 'showing off' my new flash. :)

A Canon on Av mode is programmed to use its flash as 'flash fill', using the shutter speed in a slow mode to permit the ambient light to register on the sensor. That is why the Time value of the shutter was set to 1/10 by the camera. You did nothing wrong, other than merely not have any idea that Canon engineers designed the camera to behave in that manner!

[Curtis N]

I was using Av at that time and the aperture was set for like 3.5 or something.When you use Av or Tv mode, you're telling the camera that you want it to expose for ambient light. Those modes are pretty useless when flash is your main light source. Indoors with flash, M works best.

[René Damkot]

Then adjust aperture and ISO to get correct exposure, you can also adjust the flash.

adjusting aperture and ISO will have no effect whatsoever on flash exposure (assuming withing range), since ETTL determines exposure.
aperture and ISO will affect ambient exposure, as will shutterspeed. FEC will affect flash exposure.

[Redbird_xo]

adjusting aperture and ISO will have no effect whatsoever on flash exposure (assuming withing range

I have discussed this in another thread and I, too, made a mistake thinking aperture and ISO have something to do with flash exposure. Did a test a couple of hours ago and confirmed what you said is true. In my test, shutter of 1/1000 sec actually produced a slightly brighter picture than 1/500 sec, 1/250 sec and 1/125 sec given constant aperture and and ISO throughout.

Learned something new today and thanks to Leo.

[Wilt]

Redbird, your observations are in the dangerous area of HSS...speeds of 1/1000 and 1/500 cause the flash to behave somewhat differently because it has to output its light in a manner which permits the moving slit of the shutter curtain to provide even flash exposure...which very severely limits the max range of the flash. (see a recent thread and table published by Curtis on this topic, quantifying the reduction in distance). Do not base your conclusions on observations made at those speeds! Rely solely on observations below 1/250 first, and then come to your conclusions. after that, see how HSS causes those previous observations to be deviated from!

[Redbird_xo]

Hi Wilt, being as curious as George (I won't end up with a flash in my tummy), I did a number of shots mainly to see if shutter speed is irrelevant in terms of exposure when the flash unit is operating with its range. I started out below 1/100 sec and went up with small increments (like 1/3 of a stop or something like that). The sole reason to go as high as 1/1000 sec is, again, being curious. From looking at the histogram, I saw fairly constant distribution long before I hit 1/1000 sec. Therefore, I didn't draw any conclusion based on 1/1000 sec shutter speed. Though I thank you for your input. Now I am curious to see the table published by Curtis. :)

[Wilt]

Redbird, it will surprise you just how intensely high shutter speeds can cause limited range with the HSS flash. Yes, if you stay within range, you're fine. You simply run out of range sooner than you think! Read Curtis N's first message in this thread http://photography-on-the.net/forum/showpost.php?p=1905789&postcount=1

[Curtis N]

Redbird,
It should be pointed out that, while shutter speed (at flash sync or slower) does not affect flash exposure, it DOES affect the ambient light exposure. So if using slower shutter speeds gives you brighter images, it could be that it's the ambient element of the exposure that is causing that.

If you try those experiments again in a dark room, I'm guessing you won't see a difference in exposure of flashed pictures when you vary the shutter speed.

[Redbird_xo]

Redbird,
It should be pointed out that, while shutter speed (at flash sync or slower) does not affect flash exposure, it DOES affect the ambient light exposure. So if using slower shutter speeds gives you brighter images, it could be that it's the ambient element of the exposure that is causing that.

If you try those experiments again in a dark room, I'm guessing you won't see a difference in exposure of flashed pictures when you vary the shutter speed.

Hi Curtis, I am aware of the ambient light impact on flash exposure. Nevertheless, thanks for pointing it out. I did my test with a letter size Kodak gray card filled the entire frame. I also make sure the flash was operating within its range. The ambient light is mostly from 6500K tubes in the room. But I suspect its effect was minimal (but definitely present) due to the close proximity between the camera and the gray card. The test was done to prove that I was incorrect about shutter speed in flash exposure as it was pointed out by Leo.

[MrWills]

adjusting aperture and ISO will have no effect whatsoever on flash exposure (assuming withing range), since ETTL determines exposure.
aperture and ISO will affect ambient exposure, as will shutterspeed. FEC will affect flash exposure.

Is that also true for manual mode on the flash. I shoot in manual for camera and flash most of the time?

[Curtis N]

Is that also true for manual mode on the flash. I shoot in manual for camera and flash most of the time?No. With your flash in manual mode, the exposure will be affected by distance, flash zoom setting, aperture and ISO. Change any of those things and you'll see the distance scale on the flash change.

[MrWills]

Thanks curtis thats what I thought my first comment in the thread was ment in manual mode on the camera and flash.