# please help with t2i shutter speed



## samcolby (Apr 12, 2012)

when i'm using the built in flash, it will only let me set a maximum shutter speed of 1/200, even in tv mode. is this just because the flash is built in? thanks


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## 1000_Islander (Apr 12, 2012)

Yes, the max sync speed is 1/200 sec


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## samcolby (Apr 12, 2012)

oh ok, thanks, but with an external flash i would be able to set the shutter speed faster right?


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## LuckySe7en (Apr 12, 2012)

I have an external flash and I can only go up to 200 as well.  But I've never used if off camera so that may change things


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## Rgollar (Apr 12, 2012)

Once I put my external flash on it allows me to higher than 200.


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## marmots (Apr 12, 2012)

if you have an external flash, and put it on high speed sync, you can bump the shutterspeed higher


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## Overread (Apr 12, 2012)

!

It's only 9 or so mins long but that video gives you an easy to understand explanation for why you can't shoot faster than 1/200sec with your flash. If you find you get lost a little in some of the descriptions don't give up; just let it run its course and then watch it again to let the important parts sink into your mind.

In a very short version of an answer without explanation (because I'd only be repeating the video and leaving bits out) you can't shoot faster than your flash sync speed on a camera; that stands for any flash be it a built in pop-up or an external or a big studio flash. 1/200sec is your limit. However some will have a highspeed sync mode which will let you shoot faster, but the flash power will be significantly reduced as a result - good for fill lighting, but not quite strong enough for flash dominated shooting (unless you use more flashes) .


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## dimakuzmich (Apr 12, 2012)

it is always like that, with on camera flashes, you just got to work with you ISO or Apeture, i have the canon 580ex ii speed light flash and it can only let me go up to 200 max for the shutter speed,


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## TCampbell (Apr 14, 2012)

Here's the deal.  The focal plane shutter on the camera has to mechanically open and then later close the shutter.  The shutter takes time to move.  Each camera has a maximum flash-sync speed.  For your camera that speed is 1/200th.  This is the amount of time it takes for the focal plane shutter to open completely.  

It turns out the shutter has two moving halves referred to as "curtains".  You'd think the two halves would meet in the middle, but this doesn't give an even exposure.  Instead, they start at one edge.  The first curtain opens... The second curtain just sits still.  After the exposure is complete, the second curtain closes.   This is how it works when the shutter speed is at or slower than the sync speed (1/200th in your case).

For faster exposure, the first curtain starts traveling across and the second curtain starts "chasing" the first curtain -- even before the first curtain can fully open.  This means you effectively has a "slit" sweeping across the sensor to expose the image.  Each point on the sensor will only have been exposed for the set time... but they technically don't all get exposed at the same precise moment.  If the shutter speed is set to 1/1000th then the slit will expose only 1/5th of the sensor at a time.  

And this is a problem for the flash.  If the momentary burst of light occurs and any part of the sensor was blocked by the shutter curtain then you'll get an image with the exposed slit being bright, and the rest will be too dark.  To compensate, better flashes have a "high speed sync" mode.  This causes the flash to pulse repeatedly (VERY rapidly) so that each section of the sensor gets the same amount of light.  The downside is that since the flash will have to fire repeatedly and very rapidly, it can't fire at full power (otherwise the capacitors would have time to recharge for the next burst.).  The flash has to ration the power of each rapid pulse  to make sure it can expose the whole sensor for an evenly eased shot.


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## samcolby (Apr 16, 2012)

hmm, ok thanks for the help


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