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PostPosted: Tue Jan 11, 2011 9:27 am 
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It seems you don't understand what the difference between shutter speed and sync speed is.
Watch this video and it will become clear.
http://www.5min.com/Video/How-Camera-Sh ... k-72416499
Whatever the flash speed, it is fast enough to freeze motion.
Flash speed varies according to the mode used or the power setting. But for current use it's always faster than 1/1000. You may find on the net many thousands of pictures with flash that stop a jumping person in the air or any other fast moving subject, and only in high end DSLR cameras the sync speed is more than 1/250
But if shutter speed is not fast enough, you may have blurred background (the parts in the picture not illuminated by the flash) due to camera shake or movement.

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Radu
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera
Canon580EXII
http://www.errre.net


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PostPosted: Tue Jan 11, 2011 2:33 pm 
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About flash duration
http://www.photosbykev.com/wordpress/20 ... -duration/

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Radu
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera
Canon580EXII
http://www.errre.net


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PostPosted: Tue Jan 11, 2011 5:27 pm 
Thanks for the info. When using off camera flashes such as the YongNuo 460II can i shoot @ 1/500th of a second to freeze motion ? If i use a second curtain sync setting ?

Also the YongNuo 460II boasts a FP Sync (hi speed sync) mode can someone confirm this please ? It also advertises a F (Fast) Sync mode. Some ideas on how this works would be very helpful.

I read that the lower the flash power setting like 1/64 instead of 1/1 will give a faster flash rate ? Is this common to all flashes ?


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 Post subject:
PostPosted: Tue Jan 11, 2011 11:06 pm 
Your shutter will always fire at your shutter sync speed no matter what you do with flash. To obtain a faster exposure to light may I suggest a lens that is at least an F2.8.

But yeah the shutter sync speed will always be the maximum you can use your flash at and as far as I know there is no way of making it faster.


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PostPosted: Wed Jan 12, 2011 5:56 am 
I have the 50mm f 1.8. :D . Niffty Fifty. But being a prime limits my shot composition.

But i still want to know for an offcamera flash. Being used independently. Im sure the camera doesnt TALK to the flash except give an electrical discharge which is relayed via wireless and the flash fires.

Your saying the minute a flash transmitter is hooked onto the hotshoe, the camera will move into limited shutter speed (x sync limit) mode ?

Im right now seeing pics of people doing mid-air freeze shots with aftermarket flashes and a 350d ive invested in a 500d and a 550d (soon be getting a 7d, i know i cud have got a 5d for this many bodies but i preferred staying within the EF-S lens mount family) and i cant get shots like that using these strobes or bodies ?


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 Post subject:
PostPosted: Wed Jan 12, 2011 6:26 am 
to be honest, I have no experience using flash in this way to capture fast action. i am a portrait photographer. However, what I am saying is that when you try to dial up your shutter speed, it will stop at 1/200 second while you have a flash set up with it via remote trigger or Shoe mount.

Also I ran across this when searching for an answer for you.

http://forums.steves-digicams.com/canon-eos-dslr/169895-yongnuo-yn467-550d-4.html


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 Post subject:
PostPosted: Thu Jan 13, 2011 5:39 am 
Then what im wondering is how come someone with a 350d body has shot a jump picture of them frozen in air with and off camera flash. Im sure the shutter speed must have at least been 1/400th and above ?


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PostPosted: Thu Jan 13, 2011 10:46 am 
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Ok, let's try again.
We are talking about 3 speeds
1. Shutter speed –the speed set on your camera
2. Flash speed –the duration of the flash light burst (equal or greater than 1/1000- depending on the flash power used, it can reach 1/35000 with canon 580exII at minimum power)
When the flash is in the hot shoe or connected with a TTL device (cable or wireless) the power or the duration is set by the camera in order to expose correctly. Flash speed depends on the power setting, the more power the longer it is, in normal situations (that is you don't shoot a bullet in midair) the duration is short enough to freeze almost anything.
3. Sync speed, the maximum speed on your camera at which the shutter is fully opened (Hope you watched that video.)
In an off camera flash situation where the flash doesn't talk to the camera:
1. The background is exposed by shutter speed and aperture, like a normal picture without flash. The fastest you can get is the sync speed(otherwise you’d get a partially illuminated frame because the shutter is not FULLY opened when the flash fires - do watch that video)
2. The foreground (your jumping guy) is exposed by flash light that hits it and aperture. So the jumping guy is always exposed with a speed greater than 1/1000 enough to freeze him in the air.
3. Because the flash doesn't speak with the camera it doesn't set its power automatically in order to expose the guy correctly, you have to set it manually. How? Test shots are the cheapest way.
4. So if you set your camera to the sync speed, the flash burst, because is so much shorter than the sync speed, will freeze your jumping guy in the air.
5. In conclusion, how do you do it? Put your camera in manual mode. Set aperture and shutter speed to expose the background correctly. Aperture has to be set for the DOF needed. Shutter speed you set according to what you want your background to look like ( darker or brighter) and fast enough to avoid camera shake. Your upper limit is the sync speed. Do some test shots without your subject. Now without changing you camera settings place you're off camera strobes in manual mode and do some test shots with the subject. If it's too bright turn down power, if the subject is too dark, crank it up or place the strobes closer, whatever suits your frame.

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Radu
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera
Canon580EXII
http://www.errre.net


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PostPosted: Thu Jan 13, 2011 11:38 am 
Ah Radu,

Thanks a ton for explaining so simply.

I grasp the concept correctly now. In other words we go fully manual ofcourse to highest sync speed as possible and then do the rest as usual as if i was just clicking merely a landscape shot and how bright or dark with saturated skies etc i wanted it. Then to this shot i add strobes sort of as a superimpose element and adjust to taste. In other words using my strobes to make him fit into this pretuned to landscape shot. Correct ?

The flash is 1/1000th of a sec so he is frozen in mid air. BUT since the cams actual shutter speed is slower than the flash burst speed......will it cause a trail or blur of the jump guy in addition to the frozen flashed part. Or it may show a residual part of the jump. Maybe underlit since theres no flash but yet ill have a clear frozen shot of him and then a slight blur also of the non-flashed time he was moving in front of the frame. Since the shutter is hypothetically at 200 on the body, this may not be very noticeable. But it will still be there ? Or am i wrong and will i get a razor sharp freeze of him ? This is the only part now that i dont get and an answer to this would enable me to order the YN flashes on ebay with peace of mind.

Regards


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PostPosted: Thu Jan 13, 2011 12:36 pm 
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To answer your last question.
It all depends on the speed of the subject and the amount of light you allow to reach the sensor. If your aperture is closed enough and/or shutter speed is short enough your fast moving subject will leave a very small impression on the sensor, not enough to be noticeable at all. So you guessed well, you have the latitude to change your settings in order to have a sharp frozen subject, or to have it leave trails on the frame. If the ambient light is strong enough you don't need strobes to freeze motion just set the appropriate shutter speed. If it isn't, then you can set up your camera like in my previous post and the main light on the subject is from the strobes and those will freeze motion and the picture will be very sharp.
Or if you want your subject to leave trails in the frame so suggest motion, set your shutter speed to a low value, let's say 1/15 then you'll have a very sharp frozen subject AND the trails. If you think a bit, you'll realize that because the flash fires when the first curtain has reached the edge of the frame the trails will be recorded AFTER the flash has fired until the second curtain closes the shutter, and will appear in FRONT of the subject. If you want the trails to follow the subject, as is more logical to suggest motion, then you have to set your flash/camera to the second curtain sync. In that mode the first curtain opens and the sensor records the trails and just before the second curtain starts to close the flash fires and you'll get a sharp subject and the trails behind it.

_________________
Radu
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera
Canon580EXII
http://www.errre.net


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PostPosted: Sun Jan 16, 2011 6:20 am 
But what if i want zero trails Radu ?

You said if ambient light is high just set the shutter speed high. But it wont let me go beyond 1/200th right when the flash transmitter is attached to the cam hot shoe ?

The YN flashes have a Fast Sync mode which basically flashes a series of times to capture fast motion so that as the slit in the shutter travels across the sensor it catches the entire image. How well does that work ?

Regards


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PostPosted: Sun Jan 16, 2011 8:48 am 
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Even with powerful flashes it's hard to beat sunlight at noon on a sunny day. Some use ND filters some shoot early in the morning, or late afternoon, in shade, use 4 to 8 strobes, and so on. Anyway it's not that easy. But, as you can see, not the flash is the real problem, the power differences are not that significant, the sun light is. So if you choose the right conditions it can be done. If your ambient light is not that harsh, you can get your subject frozen without trails. The there are many variables that come into play, one is the focal length another is the speed of your subject across the sensor. You have to experiment; I can't give you a precise recipe.
About the FP mode (high speed sync), it lets you use faster than sync speed but it has 2 important downs. First your flash power decreases drastically limiting your maximum distance to the subject and the balance with the ambient light, second you have to use TTL, that is, your flash(es) must be on your hot shoe or connected via TTL link , cable or wireless. Wireless TTL triggers are obscenely expensive, by the way. This mode is best used as a fill flash for portraits in broad daylight, when your sync speed is not enough if you want to shoot with an opened aperture in order to have a shallow DOF.

_________________
Radu
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera
Canon580EXII
http://www.errre.net


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PostPosted: Tue Jan 18, 2011 7:30 pm 
Thanks

Can someone here tell me if should get a white shoot thru umbrella or a reflective umbrella with my flash ?

Also while shooting strobist pics on roads etc (my country is a little conservative on these things so i cant set up light stands) is it ok to hold the shoot thru umbrella in the hand while the wireless receiver and flash unit is attached to the main rod of the umbrella. Have any of you worked this way holding the umbrella flash manually ?

Regards


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 Post subject:
PostPosted: Tue Jan 18, 2011 9:38 pm 
If you plan on shooting outdoors, Id suggest a soft box instead of an umbrella. You will find that a softbox will resist a little more wind and prevent it from blowing it over and wrecking your flash.

As far as holding it, It's very doubtful that you could hold a flash unit, aim it at the center of the umbrella and operate your camera all at once. Perhaps with an assistant holding it and a universal umbrella mount, you could do it but even then, they would have to hold it virtually in the same position for extended amounts of time in order to get a consistent exposure from photo to photo. I have found though most times you need an assistant, they are not available unless your paying them to be there.


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PostPosted: Wed Jan 19, 2011 3:44 pm 
Im so sorry that i didnt mention id ofcourse have someone helping me to hold the strobes. I thought the strobe will be mounted on some kind of clamp which is fixed onto the umbrella main post. A little high up and close to the spokes portion.

The person then has to only hold it at the place where there is usually a plastic hand grip. As one would typically hold a normal umbrella. The it can be pointed at the subject during the shot time. ???


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