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01-28-2008, 06:07 AM   #1
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Flash high speed sync.

Why are the flash sync of dslr cameras so slow?

I was testing my fuji f20 p&s and it would sync even at 1/600s or more.

01-28-2008, 06:43 AM   #2
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I cannot speak of the camera you mention, but with a focal plane shutter, such as a DSLR or Film SLR the flash must be fired when the shutter is fully open.

For my *istD this is 1/150 and the K10 this is 1/180. At speeds above these, the shutter speed is effectively achieved by having a small slit pass over only a portion of the sensor.

I too have questioned the sync speed, but for another reason. My PZ-1 had a shutter capable of 1/8000 shutter speed, with a sync speed of 1/250. If you consider that the sensor is only 16mm high (vertically travelling shutter) and not 24 as it was on the PZ-1, then assuming the same front and back curtain speeds, and shorter distance, I would have expected 1/400

Note there is also available on the K10 high speed sync, where the flash is fired multiple times, as the "slit" mentioned above moves past the sensor. This can allow flash photography (but at reduced flash power) at speeds higher than 1/180.

It may be, and perhaps a P&S techie can respond that the camera you mention takes advantage of the even smaller sensor to achieve the higher speed, it may also be that they do not use a focal plane shutter, but simply sample the chip over a short er time. Remember, the P&S cameras have the sensor powered full time, and take image information for things such as focus, and white balance adjustment. Perhaps they just sample the chip at 1/600 of a second
01-28-2008, 07:12 AM   #3
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Take a read here at Strobist.com. P&S often have electronic shutters where the "physical shutter is open all at once for all of your shutter speeds. I.e., no slit for the flash to deal with." - David Hobby, Strobist.

Thanks
01-28-2008, 02:55 PM   #4
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QuoteOriginally posted by Mikhail Quote
Take a read here at Strobist.com. P&S often have electronic shutters where the "physical shutter is open all at once for all of your shutter speeds. I.e., no slit for the flash to deal with." - David Hobby, Strobist.

Thanks
that's a very interesting, does this mean that cameras equipped with live-view theoretically have extremely fast maximum flash-sync speeds? if so, i think this could be one of the greatest advantages of live-view.

01-28-2008, 03:33 PM   #5
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QuoteOriginally posted by bb.hyena Quote
that's a very interesting, does this mean that cameras equipped with live-view theoretically have extremely fast maximum flash-sync speeds? if so, i think this could be one of the greatest advantages of live-view.
I dont believe so as the shutter mechanism is still the same, ie. not electronic. For live view the shutter remains open and the LCD reads what the sensor is reading, the shutter mechanism hasn't change. Atleast not to my knowledge..

Thanks
01-28-2008, 04:51 PM   #6
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QuoteOriginally posted by Lowell Goudge Quote
I cannot speak of the camera you mention, but with a focal plane shutter, such as a DSLR or Film SLR the flash must be fired when the shutter is fully open.

For my *istD this is 1/150 and the K10 this is 1/180. At speeds above these, the shutter speed is effectively achieved by having a small slit pass over only a portion of the sensor.

I too have questioned the sync speed, but for another reason. My PZ-1 had a shutter capable of 1/8000 shutter speed, with a sync speed of 1/250. If you consider that the sensor is only 16mm high (vertically travelling shutter) and not 24 as it was on the PZ-1, then assuming the same front and back curtain speeds, and shorter distance, I would have expected 1/400

Note there is also available on the K10 high speed sync, where the flash is fired multiple times, as the "slit" mentioned above moves past the sensor. This can allow flash photography (but at reduced flash power) at speeds higher than 1/180.

It may be, and perhaps a P&S techie can respond that the camera you mention takes advantage of the even smaller sensor to achieve the higher speed, it may also be that they do not use a focal plane shutter, but simply sample the chip over a short er time. Remember, the P&S cameras have the sensor powered full time, and take image information for things such as focus, and white balance adjustment. Perhaps they just sample the chip at 1/600 of a second
Thanks for your explanation. I have the Z-1P as well, great camera.

Using powerful flash and higher Iso, I would guess that most could get good results going with high-speed-sync.
01-28-2008, 11:09 PM   #7
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Usually not needed

High flash sync speed is something not usually needed... even a 1/90 sec shutter speed with a flash will not produce blur, because the exposure takes place in the 1/10,000 of a second that the flash is firing in. Slower shutter speeds actually allow in more ambient light, and many times a better looking picture. Even a 300mm lens won't blur with slow flash sync. Where it does become a problem is outdoors with bright light when you're using your flash as a fill and your exposure time tends to be higher. In that case, turn down your sensitivity, stop down the lens, or add ND filters.
01-29-2008, 12:01 AM   #8
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QuoteOriginally posted by proudtoshootpentax Quote
High flash sync speed is something not usually needed... even a 1/90 sec shutter speed with a flash will not produce blur, because the exposure takes place in the 1/10,000 of a second that the flash is firing in. Slower shutter speeds actually allow in more ambient light, and many times a better looking picture. Even a 300mm lens won't blur with slow flash sync. Where it does become a problem is outdoors with bright light when you're using your flash as a fill and your exposure time tends to be higher. In that case, turn down your sensitivity, stop down the lens, or add ND filters.

flash sync speed is the number 1 on the list of features that people do not understand. You see the users that understand what it does and they complain about the slower-than-all-the-competition sync speed of the current Pentax dSLRS, and then you see the ones that do not understand it that will say things like "thats no problem just use HSS on the flash!".

Your approach is new though Maybe the people who designed the canon 350d was thinking like that. In Av mode on the 350d, you will always be in slow sync mode. (unless you disabled it in the custom menu).
Although you do recommend the brute force approach to fighting with sunlight, but remember that we are talking about speedlights here, they are low power, if you want to overpower the sun by force then you need a studio flash and a portable battery. if you had a p&s with a hotshoe you could beat the sun with a speedlight though.

01-29-2008, 01:18 AM   #9
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QuoteOriginally posted by and Quote

flash sync speed is the number 1 on the list of features that people do not understand. You see the users that understand what it does and they complain about the slower-than-all-the-competition sync speed of the current Pentax dSLRS, and then you see the ones that do not understand it that will say things like "thats no problem just use HSS on the flash!".

Your approach is new though Maybe the people who designed the canon 350d was thinking like that. In Av mode on the 350d, you will always be in slow sync mode. (unless you disabled it in the custom menu).
Although you do recommend the brute force approach to fighting with sunlight, but remember that we are talking about speedlights here, they are low power, if you want to overpower the sun by force then you need a studio flash and a portable battery. if you had a p&s with a hotshoe you could beat the sun with a speedlight though.
I agree. I've never personally had a problem with my flash sync speed being too slow even in direct sunlight. It just bugs me that people always wine about slow flash sync when in most cases it makes no difference. I has a ZX-7 before this with a 1/100 sec sync. I shot alot of weddings, and alot of candid telephoto shots in the range of 200-300mm with no problems.
01-29-2008, 01:20 AM   #10
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then again...

Then again, I'm a big fan of slow speed sync and shutter dragging anyways...
01-29-2008, 01:44 AM   #11
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QuoteOriginally posted by proudtoshootpentax Quote
Then again, I'm a big fan of slow speed sync and shutter dragging anyways...
Just remember to gel your flash
01-29-2008, 07:30 AM   #12
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Having a max-sync speed of 1/180s is no problems outdoors in bright light IF you stop down the lens. If you want an outdoor portrait at f/2.8 (or wider, gasp!) and need fill-flash, I'm pretty sure your background (and possibly subject) would be blown out at 1/180s, f/2.8, ISO100. Switching my 540 into HSS solves this problem.
01-29-2008, 09:24 AM   #13
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QuoteOriginally posted by Mikhail Quote
I dont believe so as the shutter mechanism is still the same, ie. not electronic. For live view the shutter remains open and the LCD reads what the sensor is reading, the shutter mechanism hasn't change. Atleast not to my knowledge..

Thanks
i remember reading that one of the advantages of live view (in a different brand atleast, not sure about pentax) is almost silent shooting. i think this implies that the normal shutter mechanism isn't being used but rather an electronic shutter is used and i think these work by just recording whenever the shutter release button is pressed rather than using the mechanical shutter mechanism. i'm not completely sure about this though, feel free to correct me.
01-29-2008, 06:20 PM   #14
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QuoteOriginally posted by bb.hyena Quote
i'm not completely sure about this though, feel free to correct me.
Most of the sound from the shot comes from the mirror slapping up to get out of the way. in live view, the mirror is already up and so it doesnt make a sound.
01-29-2008, 07:15 PM   #15
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QuoteOriginally posted by bb.hyena Quote
i remember reading that one of the advantages of live view (in a different brand atleast, not sure about pentax) is almost silent shooting. i think this implies that the normal shutter mechanism isn't being used but rather an electronic shutter is used and i think these work by just recording whenever the shutter release button is pressed rather than using the mechanical shutter mechanism. i'm not completely sure about this though, feel free to correct me.
As "and" posted below most of the vibration and noise is from the mirror going up and down, put your camera on 2sec or 12sec self time, and when you press the shutter button you will hear the mirros slap up and then a faint opening and closing of the shutter followed by the mirror coming back down.

Atleast thats what I know to my knowledge.

Thanks
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