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08-15-2010, 03:56 PM   #1
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K-m max shutter spees with flash???

Why when I'm using a flash is my max shutter speed 1/180?

at F2 all by pics come out white!

Does anyone know if there is a camera setting to increase shutter speed with a flash?

08-15-2010, 04:02 PM   #2
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That's the max shutter speed with flash, the reason why is because at speeds faster than 1/180th of a second the whole sensor is never uncovered at one time, which is vital to effective flash

The only way to use faster shutter speeds is to buy a really nice flash that supports high speed sync, instead of using one big flash it lets out a rapid burst of flashes allowing you to use faster shutter speeds

for now you'll probably just have to close up the aperture when using flash
08-15-2010, 04:05 PM   #3
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Ok thanks! Thats what I have been doing.

I was just wondering if I could increase the speed.
08-15-2010, 04:56 PM   #4
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If your pics are all white at F2 and 1/180, they will still be all white at F2 and any other faster shutter speed. The flash dumps all of its power in less than a thousandth of a second. Long story short: shutter speed will have NO effect on the flash exposure.

08-15-2010, 05:54 PM   #5
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QuoteOriginally posted by Wesbo Quote
If your pics are all white at F2 and 1/180, they will still be all white at F2 and any other faster shutter speed. The flash dumps all of its power in less than a thousandth of a second. Long story short: shutter speed will have NO effect on the flash exposure.

I experience this too on my M 50 f2.

my F2 came out white..
now I know..

thanks
08-15-2010, 09:00 PM   #6
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The real problem here is that the flash always fires full power using M lenses. Shutter speed, as mentioned, has virtually no effect on exposure when using flash. Look up the term "guide number" to see how to calculate the appropriate aperture to use when using full power flash. there is only one aperture that works; any smaller aperture will underexpose, any larger aperture will overexpose, and shutter speed has no bearing on this.
08-16-2010, 01:18 PM   #7
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I found that 2.8~4.0 worked best with the flash @ 1/180

2.0 @1/750.

Thanks everyone.

Man I have so much to learn!
08-16-2010, 09:17 PM   #8
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QuoteOriginally posted by ckusnierek Quote
I found that 2.8~4.0 worked best with the flash @ 1/180
That's going to be completely dependent on the ISO you have set and the distance to subject. Do Google the term "guide number" as I suggested above - any references that come up should explain how this works.

08-17-2010, 08:06 AM   #9
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QuoteOriginally posted by Wesbo Quote
If your pics are all white at F2 and 1/180, they will still be all white at F2 and any other faster shutter speed. The flash dumps all of its power in less than a thousandth of a second. Long story short: shutter speed will have NO effect on the flash exposure.
Chances are the photo is all white BECAUSE of the ambient exposure, and NOT the flash exposure. If they turned OFF the flash and also shot at f/2 1/180s (and whatever ISO they used, hopefully not ISO1600 ) they would probably get a very similar looking photograph (all white!)

So in this case, you could either use a faster shutter speed provided you have an external flash that supports HSS, OR stop down the aperture so your ambient exposure is not being blown out.

So your assertion that "shutter speed will have NO effect on the flash exposure" is indeed correct, BUT in 99% of these cases it's the actual ambient exposure that is causing the blowout.
08-17-2010, 08:15 AM   #10
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That depends on the setting. Outdoors, sure, f/2 and 1/180" is likely to overexpose with or without flash, and you'd have to spped up the shutter a lot to prevent that. the flash would be having little or no effect on the exposure. But indoors in low light - the situations where most people normally think of using flash - f/2 and 1/180" is likely to produce a very dark picture without flash unless you're at ISO 12800 or something. And normally one wouldn't be at such high ISO when shooting flash. So I'm assuming the context is low ISO, dark environment - in which, ambient light is not going to come into play unless you get the shutter speed down to a full second or so.
08-18-2010, 04:51 AM   #11
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QuoteOriginally posted by Wesbo Quote
If your pics are all white at F2 and 1/180, they will still be all white at F2 and any other faster shutter speed. The flash dumps all of its power in less than a thousandth of a second. Long story short: shutter speed will have NO effect on the flash exposure.
The flash may not but the Ambient may, shooting at f2 and 1/180th of a second is still a fairly dark environment at 100 ISO to get a correct exposure, at sunny 16 you would be looking at needing a shutter speed of 1/8000th to get a correct exposure at f2, regardless of what the flash is doing, it is likely that the OP was either using fill flash in daylight or in lower light but still having the required exposure at 1/180th being around f5.6-8 would still produce completely over exposed images at f2.

This is a common mythconception about flash photography the shutter speed controls the ambient exposure while the aperture and ISO control the flash and ambient exposure and you have to take the ambient into account with any flash exposure. Further more if you have a flash with a long duration (say the metz 58 with its 1/125th of a second full power duration) a shorter shutter speed can effect the flash exposure.
08-18-2010, 06:17 AM   #12
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I gather from the above discussion that the Pentax DSLR's actually have a shutter which uncovers the sensor and then covers it again.

I have assumed that the term "shutter-speed" is used in a figurative sense, the effect of a shutter being simulated by switching on and off electrical circuitry. I feel sure that this is how it is done with my compact point-and-shoot digital. How would the continuous image be formed in the view-finder if the sensor is covered except during an "exposure", [which term is also presumably used only in a figurative sense in the case of the compact digital camera for "recording time"]?

If there is a real shutter in my Pentax Km that would explain why the built-in flash would not synchronise properly if an exposure of less than 1/180 is set. It still would not explain why my Pentax Km will not synchronise with an external slave-flash triggered by the built-in flash even at exposure settings as long as 1/30 second. My old Fuji S5500 synchronised with the slave-flash at exposure times as short as 1/1000 second but of course that was not an SLR, only an SLR look-alike. When that was lost on a trip abroad I replaced it with the Pentax Km, not dreaming that it would not do the job just as well.

Anyone have any ideas, information or suggestions?

Last edited by Kendrick; 08-18-2010 at 06:19 AM. Reason: typo
08-18-2010, 09:47 AM   #13
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QuoteOriginally posted by Kendrick Quote
I gather from the above discussion that the Pentax DSLR's actually have a shutter which uncovers the sensor and then covers it again.
As far as I know, *all* DSLR have mechanical shutters.

QuoteQuote:
How would the continuous image be formed in the view-finder if the sensor is covered except during an "exposure"
Because the viewfinder gets it's image from the mirror, which intercepts the light that was headed toward the sensor *before* the shutter. I'm sure if you do a quick Google search for "SLR", you'll find a diagram that explains it.

QuoteQuote:
My old Fuji S5500 synchronised with the slave-flash at exposure times as short as 1/1000 second but of course that was not an SLR, only an SLR look-alike. When that was lost on a trip abroad I replaced it with the Pentax Km, not dreaming that it would not do the job just as well.

Anyone have any ideas, information or suggestions?
Depends entirely on what specific unusual application you have in mind that would require a faster shutter speed - it's not something the average person would ever need. Fill flash when trying to do outdoor portraits with shallow DOF, I guess?
08-18-2010, 12:22 PM   #14
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QuoteOriginally posted by Kendrick Quote
I gather from the above discussion that the Pentax DSLR's actually have a shutter which uncovers the sensor and then covers it again.
Every DSLR by all the major manufacturers use a "real" shutter (actually two shutter "curtains" just like on old film SLRs) whereas P&Ss use an electronic shutter.

QuoteQuote:
Anyone have any ideas, information or suggestions?
Buy an external hot-shoe mounted flash which supports high-speed sync.
08-18-2010, 01:19 PM   #15
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QuoteOriginally posted by Marc Sabatella Quote
As far as I know, *all* DSLR have mechanical shutters.
Most, not all, are exclusively mechanical -- the Nikon D70 is a notable exception. I don't know if there are others.

Nikon D70

The D70 has both a mechanical shutter and an electronic shutter -- the latter allowing it to achieve pretty remarkable flash sync speeds for a DSLR.
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