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04-24-2013, 05:10 PM   #16
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With a flash attached, I realise that you can go into HSS mode on the speedlight to enable fast shutter speeds (higher than 1/180s) on the K-5, but I have a question:

Can you force a higher shutter speed than 1/180s without going into HSS mode on the speedlight for creative purposes (in order to cause some vignetting of the image intentionally due to inability of the shutter to sync)?

Thanks,

Luke.



04-24-2013, 07:44 PM   #17
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QuoteOriginally posted by Eberbachl Quote
Can you force a higher shutter speed than 1/180s without going into HSS mode on the speedlight for creative purposes
no, the 1/180th is a hardwired flash synch limit.
04-25-2013, 02:44 AM   #18
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QuoteOriginally posted by Eberbachl Quote
With a flash attached, I realise that you can go into HSS mode on the speedlight to enable fast shutter speeds (higher than 1/180s) on the K-5, but I have a question:

Can you force a higher shutter speed than 1/180s without going into HSS mode on the speedlight for creative purposes (in order to cause some vignetting of the image intentionally due to inability of the shutter to sync)?

Thanks,

Luke.

You wouldn't see vignetting in any event, you would just have a image with a rectangle exposed by flash and another rectangle where its not.
04-25-2013, 03:47 AM   #19
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You would indeed see vignetting; just not the circular vignetting you're accustomed to. If there is sufficient ambient light to illuminate the scene and the flash is used for fill, you can use this as a creative effect to cause a horizontal vignette.



04-25-2013, 06:51 AM - 2 Likes   #20
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QuoteOriginally posted by Eberbachl Quote
Can you force a higher shutter speed than 1/180s
Look up 'focal plane shutter' and 'leaf shutter' for more information.

Leaf shutters are often built into the lens itself. Because of this, they are rare on smaller cameras with interchangeable lenses. It adds substantially to the cost to build a shutter mechanism into every lens. To get vignetting in an image caused by the shutter, the shutter would have to be reasonably circular like the aperture. This may be true of higher-end leaf shutters, but many leaf shutters are just one or two blades that flip across the optical path inside the lens.

Focal plane shutters are built into the camera body itself and are located at the back of the optical path near the sensor/film. A focal plane shutter has to be as big as the sensor/film so there is a much greater mass to move.

A focal plane shutter is typically composed of two curtains. When you press the shutter release, one curtain jumps across the opening to expose the sensor/film to light. At the specified interval, a second curtain jumps across the opening to stop the exposure. On current Pentax bodies, it takes 1/180th of a second for a curtain to completely cross the opening. The curtain movement speed is the same for every shot you take, regardless of your shutter speed.

Here is what that means- For all shutter speeds up to 1/180th of a second, the first curtain completely opens before the second curtain starts moving. That is why flash sync is 1/180th. It is the fastest speed in which the shutter is completely open. The flash duration is MUCH shorter than 1/180, so the camera can leisurely trigger the flash anywhere within that 1/180 (or longer) time span. So how do we get shutter speeds faster than 1/180th? Simple. The second curtain doesn't wait for the first curtain to fully open before starting its dash across the opening. The result is a moving slit across the face of the sensor/film. The higher the shutter speed the narrower the slit.

The electronic flash is still much faster than the highest shutter speed for the camera. If it goes off at any shutter speed higher than 1/180, Your sensor/film will capture a slit with black borders. Your shutter speed determines the size of the slit. I guess that's vignetting of sorts, but most folks won't see much artistic value in this.

So how does high shutter speed (HSS) flash work? The flash strobes to create multiple exposures on the sensor/film, one flash for each width of the travelling slit.

This is also why HSS flash is mostly useless for stop-action photography. You aren't taking a single fast exposure of a moving object. You are taking many fast exposures. The result is a ghost-like repetition of the subject for every flash. Further, to strobe like this, the flash can only put out a fraction of its normal power with each strobe so working distances are much shorter. There are two situations where HSS flash is of value - first, when you WANT this multiple exposure streaking for artistic reasons; second, when the subject ISN'T moving but the background is very bright requiring a higher shutter speed and you need fill flash on the subject.

This limitation of HSS flash is likely why Pentax didn't bother trying to build this capability into the dinky built-in flash on its current dSLR models.
04-25-2013, 11:52 PM   #21
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Hi Jim,

Thanks for your detailed reply, but I know how the shutter works

You'll see by my post above that I'm not at all referring to circular vignetting, but a darkening of a single edge of the image by pushing the camera above it's sync speed without enabling HSS on the speedlight. Where ambient light is sufficient and the speedlight used as fill this can have a desirable effect.
04-26-2013, 01:29 AM   #22
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QuoteOriginally posted by Eberbachl Quote
pushing the camera above it's sync speed without enabling HSS on the speedlight
this cannot be done with a pentax camera - the hot shoe goes cold at any speed above 1/180th
04-26-2013, 03:14 AM   #23
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QuoteOriginally posted by Digitalis Quote
this cannot be done with a pentax camera - the hot shoe goes cold at any speed above 1/180th
Besides the type of vignetting that would be obtained can be duplicated by simply masking the edges with black rectangles in post-processing.

04-26-2013, 03:27 AM   #24
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..or by using a GND filter badly.
04-26-2013, 03:48 AM   #25
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QuoteOriginally posted by Scootatheschool1990 Quote
Is there any Pentax camera that can go faster than 1/180th? I'm new to photography (3 years) and Pentax ( 6 months).


How is it that I captured this photo at 1/800th of a second with pop-up flash and on my DMC-Fz30 (plus two strobes) but can only go to 1/180th on my K5?
Here is a link to the photo. Skate session with Alex Murry | Flickr - Photo Sharing!
Does the DmcFz30 have a faster sync speed?
I hope not, because I want to capture more action shots like this with my K5's resolution.
There has been a long debate about the limit of sync speed between Pentax at 1/180 and canikon at 1/250 but regardless of this, neither is really what you are asking for.

The shutter technology used bby all DSLRs is limited in this respect.

Why not look for example at high speed sync as others have suggested.

Also consider that you do not always need to use flash.
04-26-2013, 04:08 AM   #26
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The DmcFz30 is a Panasonic bridge camera. I suspect most cameras without an interchangeable lens uses a leaf shutter. And as I noted in an earlier post, except for some high end lenses, most leaf shutters are simple blade construction, so it could look like a focal plane shutter.

Since leaf shutters are located within the lens, they are smaller and have much less mass than a focal plane shutter. So yes, they typically are capable of higher X-sync speeds than focal plane shutters.

Eberbachl - there are a limited number of lenses for SLR cameras that have their own built-in leaf shutters. They typically go for way beyond my budget. Further, you have to operate your focal plane shutter equipped camera body in bulb exposure mode and release the shutter at the lens.

Either go back to your bridge camera if this is the shot you want, use the suggested neutral density filter, or spend a couple minutes in post processing.
04-26-2013, 08:16 AM   #27
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The new K to Q adapter has a 1/1000th leaf shutter, which is great. Unfortunately the Q has a 5.5x crop factor, which is not. What would really make the Q a viable system for the type of shots I'd like to take (i.e. "night time" portraits at noon) is a telecompressor like the new Metabones Speedbooster with a leaf shutter. Throw in autofocus too for good measure, why eat hamburger when you can have steak? That would be one mother of an adapter, probably cost twice what the Q does, but hey.
04-27-2013, 05:55 PM   #28
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Thanks for the replies. It's not a deal breaker, and I realise I can simulate the effect in post. It's just a technique I read about and I had an inclination to try it. I figured after looking through the settings on the K-5 and flicking through the manual that I was locked out beyond 1/180, but thought I'd ask in case I'd missed a hidden setting somewhere.

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