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07-15-2015, 02:49 PM   #1
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1/180

Is it so hard for pentax to get a sync speed faster than this?? What's holding them back exactly

07-15-2015, 03:06 PM - 3 Likes   #2
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It's time for . . . MORE IGNORANCE based on my LIMITED KNOWLEDGE of PHOTOGRAPHY!

QuoteOriginally posted by shaolen Quote
Is it so hard for pentax to get a sync speed faster than this?? What's holding them back exactly
I'm open to correction here, because I'm largely working off memory.

The shutter has two "shutters" -- the "first curtain" and the "second curtain." When it's "cocked", which on a DSLR is whenever the mirror is down, the first curtain covers the sensor, and the second curtain is ready to cover the sensor. (That is, the first curtain is up and ready to come down, like a garage door that comes up out of the floor and is closed. The second curtain is up and ready to go down, like a real garage door that is open.) At slow shutter speeds, the first curtain comes down, waits a certain amount of time, and then the second curtain comes down at the right time for the shutter speed. (Meaning if it's 1/60 sec., then there's exactly 1/60 sec. between these.) This works up until you get to the "sync speed" of the camera, which is the fastest shutter speed that has enough time for the first curtain to open completely before the second curtain starts going down. To get faster shutter speeds, the camera starts the second curtain before the first curtain is fully done, making a slit that travels across the sensor. This slit gets narrower and narrower until you get to the fastest shutter speed of the camera, which is narrow enough to expose a part of the sensor for only 1/6000 or 1/8000 of a second. But it doesn't expose it all at once -- it slides across the sensor. (This is one of the reasons that car tires look oval when shot with fast shutter speeds while the car is travelling.)

The problem is the flash bulb in a flash doesn't output constant light over time. And the maximum duration is very short -- maybe 1/500 sec. on a typical flash (that would be at full power). And even at full power, it's not putting out constant light over that 1/500 sec. duration -- it's peaky at the beginning and falls off. So you'd get a bright spot at the top (or bottom -- maybe the shutter is upside-down?) of your photo. So you have to develop a way to pulse the flash over that 1/180 sec. duration regardless of your shutter speed, because that's how long it takes to actually take the picture. And then you have to get the lighting even over that duration and still have a way to adjust the power. (You can't use duration, because all of them are way too short.) I know some companies claim "high speed shutter" sync, but I think if it actually worked well, fewer people would buy studio strobes.

I also thought Pentax had a so-called "high speed sync" that worked with their flashes. I've never tried it -- does it?
07-15-2015, 03:13 PM   #3
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yes pentax has high speed sync but it is less power. But most other companies have a standard flash sync of 1/250 so I just don't know why pentax couldn't do the same
07-15-2015, 03:28 PM   #4
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1/200

Most other companies are 1/200 e.g. nikon 5500 Canon 760d. Not much in it really.

07-15-2015, 04:26 PM   #5
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fredralphfred's post explains the issue. A shutter that can do a faster sync speed just costs more - the two curtains would have to move faster. A more expensive shutter might bump the price point of the camera above what most would pay.

So it can be done, it is a cost issue. The top models in the Pentax Z-series film SLRs had a top speed of 1/250s. And that was about 20 years ago...
07-15-2015, 04:43 PM   #6
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QuoteOriginally posted by Ole Quote
fredralphfred's post explains the issue. A shutter that can do a faster sync speed just costs more - the two curtains would have to move faster. A more expensive shutter might bump the price point of the camera above what most would pay.

So it can be done, it is a cost issue. The top models in the Pentax Z-series film SLRs had a top speed of 1/250s. And that was about 20 years ago...
And the difference between 1/180 and 1/250 is only half a stop. Not really a big deal. You can use HS sync which pulses the flash but reduces the output. Or get a camera with a between the lens shutter that lets you sync at higher speeds. For instance the Panasonic LX100 (which I am considering buying for a travel/casual event camera) syncs up to 1/4000 making it really useful for fill flash on sunny outdoor shots.
07-15-2015, 06:24 PM   #7
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QuoteOriginally posted by Ole Quote
fredralphfred's post explains the issue. A shutter that can do a faster sync speed just costs more - the two curtains would have to move faster. A more expensive shutter might bump the price point of the camera above what most would pay.

So it can be done, it is a cost issue. The top models in the Pentax Z-series film SLRs had a top speed of 1/250s. And that was about 20 years ago...
The Nikon d7200 has a 1/250th sync speed and it is the same price as the comparable K-3 series..

I too have limited knowledge on this issue, but it seems, knowing the light from a flash falls off quickly and that the camera itself can obtain a 1/8000th of a second minimum shutter speed, that the sync speed could be increased dramatically?? From what I know (which, again, isn't much) HSS works by constantly and rapidly pulsing the light from the flash unit at lower amounts.. why not just one giant poof from the flash at say 1/2000th of a second?

It seems most cameras stop the sync speed at 1/250th or slower.. so obviously I'm missing something.
07-15-2015, 06:30 PM   #8
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Could the lower sync speed increase the reliability of the shutter?

07-15-2015, 08:36 PM   #9
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QuoteOriginally posted by mee Quote
The Nikon d7200 has a 1/250th sync speed and it is the same price as the comparable K-3 series..

I too have limited knowledge on this issue, but it seems, knowing the light from a flash falls off quickly and that the camera itself can obtain a 1/8000th of a second minimum shutter speed, that the sync speed could be increased dramatically?? From what I know (which, again, isn't much) HSS works by constantly and rapidly pulsing the light from the flash unit at lower amounts.. why not just one giant poof from the flash at say 1/2000th of a second?

It seems most cameras stop the sync speed at 1/250th or slower.. so obviously I'm missing something.
You went the wrong way. If the flash was SLOWER the sync speed might be HIGHER; a shorter duration speed doesn't help at all. The slit passing over the sensor only would be exposed during the duration of the flash. The pulsing flash for HSS is designed to stretch the light illumination over a longer time to allow time for the curtain to pass over the entire sensor. This seems counter intuitive because you think - the faster shutter speed means I need faster flash - but it's the other way - the narrower slit takes a while to traverse the sensor (more than the time the flash stays on in normal flash mode) and so it fails to illuminate evenly.

Here's a site that explains it with pictures and details that I can't possibly do a better job of explaining.

Understand Flash Sync Speed so You Don't Sink Your Photo Shoot - Digital Photography School
07-15-2015, 09:12 PM - 1 Like   #10
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QuoteOriginally posted by shaolen Quote
Is it so hard for pentax to get a sync speed faster than this?? What's holding them back exactly
You can accomplish the same thing with iso. The reason to have a faster shutter with flash is to let in less ambient light. You can accomplish the same thing by lowering your iso, and opening up your aperture 1 stop. The subject will stay properly exposed while the background is underexposed by 1 stop. Flash sync speed is way to minor an issue when compared to the many positive reason to shot Pentax.
07-15-2015, 09:25 PM   #11
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This raises the question though: how much longer will we be using mechanical shutters?

Unfortunately, as megapixel counts rise on CMOS sensors, the speed at which they can be sequentially read column by column decreases, limiting the speed of electronic shutters based on that strategy. But presumably the read-speed per column is increasing with improving technology. So it's a race between increasing read speed per column and increasing number of columns. Will it ever catch up enough to give us better than 1/180?
07-15-2015, 10:38 PM   #12
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QuoteOriginally posted by Paul the Sunman Quote
This raises the question though: how much longer will we be using mechanical shutters?

Unfortunately, as megapixel counts rise on CMOS sensors, the speed at which they can be sequentially read column by column decreases, limiting the speed of electronic shutters based on that strategy. But presumably the read-speed per column is increasing with improving technology. So it's a race between increasing read speed per column and increasing number of columns. Will it ever catch up enough to give us better than 1/180?
That sensor could be read instantly with enough $, especially a BSI one that can put more electronics right behind each pixel site. The trade-off is increased power consumption, heat generation, and cost. Remember -- 5 GHz PC's are out now.

I think Canon claims their latest Cine camera (available in both EF and PL-mount) nearly eliminates rolling-shutter problems with improved electronic readout, and has dedicated cooling to reduce problems with long video takes. But it's far more pricey than their most expensive DSLR body. Cinema Camera 35mm 4K - EOS C500 | Canon Cinema EOS

---------- Post added 07-16-15 at 12:50 AM ----------

QuoteOriginally posted by mee Quote
The Nikon d7200 has a 1/250th sync speed and it is the same price as the comparable K-3 series..

I too have limited knowledge on this issue, but it seems, knowing the light from a flash falls off quickly and that the camera itself can obtain a 1/8000th of a second minimum shutter speed, that the sync speed could be increased dramatically?? From what I know (which, again, isn't much) HSS works by constantly and rapidly pulsing the light from the flash unit at lower amounts.. why not just one giant poof from the flash at say 1/2000th of a second?

It seems most cameras stop the sync speed at 1/250th or slower.. so obviously I'm missing something.
OK. I had a long post. Here's a summary:

It always takes a Pentax at least 1/180 sec. to take a picture. That's the fastest the shutter goes. Faster shutter speeds are achieved by trickery.

If you have a flash that goes in 1/2000 of a second, you will get a bright bar in the middle of a dark picture.

Hope that helps.

Last edited by fredralphfred; 07-15-2015 at 10:44 PM. Reason: changed "shutter" to "sensor", which is what I meant (2nd word of reply)
07-15-2015, 11:40 PM   #13
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In the words of Shakespeare the difference between 1/180 and 1/250 of a second is much ado about nothing,
I cannot believe this discussion keeps coming up and over the years have yet to see a genuinely valid reason for requiring the extra 2/3 stop in order to achieve a image.
07-16-2015, 05:18 AM - 1 Like   #14
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Almost surely cost vs overall benefit/appeal to their user base is the deterrent.

QuoteOriginally posted by macman24054 Quote
You can accomplish the same thing with iso. The reason to have a faster shutter with flash is to let in less ambient light. You can accomplish the same thing by lowering your iso, and opening up your aperture 1 stop. The subject will stay properly exposed while the background is underexposed by 1 stop.
If you lower your iso by 1 stop and open your aperture by 1 stop, the exposure on the background and subject will stay the same. ISO and aperture affect both ambient and flash equally.

ISO is no substitute for shutter speed when you want to change the relative brightness of flash to ambient.

QuoteOriginally posted by adwb Quote
In the words of Shakespeare the difference between 1/180 and 1/250 of a second is much ado about nothing,
I cannot believe this discussion keeps coming up and over the years have yet to see a genuinely valid reason for requiring the extra 2/3 stop in order to achieve a image.
It's a matter of convenience for me. There are usually workarounds, but I'm often just pushing up against this boundary outside and I'd like the flexibility to step a little more. It's not a deal breaker, but it would be nice.

It's really not much different in people purchasing a FA50/1.4 instead of a FA50/1.7. That extra tiny bit available can be worth having around when you need it, and for these lenses the extra cost and weight of the 1.4 is marginal (ok this lens choice may be a little more complicated as some swear by the FA50/1.7). At the same time you'd be hard pressed to find a photo that was ruined because you could only open up to f/1.7 and not f/1.4.
07-16-2015, 05:54 AM - 1 Like   #15
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QuoteOriginally posted by adwb Quote
In the words of Shakespeare the difference between 1/180 and 1/250 of a second is much ado about nothing,
I cannot believe this discussion keeps coming up and over the years have yet to see a genuinely valid reason for requiring the extra 2/3 stop in order to achieve a image.
You've been reading threads about this subject for years, and have not read a valid reason for people wanting a faster sync speed? Honestly?
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