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04-18-2012, 10:14 AM   #1
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SR, shutter size, and flash sync speed: Suggestions about shutters in the next camera

I've been wondering why the flash sync speed is 1/180s instead of at least 1/200s. After giving it some thought, it seems that this is related to the SR system.

The SR system requires additional space on the sensor plane so that the sensor can shift to compensate for camera shake. Because of this fact, the shutter needs to be APS-H sized, rather than APS-C sized. This means that the shutter curtains needs to travel farther, reducing the sync speed.

We know that the shutter is manufactured by Copal. Copal is likely the manufacturer responsible for the full-frame carbon-fiber shutters good for up to 400,000 cycles as seen on the Canon EOS-1D X and Nikon D4. It's unlikely for Canon and Nikon to independently develop such shutters, though differences in sync speed (1/250s on the D4, 1/200s on the EOS-1D X) may indicate slight differences in the way it is operated, given that the EOS-1D X is designed to shoot faster than the D4 (14 fps vs 11 fps). I don't see why this design can't be scaled down to APS-H, gaining 1/250s sync speed while increasing the shutter durability fourfold.

Perhaps the aforementioned carbon-fiber shutter is too expensive for Pentax to use, but there are units good for 150,000 cycles and capable of 1/250s sync speed that Pentax should strongly consider for use in the next-generation K-system camera. These shutters exist for both APS-C and full-frame, so an APS-H version required to accommodate the SR system can certainly be made.

The current shutter has only a 1/180s sync speed and lifespan of 100,000 cycles. The typical shutter used in the class of cameras which the K-5 is in has a sync speed of 1/250s and lifespan of 150,000 cycles. Why can't Pentax choose a better shutter? The fact that an APS-H shutter is needed should not be a serious constraint. As it stands, I'm very disappointed that the shutter in my K-r is failing at 30,000 cycles.

--DragonLord

P.S. We know full-frame with in-body image stabilization is possible (Sony has proven so in the A900 and A850), but this would require that the mirror box be wider near the sensor plane than near the mount in order to stay within the physical constraints of the mount. This would require an even larger shutter (approaching medium-format size), which would pose an additional challenge to Pentax to produce a full-frame camera.


Last edited by bwDraco; 04-18-2012 at 11:18 AM.
04-18-2012, 11:07 AM   #2
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EFSC please
04-18-2012, 11:08 AM   #3
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QuoteOriginally posted by Nass Quote
EFSC please
Huh?

Edit: You meant an electronic first shutter curtain. This certainly helps in live view or when the mirror is otherwise locked up, but isn't useful otherwise.

--DragonLord

Last edited by bwDraco; 04-18-2012 at 11:16 AM.
04-18-2012, 12:50 PM   #4
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Useful for me =)

04-18-2012, 01:19 PM   #5
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The shutter is subpar compared to the competition, but as I stated, it needs to accommodate the SR system. It isn't impossible to make it better, though. To me, an electronic first curtain isn't particularly useful, but it can help avoid the need to use two shutter cycles to take a single shot in Live View and reduce vibration.

Off-topic
: note updated signature, I'll post an overview of the D-BG4 when I get a chance.

--DragonLord

Last edited by bwDraco; 04-18-2012 at 01:25 PM.
04-18-2012, 03:05 PM   #6
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sorry for my statement to follow but i think this is a load of BS

My PZ-1 has a 1/8000 shutter with 1/250 sync and that is a full frame film camera

it can be done, thats all.

the issue is curtain speed, vs acceleration and life, its a design trade off
04-18-2012, 03:11 PM   #7
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The issue is that Pentax is using a consumer grade shutter normally rated for 1/200s sync at APS-C size. The shutter is scaled up to APS-H size to accommodate the SR system, and the shutter has to be derated to 1/180s sync speed as a result. There are better shutters out there and Pentax should choose a better shutter for its next K-system camera.

--DragonLord
04-19-2012, 06:53 AM   #8
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QuoteOriginally posted by DragonLord Quote
The issue is that Pentax is using a consumer grade shutter normally rated for 1/200s sync at APS-C size. The shutter is scaled up to APS-H size to accommodate the SR system, and the shutter has to be derated to 1/180s sync speed as a result. There are better shutters out there and Pentax should choose a better shutter for its next K-system camera.

--DragonLord
I doubt that has much impact at all, when you consider they have in the past produced larger shutters with full frame and higher sync there is no reason why it cannot be done., this is not a consumer grade issue. the shutter is designed for an intended market and function, but really who gives a $#!+ any way, we have had the 1/250 debate before, it is not all that important, and is now less important as minimum ISO ratings like the K20 at ISO80 are coming out, it was a much bigger issue on the *istD and all 6MP sensors that only offered ISO200, but even then there was high speed sync for fill flash.

So what is really driving the "perceived need for 1/250 sync, other than specmanship???

You also need to remember that much different flashes are required, specifically higher burst intensity with shorter duration to up the Sync speed. That makes life hard , in vact very hard on the flash capacitor, and tube.

04-20-2012, 06:39 AM   #9
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QuoteOriginally posted by Nass Quote
EFSC please
ohh I'm sure it can be done - just expect to have to deal with sensor bloom:

Last edited by Digitalis; 01-28-2015 at 12:35 AM.
04-20-2012, 10:35 AM   #10
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As a note, the image from above originates from a Nikon D70 using the electronic first curtain. See ModelMayhem.com - nikon d70 or d3000?.

--DragonLord
04-20-2012, 12:44 PM   #11
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You do realise this is just a bit unrepresentative - as in I can find you 100s of amazing shots taken with EFSC, or even find you 100s of terrible ones taken with K-5...
04-20-2012, 06:56 PM   #12
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QuoteOriginally posted by DragonLord Quote
As a note, the image from above originates from a Nikon D70 using the electronic first curtain. See ModelMayhem.com - nikon d70 or d3000?.
I used to have a D70 - I had heard about the blooming effect, but I have never seen it in my usage of the camera - my D70 died from BGLOD a few years ago. It has since been replaced by my D300s
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