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AVCHD Format Discussion
Inexpensive High Definition H.264 encoding to DVD, Hard Disc or SD Card.


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Old October 22nd, 2007, 02:13 AM   #16
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I don't think that the Wikipedia article implied that the head gap was maintained by air pressure, it merely states that you need adequate air pressure in the drive enclosure, which is true, since reduced air pressure will cause the head to lose lift and eventual disk damage. This principle is well described by a statement in this article:
"When the disk spins up to operating speed, the high speed causes air to flow under the sliders and lift them off the surface of the disk--the same principle of lift that operates on aircraft wings and enables them to fly... If a drive is used at too high an altitude, the air will become too thin to support the heads at their proper operating height and failure will result; special industrial drives that truly are sealed from the outside are made for these special applications."
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Old October 22nd, 2007, 03:25 AM   #17
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"The HDD's spindle system relies on air pressure inside the enclosure to support the heads at their proper flying height while the disk rotates."

Well, it certainly sounds like they said it was the air pressure that supports the heads (while the disk rotates.) In fact it's exactly what they said.

At best it's mis-stated. You could have 10k PSI inside the enclosure and rotate the disk at 1 RPM and the head wouldn't fly any better than if you had 0 PSI, even though you a) had ample air pressure and b) were rotating the disks.

By the way - nice reference, Thanks!
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Old October 22nd, 2007, 10:35 AM   #18
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You're absolutely right, that statement is somewhat misleading...
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Old October 30th, 2007, 05:13 PM   #19
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Seagate has new PATA and SATA EE25 drives rated to 16,400ft.

I'm now headed to Lhasa and EBC, so will be taking these along.

EBC is at 17,700, so I'll be waiting until I am down at Xeger before using the computer.

Douglas, would love to hear your experiences when you get back, I'm off on Nov 17th, hopefully with a new Sony XDCAM EX in hand.
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Old March 20th, 2008, 11:29 PM   #20
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I'm about to buy a Sony SR12. We'll be travelling to Alaska and the Canadian Rockies in May and will be doing several helicopter and float plane trips. I've looked up elevations of major places we'll be visiting (Banff, Lake Louise, Jasper, Whistler, Ketchikan, Juneau, Skagway, Anchorage, Fairbanks etc.) and all seem to be well under the 3000m limit for HDD camcorders.

The highest point along the Icefields Parkway between Lake Louise and Banff is Bow Summit at 2,069 metres (6787 feet above sea level) while the elevation at the Village of Lake Louise is 1,534 metres (5,033 feet). The top elevation of the Lake Louise Mountain resort is 2,637 m (8,652 ft).

If we do helicopter flights I don't think it's likely we would fly high enough to go over the 3000m limit. Has anyone used a HDD camcorder in areas like this and had any problems? Would it be better if I recorded to memory stick in higher elevations rather than to the HDD?

Thanks for any advice.

Ken
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Old March 20th, 2008, 11:53 PM   #21
 
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You shouldn't run into issues regardless, unless you fly over 9400 MSL. But...Supposedly, if you place a card in the mem slot and CHOOSE the MSPD for recording, the HDD head parks. I've been waiting for a test unit from Sony to check this out.
In other words, you should be fine.
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Old March 21st, 2008, 12:22 AM   #22
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Quote:
Originally Posted by Ken Grady View Post
Would it be better if I recorded to memory stick in higher elevations rather than to the HDD?
It may not be. I was asking this question in another thread; that is, if the hard disk shuts down when you record to card. After listening to their units, people that have SR12's seem to have determined that the disk does NOT spin down when using the card.

Unfortunately, just parking the heads is not good enough, the drive must spin down completely to be safe. Parking just means that the heads are positioned over the landing zone; in modern drives, parking the heads does not mean that the heads are physically pulled away from the platter, although that misconception is rather common. The landing zone is safe for brief head contact during head take-offs and landings, but not if the head begins to rub constantly because of insufficient pressure.

Here's a good description of head parking and landing zones:

http://www.storagereview.com/guide20...ctParking.html

Unfortunately, if the disk truly does not spin down, the safest thing would be to refrain from using the camera at all above 10,000 feet.

I'll definitely be curious if you find out from Sony that these assumptions are incorrect.

I'm going through the same dilemma right now. I would like to get an SR11, but a lot of my usage will be on climbing/skiing/backpacking trips, so I will have to stick to either tape or Flash-only cameras. I wish there was some knowledge of when a CX9 might come out ;-)

Last edited by Dave Rosky; March 21st, 2008 at 01:11 AM.
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Old March 21st, 2008, 07:28 AM   #23
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Quote:
Originally Posted by Douglas Spotted Eagle View Post
You shouldn't run into issues regardless, unless you fly over 9400 MSL. But...Supposedly, if you place a card in the mem slot and CHOOSE the MSPD for recording, the HDD head parks. I've been waiting for a test unit from Sony to check this out.
In other words, you should be fine.
Doug it would be great if you could get back to us on that. I know on my SR12 I do hear a very low sound and a very subtle vibration even when recording to a memory card. I don't plan on recording at these elevations anyway, but I've been asked this question by a number of people.

Some have said that even if the platter is spinning the head could still be parked. I don't enough about the mechanics of these things to comment.

P.S. I just read Dave's comments above and I'm confused about one thing. I would think if atmospheric pressure lowers, that would lessen the chance of contact between the head and the platter. I can see increasing atmospheric pressure heightening the chance of contact as additional pressure pushes down on the heads. So I guess I'm confused about this seemingly contradictory correlation. I guess it's my lack of understanding of this process. I guess my degrees in Meteorology aren't helping me here! :)
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Old March 21st, 2008, 08:31 AM   #24
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I think its the density of the air that matters. At high altitudes the air is thinner and just like an aircraft wing the head would need to move faster over the platter to get lift or would need a larger surface area to get the lift. Normal heads are designed to lift at the densities associated with lower altitudes. Increasing pressure increases the density, increase the pressure enough and the gas will turn to a liquid in most cases.

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Old March 21st, 2008, 08:36 AM   #25
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Ron, that makes perfect sense. I wasn't thinking about it in that manner at all, but I should have been.
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Old March 21st, 2008, 10:53 AM   #26
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Originally Posted by Ken Ross View Post
Some have said that even if the platter is spinning the head could still be parked. I don't enough about the mechanics of these things to comment.
There's always a chance I could be wrong about this. I know a fair amount about disk drives having designed chips for disk drives for a number of years, but I'm the first to admit I don't know everything, especially about the mechanical side. What I am pretty sure of is that *conventional* drives (like the type in most computers and laptops) don't have a special mechanism that forcibly lifts heads away from the platter when the heads are parked - they are just floating over the landing zone.

It *may* be possible that there are special drives that can do this, just as there are special pressure-sealed drives that can be used in low pressure environments, but I'd be surprised if these would be used in a consumer level camera.

In addition to this, there are other concerns. For example, we can't easily know that the camera doesn't use the drive for other things, such as storing firmware or device state information - many systems with embedded hard drives do this. Also, the drive may be accessed as part of the normal POST procedure when the camera is powered on or off.

Personally, I wouldn't risk it unless given the go-ahead by a Sony engineer or technical support person. At least in that case, if it bricks your camera, they will probably take responsibility since they told you it was OK.
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Old August 24th, 2008, 03:06 AM   #27
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Hi from Greece. First sorry about my english - american. In 2 days i will fly above the agean sea and i would like to capture some footage. I will fly with an airplane. I don't know exactly the height the airplane fly. Would be any problem to use my GZ-HD3(JVC) with HDD inside the airplane? Or all what you say is to walk by feet on these heights?
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Old August 24th, 2008, 04:19 AM   #28
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I'm curious about the G-force sensors? What happens when the G-force is exceeded? The drive likely doesn't stop spinning. Is the head pulled away from the disk or simply moved to a parking zone?

I wonder of laptop and camera drives might actually pull the head free of the disk because they are at such risk of shock? Especially, when the drive is off.

To keep start-up time to a minimum, the drive may be kept spinning. And, the head pulled away when not writing or reading.
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Old February 3rd, 2009, 09:51 PM   #29
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HDD and altitude (Sr12)

[This is the response I got from sony after the fourth attempt to get some continuity. All answers previously received were diiferent. sony US wouldn't answer me because I bought my Sr12 in Au.
Hi Geoff,

Below is the best response I can get from Sony.

Thanks, Jeff(this Jeff is a video technician)



a. Is the HDD completely independent of the operation of the MS?? Yes


b. Does the HDD spin while recording video to MS?? I would say No


c. I am travelling to Sth America in March and want know if I can

safely ONLY using MS, record to MS then the back up using portable DVD
burner

at Cuzco (Peru) and La Paz (Bolivia) both place are above 3000M?? Out of
the Operation Manual "Note on using the camcorder at high altitudes - Do
not turn on the camcorder in a low pressure area, where altitude is more
than 3000 meters or 9800 feet. Doing so may damage the hard disk of your
camcorder. This is also when using memory stick because when turning on
camcorder will initialise and activate hard drive.


A suggestion if he's after a non HDD, he could research the HDRTG1E.
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Old February 4th, 2009, 12:02 AM   #30
 
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Or a CX100, or a CX6/12.

CX100 is very impressive. So is the MC1.
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