a couple of newbie q's at DVinfo.net

David Downes · May 15th, 2005, 07:27 PM

Please excuse the newbie questions regarding 1080i on the Sony FX1/Z1E. Firstly, if you shoot 50i with the shutter speed at 25, arent you essentially shooting progressive frames?

Secondly, I keep reading about 1080i being a resolution of 1920 x 1080 pixels but isnt it true that the actual number of horizontal captured pixels is 1440, each pixel being 'stretched' to fill a 1920 (square) pixel frame width? Can someone tell me why non square pixels are better (or worse) than square ones?

Douglas Spotted Eagle · May 15th, 2005, 08:26 PM

Quote:

Originally Posted by David Downes

Please excuse the newbie questions regarding 1080i on the Sony FX1/Z1E. Firstly, if you shoot 50i with the shutter speed at 25, arent you essentially shooting progressive frames?

Secondly, I keep reading about 1080i being a resolution of 1920 x 1080 pixels but isnt it true that the actual number of horizontal captured pixels is 1440, each pixel being 'stretched' to fill a 1920 (square) pixel frame width? Can someone tell me why non square pixels are better (or worse) than square ones?

No, you're not shooting at 1080p, because the Z1 image is always interlaced in HDV mode.
Stretched pixels or square pixels is not really an issue. The real issue lies in how the pixels are generated. DV also uses a stretched/non-square pixel aspect ratio. The concern that some folks have with HDV is the compression coupled with the non-square pixel issue.

Tommy James · May 15th, 2005, 08:55 PM

Electronically the image may be interlaced but for all pratical purposes shouldnt shooting in cf30 produce progressive like images?

Jack Zhang · May 15th, 2005, 09:21 PM

Quote:

Originally Posted by Tommy James

shouldnt shooting in cf30 produce progressive like images?

No, CF30 is "field doubling," it's still interlaced, it's way better to shoot interlaced footage then de-interlace and interpolate feilds on your PC/Mac. you can watch some CF30 footage and see for yourself below: (in the de-interlacing panel of VLC, choose Bob to see the footage at 60 fields)

Andrew J Hall · May 15th, 2005, 11:53 PM

My own newbie question, how does the camera shoot 1/25 (or 1/3) second while delivering 50/60i?

Andrew

Ron Evans · May 16th, 2005, 06:48 AM

In simple terms the CCD's in a camera collect light for the time period defined by the shutter speed( there isn't a real shutter as in a still film camera). The collected data for each pixel is then read out into a buffer that is sampled at either 50 or 60 times a second alternating between odd and even lines to create an interlaced image for recording to tape. When the shutter speed is equal to or faster than the buffer sample rate new data is provided at each sample. If the shutter speed is slower than the sample rate there will be repeat samples. That is, movement in the image will be affected.
This is a simple explanation, it is a little more complicated in practice due to the way CCD's collect light charge and transfer to the read buffer!!.

Ron Evans

May 15th, 2005, 07:27 PM	#1
David Downes Tourist Join Date: May 2005 Posts: 2	a couple of newbie q's Please excuse the newbie questions regarding 1080i on the Sony FX1/Z1E. Firstly, if you shoot 50i with the shutter speed at 25, arent you essentially shooting progressive frames? Secondly, I keep reading about 1080i being a resolution of 1920 x 1080 pixels but isnt it true that the actual number of horizontal captured pixels is 1440, each pixel being 'stretched' to fill a 1920 (square) pixel frame width? Can someone tell me why non square pixels are better (or worse) than square ones? Last edited by David Downes; May 15th, 2005 at 07:55 PM.

May 15th, 2005, 11:53 PM	#5
Andrew J Hall Regular Crew Join Date: Feb 2005 Location: Wellington, New Zealand Posts: 80	My own newbie question, how does the camera shoot 1/25 (or 1/3) second while delivering 50/60i? Andrew __________________ http://www.ps-scripts.com/ Intel Core2 Quad Q6600 2.4GHz, 2x 2Gb Ram, ATI Radeon HD 3850

May 15th, 2005, 08:55 PM	#3
Tommy James suspended -- contact admin Join Date: May 2005 Posts: 214	Electronically the image may be interlaced but for all pratical purposes shouldnt shooting in cf30 produce progressive like images?

May 16th, 2005, 06:48 AM	#6
Ron Evans Inner Circle Join Date: Mar 2003 Location: Ottawa, Ontario, Canada Posts: 4,222	In simple terms the CCD's in a camera collect light for the time period defined by the shutter speed( there isn't a real shutter as in a still film camera). The collected data for each pixel is then read out into a buffer that is sampled at either 50 or 60 times a second alternating between odd and even lines to create an interlaced image for recording to tape. When the shutter speed is equal to or faster than the buffer sample rate new data is provided at each sample. If the shutter speed is slower than the sample rate there will be repeat samples. That is, movement in the image will be affected. This is a simple explanation, it is a little more complicated in practice due to the way CCD's collect light charge and transfer to the read buffer!!. Ron Evans