XL1-S Vertical Distortion at DVinfo.net

Richard J Morris · April 30th, 2005, 12:46 PM

I apologise if this has been covered elsewhere - but I have had a look and could not find it.

I have been trying to undertake some image analysis using my XL1-S.

Am I right in thinking that the CCD system stretches the image vertically by about 7%? Or to put it another way, the effective pitch of pixels in the vertical is not the same as the effective pitch of pixels in the horizontal?

I am using a PAL camera with the 3x lens in frame mode.

My subject was a perfect square, with the camera as close as possible to perpendicular on the centre point. I grabbed a 720x576 image (representing my understanding of the effective resolution of the CCD system), the square extending to near the top and bottom of the frame (with larger gaps to the sides of course)

I tried this with several camera distances, zoom levels, and even with the camera on its side - always the same result (or at last very close) - The square is appears to be stretched vertically by an average of about 7.2%.

Am I doing something strange? Are all cameras like this? Or just the XL1-S? Or is it a result of using Frame mode?

Any comments gratefully received.

Jack Smith · April 30th, 2005, 07:00 PM

Just curious, how did you determine that it was 7.2%?
Did you capture to something?

Richard J Morris · May 1st, 2005, 03:01 AM

I grabbed a 720 x 576 pixel bitmap image from the camera using Pinnacle Studio.

The image was of a square, 280mm x 280mm, printed on an A3 sheet with centre lines on the square aligned as close as possible to the centre of the image. I then counted the number of pixels along each centre line to the edges of the square.

My conclusion is that the effective pixel rows are squashed together slightly more than the effective pixel columns.

I tried it 5 times with the camera at different distances and zooms and even twice with the camera on its side - the results were pretty consistant.

Jack Smith · May 2nd, 2005, 09:58 PM

Are you viewing this on a computer monitor?
The monitor will be resizing the image to fit. eg. monitor set to 800 x 600
the 720 is increased by about 111% ( 800 divide by 720)but the 576 is only increased by 104%(600 divide by 576)
so it will look squished , stretched out sideways.
Now 111 minus 104 is 7 but ............ just kidding

Richard J Morris · May 3rd, 2005, 06:04 AM

Hi Jack - thanks for the comments.

I am looking at the grabbed image on a monitor - but the pixels are indentified using the "Cursor:(x,y)" information at the bottom left corner of MS Photo Editor. This identifies the cursor position over a pixel in the bitmap image file, not the pixel on the screen - you can tell because zooming in and out in MSPE has no effect on cursor pixel status - so its not a monitor scaling issue.... I don't think....

Jack Smith · May 3rd, 2005, 09:53 PM

I think you may still have resizing happening.The pixel identifier may be correct but they are resized to output to the monitor.try by creating a photo 720 x 576 in photoprogram and looking at that.or how about you load the grab onto the timeline and render to an dv avi then send it back to the camera then view it on TV and/or the viewfinder

April 30th, 2005, 12:46 PM	#1
Richard J Morris Regular Crew Join Date: Mar 2005 Location: Hinckley UK Posts: 25	XL1-S Vertical Distortion I apologise if this has been covered elsewhere - but I have had a look and could not find it. I have been trying to undertake some image analysis using my XL1-S. Am I right in thinking that the CCD system stretches the image vertically by about 7%? Or to put it another way, the effective pitch of pixels in the vertical is not the same as the effective pitch of pixels in the horizontal? I am using a PAL camera with the 3x lens in frame mode. My subject was a perfect square, with the camera as close as possible to perpendicular on the centre point. I grabbed a 720x576 image (representing my understanding of the effective resolution of the CCD system), the square extending to near the top and bottom of the frame (with larger gaps to the sides of course) I tried this with several camera distances, zoom levels, and even with the camera on its side - always the same result (or at last very close) - The square is appears to be stretched vertically by an average of about 7.2%. Am I doing something strange? Are all cameras like this? Or just the XL1-S? Or is it a result of using Frame mode? Any comments gratefully received. __________________ Richard M

May 1st, 2005, 03:01 AM	#3
Richard J Morris Regular Crew Join Date: Mar 2005 Location: Hinckley UK Posts: 25	I grabbed a 720 x 576 pixel bitmap image from the camera using Pinnacle Studio. The image was of a square, 280mm x 280mm, printed on an A3 sheet with centre lines on the square aligned as close as possible to the centre of the image. I then counted the number of pixels along each centre line to the edges of the square. My conclusion is that the effective pixel rows are squashed together slightly more than the effective pixel columns. I tried it 5 times with the camera at different distances and zooms and even twice with the camera on its side - the results were pretty consistant. __________________ Richard M

May 3rd, 2005, 06:04 AM	#5
Richard J Morris Regular Crew Join Date: Mar 2005 Location: Hinckley UK Posts: 25	Hi Jack - thanks for the comments. I am looking at the grabbed image on a monitor - but the pixels are indentified using the "Cursor:(x,y)" information at the bottom left corner of MS Photo Editor. This identifies the cursor position over a pixel in the bitmap image file, not the pixel on the screen - you can tell because zooming in and out in MSPE has no effect on cursor pixel status - so its not a monitor scaling issue.... I don't think.... __________________ Richard M

April 30th, 2005, 07:00 PM	#2
Jack Smith Major Player Join Date: Nov 2003 Location: ontario Posts: 445	Just curious, how did you determine that it was 7.2%? Did you capture to something?

May 2nd, 2005, 09:58 PM	#4
Jack Smith Major Player Join Date: Nov 2003 Location: ontario Posts: 445	Are you viewing this on a computer monitor? The monitor will be resizing the image to fit. eg. monitor set to 800 x 600 the 720 is increased by about 111% ( 800 divide by 720)but the 576 is only increased by 104%(600 divide by 576) so it will look squished , stretched out sideways. Now 111 minus 104 is 7 but ............ just kidding

May 3rd, 2005, 09:53 PM	#6
Jack Smith Major Player Join Date: Nov 2003 Location: ontario Posts: 445	I think you may still have resizing happening.The pixel identifier may be correct but they are resized to output to the monitor.try by creating a photo 720 x 576 in photoprogram and looking at that.or how about you load the grab onto the timeline and render to an dv avi then send it back to the camera then view it on TV and/or the viewfinder