Alaa
Posts: 5
Location: Ashburn VA, United States
Registered: 31 Dec 2006
|
Why the Declining in quality ?
Posted: 29 Sep 2008 at 17:51 GMT
|
reply
|
Whenever I'm done converting my Pano from Cubic, back to Equirectangular in Pano2QTVR, and creating the movie, and opening it in Quicktime I feel a huge declination in quality/sharpness, and contrast; although right before this process the quality is great, would anyone know what is going wrong ? and why?
Thanks
|
|
alert moderator
|
|
John Houghton
Posts: 2317
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
|
Re: Why the Declining in quality ?
Posted: 29 Sep 2008 at 18:51 GMT
|
reply
|
You need to discover at which step in the process you get significant deterioration. For instance, how does the equirectangular from Pano2QTVR compare to the original stitched panorama? The QTVR display is often noticeably degraded, depending on the tile size/compression/interpolator options selected in the conversion.
John
|
|
alert moderator
|
|
Alaa
Posts: 5
Location: Ashburn VA, United States
Registered: 31 Dec 2006
|
Re: Why the Declining in quality ?
Posted: 29 Sep 2008 at 19:17 GMT
|
reply
|
Hi John,
Thank you for your reply, and I did try to find at which point it does, what puzzles me is once the pano is converted to cube it looks good, then back to equirectuglar still ok, the minute I create the movie in Pano2QTVR is where the very obvious degradation appears. I haven't looked at the tile size/compression/interpolator options, all I did is choosing the window size to 900x600 in the movie properties. The tile settings are as follow Cube face size: 0 px marked auto
Subdivision 1x1 Quality 90.
|
|
alert moderator
|
|
John Houghton
Posts: 2317
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
|
Re: Why the Declining in quality ?
Posted: 29 Sep 2008 at 22:05 GMT
updated: 29 Sep 2008 at 22:06 GMT
|
reply
|
Try setting the tile size to the width of the equirectangular image divided by pi (3.142) and the compression (quality) to 70, interpolator to spline 36. For good quality fullscreen display, the equirectangular should be around 5000x2500 to 6000x3000.
John
|
|
alert moderator
|
|
John Willetts
Posts: 49
Location: Bath, United Kingdom
Registered: 13 Mar 2008
|
Re: Why the Declining in quality ?
Posted: 30 Sep 2008 at 9:01 GMT
|
reply
|
John is quite correct in everything he says.
But what I have noticed that when you convert an equi.. (usually at 300dpi) into cubes, the dpi drops to 72. When you covert back to equi... it stays at 72.
Thomas claims it doesn't lose quality - but I think it does.
|
|
alert moderator
|
|
halflife
Posts: 145
Location: Romania
Registered: 3 May 2006
|
Re: Why the Declining in quality ?
Posted: 30 Sep 2008 at 10:39 GMT
|
reply
|
Hi,
DPI is only relevant when you are actually printing, what determines the file size is the pixel dimensions. So, if you are keeping the same numbers of pixels, you are not actually changing a low res to a high res file. When you print, if you are telling the printer to print to a certain size of paper, it will set the DPI of the file to cover the size that is required. 72 DPI is screen resolution and say 300 DPI is a good amount for an A4 print(?).
This is how I see things, somebody please tell me if I'm wrong!
Eugen.
|
|
alert moderator
|
|
John Willetts
Posts: 49
Location: Bath, United Kingdom
Registered: 13 Mar 2008
|
Re: Why the Declining in quality ?
Posted: 30 Sep 2008 at 12:44 GMT
|
reply
|
I read what you say, but I can't quite understand the logic.
I think in terms of film, where I know the size of format - eg 35mm v 6*6 changes the resolution. Are you saying digital is not the same?
If it is, is their no difference in quality when you are shooting at 5mb rather than 12 in the same format and, if that is the case, what is the optimum size?
John
|
|
alert moderator
|
|
John Houghton
Posts: 2317
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
|
Re: Why the Declining in quality ?
Posted: 30 Sep 2008 at 20:26 GMT
|
reply
|
It depends on what you mean by "quality" and "resolution". The dpi (aka ppi) assigned to a file is merely a parameter value in the exif data that indicates the intended default print resolution: pixels per inch. You can change it to whatever you like in Photoshop's Image Size dialog (uncheck the resample option), and the pixel values will be completely unaffected, so the quality of the image file will be unchanged. Apart from print software, few programs will take any notice of the ppi setting. As already pointed out, the ppi setting simply determines the default print size, but most programs will allow this to be overridden and will print the image at any size. The larger the print (lower ppi), the more spread out the pixels are and the print quality gets worse. Conversely, the smaller the print (higher ppi), the better the quality. Higher ppi gives higher print resolution but a smaller image. The total number of pixels remains the same.
John
|
|
alert moderator
|
|
