06-12-2010, 11:08 PM
[quote name='Chris F' date='12 June 2010 - 04:35 PM' timestamp='1276356910' post='452']
I think from a quality point of view, it doesn't make a difference whether you stretch or squash. Bottom line is that you'll always lose resolution by correcting for distortion. Even if the image is stretched to compensate and maintain the pixel resolution, you don't actually gain anything over the squashed version because you need to stretch by interpolation, which doesn't give you real resolution. I guess personally I prefer the approach where you lose resolution, because you can then decide for yourself whether you want to stretch the picture later, and to what extent.
[/quote]
Hi Chris
The issue is that if you scale down to include the whole image, it's fine for the stretched part at the top of the image (assuming it's converging verticals we are correcting) because they, having been interpolated, probably look better that way.
But there's not much change at the pixel level at the bottom of the image -- and that gets downscaled as well of course.
Now, if the image has mainly sky at the top, then it doesn't matter if the interpolated pixels are there - so the downscaling of the top has no real benefits. But the detail likely at the bottom does suffer slightly.
I think from a quality point of view, it doesn't make a difference whether you stretch or squash. Bottom line is that you'll always lose resolution by correcting for distortion. Even if the image is stretched to compensate and maintain the pixel resolution, you don't actually gain anything over the squashed version because you need to stretch by interpolation, which doesn't give you real resolution. I guess personally I prefer the approach where you lose resolution, because you can then decide for yourself whether you want to stretch the picture later, and to what extent.
[/quote]
Hi Chris
The issue is that if you scale down to include the whole image, it's fine for the stretched part at the top of the image (assuming it's converging verticals we are correcting) because they, having been interpolated, probably look better that way.
But there's not much change at the pixel level at the bottom of the image -- and that gets downscaled as well of course.
Now, if the image has mainly sky at the top, then it doesn't matter if the interpolated pixels are there - so the downscaling of the top has no real benefits. But the detail likely at the bottom does suffer slightly.