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Guest

Does anyone know if the vertical perspective controls in LR3 exhibit the same behaviour as the CS4 and earlier ones? In particular, is the image squashed vertically? (PT lens, for example, stretches the image vertically to compensate).



Another issue: if you use the perspective controls, the top of the image will gradually fall outside the frame. You can compensate by scaling the image down - but this is not an ideal solution, since you are then losing resolution at the bottom of the image (and often it's just sky at the top so it doesn't matter much that it is interpolated heavily)



Only work around I can think of is to take the image to photoshop, expand the canvas, and then either bring it back or else use the lens correction in photoshop then. But it's just as rather use PTlens than go though all that.
Under this point of view, Silkypix is still the best, by far. You can correct vertical and horizontal perspective and the picture cover the frame automatically; Sadly it now is behind about resolution: in the past it was "good enough", at least to me, but the other improved a lot resolution wise. But features like perspective correction and the almost magical CA correction (simple like a click, no lost of resolution), make me still use it (not to talk about the color rendition, still the best of the bunch to me).

If you shoot architecture and need a lot of perspective correction, you might want to try it.

Guest

[quote name='exuvia' date='12 June 2010 - 10:04 AM' timestamp='1276333476' post='448']

Under this point of view, Silkypix is still the best, by far. You can correct vertical and horizontal perspective and the picture cover the frame automatically; Sadly it now is behind about resolution: in the past it was "good enough", at least to me, but the other improved a lot resolution wise. But features like perspective correction and the almost magical CA correction (simple like a click, no lost of resolution), make me still use it (not to talk about the color rendition, still the best of the bunch to me).

If you shoot architecture and need a lot of perspective correction, you might want to try it.

[/quote]





Thanks!

Actually covering the frame is not a problem with perspective correction in LR; you can just use the scale slider until all is visible. The problem is that doing this effectively reduces resolution (as against PTlens). But I think that even with the reduced method the result is better than I've been able to get with SilkyPix.

Guest

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 name='DavidBM' date='12 June 2010 - 02:38 AM' timestamp='1276306731' post='447']

Does anyone know if the vertical perspective controls in LR3 exhibit the same behaviour as the CS4 and earlier ones? In particular, is the image squashed vertically? (PT lens, for example, stretches the image vertically to compensate).



Another issue: if you use the perspective controls, the top of the image will gradually fall outside the frame. You can compensate by scaling the image down - but this is not an ideal solution, since you are then losing resolution at the bottom of the image (and often it's just sky at the top so it doesn't matter much that it is interpolated heavily)



Only work around I can think of is to take the image to photoshop, expand the canvas, and then either bring it back or else use the lens correction in photoshop then. But it's just as rather use PTlens than go though all that.

[/quote]

Guest

[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.