On 6/7/2013 8:15 AM, Chuck Norcutt wrote:
> Pretty much what Moose said. I learned early on that, when doing
> perspective correction, a complete correction never seems to look right.
Yup
Although perfect verticals often look good with modestly distorted horizontals,
as in the sample I posted. I think the
long, strong verticals make that image. Leave them slightly tilted - or correct
the horizontals - and it goes flat.
> Although we don't generally see (or at least notice) much in the way
> of perspective problems with our eyes (like our cameras do) we
> nevertheless do see some. If we do a full horizontal and vertical
> correction the image looks a bit strange since we don't normally view
> real world objects like that. It took a while but I eventually realized
> that I don't need scales or levels or vertical gauges when adjusting
> perspective... just do it until it looks right to the eye.
I do usually use a grid. It makes it easier to see when I am just short of full
correction.
Away from building-scapes, many smaller subjects, paintings, some interiors,
etc. do seem to respond well to correction
as close to 'perfect' as possible, without going at all past.
All the images with vertical and/or horizontal lines are corrected to a fare
thee well vertically, and horizontally too
where there is no depth perspective, in this set of formal compositions.
<http://www.moosemystic.net/WP_Gallery/?p=114>
Even the one of arcs of light was carefully corrected to be sure the ends of
the arcs are in the same horizontal planes.
I think it works well for the subjects.
> One thing that Moose did not mention is that the corrected images lose
> content from the edges as they are pushed out and ultimately cropped
> off. Notice that the vertical correction has lost image content at the
> left and right sides and the horizontal correction has lost very
> significant content at the bottom and required adding a lot of sky at
> the top to maintain the same aspect ratio.
>
> If you're using (especially) a wide angle lens and pointing it either up
> or down and can anticipate the need for perspective correction you may
> want to include a larger field of view to compensate for the crop that
> will be required later on. (advice I rarely remember myself :-))
Exactly. I do tend to forget to leave room. Content Aware Fill is often the
solution for that. It's where that extra sky
came from. Crop to the outer ends of the corrected image that you want to save,
then use CAF to fill in the blanks. Once
in a while, it's useless, sometimes it pure magic, almost always a big help.
> If I had processed this particular image I would have corrected the
> verticals to maybe 90-95% of full vertical and would not have corrected
> the horizontal at all.
I would do something along those lines. The fully corrected one is pretty
boring. But I was not trying to create a
better image. I was demonstrating to someone newly discovering perspective
correction an idea how far it can go, if one
wants. Even if never going to the ends, knowing how wide they are makes it
easier to play creatively within them.
Perspective Playground Moose
--
What if the Hokey Pokey *IS* what it's all about?
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