Pretty much what Moose said. I learned early on that, when doing
perspective correction, a complete correction never seems to look right.
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.
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 :-))
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.
Chuck Norcutt
On 6/5/2013 9:25 PM, Moose wrote:
> On 6/5/2013 9:11 AM, Paul Braun wrote:
>> This photo:
>>
>> http://zone-10.com/tope2/main.php?g2_itemId=5725
>>
>> Was shot with the E-M5 and the 12-50 at 12. The original has quite a bit
>> of wide-angle leanback.
>>
>> I discovered some tricks with the lens-correction sliders that are scary
>> good - almost like having a view camera.
>
> I'm happy for you.
>
> What you have discovered is nothing new or unique. It's available in all
> sorts of editors and stand alone lens
> correction apps.
>
>> While the right-hand edge still
>> leans a bit, I was able to straighten the left-hand edge almost totally
>> vertical.
>
> It's kind of hard to get extreme distortions right in that ACR/LR tool. In a
> more serious tool, in PS, much more may be
> done.
> <http://www.moosemystic.net/Gallery/Others/Braun/West_Tower_Defiant%20.htm>
>
> The verticals may be fully corrected. That still leaves a quite unnatural,
> but dramatic, 'prow of a ship" look. It also
> tends to make verticals that are actually true look tilted.
>
> If desired, the horizontals may be corrected, as well, leaving a quite
> natural, if rather dull looking, building.
>
> I often only partially correct the horizontals, to retain some of the drama
> and apparent height, as here.
> <http://galleries.moosemystic.net/Brooklyn/Things/Structures/slides/_MG_3299corcr.html>
>
> Skewed Moose
>
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