On the few occasions I've done it, I was adjusting one dimension I
think. I was passing on the advice of my photo-instructor cousin who
advised with an 'up-view' distortion (which actually gives the opposite
of a keystone taper - I've built a rock arch!) that it was better to
compress the base than stretch the top - although most people
instinctively do the reverse, trying to correct what they see as the
perspective fault at the top. He reasons that you lose information in
the stretched area so that although it is unavoidable at times,
compression is to be preferred. This is untested by me as yet but he
does teach degree level and write for a couple of flashy digital
magazines so I trust his advice.
AndrewF
On 15/10/2004, at 11:13 AM, Rob Harrison wrote:
> On 10/14/04 2:47 AM, "Andrew Fildes" <afildes@xxxxxxxxxxxxxx> wrote:
>
>> Basic rule of perspective correction - always compress, never stretch.
>
> With the distortion typical of wides though, wouldn't one always be
> stretching? I suppose if it was strict keystoning you were trying to
> correct
> you could start with the top of the building as the given and compress
> the
> bottom...but then wouldn't you have to stretch it again to regain
> proportions?
>
>
> LensDoc is pretty cool by the way. As Skip said, very simple and nice
> interface.
>
> -Rob
> Seattle
>
>
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