Author Topic: Horizontal / Vertical ratio  (Read 2322 times)

nputtick

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Horizontal / Vertical ratio
« on: January 03, 2016, 10:36:26 pm »
When correcting perspective, sometimes the H:V ratio becomes incorrect.  Correcting it using the slider is subjective - for instance, there may be a circular object visible (clock, window etc) which makes it easy.  Or you may have an image of the same building from further away, and you can measure the H:V ratio from that and replicate it.

But -is there a way for doing this correctly without such a separate reference?  It would be good to be able to reproduce building dimensions correctly.  Any suggestions?

KolinP

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Re: Horizontal / Vertical ratio
« Reply #1 on: January 06, 2016, 04:25:15 am »
I scratched my head about this also when I first used ViewPoint a long time ago, but once I saw that we have an option to choose a 'Natural' adjustment on the Perspective sub-pallette (you'll recognise it in my attachment) ... I took this as a big hint that Perspective corrections would always be more or less subjective.

Then when I saw the description of this 'Natural' Perspective option in the ViewPoint Help, where it says "Natural: Applies a correction with the intensity pre-set to 75 for a more realistic rendering", I felt even more certain that ViewPoint did not (and probably could not) give me an absolute, or automatic, perspective adjustment for any of my photos.

I only do architectural photography occasionally, and only as a hobby, so I don't know what methods 'real' architectural photographers might employ to be sure of getting the 'best' perspective each time from their photos, but I'll bet that even they would agree that these adjustments are more of an 'art' than a 'science'!

I'd be very happy to be proved wrong of course  ;D

Colin P.
Nikon D700. DxO Optics Pro Elite. Capture NX2. IMatch. NEC PA241W Pre-calibrated Monitor. No plans ever to use Photoshop.
Keen to learn & happy to share.

nputtick

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Re: Horizontal / Vertical ratio
« Reply #2 on: January 07, 2016, 09:44:53 pm »
Thanks Colin - I have seen and used this control, ideal for a quick fix rather like the automatic option in Lightroom.  I've emailed an architectural photographer I know, and if I get a useful answer, I will repost here.  Meantime I will keep fudging it.  A useful guide is if there's a circle anywher on the building, such as a round window or a clock.

Cheers
Nigel

Nick_

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Re: Horizontal / Vertical ratio
« Reply #3 on: February 08, 2016, 03:03:15 pm »
I had the same issue several times. I don't know if the correct ratio may be calculable from the ratios and angles of the polygon in the image. I did corrections subjectively too. Most of the times I knew no one could check the accuracy but it's not a real consolation. ;-)
Nick

 

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