Perspective plugin for Mac

Started Jun 27, 2013 | Discussions thread
richardplondon Forum Pro • Posts: 10,563
Re: LR built-in corrections no good?

My problem occurs when the distorted parts of the image on the left and right of the photo are not at the same distance from the camera. When that happens the "lean" of those parts of the image are not the same and the attempt to correct the distortion for one part of the image is either too much or too little for the other part of the image. When I have an issue like that I have only been able to properly adjust for both when I use something like the distortion functionality in PhotoShop.

It doesn't matter what the camera-subject distance is, just where in the visual field the item occurs. A small nearby pole that is located a certain number of degrees to the left of the camera axis, and whose height subtends a certain number of degrees as seen from the camera, will exhibit exactly the same (but mirroerd) convergence, as a very tall but distant radio mast that is located the same number of degrees to the right of the camera axis, and that subtends the same number of degrees above the horizon. They will appear identical to the camera sensor (focus aside).

All you need is to get some line that is meant to be horizontal or vertical, and which passes through (or which if projected further, would pass through) the centre of the uncropped original frame, to be horizontal or vertical - with the rotation slider in Lens Corrections. Then your Vertical adjustment will bring the tops of the small pole and of the distant radio mast inward, in exactly the same mirrored way and by the same amount in picture terms, until they become parallel - along with all the other vertical items spread around the scene, whether near or far.

With the appropriate rotation set, the Horizontal adjustment will also (optionally) work - predictably and evenly - in relation ot the same optical centre, without spoiling the good work that the vertical adjustment has done.

My immediate response to a comment like that would be that someone needed to do a more thoughtful job of composing the image, but that is not always possible and not always desireable.

After this is done, you can find the compositional crop that you want... the perspective tool does allow for off-centre cropping automatically,  but it is harder for the user to assess the optical centre, when the picture's perspective presentation is eccentric.

I assume you will understand what I am saying but I can, of course, post some images to explain more clearly if you wish.

Most importantly there's no need to commit your current edits into any external file... which would be the case with a plugin, or external utility such as PTLens. So all your other adjustments remain live and reversible.

Yes, but all of my images are shot in raw so, in a sense, all of my adjustments are non-destructive.

They stop being that the moment you use one of the utilites recommended higher up (such as PTLens, or anything inside Photoshop) - since the current image needs to be rendered into a TIFF or a PSD. Exception: if you embed your Raw and its adjustments into a Smart Object and then warp that nondestructively inside PS, which would probably be my suggestion for tackling the "Volume Anamorphosis" mentioned in another post.

But if it is straight adjustment that you need, and you are already in LR, and can get its tools to do what you want (which I would suggest, is generally possible)... then why not make perspective correction one of these same, nondestructive, on-the-fly LR/ACR adjustments TOO, instead of using some other system which is not so integrated? Regardless whether as part of a Smart Object workflow, or whatever.

With LR5 there are some new options to auto-straighten verticals only, both verticals and horizontals, or Auto restricts itself to "conservative" strength corrections only.

I have tried to correct this sort of thing in LR4 without success, but I will try LR5 to see if the new functionality helps

There are no new types of adjustment in LR5, it is just that LR can now automatically analyse the picture and set provisional values for these same sliders for you, if you want.

regards, RP

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