Changing the perspective view of an image

[dutchman]

In another thread some users think other programs have better tools to change the perspective view of an image.
Altough I'm not an expert, I think PL can handle this with ease.
My question to all those users with other programs (I don't have ones) to show us, how other programs do a better job.
My image as study object to improve:
https://drive.google.com/open?id=0B0TE6 ... ndtMUprT1U
My improvement:

martinskirche3.jpg

[bruce1951]

I haven't a comparison of many editors. Everyone I have tried seem capable enough. My only comment is on the 'over' use of perspective correction. Change in perspective is a natural occurrence. IMHO too many folks over correct.

regards

[dutchman]

Well... that's also the reason, why I ask for comparisons.
I would like to see "what is correct".
In my opinion is it a bit of taste, like color tones, or temperatures.
Some like it so... others not.
So show us what is correct and not overdone, or completely not done!
For me it's hard to tell.

Regards
toni

[bkh]

As I wrote in the other thread, getting this "right" isn't a matter of what program to use, but rather to know the rules of perspective.
In the case of your image, I'd suggest only to correct rotation and vertical distortion and to keep the horizontal distortion as it is. (Note that you can't change the perspective of a 3d object, you can only pretend another perspective, which will sometimes result in an unnatural look – in that case, it's advisable to undercorrect the image.

Anyhow, for the image to look correct, you need to make sure that
1) all vertical lines are vertical
2) horizontal lines at eye height are horizontal (a horizontal line somewhere below the church windows
3) the image isn't stretched horizontally (try to keep vertical lines in place).

Here's the solution I'd suggest (using PL's crop tool).

crop.jpg

Note that the tower does not look correct – the image seems to be taken from half the tower height but the perspective of the tower doesn't fit – a slight unercorrection usually helps).

And here's the entire distorted layer in PL.

correction.jpg

(I switched to document mode to get a distorted layer instead of a resampled one.)


Cheers

Burkhard.

[bruce1951]

IMHO vertical lines don't work. Yes the walls are vertical in real life. But go outside and look up at the church. Ask yourself if the walls are still vertical and parallel all they way. Technically they are. Unless built by a shonky builder. Stand at the foot of the Empire State Building and look up. Are the walls parallel to your eye? If yes then you have serious eye issue.

My point being. - Technically we 'need' parallel walls. But that's not how our brain works. With perspective correction we have to tread a fine line between what 'is right' and what 'looks right'. I've seen too many fine images destroyed by over correction.

regards

[photoken]

I think that everyone is right when they say that "correcting" the distortion in an image is a matter of individual judgement.

This has been true long before the advent of digital image editing -- look at the architectural photos from the early 20th century. The professional architectural photographers who took those photos used the adjustable front and back planes of their view cameras (as well as tilting the negative holder and paper holder when printing the image) to "correct" the perspective to give absolutely vertical lines. To my eye, most of those images look "overcorrected" and actually detract from the beauty of the buildings -- I hate the severely distorted arches and other circular elements.

So, for me, the existing PL tools for "correcting" perspective are enough. Judicious use of perspective "correction" is the key -- less is more....

My interpretation of this image is nearly indistinguishable from Dutchman's:

perspective 01.jpg

[dutchman]

Note that the tower does not look correct – the image seems to be taken from half the tower height but the perspective of the tower doesn't fit – a slight unercorrection usually helps).

NO!
I was standing on the market place when I took the pic of this church:
More! The church is even leveled UP, so you only can reach the doors by using the stairway with about ten steps(I don't know the name for that).

My goal here is to ask you what is correct! And can PL do it's job reasonable/acceptable?
And yes... the meanings and thoughts of you all (till now) sounds unisono... "what is correct???"
And yes... PL can handle this job nearly perfect.

And yes... I wish a bit more of convenience to adjust the points of "filter/Digital Camera/Rectify" in the preview of the tool.
But I disagree that PL can't handle this "CORRECTLY". (Sorry Martin (Stricker))
BUT... as I wrote, the tool could be more convenient.

Best regards
toni

[bkh]

Note that the tower does not look correct – the image seems to be taken from half the tower height but the perspective of the tower doesn't fit – a slight undercorrection usually helps).

NO!
I was standing on the market place when I took the pic of this church:
More! The church is even leveled UP, so you only can reach the doors by using the stairway with about ten steps(I don't know the name for that).

That's a misunderstanding. Of course, I know where you took the photo.

BUT: if you do a perspective correction of the vertical lines, the image looks (at first glance) as if it was taken from a higher viewpoint. Our brains try to interpret the image that way, and fail because things don't match up. That's why you usually under-correct (so the brain still knows that it's "looking upward").

My goal here is to ask you what is correct!

There is no way to do it correctly (for a 3D scene), i.e., you by distorting the image, you can't change the perspective in such a way that the image looks natural when you look straight at it. You can only create so much of an illusion. (Otoh, whatever perspective distortion you apply to an image, there's always a way to hold it and look at it in such a way that it looks natural.)

Yes, PL can do the same perspective corrections as any other program, the only question is whether there is a better GUI to do so. (One problem in PL is that you can also stretch the image horizontally or vertically, without being aware of it.)

Cheers

Burkhard.

[Martin Stricker]

But I disagree that PL can't handle this "CORRECTLY". (Sorry Martin (Stricker))

I haven't said, that PL can't handle this correctly. Please read again.
So if this was the reason you started this all you missed the point.
I m interested to refine the capabilitys of PL to the benefit of everyone.

[dutchman]

I haven't said, that PL can't handle this correctly. Please read again.
So if this was the reason you started this all you missed the point.
I m interested to refine the capabilitys of PL to the benefit of everyone.

Sorry for that... But the discussion is interesting for me. And I learned some techniques and a way to see things different.
I agree that the tool could be more convenient.

[Lundberg02]

I don't think many people know about DXO's nice little standalone called simply "Perspective". It's free if I remember right. I've had it for years.

[peter-funken]

I don't think many people know about DXO's nice little standalone called simply "Perspective". It's free if I remember right. I've had it for years.

Only for Mac. And I don't know if it is still free of charge. For PC (and Mac) they have Viewpoint for €80 as standalone plus PS plugin that, alas, doesn't work with Photoline.

[peter-funken]

A plug-in that works well with Photoline is Thomas Niemann' s PTLens (http://epaperpress.com/ptlens/).

[dutchman]

Hi,
10 images free, than you have to purchase the program for 25USD.
In general, it looks and feels very good.
Because of the BETA-version of PL, it's a good idea, that the developers take look at the programm.
BUT the solution so far for PL it's nearly perfect. ( for me )

[greenmorpher]

A plug-in that works well with Photoline is Thomas Niemann' s PTLens (http://epaperpress.com/ptlens/).

PTLens -- I've used it for years, first with Canvas, then with PL. I use it as a plug-in -- for your $25 you also get a stand-alone version. That's a one-off buy; to update, you download the app free and dump it into your app folder (on Mac), in my case, into the PL plug-ins folder. Too easy.

I've just updated mine -- for free -- to handle files from my new Panasonic Lumix G85 and a range of lenses.

PL's perspective correction tools are useful and do the job, but it is no surprise that the dedicated mini-app or plug-in does the job better/easier. PTLens also does rotation and CA correction.

AND it does lens/camera barrel/pincushion distortion automatically -- using algorithms for specific lens/camera combinations with different algorithms for RAW and JPEG output.

How that works is simple: Tom asks users whose lens/camera combinations aren't covered to shoot simple test files and send them in. He will take those files and calculate the corrections needed and add them to the database. Then he'll let you know and you simply download the latest version of the app and install it.

I use it practically daily for the distortion correction facility (nothing like those straight lines near the edge of the frame being actually straight!) and less often but very frequently for perspective correction -- mostly for internal pix of tourist facilities. While I find PL's tools okay, the dedicated PTLens is a superior tool for the job in my view.

SOME GENERAL REMARKS

HEIGHT/WIDTH

When perspective is corrected the relationship between the height/width dimensions are interfered with. in the case of the church picture, the church has been stretched upwards. When the perspective correction has been completed, you need to either grab the bottom of the picture and squash it up a bit or pull out the sides to return the proper perceived relationship to height-width. (PTLens had a "friendly competitor" on Mac, the name of which now escapes me, which used the PTLens database. It had an advantage over PTLens -- it automatically adjusted the height/width as required to retain the correct relationship as perspective was corrected. Sadly, this app died. Just not enough business around to make it work it, I gather.)

I make these adjustments by eye. There are more precise ways, but for my work, the degree of precision offered is unnecessary. PL's tooks for this stuffare excellent.

PERFECT OR NOT QUITE RIGHT?

With externals of buildings, I do like to leave a degree or so of under correction in place. Just a little. It looks more natural to me. I like Ken's and the Dutchman's interpretations.

COMPOSITION

One of the problems I see in the church picture is that the composition is not good -- the tower needs to be further from the edge, preferably quite a bit further, with the other end of the church where it currently is. A bit of shrubbery at the foot of the tower would help too. If this was added and a bit of the "stretch" taken out of the picture,

If you are taking a leaning tower which you plan to correct for perspective later, you should compose the shot to allow for some cropping on the sides. in the case of the church, there is not enough allowance in the original shot so the corrected pic has the tower pushed over too close to the left-hand edge.

USE OF CORRECTION

I agree with some comments above -- not every picture needs to be corrected! Those soaring shots of skyscrapers reaching towards the stratosphere and dwindling to practically nothing at the top, are wonderful. Correct them at your peril because that is how we see them from ground level -- they tower over us, they are beyond human scale; even if we move back a considerably distance, they still tower and taper! On the other hand, I would correct a picture of the modest church example here every time -- it is not out of human scale. We can see it and envisage it as a whole; it's not much bigger than many houses. Step back a little and it is straightening up significantly. Correcting the photo is simply giving the church the appearance that we "see" even if we are up quite close.

Shooting accommodation interiors, I try to shoot straight and level all the time -- the distortions introduced by the rectilinear UWA lens I use for the job, the 9-19mm Olympus on the Lumix G85 m43 body (currently) (that gives 18-36mm FF quiv), mostly shot at 9mm (18mm FF) are quite enough to be going on with!

Mostly!

But sometimes I deliberately introduce distortion with PP corrections in mind to include in the picture elements that "straight and level" would leave out or would include in the picture but not in the desired relationship. For example, yesterday I had a set table in the foreground and beds and chairs in the background. Straight and level, the table would obscure the stuff behind or most of the table would not be in the picture. So I pointed the camera down a bit to include more table. In addition, I pointed it off to one side to include the chairs and TV, knowing that doing that would introduce nasty lines at the ceiling/wall intersections (operating on my own, I couldn't get rid of the mini-fridge!).

I knew before I started that some elements in the foreground would be a bit odd, but that was not a concern. They were commonplace things like cups and plates and people looking at the picture would see "the room", not those details which they would mentally correct to normal anyway.

By the way, the picture shown is just one of seven frames overlaid in Bracketeer to extend the DR to include a little of the outside in the picture.

Cheers, Geoff

PS: I also pasted a picture into the TV. What a whore! LOL!