Tilt shift lenses and VRay vertical correction

[cg_Butler]

Hello everybody.

 

I have recently finished a montage for a client. The photograph of the site was taken from around 300ft with a fixed 14mm lens so we could get the whole site in to one photograph. In doing this, the edges of the photograph weren't vertical and we had the classic request from our client to make all the buildings appear vertical.

 

So once we had rendered and composited it in to the photograph we went about the task of straightening the image by using warp, distort and perspective adjustments in photoshop.

 

We got everything looking vertical as best we could without the image looking really weird but the client still wasn't happy.

 

The main problem I found with this particular view was that vertical correction doesn't work at all. It stretches the foreground and squashes the background.

 

My main questions that have arisen from this are.

 

1. Does vertical correction accurately portray what a photograph taken with a tilt shift lens would take?

2. Has anyone used tilt shift photographs for a montage, or is it best to take with a normal lens and straighten in photoshop afterwards?

3. If you are elevated above a site and the client wants a photograph to be straightened, what procedures have you used that worked and gave you a good result?

 

This is not personal work, it is professional and for a paying client and we are trying to find ways to give them what we want, even though we think from the angle they are demanding, it is impossible.

 

The lower we come, the better it looks and the less distortion vertical correction gives, but we knew that already and it's not what the client wants.

 

Thanks in advance.

Edited October 15, 2013 by cg_Butler

[Scott Schroeder]

What if you do the vertical correction in photoshop's lens correction tool? Where you draw the line that you want to be vertical and let photoshop make the adjustments. You can also fine tune the controls in the vertical and barrel distortion sliders.

 

Though there is only so much adjusting you can do before things start to look strange. You may have to overlay multiple corrected images and try to seam them together if you want all of your lines to be perfectly vertical.

[cg_Butler]

That's the tricky part! We tried that.

 

I didn't mention that the site photograph that we have is taken up an existing high rise tower at around 350ft high with 14mm fixed lens, angled downwards to the site, so straightening the lines is almost impossible it seems. The only thing we can think of is to take multiple pictures and stitch them together. But that would require a lot of careful work in 3dsmax/vray to match each photograph and stitch together exactly the same way.

 

I ca'nt show you the photo or the match as it's confidential at the moment, but i'm sure you can imaging it's distortion.

[notamondayfan]

What happens if you remove the barrelling, then straighten the verticals?

 

I personally would use photography that doesn't use tilt shift, then comp in the 3D part, then adjust the verticals in post, as in theory the camera match would be better. Saying that though, for the camera match it's OK to use tilt shift photography if you have plenty of reference points to line up your 3D, rather than relying on the camera lens for a good match.

 

Dean

[cg_Butler]

It's the straightening that's the problem because of the high angled down viewpoint. To straighten the buildings on the site, one of which is a 300ft tower which in the render angles to the left and also tapers wider as it goes higher in the render (although in reality it is perfectly vertical with no tapering)we had to use warping, distortion and a small amount of lens correction in Photoshop to achieve what the client wanted. We got there, but in our opinion it looks less realistic, and the tower looks like it's falling backwards.

 

One of the pitfalls of the client having a requirement and in reality it's not possible!

[Crazy Homeless Guy]

The image is hard to visualize without visualize. It the sounds of it you need to retake the photo with the end results in mind. Sure we all push photos to their limits but shit is so much easier and better if the amount of manipulation doesn't involve a great deal of trying to re-orient photographic perspective.

 

The other option is to try and educate your client on the limitations of what they are asking. I find that most clients are happy to be educated to the process and limitations. In the end it produces better results for them, and better results for us.'

 

The later is not easy but it is more rewarding at the end of the day.

Edited October 16, 2013 by Crazy Homeless Guy

[cg_Butler]

Totally agree. We did what the client asked which was to take the photograph from the tower, making sure we encompass the entire site. We did that, matched it, montaged it, then they ask "why are the buildings leaning over?" Then we had the problem of straightening it so we had done all the hard work before they mentioned what they really wanted.

 

We are giving them some options of alternatives and directing them now with what we know is achievable so it's all good. But I just wondered if anyone had been through this sort of problem and achieved a good result. Our final result was good, but they've realised it wasn't what they wanted and now we are being commissioned to do alternatives. It's all part of the process.

[jinjinn]

What is the angle looking down. If it is too much of a angle paired with a wide angle lens the client will have to accept that this is what you see at that angle. Otherwise you will have to go all CG and maybe photomontage a few elements in.

 

I had a client once ask to remove all the shadows on the building. I told them no, that this would flatten the image. I gave them a few options and everything was fine. Unfortunately Visually educating a client is part of the job.

[Darawork]

Would a point cloud scan of the scene help?

You can get a Faro Focus 3D scanner for hire for £1500 a week.

 

http://www.surveyequipment.com/faro-hire#.UoOxsuLwp7w

 

Then it's 'simply' a matter of UVW mapping the cloud... hrm, perhaps not.

How realistic does it have to look?

[cg_Butler]

In this instance it wouldn't help as it doesn't exist!

 

Cool piece of equipment though!