re: Lens profiles & corrections [WORKFLOW for best results]

[Timothy Selvage]

Hello all, I'm new to PTGui but have used other programs for stitching panos.

My workflow:

Shoot in raw 

Import into lighroom

Correct for WB, Chromatic aberration, apply auto lens corrections in Lightoom

Export to .tiff (pro photo 16bit)

Load images into PTGui - tick box 'Automatic' (use EXIF data from camera)

[note: Both pieces of software recognise EXIF from my camera and lens. D800, 14-24mm]

Align images, etc...

My concern is that this workflow applies lens corrections twice as I'm assuming that PTGui also corrects for lens distortion. I am currently experimenting with trying different variations (it's early days and there is still a lot to learn) but wanted to know other people opinions, experiences and practices are.  

I was also wondering whether if I choose to use PTGui whether it is better to use 'Automatic' (use EXIF data from camera) or enter the data in manually. I have a feeling that PTGui treats the Nikon 14-24mm as a fisheye rather than a rectilinear.

So my two questions are:

Q1) Should you correct for lens distortion BEFORE loading into PTGui?

Q2) Is it better to to use 'Automatic' (use EXIF data from camera) or enter the data in manually?

The context and area of photography I'm interested in is primarily architecture - click on the link below for some examples.

https://plus.google.com/b/110020294581095818378/110020294581095818378/posts

[PTGui Support]

Hi Timothy,

You're right, PTGui will by default wrongly recognize your lens as a
fisheye lens. Please see 3.3 for more information:
http://www.ptgui.com/support.html#3_3

And it's not recommended to correct for lens distortion before loading
into PTGui. PTGui can do a nearly perfect correction because it can use
information from the overlapping images. Lightroom does not have this
data and it might correct or overcorrect the images in a way that cannot
be undone by PTGui.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

-----------------------------------------------
PTGui - Photo Stitching Software

www.ptgui.com
For support see: http://www.ptgui.com/faq/
-----------------------------------------------

On 25/07/14 10:45, Timothy Selvage wrote:
> Hello all, I'm new to PTGui but have used other programs for stitching
> panos.

> *
> *
> *My workflow:
> *

> Shoot in raw
> Import into lighroom
> Correct for WB, Chromatic aberration, apply auto lens corrections in
> Lightoom
> Export to .tiff (pro photo 16bit)
> Load images into PTGui - tick box 'Automatic' (use EXIF data from camera)
> [note: Both pieces of software recognise EXIF from my camera and lens.
> D800, 14-24mm]
> Align images, etc...
>
> My concern is that this workflow applies lens corrections twice as I'm
> assuming that PTGui also corrects for lens distortion. I am currently
> experimenting with trying different variations (it's early days and
> there is still a lot to learn) but wanted to know other people opinions,
> experiences and practices are.
>
> I was also wondering whether if I choose to use PTGui whether it is
> better to use 'Automatic' (use EXIF data from camera) or enter the data
> in manually. I have a feeling that PTGui treats the Nikon 14-24mm as a
> fisheye rather than a rectilinear.
>

> *_So my two questions are:_*
> *Q1) Should you correct for lens distortion BEFORE loading into PTGui?*
> *Q2) Is it better to to use 'Automatic' (use EXIF data from camera) or
> enter the data in manually?*

>
> The context and area of photography I'm interested in is primarily
> architecture - click on the link below for some examples.
> https://plus.google.com/b/110020294581095818378/110020294581095818378/posts
>

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[Timothy Selvage]

Thank you Joost. It confirms what I thought. As I do not own a fisheye lens I will follow the step:

"If you don't use any fisheye lenses, you can configure PTGui to always assume rectilinear projection for your lens: go to Tools/Options (on Mac go to the PTGui menu, Preferences), EXIF tab and change the 15mm values to e.g. 9mm. From now on PTGui will assume any lens with a focal length higher than 9mm is a rectilinear lens".

HOWEVER, after doing this will I then be able to click the box 'Automatic' so I don't have to always enter the focal length manually (being a zoom I change focal lengths)?

Please note that your support title says: Nikkor 10-24mm lens (this might confuse people / lead to people to skip the advice e.g. who are using a 14-24mm f2.8 or the 12-24mm f3.5. It might be worth adding these lens or add a text to state 'and other rectilinear lens with focal values less than 15' to make sure people read it all) :-D

Much appreciated. 

[Timothy Selvage]

Many thanks Joost. That is helpful. I do not own a fisheye so will follow the instructions HOWEVER:

1) Will I be able to check the 'automatic' box after this?

2) Should the focal length multiplier be changed (it currently says 1.85)?

Note that your support title says Nikkor 10-24mm lens. It might be worth adding 12-24 and 14-24 (or text simply stating retilinear lenses with focal ranges below 15mm). Otherwise people might skip it ;-)

Much appreciated.

On Friday, 25 July 2014 09:52:43 UTC+1, PTGui Support wrote:

[Keith Martin]

On 25 Jul 2014, at 9:45, Timothy Selvage wrote:

> I was also wondering whether if I choose to use PTGui whether it is
> better
> to use 'Automatic' (use EXIF data from camera) or enter the data in
> manually. I have a feeling that PTGui treats the Nikon 14-24mm as a
> fisheye
> rather than a rectilinear.

In PTGui's Preferences, in the EXIF section, you can control the focal
length threshold that PTGui uses for assuming something's a fisheye
lens. The default is:

35mm equivalent focal length is [15] mm or less, or
focal length is [16] mm or less, and focal length multiplier is less
than [1.85]

(At least I assume that's the default, I may have tweaked it
experimentally some years back... ;)

Once you have this working well, consider saving a document as a
template. That can save a tremendous amount of time AND make sure you
don't accidentally forget some important detail as you work through pano
after pano.

k

[Timothy Selvage]

Thanks Keith. I've now followed Joost's recomendations in the preferences so that PTGui recognises my lens as rectilinear (8mm or less recognise as fisheye). Why would the focal length multiplier be less than 1.85 (I've kept this as is but wondered why)?