Luminous Landscape Forum

Equipment & Techniques => Digital Cameras & Shooting Techniques => Topic started by: sharperstill on July 24, 2018, 11:07:40 pm

Title: Increasing FOV for cramped architecture
Post by: sharperstill on July 24, 2018, 11:07:40 pm
Hi all,
A client wants an elevation view of a new 7 story apartment building with a double lane street out the front. That's as far away as I can get directly away from the building. Oblique images across the face of the building understandably have a lot of perspective distortion which the client doesn't like. Getting further away in an oblique direction is made more difficult by the presence of power poles.
From directly across centre of the building it is just too wide for my Canon 17TS and I need significant upward shift to include the upper levels.
I haven't come across the situation too often. Last year I did a 'shift panorama' (is this what is referred to in these forums as a 'flat stitch'?) for an indoor pool I photographed (17mmTS). I wasn't entirely happy with the result as there was some distortion noticeable down in the lower area of the image. Unfortunately I didn't do a panned & stitched composite for comparison. Image attached
With the image of the apartment block though, I need to use most of the rise in order to include the upper levels, so I can't do a 'shift panorama'.
My options for increasing the field of view to include the whole building therefore seem to be;
1) Hire the Canon 11-24, no movements but at 11mm I will probably get the upper level of the building in. May have some room for cropping once alignment/distortion is dealt with.
2) Do a pan & stitch panorama.
So, based on the second option this morning I found a similar size building with a similar shooting distance in a nearby suburb and tried a pan & stitch as a practise run (the actual building is still under landscaping/paving works). The results aren't pretty. In fact, I can't even get Photoshop's Photomerge function to include all the images and produce something even vaguely resembling the desired outcome.. It is seemingly getting confused by the perspective differences in the source images. The second attachment shows my desired outcome, just to be clear. A pure elevation view.

I'd appreciate any advice on how best to tackle this, especially whether it is possible to get the desired result using the pan & stitch mode ( there is no lens rental in this regional city).

Thanks,

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on July 25, 2018, 02:29:53 pm
I'd appreciate any advice on how best to tackle this, especially whether it is possible to get the desired result using the pan & stitch mode ( there is no lens rental in this regional city).

Hi Jon,

Pan and stitch, and use a dedicated pano-stitcher, like PTGUI-Pro.

One thing you will never be able to solve is that the perspective of the resulting stitch will always give an impression of being distorted, but that's just caused by viewing the resulting output from too far away. It's simple geometry, and there's not much that can be done about it.

If the facade is very flat, with few recesses and protrusions, one could attempt a different kind of stitch, for which you also need an application such as PTGUI-Pro. It uses a technique that was pioneered by Max Lyons, as explained on his Webpages:
http://www.tawbaware.com/pta_help/ptasmblr_help_camera_position.htm

That would involve using different camera positions, the images of which can be reassembled because they are in a flat plane shot from different angles. And since a flat plane has no depth, there will be no parallax error on the facade. The street in front will require a different approach, because that street is sensitive to parallax errors if the entrance pupil is not stationary. A montage in post between the two will be in order.

The current Beta version of PTGUI can also mix shots with different focal lengths, which might be useful for a pan and stitch of the street in front, and or of the facade if it is not flat. That would allow shooting the more distant parts with more detailed tile taken with a longer focal length.

Lots of planning and postprocessing is inevitable to achieve the physically impossible. It might take some testing to get the hang of the procedures.

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: alan_b on July 25, 2018, 05:53:06 pm
No matter what lens / perspective correction / stitching method you use, at a certain building height and shooting distance, things are going to look too stretched at the top.  At that point, you could raise your shooting point with a ladder/lift or get access to the building across the street.  You'll lose the ground-level viewpoint into the first floor - everything is a tradeoff!

When I'm scouting such a situation, I take a tilted up shot and post-correct the perspective.  I then ask myself how many of the top floors look wrong - that tells me how high to raise the camera position.
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 25, 2018, 06:25:49 pm


Pan and stitch, and use a dedicated pano-stitcher, like PTGUI-Pro.


This is the best solution. If you go this route, you will also need a pano-head. A pano-head isn't cheap and it needs carefully setting-up ó i.e. finding the no-parallax point for your chosen lens (a 35mm or 50mm would be good for a job like this).
Title: Re: Increasing FOV for cramped architecture
Post by: kirkt on July 26, 2018, 09:57:16 pm
How about using a drone to acquire a flat stitch set of images?  I have performed the previous technique of elevating the camera (I used a 14 ft long pole with a Canon 15mm fisheye) and sprayed the facade (approx 120 ft high church) and stitched.  As you would expect, there was still significant distortion at the top level of the facade and spire.

If you were able to "scan" the facade with a drone, perhaps the flat stitch would work.  You could shoot the surrounding street level, etc. with standard techniques and composite the result into something that achieves the look the client wants.

 I do not profess to know how to use a drone, but just thinking out loud.

kirk
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 26, 2018, 11:14:35 pm
Thanks or the replies. I'll attach some phone snaps from this morning to give context to the shoot and the distances and angles. I also borrowed a 14mm for a quick recon on the FoV of that lens straight on. You'll see it just fits the width without much wriggle room.

I'm surprised to read that pan & stitch is the preferred technique when yesterday's attempt was such an unmitigated disaster.

Bart, the facade has enough depth that the use of different camera positions would not work, also because of the limited positions for the cameras in the first place.

Elliot, I have a rail, and I have the measurements for the magic spinning point for my lenses. What advantage would a pano-head have over this?

Jon
Attachments;
Phone pic of building and tripod position
Phone panorama of lower part of building
Street level view with 14mm
Title: Re: Increasing FOV for cramped architecture
Post by: Martin Kristiansen on July 27, 2018, 02:49:46 am
The problem with shooting a building that height from so close and doing such a strong perspective correction to fix the keystoning is it looks odd. You end up seeing the ceilings of the upper floors while the building is squared up.  That is an impossible perspective in reality.

I think you need to get some height. I canít see properly but it looks like there is a building opposite. Try to get access. Or get a cherry picker. Any height at all is going to help. If the client wants it shot from ground level and corrected for converging verticals then you are going to need to manage his expectations.
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 27, 2018, 06:53:33 am
Elliot, I have a rail, and I have the measurements for the magic spinning point for my lenses. What advantage would a pano-head have over this?

A pano-head (at least by my definition) allows you to shoot rows as well as columns. But looking at your test shots, that might not be necessary. Your 14mm shot, when corrected for perspective distortion, gets close to what you're looking for. But it is clearly not wide enough. The 11mm lens you mentioned in your first post would do it (but the perspective distortion correction would lose a lot of resolution). Better, use the 14mm lens, mounted in portrait format on your rail, and shoot 3 frames, left to right, then stitch with PTGui. You'll need to step forward a couple of feet to clear the power cables, road sign, and nearside cars.

A difficult shoot for sure. I agree that an elevated position would be preferable, but the power cables might prevent that.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on July 27, 2018, 09:24:49 am
Thanks or the replies. I'll attach some phone snaps from this morning to give context to the shoot and the distances and angles. I also borrowed a 14mm for a quick recon on the FoV of that lens straight on. You'll see it just fits the width without much wriggle room.

I'm surprised to read that pan & stitch is the preferred technique when yesterday's attempt was such an unmitigated disaster.

Bart, the facade has enough depth that the use of different camera positions would not work, also because of the limited positions for the cameras in the first place.

Hi Jon,

Thanks for the snaps that give more context.

Pan and Stitch it is. And do make sure to use PTGUI Pro. The Pro edition can use masking which will come in handy when removing the powerlines, road signs, etc., when healing them out won't work. Just shoot from 2 slightly different positions, so that one shot can look behind the obstruction. It is then possible to align the two shots in the flat plane, and take away the obstruction by revealing the area behind with a mask.

I'd also use a longer focal length and more tiles, to make sure you get the required level of detail after software warping. PTGUI also allows compressing the Horizontal and Vertical dimension, to achieve a slightly more natural look.

But the short distance perspective will remain a difficult thing to tame in small output sizes. The larger the output size, the easier it will become to look at it from the correct (distortion free) viewing position. My estimate is that anything output smaller than, say, 135 cm (53 inches) wide and at the same time viewed at further than 10-inch reading distance, will 'look' distorted. So it will remain a compromise that even PTGUI can only partially improve on.

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: mcbroomf on July 27, 2018, 04:21:34 pm
Pan and shift should have worked out fine and it's the easiest to do which is why it has been recommended so I wonder why your test failed. 
Were you careful to make sure there was adequate overlap, especially along the top which would need a lot more images to cover (the width)? 
What lens did you use? 
If you used your 17mm TSE did you leave it centered or did you apply some shift to some or all images?
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 27, 2018, 09:47:27 pm
Pan and shift should have worked out fine and it's the easiest to do which is why it has been recommended so I wonder why your test failed. 
Were you careful to make sure there was adequate overlap, especially along the top which would need a lot more images to cover (the width)? 
What lens did you use? 
If you used your 17mm TSE did you leave it centered or did you apply some shift to some or all images?

In my test I used significant vertical shift, to include the top of the building. I wondered whether repetitious building elements were confusing the software ( windows and other elements that are the same on multiple levels of the building etc. I though I had left April 1/3 frame width (in portrait) as overlap.
my test was done on street level but I have access to the first floor balcony of the house opposite, which will raise viewpoint by about3.5 metres.  Some works have completed and I might be able to run a test in situ next week.
Title: Re: Increasing FOV for cramped architecture
Post by: mcbroomf on July 28, 2018, 04:57:28 am
I've had problems combining images with vertical shift and without as (I suppose) the stitching software sees them as different images, ie effectively one set is distorted compared to the other.  Repeated elements should not screw up the software and PS/LR are much better than they used to be.  Try repeating it with no shift at all.  It should work fine.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on July 28, 2018, 05:55:01 am
In my test I used significant vertical shift, to include the top of the building. I wondered whether repetitious building elements were confusing the software ( windows and other elements that are the same on multiple levels of the building etc. I though I had left April 1/3 frame width (in portrait) as overlap.

Hi,

Non-dedicated stitchers cannot handle shifted images, but PTGUI can (by using an offset).

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 29, 2018, 05:12:28 am
Thanks for all the replies. Iím going to try another test on Tuesday and also try out PTGUI Pro.
I have another question. What can I achieve with a Ďpano headí that I canít achieve by just adjusting the tilt angle on my Manfrotto 405 geared head?  Canít i use my feared head for a multi tow panorama.
Related question:  As i have never done one before would I be stupid to attempt a multi-row in this instance and what focal length would be ideal?

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 29, 2018, 07:48:04 am
What can I achieve with a Ďpano headí that I canít achieve by just adjusting the tilt angle on my Manfrotto 405 geared head?  Canít i use my geared head for a multi row panorama?

When you tilt with your Manfrotto head, you won't be tilting around the lens's no-parallax point. This will cause stitching errors. A pano-head supplies a second 'upper-rail' which solves this problem.  But as has been already said, you can satisfactorily make this image with a single row, shooting several frames with the 14mm lens in portrait orientation. A multi-row panorama, shot with say a 35mm or 50mm lens, will offer you significantly more resolution (possibly more than you need), but it won't have any effect on the geometry of the image (i.e. it will look the same as a single-row shot with the 14mm lens).
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 29, 2018, 08:14:18 pm
When you tilt with your Manfrotto head, you won't be tilting around the lens's no-parallax point. This will cause stitching errors. A pano-head supplies a second 'upper-rail' which solves this problem.  But as has been already said, you can satisfactorily make this image with a single row, shooting several frames with the 14mm lens in portrait orientation. A multi-row panorama, shot with say a 35mm or 50mm lens, will offer you significantly more resolution (possibly more than you need), but it won't have any effect on the geometry of the image (i.e. it will look the same as a single-row shot with the 14mm lens).

Ah, of course.

Thanks
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on July 30, 2018, 09:23:25 am
Ah, of course.

Personally, I prefer to avoid the Parallax-Error risk ('Murphy'  tends to strike when you can least use it) and therefore use a full-fledged MultiRow Pano setup.

However, with PTGUI Pro and the specific scenario of a frontal facade shot, it might be worthwhile to test a Multi-Row stitch even with a Single-Row stitching setup. When you tilt the tripod head, you will introduce parallax error because the entrance pupil moved relative to the other Row(s). But that parallax will occur mostly at street-surface level and at closer distances.

Well, PTGUI Pro has Masking functionality that can mask out the street-level Parallax where the Rows might overlap, while minimizing the more distant (and less visible) Facade Parallax errors. Parallax errors are most prominent at close distances and can be minimized for a given (facade) distance.

Parallax will be zero at one specific distance, especially when the control points are all placed at only that distance. So make sure that at the bottom of the facade, only control points are placed on the facade as part of the facade row. And as always, avoid control points on clouds (which usually move between exposure of neighboring tiles). It's a bit of extra work, but it is possible when the software allows manual control. Photoshop and similar don't offer that level of control.

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 31, 2018, 06:39:49 am
Hi all,
I did a dry-run this morning. It took some finagling to get the tripod into a position where the balcony ny ceiling was not visible. I basically did 3 tests.
The first was a pan -n- stitch with a horrible borrowed 14mm in portrait orientation.
Second was a pan -n- stitch with my 17 TS shifted about 9mm up. I shot 5 frames, although this was possibly too much.
Then, for the heck of it, I did a shift stitch with the 17mm.
On my first go of PTGUI Pro I used the 5 frames shot with the 17. Result had some bad stitching errors and I had to leave it for a while. I gorged on a few YouTube tutorials to get across the finer points of the software. I then had another go but used only 3 of the images and got a result without stitching errors.
One thing I didnít like, and I havenít yet figured out why this happened, but PTGUai has done something funky with the tonality and colour of my images. Thatís tonightís homework.
Lastly I merged the shift pano images in Photoshop. I canít get the 2x3 image ratio that the rest of my work for this client confirms to with this method.
I doubt at this stage Iíll bother with a multi row attempt. Client wants to proceed.
My favoured option at this stage would be to do the 17 shift-pan-n-stitch again with more finesse in better light.
Iím pretty certain Iím going out to buy a Rogeti TSE frame at some stage but it wonít come in time for this shoot, and anyway the coverage of the scene is beyond the image circle in this case.
Iím also not sure I would gain anything from hiring the 11-24.
Iíve attached the results so far.

Jon

 
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 31, 2018, 06:50:41 am
Re. the colours in PTGui, what are you feeding it? Best practice is tiffs.
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 31, 2018, 07:02:44 am
How 'horrible' is the 14mm lens? If you're talking about the distortion (barrel/moustache) that was evident in your earlier shots, this will be totally removed in the PTGui stitching process. (If it's soft, that's a more serious problem.) The 14mm would give you some useful space around the building.

It looks like you're getting there with the PTGui stitch, but there are clear stitching errors in the power cables. Of course, you will clone out these cables, but have you zoomed into the image to check for stitching errors on the brick-work of the building?

Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 31, 2018, 07:27:47 am
Re. the colours in PTGui, what are you feeding it? Best practice is tiffs.

I fed it the full RAW files from the Sony :P . That was a question I forgot to ask on the previous post so thanks for answering it. Is it advisable to do much by way of capture sharpening, chromatic aberration correction etc before producing the TIFFs? I'm going to try and find some homework in this area now.

With regard to the power cables, I saw those errors. I think the building is OK in this version, but I'll double check tomorrow. The earlier version that used 5 images had a pretty bad seam between image 4 and 5. I actually removed some of the control points from the power cables. They were among the worst in terms of the distance and I didn't want to encourage the software to try to incorporate them correctly, so I moved those points back to places on the facade.

I haven't tried to stitch the 14mm version yet. Perhaps I'll give it a go in the morning. Yes, I was turned off by the visible distortion and also by the fact that it is so hard to focus, even under magnification. It's a dirt cheap Samyang or something. If I can find a profile for it should I apply that profile before sending the images to PTGui?

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 31, 2018, 07:43:50 am
Yes, you should sharpen and fix chromatic aberration before stitching. But you should not attempt to fix any lens distortions - that will confuse PTGui. Vignetting? It's best to leave that to PTGui too. All the component images should have the same colour and tonal corrections applied. Best to go for a conservative treatment - you can punch it up on the final stitch.

Yes, you should remove ALL control points from the power cables.

Re. the 14mm Samyang. Don't apply any profile to it. When PTGui applies its control points, it is making a complex and accurate calculation of a lens's distortion characteristics. When it performs the stitch, all lens distortions are corrected for.
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 31, 2018, 07:47:30 am
I just edited my previous post to say that I fed PTGui with the RAW files from the Sony.

Also, if the 14mm lens's faults are fully corrected (apart from sharpness) would I gain anything from hiring the 11-24? It's supposed to be an excellent lens.

J
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on July 31, 2018, 07:55:10 am
AFAIK, the raw conversion engine in PTGui is rather basic. It's best to convert the raw files first and then feed the resulting tiffs into PTGui.

Re. lens faults. PTGui allows lesser lenses to be used to good effect. This is because (1) it corrects lens distortions very well, and (2) in a stitch you are only using the good part of the lens (i.e. the edges are being cut off in the stitching process). That said, I still prefer to use really good prime lenses.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on July 31, 2018, 09:47:35 am
AFAIK, the raw conversion engine in PTGui is rather basic. It's best to convert the raw files first and then feed the resulting tiffs into PTGui.

I agree. I typically only correct for tonality and Color Balance,  Chromatic Aberration, and do the bare minimum of Capture Sharpening in my Raw Converter of choice, full image, no cropping. I then save/export as a 16-bit/channel TIFF with the required color-space assigned (e.g. Adobe RGB or ProPhoto RGB). No distortion corrections needed, because those will be eliminated in the stitching process. The resulting Pano will have the source images' Colorspace assigned.

BTW The distortion correction parameters that PTGUI finds by analyzing overlapping images with lots of detail, can also be used to correct a single image. It will even allow adjusting for small amounts of decentering that almost every lens has. That's a great help for special lenses or lenses with mediocre distortion by the Raw converter application. Decentering is obviously rotation dependent, so take notes of the Vertical and Horizontal shift parameters (in the global Optimization parameters in Advanced mode) and the image orientation (e.g. rotation 90 degrees Clockwise).

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on July 31, 2018, 11:16:32 pm
Here's the latest attempt after purchasing the software license and using TIFF files rather than the RAW. This is with the shifted 17mm. It seems PTGui can detect the lens has been shifted so unless I'm wrong there's nothing to do there Bart?
I used some vertical control lines in this version after learning about them last night. Yet to do horizontal ones but the tutorial I read seemed to say that PTGui would work out the horizontal stuff
So this looks like it's going to work.
The example below is the preview from PTGui and hasn't had any subsequent P'shop work. The second attachment I presume shows me how well or otherwise my camera position was levelled? Yaw is lateral horizontality? Pitch is fore/aft horizontality? Roll is??
So my last conundrum is whether to bother with the hire of the 11-24.


Jon

Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on August 01, 2018, 02:06:36 am
I didn't spend as long on this but here's the stitch of the wobbly 14mm. Seems if I move the panorama down to fit more sky (the only benefit of using the 14mm I think) then I lose the geometry of the building a bit.
Not sure why this is happening.
These are just screenshots from PTGui and I realise some of that (all of that) could be corrected in PS.
Also, sharpness is not quite the equal of the 17, so I think I'm going to go with a 3 shot stitch of the almost fully shifted 17mm.

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: mcbroomf on August 01, 2018, 03:44:25 am
You could also try a "normal" pan with the 17mm as you did with the 14mm, shooting wider to get the 3:2 your customer wanted and a sharper image than the 14mm.  Or at least take both and compare them ...
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on August 01, 2018, 07:16:44 am
You're making good progress. The 17mm pano looks cramped - you need more sky - but as long as you pan wide enough, you can extend the sky in Photoshop and keep your 2:3 ratio.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on August 01, 2018, 10:35:03 am
Here's the latest attempt after purchasing the software license and using TIFF files rather than the RAW. This is with the shifted 17mm. It seems PTGui can detect the lens has been shifted so unless I'm wrong there's nothing to do there Bart?

Hi Jon,

Let me share a little tip that is overlooked by many.

While PTGUI is able to detect many sources of geometric distortion in our image tiles, it also makes it a more challenging task for the software to do it all automatically. The software challenge is known as an "ill-posed math problem", because there are multiple solutions that can reach a mathematical optimum. But only a few of those solutions make sense to a human observer, and only one is really optimal.

The more parameters we select to be optimized at the same time, the harder the challenge. For that reason, the Vertical and Horizontal shift parameters are usually disabled when finding an optimal solution.

My solution is to disable (!) all other optimization parameters, and let the software seek for a solution for only Vertical displacement. If you know how much shift you used when shooting, you can enter the values manually. In PTGUI version 10, one can calculate the amount to enter by taking the mm of shift, divided by the total tile height in mm, multiplied by the total number of pixels of the tile in the vertical dimension. If you run the detection automatically, verify that it approximately finds the same number of pixels you calculate by hand.

Once you have a decent approximation of the Vertical shift in pixels, now disable this parameter for the subsequent optimizations. Once you've reached a new optimum, you can again try only optimizing for the Vertical shift once more, and see if it changes much.

Also make sure that you only apply this optimization for the Row(s) of tiles that had shift involved.

This all will make sure that all the other geometrical aberrations, which are rather symmetrical around the real optical center of the cropped image circle, can be compensated to achieve the maximum accuracy.

Even on unshifted images, I usually follow up on a regular optimization, by one run of only Vertical shift, and one run of only Horizontal shift. If the resulting shift amounts are small, they probably will improve a subsequent general optimization with even smaller residuals. I often get only sub-pixel residuals for most of the control-points.

It's this level of control that only dedicated stitching applications can offer.

I also do a rigorous inspection of which (automatic) control-points are used. Always making sure that the main subject structure is well covered, and nothing that moves (such as trees, or plants, or cars, or people, or clouds, or even birds/insects). I may be a bit obsessive about that, going through all possible image pair overlaps, but you only have to do it once and it will help the final result/quality.

Quote
I used some vertical control lines in this version after learning about them last night. Yet to do horizontal ones but the tutorial I read seemed to say that PTGui would work out the horizontal stuff.

Yes, your test run showed lots of reliable corners and lines on which to place these additional control points. Some architecture may be deceiving with slightly receding or protruding elements that hide true verticals and horizontals, but your example looks 'straightforward'.

Another tip, one can also use Horizontal and/or Vertical control points on single images or tiles. Just use the Controlpoints Tab and select the same image twice, clicking on one end of the line in one image pane, and the other end of the line in the other image pane.

And another tip, some architecture will look a lot better with a tiny amount of keystoning left in the image. This can be achieved by disabling all optimization parameters and manually adding a slight amount of Pitch to all images, then disabling the pitch optimization and running a general optimization.

Since the "ill-posed math problem" issue remains, the optimization engine can lose track in the midst of things, and a previously acceptable stitch can turn into something totally screwed up. So always save the intermediate result before experimenting with more optimizations. Just in case the undo function doesn't work...

Quote
So this looks like it's going to work.

I'm confident it will. It's just a bit of a learning curve to get the optimal result, but the application is a real workhorse. Also things that are under the hood, like much better interpolation algorithms than most image editors use, will result in higher output quality. Especially important with so much deliberate distortion and warping going on.

Quote
The example below is the preview from PTGui and hasn't had any subsequent P'shop work. The second attachment I presume shows me how well or otherwise my camera position was leveled? Yaw is lateral horizontality? Pitch is fore/aft horizontality? Roll is??

When shooting perpendicular to the front of the building, the Yaw (horizontal angle around the vertical axis through the entrance pupil or no-parallax-point), the Pitch (the up/down angle around the horizontal axis through the no-parallax-point), and the Roll (sideways rotation along the front/rear axis through the no-parallax-point), the lower the values for the center image tiles are, the more squared/perpendicular your lineup (after software adjustments) is.

However, do note that you can deliberately deviate from those values with a manual override for esthetical reasons. As mentioned, a slight amount of Pitch can help in reducing the mistaken suggestion of vertical stretching, and you can still add dynamism by manually overriding the Yaw angle, as if you were shooting a bit more from the side instead of head-on. Just modify how the image is cropped after manually overriding the optimization parameters.

Quote
So my last conundrum is whether to bother with the hire of the 11-24.

My experience tells me that when you get the hang of stitching, it hardly adds time when shooting, it only adds a bit of time in postprocessing, but with higher image quality. A wider angle lens may save time, but rarely improves image quality, unless it's an exceptinally good lens. Wider angles usually/inevitably will also result in more veiling glare that reduces image contrast and acuity. I even use my TS-E 24mm II for stitching, unshifted, and with a different/deeper lenshood for a 24mm lens, thus optimizing the use of the center of the image circle, and larger magnification than the 17mm version, and let the stitching software make a better leveling and keystone correction than I possibly can, even on a Manfrotto Geared head and an electronic level. The reason is that many sensors have a very tiny rotation that even the stitching software will have to compensate for.

Cheers,
Bart

P.S. Sorry to add to an already long message, but, buyers of the current PTGUI Pro version 10 License can also use the Beta version 11. While already quite stable, it is still a beta version. However, it has changed the Horizontal/Vertical shift in pixel amounts, to relative shifts for the Long/Short dimension of the image tiles. The benefit is that a mix of landscape and portrait orientation tiles can be intermingled in the same pano stitch. That's just one of the improvements, so make sure to check it out.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on August 01, 2018, 10:59:07 am
Here's the latest attempt after purchasing the software license and using TIFF files rather than the RAW.

Hi Jon,

You're moving in the right direction.

Disregard the slight parallax errors in the lines in the foreground, that's possibly caused by them moving in the wind anyway. Only place control points on the building.

You can get rid of the lines/ribbons when you shoot the same panorama again, after raising or lowering the camera enough to clear the details that are now obscured. Then, either in PTGUI mask out the lines and ribbons, or later in Photoshop Mask and clone in the details from two images.

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on August 01, 2018, 06:34:51 pm
Thanks for the detailed notes Bart. I've copied them to Evernote so I can refer to them when I'm doing the work later and in the future.
Going to re-shoot the building in early light over the weekend and will be working on the file next week.

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on August 07, 2018, 07:28:54 am
Ok, shoot on the weekend went as well as can be expected (for working at 6am on a Sunday)
Conditions were good etc.
I tried to make sure that the rail was very level but PTGui reports for pitch & roll as before. Maybe that is as good as you get with a spirit level and a headlamp.
I shot pretty much continuously from a point where sky lightened enough to get an exposure similar to the building artificial lighting until the open sunlight broke through too powerfully. During this time I show sequences of images from left to right, then I lowered the tripod head slightly using the central column and shot another sequence from right to left. I did this to get some images of 'behind' the powerless that were close to the camera.

A few things I need to ask:
If I include both the sequences in PTGui it creates a poor quality stitch, with visible errors, and reports that control point pairs have distances of hundreds (of pixels?) between them.
If I just use the one level sequence of images the result is much better, and the optimiser reports 'good' or 'very good'. So my strategy was to produce 2 panoramas and use the one from the slightly lower viewpoint as source material for the retouching job to remove the powerlines.
So now some questions.
Is it my task as a user of PTGui to manually manipulate the positions of control point pairs to reduce the distance between them?
Does this action result in a better quality stitch? The help page (http://www.ptgui.com/ptguihelp/main_controlpoints.htm) says "A lower value means better alignment."
If PTGui knows the distance between control point pairs why doesn't it automagically fix them?

I used about 8.5mm of vertical shift on the TS 17mm lens.
According to Bart's previous post;
"My solution is to disable (!) all other optimization parameters, and let the software seek for a solution for only Vertical displacement. If you know how much shift you used when shooting, you can enter the values manually. In PTGUI version 10, one can calculate the amount to enter by taking the mm of shift, divided by the total tile height in mm, multiplied by the total number of pixels of the tile in the vertical dimension. If you run the detection automatically, verify that it approximately finds the same number of pixels you calculate by hand.

Once you have a decent approximation of the Vertical shift in pixels, now disable this parameter for the subsequent optimizations. Once you've reached a new optimum, you can again try only optimizing for the Vertical shift once more, and see if it changes much."
So let say 9mm. 9mm over 36mm (sensor size in that direction) is 25%, of 7952 pixels on the sensor is 1988 pixels of vertical shift. I'm on a different computer now but I think PTGui was reporting about 20% of vertical shift and a tiny negative amount of lateral shift in the lens parameters panel.
So Bart, in order to follow your instructions do I uncheck everything in the lens parameters panel except the vertical and then run the optimiser again?
The stitch as it stands is without errors that I can see, and while I'm confident of getting a result that the client would accept I'm treating this as a learning opportunity.
There is noticeable softening of edges on the building as you move away from the centreline. I'm currently working on a full resolution panorama output by PTGui and haven't applied any sharpening. So that's about the only obvious improvement I'd like to see at this stage (and it will no doubt improve with some sharpening and downscaling later).
I didn't do any meaningful screenshots today so there are no pics to go with this post.

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on August 07, 2018, 11:50:05 am
Ok, shoot on the weekend went as well as can be expected (for working at 6am on a Sunday)
Conditions were good etc.
I tried to make sure that the rail was very level but PTGui reports for pitch & roll as before. Maybe that is as good as you get with a spirit level and a headlamp.
I shot pretty much continuously from a point where sky lightened enough to get an exposure similar to the building artificial lighting until the open sunlight broke through too powerfully. During this time I show sequences of images from left to right, then I lowered the tripod head slightly using the central column and shot another sequence from right to left. I did this to get some images of 'behind' the powerless that were close to the camera.

A few things I need to ask:
If I include both the sequences in PTGui it creates a poor quality stitch, with visible errors, and reports that control point pairs have distances of hundreds (of pixels?) between them.
If I just use the one level sequence of images the result is much better, and the optimiser reports 'good' or 'very good'. So my strategy was to produce 2 panoramas and use the one from the slightly lower viewpoint as source material for the retouching job to remove the powerlines.

While it can be done in PTGUI, that would require some more work and experience with the application. The benefit would be that a single project file will allow to handle everything, without the need for retouching with an additional Layer-aware photoeditor. Let's save that exercise for a later date. For now, just make two panoramas, one for each of the slightly different shooting heights, and clone/heal the obstructions away between the two layered panoramas in e.g. Photoshop or similar.

Quote
So now some questions.
Is it my task as a user of PTGui to manually manipulate the positions of control point pairs to reduce the distance between them?
Does this action result in a better quality stitch? The help page (http://www.ptgui.com/ptguihelp/main_controlpoints.htm) says "A lower value means better alignment."
If PTGui knows the distance between control point pairs why doesn't it automagically fix them?

In relatively easy cases, e.g. well-chosen no-parallax point, no moving subjects, steady tripod, and clear high contrast subject details, PTGUI will do a good job in finding the control-points in the image tile overlaps, with a good spread. That will result in an optimization with low residual control-point offsets. PTGUI will also add a text qualification indicating to how good it thinks the stitch will be (e.g. good or very good). But software can be fooled by it picking some wrong control_points (which will have higher error distances).

Then the software will have to find a compromise in combining all the required distortions (positioning errors of the no-parallax point, focal length deviations (and focus distance), lens distortions, lens decentering and/or deliberate shift, rotations, leveling, etc., all in three dimensions). As I said earlier, that's an "ill-posed math problem", but PTGUI guesses the most likely optimum, but still a compromise. In theory, one could add a control-point warping function, but that could lead to local distortions when there might be a better solution that will improve the overall result.

One thing one could do is look at the control-point errors and revisit the ones with the highest residual error. One can also let PTGUI automatically decide to remove the worst scoring ones. Then re-optimize and see if the average and maximum resulting errors are lower or not.

Quote
I used about 8.5mm of vertical shift on the TS 17mm lens.
[...]
So let say 9mm. 9mm over 36mm (sensor size in that direction) is 25%, of 7952 pixels on the sensor is 1988 pixels of vertical shift. I'm on a different computer now but I think PTGui was reporting about 20% of vertical shift and a tiny negative amount of lateral shift in the lens parameters panel.
So Bart, in order to follow your instructions do I uncheck everything in the lens parameters panel except the vertical and then run the optimiser again?

PTGUI (Pro) version 11, which was released a month ago as successor to version 10, by default already optimizes for decentering/shift. So, if it automatically found an amount of shift that's in the order of what was to be expected, I would not worry too much about improving that, assuming that the resulting stitching looks fine.

Quote
The stitch as it stands is without errors that I can see, and while I'm confident of getting a result that the client would accept I'm treating this as a learning opportunity.
There is noticeable softening of edges on the building as you move away from the centreline. I'm currently working on a full resolution panorama output by PTGui and haven't applied any sharpening. So that's about the only obvious improvement I'd like to see at this stage (and it will no doubt improve with some sharpening and downscaling later).

Hard to judge without an example, but it might be the inevitable result of the significant stretching that such a wide angle shot requires towards the edges/corners to keep straight lines straight. I wouldn't be surprised if the final panorama has a composited field of view that approaches 110 degrees horizontal FoV, or perhaps even more. The only way to increase edge resolution is by using a longer focal length (and many more tiles), so that there is the additional optical detail to work with. Of course, the larger the final stitch is, the more likely one can down-sample to the final output size, and that will also improve resolution (and PTGUI offers a selection of excellent resampling methods).

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on August 09, 2018, 07:50:02 am
Thanks again for your reply Bart.
Just to clarify. In attempting to optimise the control points I moved the points until the distance number reduced and in doing so I was more focussed on reducing the numbers than whether or not the control points occupied the same areas of the image. Should I instead move the control points until they appear to be over the same pixel(s) regardless of the distance numbers reported?

And also to clarify that by the time I had started this thread PTGui V11 was out, so that was what I had purchased and it was detecting the shift all by itself quite accurately. In the end I didn't change any of the lens parameters.

Anyway, it's been an interesting learning curve for me, and I should do some more practise with stitching and panoramas.

Attached shows where the file is at now. Doubt I'll spend much more time on it. There is a budget for this shoot. The warped appearance of the cars bugs me a bit but I think correcting that is beyond my abilities and time at the moment.

Thanks again to all respondents to this thread.

Jon
Title: Re: Increasing FOV for cramped architecture
Post by: elliot_n on August 09, 2018, 08:54:39 am
Well done! You've come a long way from those initial iPhone snaps.
Title: Re: Increasing FOV for cramped architecture
Post by: degrub on August 09, 2018, 09:52:05 am
you might be able to use the clone tool to eliminate the cars.
Title: Re: Increasing FOV for cramped architecture
Post by: Bart_van_der_Wolf on August 09, 2018, 03:15:23 pm
Thanks again for your reply Bart.
Just to clarify. In attempting to optimise the control points I moved the points until the distance number reduced and in doing so I was more focussed on reducing the numbers than whether or not the control points occupied the same areas of the image. Should I instead move the control points until they appear to be over the same pixel(s) regardless of the distance numbers reported?

The latter, make sure that the control_points are on the exact same spot in the image tiles despite differences in distortion.

Quote
And also to clarify that by the time I had started this thread PTGui V11 was out, so that was what I had purchased and it was detecting the shift all by itself quite accurately. In the end I didn't change any of the lens parameters.

Yes, last month Version 11 became the current stable version. Unlike it's predecessor, Version 11 by default does include the shift parameters.

Quote
Anyway, it's been an interesting learning curve for me, and I should do some more practise with stitching and panoramas.

Attached shows where the file is at now. Doubt I'll spend much more time on it. There is a budget for this shoot. The warped appearance of the cars bugs me a bit but I think correcting that is beyond my abilities and time at the moment.

The warping of the cars is virtually inevitable, due to the extremely short shooting distance for this wide a FoV. When the output is viewed from the correct (very close) distance, there is no distortion. The apparent distortion is caused by viewing from too far away.

Cheers,
Bart
Title: Re: Increasing FOV for cramped architecture
Post by: MichaelEzra on August 24, 2018, 10:59:39 pm
same building? https://www.behance.net/gallery/69103463/Millhorn-Wickham-Newcastle-Australia
Title: Re: Increasing FOV for cramped architecture
Post by: sharperstill on August 25, 2018, 02:05:05 am
Yes, except I shot the real one.
Title: Re: Increasing FOV for cramped architecture
Post by: Guillermo Luijk on December 21, 2018, 12:08:20 pm
Yes, except I shot the real one.

This makes me wonder how much photography work will/is being replaced by 3D renders. Most still car adverts already are synthetic 3D. Moreover think of the advantages in terms of perspective a 3D solution provides for interiors: you can "photograph" a room from a larger distance than the real room dimensions, making perspective look more natural than with a real camera. This can be specially advantageous in tiny rooms such as bathrooms where locating a camera is a pain.

Regards
Title: Re: Increasing FOV for cramped architecture
Post by: kirkt on December 22, 2018, 11:29:37 am
You can also dress and light a 3D model any way you want.

Kirk