photographing for pano stitching trouble

[tandeejay]

Hi all,

I was at the Ipswich Historical Society site today, and tried photographing a dining room in one of their old houses.

As my widest focal length is 18mm, I took several photos with the intention of stitching.

The middle photo had a bright, backlit by sunlight, window so I took 2 photos, one exposing for the window and one to match the exposure of the other photos. No problem there...

My issue is with the stitching. Notice that on the 1st 2 images, the left hand knob on the front chair is in front of a different piece of silverware

DSC_2510.jpg

This is the image that is a HDR merge
DSC_2506_HDR.jpg

DSC_2505.jpg


This was my initial attempt to stitch using the default settings in photoshop. The exposure on the right hand image is off because for this 1st stitch I accidentally included a second copy of the RH image, which was not in focus, and Photoshop aligned and masked the OOF image, and left the in focus image with nothing visible. (I moved the mask to the in focus image and hid the oof image, but the merge process didn't adjust the exposure) This one has the knob on the chair, but the back of the chair is missing an upright
Untitled_Panorama1.jpg

All my other attempts to perform the merge trying different settings, the chair ended up loosing the LH knob.

Untitled_Panorama5.jpg

Clearly, I need to do something different when initially capturing the images to ensure less misalignment of the various components.

I had the camera mounted on my tripod with a borrowed Manifrotto 498RC2 ball head, and the photos were taken by rotating the head.

What do I need to do in the future to ensure better image allignment?

Regards,
John

[Mark L]

So don't stitch all the photos at once (not knowing how many photos you've stitched)
So as a simple example, if you are using 4 photos, stitch the first two and then the next two. Then stitch the resulting two photos.
Or try Microsoft Ice. Pretty good for stitching ...http://research.microsoft.com/en-us/.../projects/ice/

[tandeejay]

Thanks Mark. I didn't think my problem was related to how I was stitching or the application I'm using to stitch, but rather how I'm capturing the images in the 1st place causing different alignment between the foreground and background items between the different images.

[bobt]

I think your problem lies in either the lens or your closeness to the subject. I usually have no trouble with panos, but this one is a problem, and I think the chair is just too close, resulting in an almost impossible stitch. I'll have another go tomorrow .... with different software, but I'm not optimistic.

[Gazza]

If it's shooting help/tips you're after, this may help explain

[tandeejay]

Thanks for that Gazza. That's just the info I need.

Looks like time to save for a pano head


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[tandeejay]

that video talks about finding the nodal point of the lens. Other sites say nodal point of a lens is not the NPP, and that NPP is often mis-named nodal point... Whether it is using the right name or not, it is still an easy tutorial to follow. Best I've seen yet.


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[Gazza]

Looks like time to save for a pano head

I always thought I'd make something to suit my 24 - 105mm (set @ 50, or whatever...) but got a little distracted with wildlife/birding (bloody Mark!)
Heading off again shortly, so I guess I'd better get busy

Even so, without that head, it looks like it pays to move your body around keeping the front of the lens as close as you can over an imaginary fixed point.



Cheers ...

[bobt]

Looks like time to save for a pano head

I wouldn't waste your money! I've been doing panos for years, way before the current range of software solutions. I rarely use a tripod even, let alone a pano head. The purpose built programs that are around will stitch pretty much anything together without blinking an eye. Never tried PS to do panos, but then I prefer programs that are designed to do one thing and do it well. PS tries to be all things to all people for all tasks.

I've had another go at your pano, and it is a tricky one. I succeeded in getting the chair right, but then it stuffed the back wall. I'll try again later when I have more time - I've got a bit much on today to spend any more time on it. Bit of a challenge though! 8*)

[tandeejay]

Would love to see if you can overcome the parallax error in pp


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[bobt]

Would love to see if you can overcome the parallax error in pp

Still trying .... not with complete success, but it certainly is proving tricky. Haven't given up yet .......

[tandeejay]

After much reading, I think the best way to make it stitch properly is to go back and photograph the scene in such a way as to eliminate the parallax error in the 1st place

Now, you might have a steady enough hand to hold the camera still in low light conditions, but I still like the stability of a tripod which leaves me with the option of a pano head...

I guess I could hold the camera still enough if I increased the ISO, but I want a lower view point than my height so hand holding at the viewpoint height I want would be very uncomfortable...

I love your persistence though

[bobt]

After much reading, I think the best way to make it stitch properly is to go back and photograph the scene in such a way as to eliminate the parallax error in the 1st place

Now, you might have a steady enough hand to hold the camera still in low light conditions, but I still like the stability of a tripod which leaves me with the option of a pano head...

I guess I could hold the camera still enough if I increased the ISO, but I want a lower view point than my height so hand holding at the viewpoint height I want would be very uncomfortable...

I love your persistence though

You are right .... a tripod in low light is very helpful. I'm just not convinced that a pano head is necessary in addition to a tripod. Certainly use a tripod to overcome low light, but other than that, hand-held is fine (provided you don't get too close to your subject). Close-up, even a pano head won't help! In normal lighting, the hand-held shots are fine, although I have used the 'ol piece of string tripod to optimise my chances of a good stitch.

I remember getting very odd looks photographing Windsor Castle with the camera attached to a bit of string on my foot - but it works!

Not many people know that trick ..... 8*)

[wayn0i]

Interesting thread, I have a ninja nodal pano head and I have different setbacks on the nodal for different lenses. It took me a bit of time to set it up but now stitching is a breeze. In my experience if you don't eliminate paralex error to start with you are up against the wall. That doesn't mean you can't stitch your images but it can often mean hours in front of the PC stretching and masking images to bring them together, not much fun.

[Glenda]

For landscapes and even architecture at a distance you can usually get good results without a pano head. But, anything with strong lines, shot close, causes heaps of problems when it comes to stitching and even the pano stitching programmes, with control points you can add, struggle and quite often fail. A pano head will solve this - a friend bought one for his Nikon, off Ebay for around $150 which works well and even comes in its own little silver case.

[arthurking83]

I was going to reply earlier but got busy, and then lost the thread:

But! What I can see as the biggest issue in this pano-stitch attempt may be the tilted perspective.

The parallax error issue is easily dealt with without the need for a pano head.
You simply move the camera laterally to the appropriate position, instead of rotating it around a central node!

Shift lenses are good for this purpose if you don't like to move.

If I can describe the process you'd do if you want to give it a go.
Start from one side of the room(not the middle!) .. and take your first image.
It's vital when you frame that first scene to keep in mind what elements are recorded in what part of the first frame.
So if you start from Left -> Right, then what part of the room/scene has been captured at up to about 2/3rd of the way to the right hand edge of that first frame.

(noteThe 2/3rds of the frame comment is not a rule as such, more overlap ensures a better quality stitch in the end, but less overlap still works well. The best amount of overlap to use depends on the lens you use, and if a zoom lens, what focal length chosen.

So continuing on for the next exposure, whatever element was captured at the 2/3rds point on the RHS of the frame, will determine where you then set the camera up for the next exposure, and what I prefer to do is to then set that same scene element at the 2/3rds point on the LHS for that next scene. (remember I'm going from left to right). Basically what you want is good overlap. .. and keep going along till you get the entire scene.

(note what camera/lens setup you choose to use would usually determine what amount of overlap is best to use.
eg. if you used a Dx frame camera but used an Fx type lens, then less overlap could easily be used(ie. less images to process and work with). But if you used a Dx camera with a Dx kit type lens, then you're best off using the 2/3rds method above.
The only point for that huge overlap is to eliminate vignetting(less important, but easier to process), but more importantly to eliminate the almost certain situation of less sharp edges to deal with.
The more detail in an image, the easier it is for automated stitching programs to calculate the content in the image to align the images.

(noteI use PTGui if I ever do stitches(very rare anyhow), and it's manual control, using control points is awesome. When you have blurry details at the periphery, it (basically) shows you why it can't ascertain sometimes why it doesn't line up perfectly.

But from the images above, you can clearly see that the OP has tilted the camera ever so slightly downwards. It may not be by much, but the verticals are not! the wood panelling at the edges is not vertical.
While this may only be a small component of the stitch issue, it's still important.
Why: Note in the final result that because of the tilted aspect verticals at the edges(using a UWA lens) are splayed outwards. That is, rhs is leaning outwards at the top, and lhs is leanign outwards at the top. Divergent lines.
For each capture, the same thing will happen at the edges. The software will try to deal with this, and the important point is to try to capture as good data as you can for the software to use.
So, the above attempt seems to have been from right to left, and so the first image must surely have been tilted in a way where the left hand post of the seat back is tilted outwards(top of chair post towards the left!) .. like this \
BUT, on the second image(on the left), that same chair post is now tilted to the right(at the top) .. like this /

What you've asked the software to do is to line up \ and / to be the same scene element(instead of | and |).
Hope it all makes sense!

So the first thing I'd be inclined to work on, it to make sure the scene is setup and captured in a way to get the best possible data capture.
Easy way to ensure vertical vertcials is to watch the edges of the frame through the viewfinder(especially using an UWA lens).
While an 18mm lens on a Dx camera is not UWA in terms of FOV(it's only wide angle .. not ultra), the 18mm focal length is very, very wide!!) tilting it creates more extreme not verticals(the wider you go, the more extreme!)

So try to use a longer focal length, shoot in portrait orientation if you need more head/leg capture space and use the periphery of the frame to guide you on what is level.
as you tilt the camera fore/aft, you can clearly see the verticals diverge/converge.
Fore/aft tilt is determined by how your body is angled, if you lean fore(forward) then that's a camera down perspective, verticals at the edges will diverge at the top .. and vice versa

This is separate from left/right tilting(leaning!) That's something else to watch for.

One last point to make: already said, use a portrait orientation to capture more head/leg scene, but try to use the longest focal length you can to frame that head/leg space.
Unless you're doing multi row stitches, then the limit for focal length should be the (vertical) head/leg space framing. The horizontal framing is limited only by 360°!
Longer focal lengths usually help to capture better data(remember for the software to use). Less distortion, less convergence/divergence in verticals if tilted slightly .. etc, etc.

Hope that helps.

[ameerat42]

Tands... (Didn't read the whole thread but) since I have been "mucking around"
with versions of MS-ICE, I thought that at least the latest version should be able to do
SOMMINK beside have a horrible interface.

Here is an intermediate step in the process, and you can clearly see the settings needed to
produce the "most natural looking" perspective. Others gave either a too wonky frame, or curved
"straight" elements, like the curtains.

>>Oh, and this is using "Rotating Motion"<<

Using MS-ICE... (PS: 4-give the color cast, as I used the wrong color profile before posting.)
Tandspan.jpg