Hints about panoramics and stitching

[ErikKaffehr]

Hi!

I'd say I agree with both of you. One important issue on my mind is that this is not about equipment but about taking pictures. Start shooting panos and start stitching, learn by doing. If you need better stuff you can buy them later, but missed opportunites are, well, missed opportunities.

Shoot, stitch, learn from experience...

Best regards
Erik

For really wide FOV's I agree with Bill, a rectilnear projection stretches things out too much at the edges of the frame (on the other hand sometimes cylindrical projections compress the horizontal FOV too much).

But stitching isn't always about super-wide FOV's, sometimes it's just to increase reslution and for that I think using flat-stitching with shift often produces more pleasing results.

[ErikKaffehr]

With due respect...

I got plenty of good suggestions and even a big nice image on this posting. I would like to add most of the suggestions to my page, with due credits to all who have posted. I hope it's OK?
It will take some time as I leave for vacation tomorrow.

Thanks for input. I hope it will be helpful for the community.

Best regards
Erik

Hi,

I would mention a couple of things regarding rendering of panoramas:

- Remove lateral chromatic aberration before merging, cannot be done afterwards.

- Perspective gets odd when shooting with camera tilted, take extra pictures beyond the expected panorama. I often find that corners are missing from my tilted panoramas.

- When preparing images for stitching I make them flat, trying to get a long tonal range. After stitching I optimize shadows, highlight, brigtness, clarity, vibrance. This would be done in Lightroom, in my case.

- It's probably best to work in 16 bits.

Best regards
Erik

Ps. I have some write up about pano shooting here: http://83.177.178.241/ekr/index.php/photoa...a-and-stitching , it's work in progress.

[Lisa Nikodym]

I got plenty of good suggestions and even a big nice image on this posting. I would like to add most of the suggestions to my page, with due credits to all who have posted. I hope it's OK?
It will take some time as I leave for vacation tomorrow.

I'm fine with that.  Have a great vacation!

Lisa

[Dick Roadnight]

A significant characteristic of shifting backs is you are stuck with the classic wide angle perspective.  The look is distinctly wide angle, the viewer is necessarily pulled in strongly towards the center of the image.

Wide angle, and their over-use for landscapes are my pet hates - I am thinking that the 100 degree fov of the Schneider apo-digitar 47XL, with shift and stitch will save me having to buy an ultra-wide-angle.

I expect to use cylinder panos for cylindrical subjects, but for a high def pic of a building or two I would use a long focus lens (e.g. 210 mm on mf) and shift and stitch.

I am thinking about doing some long panos of harbours and bays, with some sections cylindrical and some shifted!

One obvious tip is:

To shoot panoramic pictures, use a panoramic camera

See

www.roundshot.ch

The Seitz/roundshot D3 digital pano camera is not cheap, but you can use the digital capture unit on their other cameras, so you do not have to do panos all the time to justify the cost.

[BernardLanguillier]

Bernard,

I like both your writings and panoramas but I'd suggest that this image is just to big in this context. This discussion was intended to collect ideas, and having such a big image loading automatically just makes for a less than pleasant experience. The image is great, I'd just would prefer a clickable link.

Thank's a lot for all of your contributions.

Best regards
Erik

Sorry Erik, just back from a 4 days trek and read your comment. Totally agree, I didn't intend to paste the image directly... pasted the wrong link. Just corrected that.

Cheers,
Bernard

[Tyler Mallory]

if you've got a building or other object with straight lines, make sure you capture the whole thing in one frame. If you are going more than one frame with a straight-lined object, you will need to either shift stitch, accept the bowing line, or plan for extra post-prod time.

If you're going for a panoramic, have a reason to go wide. Don't get caught up in technical things and forget that the composition needs to work for that kind of framing. Think about ways that moves the interest through that kind of framing.

And while we're at it, one of mine from a trip through the Canadian Rockies. 6 frame pan.

[Panopeeper]

if you've got a building or other object with straight lines, make sure you capture the whole thing in one frame. If you are going more than one frame with a straight-lined object, you will need to either shift stitch, accept the bowing line, or plan for extra post-prod time

If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.

The real issue with clear lines is the parallax problem; this has nothing to do with straight or not. For example electric lines in adjacent frames are not easy to join seemlessly if the camera's adjustment was not accurately around the entrance pupil.

[Tyler Mallory]

If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.
The real issue with clear lines is the parallax problem; this has nothing to do with straight or not.

The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane. If you pan, you change that relationship. It is not as noticeable with rounded natural features found in nature, but if you try to do it with a pan stitch with several parts of, say a building, those lines will not come together without a bent angle in between. No matter how accurate your entrance pupil is aligned, the sensor has moved and that has affected how a straight line will map out across it.

[Panopeeper]

The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane

Tyler, I'm afraid you are using a stitcher, which is not up to the job. *If* there is no parallax error, then the stitcher must not have any problem with transforming the images such way, that they perfectly join. Straight lines may have to be bent, depending on their orientation and on the projection, but if so, then that has to occur even if that line is within a single frame.

Do you happen to have a sample pano illustrating the problem? (But a somewhat larger one than the thumbnail you posted above, pls.)

[JeffKohn]

If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.

You're right to a certain extent, but once you get into multi-row panos with fairly large fields of view, it gets much more complicated. I've found that for instance if shooting buildings you're better off sticking to single-row cylindrical panos, unless you have a lens that allows vertical shift. Because as soon as you tilt the camera up/down between rows you have a perspective problem and the edges of the buildings will no longer be straight.

[Panopeeper]

as soon as you tilt the camera up/down between rows you have a perspective problem and the edges of the buildings will no longer be straight

You don't have a perspective problem but a parallax problem. This is typical with a simple rail setup, which allows for rotation around the entrance pupil but not for tilting.

[BernardLanguillier]

The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane. If you pan, you change that relationship. It is not as noticeable with rounded natural features found in nature, but if you try to do it with a pan stitch with several parts of, say a building, those lines will not come together without a bent angle in between. No matter how accurate your entrance pupil is aligned, the sensor has moved and that has affected how a straight line will map out across it.

You've got to wonder how these lines got straight...

http://www.flickr.com/photos/bernardlanguillier/3833720762/

Most efficient panorama softwares (PTgui and autopano Pro) are pefectly able to map a faceted cylinder on a plane in such a way that straight lines remain perfectly straight and that has been the case for many years.

Cheers,
Bernard

[fike]

Lots of good advice on this thread.  Here is a short blog entry about panoramic projections:  http://www.trailpixie.net/photography/comparing_focal.htm

Some general comments:

1) Several folks have said that you need to shoot in manual mode and lock the focus.  This is good advice for many circumstances, but you can stitch images at different exposures....and you may even want to do that if there is lots of dynamic range.  When you use this technique, make sure to increase overlap.

2) Two techniques to help you take rapid fire panos:
[blockquote]A. Shoot raw (always a given for me) and then use the exposure lock button to rapidly make a pano without the effort of changing modes.  The exposure lock button allows you to set the exposure to one setting across multiple exposures.  
B. I also have mapped the focus function to the AF button on the back of my canon.  This allows me to focus on a single focal point of the pano, then recompose and set exposure (see above).  By keeping my finger off the button for the duration of the multiple frames, I don't have the camera refocus.  [/blockquote]

3) I frequently process my raw files differently to provide the illusion that the light level is remaining somewhat constant.  I set the white balance and exposure for all the images, then work back across those that are either too dark or too light to shift them subtly towards the exposure I wanted from my key image.

4) When you shoot panos, remember to note the starting angle on your panning clamp.  I can't count the number of times I have failed to do enough exposures on the second row. http://www.trailpixie.net/panoramics_go_b.htm

5) When shooting water scenes, try to get stationary objects that can be used as control points into every frame.  If this is impossible, manually create the control points and guess about their location.  You may need to do some manual blending later.

6) Partly cloudy, breezy days are the bane of the panoramic photographer's existence.