Overlap on Stitched Panoramas

[Mike Guilbault]

I've just started doing panos - my first one today (in over 30 yrs of photography) which was shot on tripod but with no pano gear - and I impressed myself!  Anyway, I've been reading that you should overlap your pano images by about 30%.  If this is more accurately done (ie, not handheld, or just twistin' the camera around on tripod) is there any benefit?  And I also read a post somewhere that someone was taking the pano images in 5 degree increments.  Does that improve quality at all?  That seems like overkill... but I really don't know.

[SeanBK]

I shoot with less than 30% overlap, though it really does depend on subject where overlap is occuring. If one is shooting a pano with a tele, whose angle is less, than 5 degrees may all wrong, while shooting with wide angle lens may be overkill.
 Also if shooting landscape when leaves are moving than U need to shoot quick, so 5 degrees is detrimental and so is 30%.
   Short answer would be judge the subject, conditions and equipment, than decide & not a moment too soon. That's my 2c. Try and try some more.

[elf]

It depends on a lot of different things:
 

• How close to the entrance pupil you can rotate the camera

This reduces parallax error and allows smaller overlap.  This is really the key to creating good panoramas.

• Subject matter

A broad featureless area can use a smaller overlap, but may be harder to stitch.
A moving subject may need more overlap to get it into one frame.

• Foreground vs background

Backgrounds are usually easier to stitch with small overlaps because they have less detail.

• How accurate each move is

If you can control the accuracy of each movement to the pixel level then a very minimal overlap is needed.

Generally speaking for landscapes, a 20% to 30% overlap works well.  If you're shooting with a well calibrated pano head, 10% is enough.  Handheld, I usually try for minimum 30% because this allows more editing room to fix parallax errors.
 

[Mike Guilbault]

Thanks guys... great tips.  I plan on shooting some this weekend on my workshop, but I don't have the pano gear yet so I'll be shooting 'free-form'. 

[SeanBK]

I use a good tripod, RRS BH-55 Ballhead and RRS Ultimate Pro Omni-Pivot package. For simple single row pano I don't bother with Omni-Pivot, but I do have a plate that has a bubble in it, so camera IS level. Have fun.

[Bart_van_der_Wolf]

I've just started doing panos - my first one today (in over 30 yrs of photography) which was shot on tripod but with no pano gear - and I impressed myself!  Anyway, I've been reading that you should overlap your pano images by about 30%.  If this is more accurately done (ie, not handheld, or just twistin' the camera around on tripod) is there any benefit?

Hi Mike,

The number one reason for having an overlap is for the software to be able and (auto)detect and assign controlpoints in the overlap region. If there is alot of detail, then a smaller overlap will suffice. In general, 30% is not a bad compromise between getting enough detail in all overlaps, and keeping the number of tiles and 'doppelgängers' down.

There can be (other) reasons to increase the overlap to e.g. 50%. One of the uses is to allow Smart blending of different exposures/white-balances between the tiles. Anther one is if there is a lot of subject/people movement, then a generous 50% overlap will create 3 images of each overlap region which will allow to eliminate people or probably get one usable version with all limbs attached.

Cheers,
Bart

[Mike Guilbault]

Here's one of the images shot last evening.  I've got this result on a few of the panos I shot.  Kinda interesting, but not exactly what I was after.  I levelled the tripod and camera as best I could - but it was shot with a 17mm on a D700 and I've been reading that wide angle lenses are harder to use.  Is this why (and what's actually happening here)?  Is the pano gear the only way to correct this? 

[Schewe]

Did you select Cylindrical or Auto? It's been my experience that Auto is sometimes kinda on drugs...also, when you shot, was the camera in vertical or horizontal? Again, it's my experience that shooting the pano in vertical orientation and using the Cylindrical will be better...

[Peter McLennan]

Did you select Cylindrical or Auto? It's been my experience that Auto is sometimes kinda on drugs...also, when you shot, was the camera in vertical or horizontal? Again, it's my experience that shooting the pano in vertical orientation and using the Cylindrical will be better...

X2

I never use "auto" and nearly always shoot vertical/cylindrical.  Then, use "select all|edit|transform|warp" to stretch the image back into shape.

[Bart_van_der_Wolf]

Here's one of the images shot last evening.  I've got this result on a few of the panos I shot.  Kinda interesting, but not exactly what I was after.  I levelled the tripod and camera as best I could - but it was shot with a 17mm on a D700 and I've been reading that wide angle lenses are harder to use.  Is this why (and what's actually happening here)?  Is the pano gear the only way to correct this? 

Hi Mike,

No, you just need to adjust the Yaw parameter of the pano project. I don't know which pano stitching software you used, but it could come out something like the attached version when using a retilinear projection method. You could also have used a cylindrical projection if you keep the horizon in the middle (otherwise it will curve up or down).

Cheers,
Bart

[Mike Guilbault]

I used the Auto feature in PS CS5.  Tried it again this morning using Cylindrical and it was much better.  Not a great image, but better.  I need to get better at pre-visualizing the end result.

Here's a different image from the same scene.  It was 7 images and I used the Cylindrical method.  I didn't see any option to adjust a Yaw parameter though.  There doesn't seem to be any options in CS5 other than selecting which method to merge with - or am I missing something?  

And if you don't want the horizon in the middle... what's the best method to use (shooting/stitching)?

[Bart_van_der_Wolf]

I used the Auto feature in PS CS5.  Tried it again this morning using Cylindrical and it was much better.  Not a great image, but better.  I need to get better at pre-visualizing the end result.

I see. Cylindrical asumes that the verticals need to stay vertical and that any horizontals except the central one will be curved (as in a barrel type of distortion). So cylindrical projection will work most of the time when there are no clear straight horizontal/diagonal lines that need to stay that way, as in many nature scenes without a visible straight horizon. The rectilinear projection is the only one that keeps straight lines straight and is normally used when there are geometrical structures and buildings in the image.

Here's a different image from the same scene.  It was 7 images and I used the Cylindrical method.  I didn't see any option to adjust a Yaw parameter though.  There doesn't seem to be any options in CS5 other than selecting which method to merge with - or am I missing something?

Well PS doesn't offer much in the sense of control. For that you need a dedicated stitching program, e.g. PTGUI or AutoPano.

And if you don't want the horizon in the middle... what's the best method to use (shooting/stitching)?

The shooting is not that critical (apart from getting an alignment of the lens' entrance pupil with the rotation point to avoid parallax errors mostly in the foreground), it's more about the postprocessing. You'll need to use a rectilinear projection to keep straight lines straight. Without the controls for Yaw, Pitch, and Roll, it's still going to take a bit of work. You would first need to expand the canvas of the top or bottom of the row(s) to get the natural horizon more or less in the middle, then stitch, and then crop off the excess you added and probably a bit more because you may get a curved horizon if you didn't add the right amount of space. For me, it's too much hassle, but then I stitch a lot so I have dedicated tools that do offer control.

For those on a Windows platform who want to wet their feet, the free Windows Image Composite Editor (ICE) application does a pretty good job automatically, plus it offers the ability to adjust the Yaw/Pitch/Roll by dragging the image, and the possibility to create dynamically zoomable web output (similar to Zoomify but based on the MS Silverlight engine). It's a really nice drag and drop solution for quick expansion of the FOV if your focal length is not short enough, or to add resolution when shooting with a longer focal length and then stitch to regain a larger FOV.

Cheers,
Bart

[NikoJorj]

There doesn't seem to be any options in CS5 other than selecting which method to merge with - or am I missing something?  

That's the big problem with photomerge, IMHO. When it works it's really great (most motably in terms of LR integration), but when it doesn't it plainly doesn't and there's nothing you can do.
A simple GUI where you could at least previsualize the stitched result, change the assembly method and set a ref point for yaw/pitch/roll would be very warmly welcome.

And if you don't want the horizon in the middle... what's the best method to use (shooting/stitching)?

Use a decent pano stitcher and tell it where the horizon is by setting the roll reference point on it (much easier to do than to explain).
Then, you can choose a cylindrical, rectilinear, or spherical projection, the horizon will stay level.