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Author Topic: Panoramas and wide-angle lenses  (Read 6095 times)

lbalbinot

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Panoramas and wide-angle lenses
« on: October 30, 2008, 04:05:57 pm »

Hello everybody!

I recently started to play around with panoramas and yes, it's a lot harder than I thought. There's a lot more than just using Photoshop's photomerge system with the automatic settings! The first thing that caught me unprepared is that I don't think it's possible to be done with ultra wide angle lenses. I did dozens of tries with a Nikkor 14-24mm on a full frame body and even at 24mm there's just no way the images will stitch well together. At first I was trying to overlap about 30% and then I went up to 50%, but even so, I couldn't do it properly. I tried Photoshop, AutoPano and PTGui. Photoshop always gave me the best results.

The best results (see attached photograph) were done with my 35mm f/2 prime lens. These were just perfect and almost wide enough for me. I guess 28mm would be perfect and still good enough to stitch.

Sure, one could just suggest that I should take a few steps backwards and use a longer lens, but sometimes you want to get that same wide angle perspective on the panorama. In those cases you just can't get too far for the wanted composition (only if I had a very tall ladder and tripod  ).

So my question is: does anyone successfully use a wide angle lens (24mm or wider) for panoramas? If so, what's the catch?  

Edit: I forgot to mention that I'm using a Manfrotto 488RC0 ballhead, which should be suitable for panoramas. Should I use something else to ease the rotation over the nodal point of the lens?

Thank you!

Luis
« Last Edit: October 30, 2008, 05:22:10 pm by lbalbinot »
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Tim Gray

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« Reply #1 on: October 30, 2008, 06:20:13 pm »

Quote from: lbalbinot
Should I use something else to ease the rotation over the nodal point of the lens?

Thank you!

Luis


Yes, particularly with wide angles, or if there's foreground in the shot you need to have the entrance pupil over the point of rotation.  If there's much edge distortion in the lens, there's nothing much you can do.

If you have the camera in portrait orientation you can get wider coverage with a longer lens.
« Last Edit: October 30, 2008, 06:21:32 pm by Tim Gray »
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lbalbinot

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« Reply #2 on: October 30, 2008, 06:29:05 pm »

Quote from: Tim Gray
Yes, particularly with wide angles, or if there's foreground in the shot you need to have the entrance pupil over the point of rotation.  If there's much edge distortion in the lens, there's nothing much you can do.

If you have the camera in portrait orientation you can get wider coverage with a longer lens.

Hmmm... so it's not related to the focal distance of the lens? What exactly should I take for the entrance pupil? The front element of the lens?

Now it makes perfect sense. The 35mm f/2 lens is very short, so the rotation was almost over the lens. The 14-24mm is a lot larger.

Thank you Tim!

Luis
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Panopeeper

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« Reply #3 on: October 30, 2008, 07:34:49 pm »

The situation is comparable to one, when a point and shooter photographer purchases a DSLR and starts complaining that the exposure is not right in aperture priority mode.

Short of turning this forum into a specialty one, I suggest you to read on one specialized forum, for example Panorama Tools Assembler

The bottom line is, that Photoshop is a no-name in the stitching industry. What you can and can't stitch with photomerge is prettey much meaningless.

For example correcting the geometric lens distortions (barrel, pincussion) is a natural task of stitching IF the presented images are good enough.

Quote
I'm using a Manfrotto 488RC0 ballhead, which should be suitable for panoramas. Should I use something else to ease the rotation over the nodal point of the lens?
A ballhead is generally useless for panorama shooting. However, the tripod itself is unnecessary in most situations, so you can stay and turn around on a ballhead if you find this comfortable.
« Last Edit: October 30, 2008, 07:50:18 pm by Panopeeper »
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lbalbinot

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« Reply #4 on: October 30, 2008, 07:48:37 pm »

Ah, thanks Panopeeper! That forum seems to be one of the best sources of information for panoramas.

Luis
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Tim Gray

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« Reply #5 on: October 30, 2008, 07:53:34 pm »

Here's a link to a description of a technique that helps you find the entrance pupil.
http://www.vrphotography.com/data/pages/te...ptalign-tn.html
The entrance pupil is actually where the plane of the aperture appears to be when you look through the lens off camera.

If you search out "nodal point" on wikipedia, there are 3 good references on the topic (which also explain why it's the entrance pupil, not the nodal point that you need to identify).

As to Panopeeper's comment on ballheads, I would say that a ball head ....with a leveling base... is extremely useful in shooting panos.  I use one from Acratech
http://acratech.net/home.php?cat=2
« Last Edit: October 30, 2008, 07:57:17 pm by Tim Gray »
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lbalbinot

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« Reply #6 on: October 30, 2008, 08:02:36 pm »

Tim,

thanks, I found some very good info on the nodal point, it's actually very easy to find it for a specific lens.

I agree about the ballhead, it's a lot easier to level. I just need a L-bracket / plate now to use the camera on the portrait orientation and to center the nodal point on the rotation axis of the head.

Thanks!

Luis
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Panopeeper

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« Reply #7 on: October 30, 2008, 08:07:08 pm »

Quote from: lbalbinot
I agree about the ballhead, it's a lot easier to level

Hold on, something is wrong.

The camera does not need to be level. It CAN NOT be level in many cases, The plane of ratation has to be level.

The role of the ballhead is the contribution to the workout when climbing up the mountain with the tripod.
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lbalbinot

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« Reply #8 on: October 30, 2008, 08:12:15 pm »

Yes Panopeeper, I know that I can't level based on the head's spirit indicators. If the camera is perfectly leveled with the head the tripod might not be leveled with the world and as a consequence I'll get tilted and weird captures.

Leveling the tripod is also a hard thing. There are some special center columns and techniques to get it right, but it's hard.

Luis
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BernardLanguillier

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« Reply #9 on: October 30, 2008, 08:35:45 pm »

Quote from: lbalbinot
The best results (see attached photograph) were done with my 35mm f/2 prime lens. These were just perfect and almost wide enough for me. I guess 28mm would be perfect and still good enough to stitch.

The main thing to understand is that field coverage and lens are 2 independant variables when you shoot panos.

You can cover the same field with a 300 mm f2.8 and a 14 mm, you will just need a lot more frames with the  300 mm lens.

This has various consequences that will determine the best lens for each scene.

If documentation is the goal, then this is of relatively little importance, if you are targetting fine art applications, then these aspects become very important and will make the difference between an average image and an outstanding one.

Since pano softwares are getting better, just abotu anybody can do a technically successful stitch nowadays.

Cheers,
Bernard

Panopeeper

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« Reply #10 on: October 30, 2008, 08:46:28 pm »

Quote from: lbalbinot
I know that I can't level based on the head's spirit indicators. If the camera is perfectly leveled with the head the tripod might not be leveled with the world
Then what is the ballhead good for?

Quote
as a consequence I'll get tilted and weird captures
Not necessarily. The pano will be perfect, except that you have to crop away a lot. You can shoot the frames upside down or in 45%, while changing the lens and even the camera, and the pano will be ok if there is no parallax error, IF the coverage is ok. This is often an issue with single-row panos.

Example: http://luminous-landscape.com/forum/index....25815&st=20

Quote
Leveling the tripod is also a hard thing. There are some special center columns and techniques to get it right, but it's hard
I found the integrated spirit indicators worthless (not accurate enough). However, my tripods have center column. I have a dirt-cheap tiny spirit level from a hardware store. which I hold to the column and adjust that to be plum. Thus the swiweling base becomes level.
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lbalbinot

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« Reply #11 on: October 30, 2008, 09:25:32 pm »

Quote from: Panopeeper
I found the integrated spirit indicators worthless (not accurate enough). However, my tripods have center column. I have a dirt-cheap tiny spirit level from a hardware store. which I hold to the column and adjust that to be plum. Thus the swiweling base becomes level.

Very good, your trick is a lot better than the one I've been using! Does your column have an adjustment or do you work on the tripod legs to get it right?

Bernard, I agree with you: it's very easy today to use panoramic software. I just love the results Photoshop will give right out of the box with photomerge. My goal is to stitch horizontal captures and I never work with multiple rows, so it works just fine for me.

Luis
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Panopeeper

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« Reply #12 on: October 30, 2008, 10:27:36 pm »

Quote from: lbalbinot
Does your column have an adjustment or do you work on the tripod legs to get it right?
I adjust the legs; this is less than ideal, but it does work.

The only tripods with adjustable column I know of are the Induro AX/CX; I am eying with the carbon fiber version.
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marcmccalmont

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« Reply #13 on: October 30, 2008, 11:53:05 pm »

About a year ago I invested in a Gitzo GT2530LVL leveling tripod and am very happy with it. I have also had better results if lens distortions are corrected first with DxO so the stitching software does not have to work as hard. PTGui consistently gives me better stitches after DxO corrections. The camera held vertically vs horizontal also minimizes the lens distortions a bit.
Marc
« Last Edit: October 30, 2008, 11:55:15 pm by marcmccalmont »
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jeffreybehr

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« Reply #14 on: October 31, 2008, 12:46:16 am »

With all this conflicting info, I'm confused and I've shot perhaps-hundreds of these.

For hi-rez, wide-angle panos:
1.  A tripod is indeed necessary;
2. A ballhead allows the camera system to rotate about the BH's vertical axis;
3. The tripod and BH must be level or else the stitched pic meanders upward or downward.  Also the camera should be level left-right or the same thing happens.  The camera need not be level front-back.
4. Using sort-of-normal-length lenses, vertically, got me my best results.  Understand that a 50mm lens used vertically has a larger vertical AOV than, say, a 35 shot horizontally.  IOW, standard-length lenses become WAs when shot vertically and stitched.  A 50mm worked best for me.

Look here http://community.webshots.com/user/jeffreybehr to see if mine are worth a damn.

« Last Edit: October 31, 2008, 06:05:02 pm by jeffreybehr »
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John.Murray

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« Reply #15 on: October 31, 2008, 01:06:46 am »

I've found a cheap fence post level folded around the center column of the tripod to be invaluable - folds flat for storage.

Great info posted!  Thanks for the resources!
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lbalbinot

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« Reply #16 on: October 31, 2008, 06:30:44 am »

Quote from: jeffreybehr
4. Using sort-of-normal-length lenses, vertically, got me my best results.  Understand that a 50mm shot vertically has a larger vertical AOV than, say, a 35 shot horizontally.  IOW, standards become WAs when shot vertically and stitched.  A 50mm worked best for me.

jeffreybehr, that's the same that happens to me. These prime lenses have the nodal point a lot closer to the body and that's why we got better results with these lenses. I was just plain lucky to use a 35mm f/2 in my tests. The longer lens (14-24mm) suffered from a lot of parallax errors when stitching.

Luis
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Christopher

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« Reply #17 on: October 31, 2008, 02:00:21 pm »

Quote from: lbalbinot
jeffreybehr, that's the same that happens to me. These prime lenses have the nodal point a lot closer to the body and that's why we got better results with these lenses. I was just plain lucky to use a 35mm f/2 in my tests. The longer lens (14-24mm) suffered from a lot of parallax errors when stitching.

Luis

I would say a tripod is not really necessary to use a tripod. I would say there are other stronger limitations. For example moving scenes.

As long as you are used to hand hold Panos there isn't a problem making them with a 21mm lens. It just takes a little longer to process.


One last thing I wanted to add. I tried PS CS4 now on quite some difficult Panos (architecture) and so far it stitched them better than my usual programs. (Pano pro, PTGui) I'm just talking about Automatic mode. If I have the time I can match the results quite well. I was just curious that CS delivered extremely good results out of the box.
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« Reply #18 on: October 31, 2008, 02:07:21 pm »

Quote from: Christopher
I would say a tripod is not really necessary to use a tripod
I would say a tripod is absolutely necessary to use a tripod  
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NikosR

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« Reply #19 on: October 31, 2008, 02:26:35 pm »

Quote from: Panopeeper
I adjust the legs; this is less than ideal, but it does work.

The only tripods with adjustable column I know of are the Induro AX/CX; I am eying with the carbon fiber version.

Most pro Gitzos can get a levelling base as an accessory.
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