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Resolution problems with warp function after using PANORAMIC photo merge


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Hello Photoshop Gurus,

I have been working with panoramic photo merge and am merging up to 40 images. The result is a very snaky image, I have been using the warp tool in transform functions to correct it, but this leads to a massive resolution loss.

Does anyone have a solution or a suggestions for how to counter this problem?

FOREST PANO TEST.jpg
 

Tom Mann

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Yup. Keep your camera level as u sweep it and u won't have the problem. Anyone who is half way serious about panos uses a tripod with an appropriate head. Photographers who are really serious add a mounting plate that allows the sweep to be done around a point in space in front of the lens, the "front nodal point".
 
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Hi Tom,

The Mounting plate that swings around the front nodal point makes sense. I will have to look for one of those. I had my heavy duty studio tripod and Foba head but there were too many movements between each image - it took too long and the big weather system and dust storms I was in changed dramatically in seconds...so there would have been no way to match up edges.

Going to have to work with what I have.

:)
 

Tom Mann

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Hi MSG -

The odd overall shape of the stitched image that you posted says that there were substantial aiming errors among its component images.

If you were trying to use one of the Foba, or any other ball head (like this one), I can understand how it would be frustrating / time-consuming because rotations around the optical axis of the lens are not constrained when using a ball head. Instead, for panos, is is preferable to use a standard pan-tilt head (like this one or even something like this) that, (a) prevents rotation around the optical axis of the lens, and (b), with the aid of an auxiliary bubble level, one can rapidly build up a large, nicely aligned and matched array of component images. Once the initial leveling of the tripod is done, I can usually knock off around one image ever 10 or 15 seconds using a pan-tilt head. I use an old Gitzo pan-tilt head on an even older (LOL) but very robust studio tripod when I'm shooting panos. If one is really into panos, a computer driven mechanical drive mechanism (eg, Gigapan) will save you lots of angst, LOL.

BTW, as I'm sure you know, the fore-aft nodal point adjustment plate is only critical when the closest object in the scene is under 10 or so meters away. With images like the trees that you posted (which are at a reasonable distance), you'll have more problems with wind induced motion making life difficult for your stitching software than with the rotation point being off by a few cm.

Sorry for the above digression from your original question about warping in software, but I find that it's always better to attack a problem like this at its source (ie, when taking the shots) rather after-the-fact, with general purpose warping tools.

So, with respect to warping, although you didn't say it explicitly, it sounds like you would like the ground to be level, and the trunks of all the trees to be vertical, not converging as you go towards the zenith. I find that if I gather the component images correctly, it's much easier to let dedicated pano software perform the correct geometric projection to retain verticals rather than doing it after the fact using PS's native warping tools. Here is a nice intro article on projections. Note the comment in the article about the extreme loss of resolution in cases like yours.

BTW, what stitching SW are you using? I find that PTgui is much, much better than the native stitching tool provided in PS. Somewhere there is an even better description of the various projections as applied to PTgui, but unfortunately, I can't locate it at the moment.

HTH,

Tom M
 

dv8_fx

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Hello Photoshop Gurus,

I have been working with panoramic photo merge and am merging up to 40 images. The result is a very snaky image, I have been using the warp tool in transform functions to correct it, but this leads to a massive resolution loss.

Does anyone have a solution or a suggestions for how to counter this problem?

View attachment 59590
I'm just curious.... would it be OK for you to upload the photos used in your sample?.... I just feel you don't have to use the Warp tool extensively.
 
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Hi Tom,

Thanks for all this info ... The trees were just the first every photo merge test I did...without tripod.
I included it as it is the most extreme I have had. Since then I used a tripod and tested the Foba ball and a standard pan and tilt but it took to long with the fast moving weather you will see in the images below. What I have been working on is out in the Black Rock desert in wind and dust storms.
I am using Photoshop CS6 and its photomerge. I have not come across PTgui until now.

I really appreciate you taking the time out to help me like this.

Below are some of the actual images I have been working on
Screen Shot 2015-10-31 at 11.09.26 AM.png
Screen Shot 2015-10-31 at 11.08.15 AM.png
 

Tom Mann

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1. Ahh - I didn't realize that the tree shot was done without a tripod. That explains everything.

2. The sinusoidal / wave-like shape of the first image in your most recent post is an absolute dead give-away that the axis of rotation was not exactly vertical, ie, the tripod was not perfectly level. This is where the bubble level that I mentioned really helps.

3. With respect to speed, if you need to do fast panos professionally, you should seriously consider a Gigapan or similar automated mount . They are not that expensive, they are fast, and one will likely pay for itself quickly. I haven't kept up with new products in this area, but I'm pretty sure that several competitors have entered the market at lower price points than Gigapan.

4. Another advantage to an automated mount is that by using it, you can use a longer lens and take more component images and with a larger overlap between adjacent pix. This will help tremendously when your stitching software needs to severely transform some of the images (eg, the tops of the trees) that would otherwise lose appreciable sharpness if fewer images were available to it.

Tom M
 
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Hi Tom,
That looks great!
I will have to save up for one of those Gigapan things!

Do you think it is therefore not possible to actually shoot upwards at tree tops with the horizon line below the camera frame for instance and get a good result?

Matchstick
 

Tom Mann

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Hi MSG - No, it is indeed possible to shoot upwards at tree tops and get very good results, but you have to do it correctly. It's all in the numbers. To make the discussion easy, let's assume we are shooting buildings with straight sides, not trees that taper towards the top.

Suppose that the tops of the buildings (in my example) are twice as far away from the camera as the bottoms of the buildings. To completely correct the keystone distortion in such shots, one has to scale the horizontal dimension of the component shots in the upper floors of the buildings by a factor of two. Actually, both the horiz and vert dimensions have to be scaled by roughly the same ratio (exact details depend on the projection used). This means that you must start with enough pixels in each component shot so that after this scaling, the resolution in the upper floors of the buildings never drops below whatever minimum value is acceptable to you.

The way to do this is to use a long lens and take many more component shots than you might originally think. Each of the component shots will be at the resolution of your camera body (eg, say, 20 Mpixels), so the overall size of the stitched image (in Megapixels) will be much larger than you might think, and will be able to support the enlargement of the upper floors of the buildings as needed to make this area appear to have the same magnification as the lower floors and prevent the resolution from dropping below whatever minimum value you set for yourself.

Keeping track of, and processing this many component shots can be time consuming and require a suitable computer, but it certainly can be done. The trick is simply to generate your panos from a very large number of telephoto shots, not be swayed by convenience and use a much smaller number of wide angle shots.

Of course, one can't have everything in life, and shooting so many telephoto shots will take more time, and, as you pointed out, in some situations, this amount of time may not be available, even if you use an automated pano mount.

HTH,

Tom M
 

Tom Mann

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I'm glad we've been able to add some clarity to the issue of obtaining good stitched panoramas.

We would love to see some of your work, and I'm sure you could teach all of us quite a bit about fashion photography, so please do come back! :)

Cheers,

Tom M
 

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