Topic: Spin and Wall correction by synther please

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Joscelin.Trouwborst (Over 1 year ago)
Spins and Walls may suffer variation in height of shooting position, due to shooting from the hand or terrain unevenness while using pods. Could the synther adjust this to have a smoother auto view path please?
Joscelin.Trouwborst (Over 1 year ago)
Maybe I should rephrase the above... As to have a smoother viewing experience in general. Or, how can I shoot better? Example spin synth
NateLawrence (Over 1 year ago)
As you know, Photosynth 2 already crops, compensates for differences in camera roll, and (when playing through the photos) moves the virtual camera to a smooth camera path which passes as closely to the solved for camera positions while preserving as smooth a curve as possible.

I'm sure that you also realize that the auto view path is the pink line when you enter global camera view. 

Looking at the synth you linked to, Joscelin, I don't see any playback roughness that stems from difference in camera height. In fact, given the constraints of where the input camera positions are, it's difficult to imagine a smoother path.

With the calculated geometry that Photosynth is projecting the images onto being so simplified, it is not possible to move the camera further away from the original camera positions without introducing even larger distortions and tears in the images.
NateLawrence (Over 1 year ago)
:: My main suggestion for the above synth would be to slow down whenever passing foreground objects. Some of the closer trees aren't seen enough times to get a good reconstruction of them to use in relation to the sculpture.

(That would push the total number of photos in the spin up, of course, though, and the Photosynth team has said multiple times that spins work best with fewer images. I'm assuming this has to do with the number of images needed to be downloaded in order to progress a satisfactory amount around the subject when giving the spin a swipe on a touch screen.)
NateLawrence (Over 1 year ago)
:: The other tip I'd add is just to try to keep the subject framed as evenly as possible throughout your shots. 

You're right that using a tripod or monopod isn't always helpful when you're not dealing with a perfectly flat floor. 

The best thing is to pick something to always center the lens on and keep an eye on the space above, below, and to the sides of your subject. 

This is especially true in cases where the physical setting simply won't allow you to walk in a perfect circle around your subject (due to streets, walls, shrubs, trees, people, etc. on one or more sides which force you to walk a non-symmetrical path.

I know that we aren't meant to change camera zoom levels between shots in Photosynth 2, but I would rather use camera zoom to try to keep my subject framed in the same way and complete the circuit, if possible, than to give up because I can't keep the same distance all the way around in such cases.
Joscelin.Trouwborst (Over 1 year ago)
Thanks for the explanation and recommendations, Nate.
NateLawrence (Over 1 year ago)
If anyone has any tips for keeping a consistent distance from the subject of a spin, I'd be interested in hearing them.

In cases where you have something geometric to work off of (such as the ledge around the pool basin) it's possible to count off a number of strides from a wall or foundation to help keep a more even distance from your subject, but this means talking up to it and walking back every time that you want to take another shot which is tedious (and it can be difficult, when doing this, to move a consistent distance sideways around your subject).

Back when I began shooting synths, I (and others as well, I'm sure) imagined using transparent fishing line as a way to keep an even distance from the subject by tying a loop around the subject and drawing the line out to the photographer and attaching it to one's self or your camera/tripod. 

I still have never actually done this, though, so can't speak to how often it is practical.
HGREGG (Over 1 year ago)
Only thing I can think of (so far) is to carry a little laser distance finder - aim at the subject and check the distance before each shot. I might try this and see how much of a hassle it is.
HGREGG (Over 1 year ago)
@Joscelin.Trouwborst - I've just looked again at your synth - it's actually pretty good! The thing that's spoiling is the stuff that comes really close to the camera - there is too much parallax there. 

Too illustrate try this: Hold you thumb up really close to your nose that look through your left eye then your right and see how much it moves relative to set object in the distance. Now try the same with your thumb at arms length (it moves less relative to that object.

So keeping object further away will help - I'm trying to work out at the moment how far away they should be kept for different focal lengths (zoom levels). Also as Nate said - more shots when you pass close object will help.

If you had shot that synth from inside the inner circle of trees if would have been really good :-)
NateLawrence (Over 1 year ago)
I'm not sure what will come of it, but I suggested a flight plan sort of feature for the upcoming apps to help keep distance more consistent.


@HGREGG, I took a quick look at laser rangefinders on Amazon just now and all of the first results appear to be under $200 (and a few under $100) which is welcome. I see that some of them list a maximum range, but I'm wondering how granular the readouts are when measuring shorter distances - whether it's always in yards or metres or can be changed to feet, inches, or centimetres.

Do you have any advice as to a particular model which is both not too pricey and also articulate in shorter distances?
Joscelin.Trouwborst (Over 1 year ago)
To keep the statue in the middle was pretty easy, because my Lumix TZ30 happens to have its focus ready indicator in the top middle of the display.

I did not want to get much closer for two reasons. 1. Statue and pedestal fountain are large. 2. I did not want those to attract al attention of the viewer either, as this is about its setting in the plaza as well, i.e. the whole scenery.

Starting the shoot I realized about all 'obstacles' up close, but got curious about how it would work out. My first with parallax. In general I feel that Parallax gives some liveliness to a scene, as it does here.

However, what I am learning here is, that when it is getting too close it gets disturbing. So, I better assess this in advance to decide on radius and shot frequency.

The synth has 68 frames, which is already a lot more than advised. I had 1 or 2 side steps between each frame. Smaller ones at close objects.
HGREGG (Over 1 year ago)
I have a Bosch PLR50 it is accurate to within 2mm!!! The PLR15 is much cheaper (accurate to within 3mm ) most laser ones are that accurate - don't go for ultrasonic ones.

We're metric over here in U.K. so we don't see feet/inches (mine's not changeable) but maybe that's not important.

I figure one of these and a monopod (to keep height consistent) should give the best results possible.

Re: Flight plan - I saw the post but not sure if GPS can give the accuracy.
HGREGG (Over 1 year ago)
@Joscelin.Trouwborst - I think the number of shots depends on the subject and background. I'm guessing the TZ30 will go pretty wide angle (I had a TZ7) so I'd try it really wide and get back there. 

I'm new to Photosynth and still learning but I used to shoot a lot of stereoscopic 3D stuff and I think the same principles apply. Best rule of thumb is try each synth several ways and see what works best :-)
PhotosynthTeam (Over 1 year ago)
To respond to Joscelin's original question -- we try hard to smooth the path with tricks such as detecting whether a spin really is attempting to "look" at the same center from every photo, and if so, locking that assumption in. That's what makes the first example above work pretty well: the statue stays rock solid in the middle of the frame. We try to so something equivalent for walls and panos, though it isn't so obvious and often not quite as effective.
Joscelin.Trouwborst (Over 1 year ago)
@HGREGG Happy you have come to join us, not only as a synther, but in the conversation as well. Contrary to you, I am not an under the hood guy in the Photosynth matter.

Yes, TZ30 has 24 mm lens, iHDR and GPS. Previously, I have used a TZ10 with GPS. Have GPS experience since 2010. As far as using Maps, whether it be Bing or Google, an other issue is errors in layering satellite imaging and map features on the co-ordinate system.

Oh, and I am still learning too. Especially, as we are entering a new era with Ps2.
Joscelin.Trouwborst (Over 1 year ago)
@PhotosynthTeam. Thanks for the effort you keep putting into all of this. Keep going! And speed up, we can hardly wait ;-) lol.