Add a way to hint to APP that you are using sets of photos  

Got some great idea or a feature request? Post it here and discuss it. The most requested concepts are usually implemented, as Autopano Pro / Giga is very community driven.
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hankkarl
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Add a way to hint to APP that you are using sets of photos

by hankkarl » Sat Jun 03, 2006 4:21 pm

Sometimes, I use several sets of photos because my camera does not have enough exposure latitude. The three cases:

1. use auto-exposure bracketing on a tripod. Camera takes 3 shots at -2, 0, +2. Each picture should have exactly the same pitch, roll, yaw, etc.

2. Use tripod with Manfrotto 303SPH. Change EV after taking one pano set becasue I need more than -2 to +2 EV. Each picture is pretty closely alligned horizontaly (there's some slight slop in the head.) The pitch (I think its pitch) is off between sets because there is no detent for pitch, you set it to "about" the right place.

3. Handheld.

I would like an option when creating panoramas to say "I used mode 1 above" if APP sees three pictures with about the same pitch, roll and yaw, but different shutter speed or ISO, it should use that as a hint that those pictures have the same parameters.

It may be a good thing to have an option to say that I used mode 2 also.

This is because I took a circular pano set of a room which had a large window. The window was blown out (it was a bright day) and I took a few extra pictures of the window, exposed for the outside. When I made a panorama from just the inside of the room APP couldn't complete a circle, and seemed to give different lens values. (Perhaps APP should look at the EXIF data or allow the photographer to hint that the lens length was kept constant). When I made a pano from the all the shots, APP did it correctly (but there was some shadowing.)

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AlexandreJ
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by AlexandreJ » Sat Jun 03, 2006 7:52 pm

This was discussed before on the forum. In a not so near future (I have to deal with other priority first), we'll add a concept of set of bracketed pictures.
A set of bracketed pictures is just as it named : bracketed pictures (same location but different exposition). I can detect that automatically using a special test on sift control point. So when some pictures are detected, I can adjust every algorithm to use this extra information, thus making the optimization faster, the color correction better, etc.
But it is still a big challenge to create this concept in the software and it efficiently.

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by GURL » Sun Jun 04, 2006 9:28 am

AlexandreJ wrote:But it is still a big challenge to create this concept in the software

Because screens and prints can't fairly reproduce images of high dynamic range subjects, those subjects are a challenge for every photographers.

The most common solution is to avoid those subjects and this results in experienced photographers finding HDR useless because they (laboriously) learned to always avoid HDR subjects as uninteresting ones (but give an automatic camera to a child and look at the results!)

The most efficient solution is to use bracketing and to combine the resulting images. A difficult problem arise:
- without a tripod images alignment errors are often as large as 100 pixels
- using the best possible tripod and a remote trigger, alignment errors are often very visible (error amount depends mainly of focal length - one should not touch the camera between shots to change settings.)

My conclusion: a stitcher is not "a programs used to stitch panoramic images" but "a program used to combine several photos into a single final image".

The goal of stitchers includes:
- high resolution images
- high depth of field images
- high dynamic range images
- high field of view images (aka panoramic images)
... plus perspective mastering (like when using shift & tilt lenses) and some other "new areas" of photography.

I use APP to combine bracketed images which more than often are not panoramas. When shooting them - with or without a tripod - I do my best not to move the camera between shots but, as stated above, in most case there is a visible difference. Multi-layer .psd from APP including "Color correction : NONE Layer 0" are just great for that.
Last edited by GURL on Sun Jun 04, 2006 9:34 am, edited 1 time in total.
Georges

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hankkarl
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by hankkarl » Mon Jun 05, 2006 4:15 am

I think our eyes do some local contrast correction -- for example, if you look around a room, you can see the dark corners and also see what's outside in bright sunlight.

You can do similar things with unsharp mask. Just start by setting the width to a very large value (like 50 or 100), the percent to 20%, and the other value to 3, and play around with things from that point. See http://www.luminous-landscape.com/tutorials/contrast-enhancement.shtml for more details.

Sorry if I'm stating the obvious, but I don't know what APP does exactly with the tone mapping. The eye does some interesting things that may let you use different parts of the HDR in different parts of the image. That is, you may have one part of a pano that maps (for example) 0-255 to 0-255, and another that maps 512-768 to 0-255, and different maps in-between. You don't need to have the whole thing use the same map. See http://web.mit.edu/persci/gaz/ and http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html for some related info.

And yes, the focal length should remain fixed. But sometimes changing the exposure variables means that you have to touch the camera and this makes it shift left or right slightly. And some camera's can't do auto exposure bracketing (mine can, but only a -2 to +2 range). And its easier to change the settings, take a full set, change the settings, take a full set,... than take a picture, change the settings, take a picture, change the settings... move to the next pano position, change the settings....'

I know almost enough about DSP to be dangerous, but it seems that if you know that the lens length is fixed, and the pictures should about line up, then you could negate one and shift it left or right, or up or down, add it to the other and look for a minimum (in the film world, you take a negative of the negative, put it over the other negative and shift it around until everything looks the "most black") (and you may only have to use a small part of the picture to get a rough idea of how they line up.)
Last edited by hankkarl on Mon Jun 05, 2006 4:17 am, edited 1 time in total.


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