Color correction modes  

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AlexandreJ
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by AlexandreJ » Thu Feb 23, 2006 5:25 pm

Panorama fanatic wrote:1. Yes/No: the only difference between auto/HDRI color correction - is described before requirement to explosure gaps between adjoining images + method to map internal HDRI color to 8/16 bits ('auto' color correction have some default method, but HDRI correction require using of color filters)

Not really. There's a fundamental difference between HDRI and standard mode, even the linear blending mode in HDRI is working differently in HDR than in auto mode.
Mapping internal value to 8 or 16 bits is done the same way if it's HDRI or auto mode. In fact in both mode, internal calculation are done as float.

Panorama fanatic wrote:2. Yes/No(describe) Default color mapping method of 'auto' correction is simply truncate DR of project, using range of anchor image. This make 'anchor' part of output equal to 'anchor' source image (if levels is not used), and another parts - over- or underexplosured, basing of anchor image.

No. I will not go too deep into describing algorithms behind the color correction as it will give hints to competitor. To be short, I'm solving the real light equation between neighboors which gaves me many informations about the way pictures were shoted. With that, I can really remap every pixels to real world value. There are no stage anywhere in the code which truncate DR of input pictures (except the final end conversion to 8bits : but if you use carrefully levels, you can have the full dynamic range of the panorama, which is more than the input pictures).

Panorama fanatic wrote:3 If auto mode is HDRI inside, why do not use 'HDR' tools to preview image in 'auto' mode.

It's not. BTW, you can use tone mapper on a standard low dynamic picture, it's a kind of shadow / highlight tool.

Panorama fanatic wrote:4 Please, describe filters. Better - with examples. It is impossible to understand without description, therefore using of filters is always expirement.

Unfortunatly, tone mappers are not really photographically describable. The best I found is to experiement. It's today always an open area in research to get a really cool and practical tone mapper for photographer.

Panorama fanatic wrote:5 I think, that there is 3 possible improvement:
- change HRDI preview selector to some, like 'scrollbar', where width of moving bar of this tools will reflect size of visible part of full DR.
- combine 'filters' and 'levels' in one tool to qiuckly see result of all changes
- allow using of 'levels' to map HDRI to 8/16 bits in HDRI correction mode

I like the scrollbar idea but not the combinaison of filters and level. It's just not the same. Level cannot be applied easily on HDR pictures.

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AlexandreJ
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by AlexandreJ » Thu Feb 23, 2006 5:26 pm

I posted the wiki tutorial on another thread to be able to continue this thread without pagination.

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by Panorama fanatic » Thu Feb 23, 2006 5:40 pm

Good starting point to think before asking questions!

Will reask my questions later :)

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by Panorama fanatic » Thu Feb 23, 2006 5:56 pm

As I understand, both blending mode (linear, multiband), always used all pixels of all images in overlapepd area. It is good, when extending DR (because shadow or light may be in any part of overlapepd zone), but not good, when adjoined images taken with equal explosure.

Blending always redice quality of image, if panorama was taken without pano tripoid and have objects, near to photographer (in my example, there is big area near of photographer). Extending area of blending will extend area with reduced quality :( 3-4 overlapped images will produce very bad quality :( I remember, that using panotools based tools (ptgui) I have seen result of blending only in small areas on the border between images.

I will play with another pano tools to give examples and continue this theme.

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by Panorama fanatic » Thu Feb 23, 2006 5:59 pm

Can you enable attaching of images in forum? Using external site is not good :(

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AlexandreJ
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by AlexandreJ » Thu Feb 23, 2006 6:02 pm

You are right if you don't use a multiband blend. Even with large overlapping zone, this blender gives good results. And I don't think such blending method can be strongly disturbed by a huge exposure difference in input pictures. With an anti-ghost blender, blending issues will totally be history.

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by Panorama fanatic » Thu Feb 23, 2006 6:25 pm

Multiband give results better, that linear - I checked :) But problem is not in huge explosure difference, no! Problem - in non-stiching images. See on my example on the left-bottom corner of image - border of road seen 2 or 3 times :)

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by Panorama fanatic » Thu Feb 23, 2006 6:27 pm

May be future anti-ghost blending will solve this problem, but now I will make a examples of current situation

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by Panorama fanatic » Thu Feb 23, 2006 9:31 pm

I tried HDRI mode again and got result similar to my previous post with error. But you have better result in your wiki article. Why? :) May be you use new version of autopano with improved alghorim?

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AlexandreJ
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by AlexandreJ » Sat Feb 25, 2006 9:01 am

No, all tutorial in the wiki are done with the standard 1.1 version.

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by Panorama fanatic » Sat Feb 25, 2006 2:23 pm

But what may be source of quality difference?

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