EXIF are useless for LDR mode (always?)  

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GURL
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EXIF are useless for LDR mode (always?)

by GURL » Sat Nov 20, 2010 10:33 pm

As I was not really sure about what I said in [url=[url]http://www.autopano.net/forum/t8832-help-with-creating-files-ready-for-layered-images[/url] ]this post[/url] I decided to do some tests...

For that I used a group three images shot at 1/2000, 1/250, 1/2000 (this a 3 ev, no less!). In the first group EXIF data are included, in the second one I removed them using ExifToolGUI. In this example at least LDR color correction is able to compensate for the difference in brightness both with and without EXIF data.

Notes:
- APG 2.5 beta 2
- HDR is grayed but a rather large dynamic range is taken into account using LDR mode :cool: :cool: :cool:








Last edited by GURL on Sat Nov 20, 2010 10:47 pm, edited 1 time in total.
Georges

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AlexandreJ
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by AlexandreJ » Mon Nov 22, 2010 1:11 pm

I played with LDR / HDR optimization during the whole last week ( to fix another bug in fact ).
* no exif is needed to make LDR color correction.
* in fact HDR and LDR color correction is quite the same except if you have really dark image ( in this case, we don't have enough information in the image and color correction rely itseft on exif data instead ).

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hermer-blr
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by hermer-blr » Mon Nov 22, 2010 6:20 pm

And for "none": Are exif data used ?

When I convert my raw files into tif, I may change the exposure; then,when I input the images in autopano, I modify the shutter speed in order to reflect the tif exposure. Is this necessary ???

When will you issue the documentation for 2.5 ? Will there be a beta3 release before the official version ? or an alpha release ? When is this planned ?
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[bo]
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by [bo] » Mon Nov 22, 2010 6:29 pm

There will be no beta 3. The next release will be 2.5 RC (release candidate). We all hope 2.5 final will follow shortly after that. No one will give you a time frame, but I expect the final to land before the year's end.
Some of my panoramas, posted in the Autopano Pro flickr group.

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GURL
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by GURL » Sat Nov 27, 2010 6:19 pm

AlexandreJ wrote:... in fact HDR and LDR color correction is quite the same ...*

Here is how I understand it:
- Differently exposed images** are converted into Autopano internal extended dynamic format. This applies both to LDR mode and to HDR mode.
- Using LDR mode one must use the Levels tool*** to compress this extended range so that it matches the smaller range that JPEG, screens and printers can accept.
- HDR mode is (or was ?) designed to record this extended dynamic range without compression into .exr or .kro high dynamic range format files.

That the internal Autopano extended dynamic format exists and that the Levels tool plays a decisive part when LDR mode (and HDR mode ?) are used is not something obvious. The worst thing about it is that HDR is often confused with tone mapping: when using Autopano on the contrary HDR is to be used when no tone mapping is desired...

Following screen captures result from an attempt to find out how it works but your comments and corrections would be :cool: :cool: :cool: !
___
* except if you have really dark image ( in this case, we don't have enough information in the image and color correction rely itseft on exif data instead.)
** NONE = No color correction is preferable when all images were shot using the same exposure setting (and for RAW preprocessed images when same processing parameters were used.)
*** or leave this task to automatic levels. Automatic levels is active when Auto color correction is selected in Edit - Settings - Detection - Automate
Georges

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GURL
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by GURL » Sat Nov 27, 2010 6:21 pm

...








Georges

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GURL
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by GURL » Sat Nov 27, 2010 6:47 pm

BTW, Ken Rockwell do know the solution :) :D :lol:

[url wrote:http://www.kenrockwell.com/tech/highlight-shadow.htm[/url] ]Here's how to get perfect highlights and shadows.

Quite simply stated, one gets perfect highlights and shadows when the lighting of the subject matches the dynamic range of the medium.

The way one gets better highlights or shadows is to be sure to light the subject in such a way that the highlights come out exactly as bright as the ability of the medium to represent them, and that likewise, the shadows are just dark or light enough to look dark, but with detail, with whatever medium you are working.
Georges


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