[ptx] Best way to compensate for different exposure/metering/white balance settings

[Brian]

Aunty Ethel's pet hamster wrote:
> On Wed, 26 Jul 2006 11:24:51 +0100, "Bruno Postle" <bruno at postle.net>
> said:
>   
>> On Wed 26-Jul-2006 at 11:01 +0100, carbon14 at fastmail.fm wrote:
>>     
>>> I'm trying to create a panorama out of five photos that I took recently,
>>> but unfortunately I took the photos before reading about fixing the
>>> metering/white balance when taking shots for a panorama.
>>>       
>> You can automatically correct exposure if you use either the 
>> PTStitcher or PTmender stitching engines instead of nona (the 
>> default hugin stitcher).
>>
>> Though you will get even better results if you use 'enblend':  On 
>> the 'Stitcher' tab, select Quick Stitcher -> High quality TIFF
>>
>> -- 
>> Bruno
>>     
>
> Unfortunately, the finished panorama that contains these vertical
> gradients (http://www.carbon.eclipse.co.uk/panorama.jpg) was stitched
> using enblend (I followed the tutorial at
> http://exolucere.ca/articles/create-panorama which said to do the
> stitching using enblend from the command line).
>
> I've since tried the "Quick Stitcher -> High quality TIFF" option to see
> whether that improves things, and the output tiff still has the same
> problems.
>
> I was wondering more whether it's possible to use the information
> contained in the exif data (such as ISO Speed data, ExposureTime and
> FNumber) to modify the photos _before_ passing them into
> autopanog/hugin/enblend. As an example, two adjacent photos have
> exposure times of 1/127 seconds and 1/92 seconds (not surprisingly, the
> second photo appears too light in the panorama) but I don't know how to
> "normalize" these two photos to have the same exposure time (and even if
> I did, would they then blend better?). I think I'll try the Gimp mailing
> list next, if no-one has any suggestions.
>
> Thank you.
>
>   

One long winded way to "normalize" the pictures is to stitch as a 
multilayer tiff.

Load this multilayer tiff into the Gimp.

Then for each pair of images:

Show red channel only, adjust gamma in "red" levels dialogue until both 
images match brightness in the red channel
Do the same for the green and blue channels, adjusting the green and 
blue levels gamma as required.

Once that has been done all the layers should have similar brightnesses.

Then save each separate layer out as an individual tiff, then stitch 
together using enblend.

Then put the kettle on for a well earned cup of tea!

Its certainly a long winded approach, but it does give good results.

-- 
Brian



	
	
		
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