Hugin changes the exposure?

[Frederic Da Vitoria]

Hello,

I am sure I already saw something about a similar issue in the group, but I couldn't find it.

I usually make my panoramas using layered tiffs (Output / User defined output sequences / Normal panorama with layered TIFF output). This process has been going on smoothly (11 panoramas in the last 3 days) until this last panorama. It is a simple one with only 2 pictures. The left one is OK, but the right picture is overexposed by Hugin. I tried fiddling with the check boxes in the Stitcher tab but I did not manage to get any improvement. The only thing which got me the correct exposure was using Output / Stitch user defined output / normal_layered_tiff.executor. I would gladly go on using this, but it generates 4 files instead on 1 multilayered tiff.

I will probably throw this panorama away anyway because the pictures are completely blurred (I forgot I was in manual focus when I took those pictures), but I'd still like to understand what is going on and how to get what I want next time.

Does anyone have a solution to my problem?

Of course I can post the PTO files if it is any use.

[Bruno Postle]

Probably the exposure/photometric optimisation has failed badly, the solution is to reset the exposure parameters and try again (with or without re-optimising exposure, it may not be necessary).

Sometimes this happens when you are using the assistant and the initial alignment is not so good, the exposure optimisation relies on a good alignment, then when you later fix the alignment you are stuck with bad exposure parameters.

The multilayer output is ok because Hugin zeroes out the Eev parameters when it creates this.

--
Bruno

[Frederic Da Vitoria]

I forgot to say that I never ask Hugin to do photometric optimization. I prefer to play with the Gimp tools. And I don't use the assistant. My procedure is : 

- automatically generate CPs

- repeat 

-   Perform geometric optimization

-   fix CPs

- until pictures align correctly

- choose the projection I prefer

- autocrop

- generate multilayered tiff

The EEVs of the 2 pictures are indeed different : 12.9 and 13.6. I did a few full resets (I usually do it when I have problems aligning because of poorly matched CPs).

[Frederic Da Vitoria]

... but I redid a loop and this is when I noticed the 2 choices on the Exposure and Colour lines. I changed both to to zero and this worked.

Thank you Bruno for leading me to this. 

I wonder why this does not happen all the time, though. In the panoramas I did recently, there were pictures with different EEVs and I did have to fix those in Gimp. So I still wonder why sometimes Hugin decides to fix the exposure and sometimes it does not.