How can I use Hugin for image averaging and HDR together?

[Nathan Myhrvold]

Normal HDR practice is to take a series of photos at different exposures - for example a 5 shot sequence could be at: EV -2, -1, 0, 1, 2.

These must be aligned and then merged into an HDR file.   If you have linear converted files, the merge becomes a weighed average of the files.  Typical weights are the 2^EV, divided by the sum of 2^EV for the sequence.

Image averaging is where you take multiple shots at the same exposure, align and then average them.  Typical weighting is 1/N.

I am doing both together - meaning that I might have multiple shots at each EV level but I want to make one HDR out of it.

Surprisingly  to me, every HDR program I have tried so far - both free and commercial - refuses to do this - if you give the software more than one shot at each EV level, they assume you made a mistake and only look at one.     

The correct behavior is not difficult - you just average them all with a slightly different weighting that takes into account that you have more one than one frame at each EV.

I am new to Hugin, but it looks to me like Hugin would work for me.  I think I might need special settings for it.

This article describes a simple version of merging a bracketed sequence with Hugin https://pixls.us/articles/aligning-images-with-hugin/, but I need to know the answer to these questions, and I hope that a Hugin expert or developer could answer them:

1. If I give Hugin a set of shots with more than one frame at each EV, will it do the correct weighted average of all of them?

2. Is this true even if I have different numbers of shots at each EV ?

3. Is it possible to see, or set, what weighting factors Hugin hdrmerge uses?

4. Will merging work even if all of the shots are at the same EV (i.e. this is image averaging not HDR) ?

5. There is an anti-ghosting option on Hugin hdrmerge.  Ideally this would work for all of the cases above - i.e. pure image averaging, or an HDR bracketed sequence, or multiple copies of HDR bracketed sequence.    Will it? 

[Terry Duell]

Hello Nathan,

On Fri, 2020-07-03 at 16:03 -0700, Nathan Myhrvold wrote:
> Normal HDR practice is to take a series of photos at different exposures - for
> example a 5 shot sequence could be at: EV -2, -1, 0, 1, 2.
>
> These must be aligned and then merged into an HDR file. If you have linear
> converted files, the merge becomes a weighed average of the files. Typical
> weights are the 2^EV, divided by the sum of 2^EV for the sequence.
>
> Image averaging is where you take multiple shots at the same exposure, align
> and then average them. Typical weighting is 1/N.
>
> I am doing both together - meaning that I might have multiple shots at each EV
> level but I want to make one HDR out of it.
>
>

I don't know the answer to your problem, but suggest that you have a look at
hugin executor, you might be able to use that to do what you want.
There are a number of executor scripts in src/hugin1/executor dir and I think
there is a description of the syntax somewhere in the doc dir which might help
you write a bespoke script.

Cheers,
--
Terry Duell <tdu...@iinet.net.au>