Re: Could aling_image_stack be hacked to work on RAW files or is this nonsense?

[Naked Robot]

it's not possible because you'll have to also warp/remap images that are aligned in a stack. this is something that you can't do with a raw file (at least, no one invented such capability yet in any stitcher program that i know of)

use 16-bit tiffs instead ?

On Tuesday, July 10, 2012 12:07:08 PM UTC+2, Max Killer wrote:

Hello,

I am using darktable to work with my RAW files (I shoot mostly in RAW).
I often shot bracketed images without a tripod (I know I should, but I am lazy....). Darktable has a "HDR" fundtion to combine several RAWs into one "HDR" DNG, but has no alignment capabilities.

Would it be possible to hack align_image_stack to work with native RAWs (Raw input --> aligned RAW output) or this not possible / feasible?
I just love the possibilities I have with darktable with my RAWs, I and would love to have this possibilities with a combined (from stacked pictures) image.

Sorry if I have chosen the wrong group for this.

Max.

[Gnome Nomad]

Max -

I use 16-bit TIFFs. They have the same color depth, and a standard
format. RAW files actually come in a number of formats, each unique to
the CCD they were captured from. So any stitcher that dealt with RAW
files would either have to know a bunch of specific RAW formats, or
would have to internally convert the RAW to a standard format like TIFF.

I tried using darktable, but the UI made no sense to me and I couldn't
actually get it to export anything. I prefer Rawtherapee.

--
Gnome Nomad
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[Lukáš Jirkovský]

On 10 July 2012 12:07, Max Killer <hal.fr...@gmail.com> wrote:
> Hello,
>
> I am using darktable to work with my RAW files (I shoot mostly in RAW).
> I often shot bracketed images without a tripod (I know I should, but I am
> lazy....). Darktable has a "HDR" fundtion to combine several RAWs into one
> "HDR" DNG, but has no alignment capabilities.
>
> Would it be possible to hack align_image_stack to work with native RAWs (Raw
> input --> aligned RAW output) or this not possible / feasible?
> I just love the possibilities I have with darktable with my RAWs, I and
> would love to have this possibilities with a combined (from stacked
> pictures) image.
>
> Sorry if I have chosen the wrong group for this.
>
> Max.
>

Unfortunately this is not possible due to the nature of RAW data. The
RAW images contains data directly from the sensor. The image points in
RAW file does not correspond to a real pixels, instead it's an array
of monochromatic points, that are usually aligned using the Bayer
filter [1].

The problem is, the align_image_stack needs to morph the image, which
requires some interpolation between pixels. However, in RAW files are
no real pixels with colors to interpolate between. To obtain the
pixels, another step, called demosaicing, must be taken. This step is
done in all RAW processing software (such as Darktable, Adobe
Lightroom or Rawtherapee) or directly in camera if you use JPEG
output. Unfortunately the demosaicing is a very difficult task. That's
why every RAW processor out there gives slightly different output and
why one application is great for processing RAW files from one camera,
but for a different camera the output is very bad.

To sum up, it's very likely there will never be any RAW support.
There's a slight change that we could support DNG, which is
standardized RAW format, but in my opinion it's not worth the work, as
it is rarely used. To reiterate what other already said – process
files in Darktable first, save them as 16bit TIFF and use the TIFF
files with align_image_stack.

[1] http://en.wikipedia.org/wiki/Bayer_filter

Lukas