Re: [APML] Is DDP Necessary?

[Vicent Peris <vicent@cepheusastrophoto.com>]

Hi Charles,

Personally, I don't like DDP! It's too much "automatic" for me. :-)
I think that making manual adjustments you have far more control
over the luminance of the image, and you can get the results you
really want.

Here is where FEATHERED curves come into play. Think that
when you apply DDP, you need to make an edge amphasis. Why??
Because, if you shrink the dynamic range of the image to view
at the same time dark and bright portions of the object, you are
losing contrast on the small scale features too.  Therefore, we need
to decrease the contrast of the global image, but increase it at small
scales (and, if you want, at large scales too <g>). To make this, the
best technique is feathered curves.

If you divide the dynamic range of the image in various sectors,
you can EXPAND the dynamic range of each sector to enhance
small and large scales. After making those stretchings, you can
combine them through masks. Take into account that the masks
must have sufficient softness to avoid false gradients!

Therefore, feathered curves are, from the point of view of the
visual perception, more correct that DDP, because you are not
generating noise and artifacts (dark halos).


Take care,
Vicent.


At 22:48 11/10/2004 -0400, you wrote:
>Hi Everyone:
>
>I was wondering whether members feel Digital Development Process (DDP) is 
>necessary. I have become rather adept at pulling out faint details of 
>nebulosity using the PhotoShop curves and levels tools. Will a DDP filter 
>be more efficient in stretching out faint details, or should I trust my 
>manual tweaking more? If someone feels DDP will get better results, please 
>let me know what software you recommend for achieving it. Thanks,
>
>-Charles
>_______________________________________________
>Astro-Photo mailing list
>Astro-Photo@seds.org
>http://seds.org/mailman/listinfo/astro-photo

Vicent Peris
http://www.cepheusastrophoto.com/Index.html

_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo