[HDR-photo] Real-World example (Was: Alignment)

[Ferrell McCollough]

Bernhard,

First I'd like to thank you,  Royce,  Roger, Geraldine and others for 
participating. It is very much appreciated.


When you wrote about the Fuji in extended mode, are you saying both RAW and 
Jpeg are converted with the camera respose curve. In general, jpeg is 
converted using a camera response curve. You can create a camera response 
curve using Ward's HDRshop although I don't think you can bring it into 
photomatix.  Regarding RAW>jpeg we all know there is a response curve 
involved but there is a little discussed response curve that takes place 
from real world>pixel value. Doesn't HDR have to unravel that also?

Also AutoPano Pro (APP) allows you to stitch the exposures and sections in 
sort of a two dimensional array. The exposures are stacked vertically and 
the sections horizontally. It uses SIFT technology for the contol points 
which is very reputable. Also you can save the stitched exposures as 16-bit 
tiff's for merging and TM'ing in another program or you can merge and Tm in 
APP. The TM operator is however, a global operator.

You may be able to get the "cripsyness" that your earlier work didn't have 
with STITCH>hdr>Tonemap using APP and SIFT technology.

The three methods for HDR pano varies when the stitching is done. It can be 
first, second or third:

STITCH>hdr>Tonemap
hdr>STITCH>Tonemap
hdr>Tonemap>STITCH

Each stage, stitching, merging and tone mapping involves blending and thus 
creates a potential for error in subsequent stages. A logical argument could 
be made that the process that involves the smallest amount of blending 
should take place first, followed by the second amount of blending and 
ending with the most drastic blending of the three. Stitching the individual 
exposures -2EV 0 +2EV has the lowest impact on the tonal distribution of the 
image set. The next would be 32-bit HDR stitching followed by stitching of 
the single tone mapped images.

your thoughts...
Ferrell







----- Original Message ----- 
From: "Bernhard Vogl" <bvogl at gmx.at>
To: "High Dynamic Range Photography" <hdr-photo at hdr-photography.com>
Sent: Friday, February 16, 2007 5:10 AM
Subject: Re: [HDR-photo] Real-World example (Was: Alignment)


> Hello Pablo,
>
>> If its a global mapping this should not be a problem, since it just
>> corresponds to modifying the response curve. If it depends on the scene
>> or uses some kind
>> of local tone mapping (which is much more computationally expensive),
>> then the mode is not suitable for the creation of scene referred HDR
>> images.
>
> I think, it's a "global operator". In-camera CPUs are not very fast and a 
> "local operator" is computationally much too expensive.
> Is is quite noticeable, how the camera slows down when switching to 
> extended mode... ;-)
>
>> If the curves are static and do not change between the images, it should
>> be possible to recover it, no matter if they are more S-shaped or not.
>> The resulting HDR image will probably show considerable quantisation
>> effects due to the shallow ends of the shaped curve though.
>
> It is far beyond my knowledge how Photomatix and other software products 
> compute the camera response curve and why this shifts exposure. It's just 
> what i encountered with my "real world examples"  :-)
> The quantisation artefacts, by the way, are noticeable in the discussed 
> example...
>
> Best regards
> Bernhard
> _______________________________________________
> HDR-photo mailing list
> HDR-photo at hdr-photography.com
> http://www.hdr-photography.com/mailman/listinfo/hdr-photo