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

[Bernhard Vogl]

Hello Geraldine.

>> I actually thought of that, but as you said, i don't know a method 
>> to import a response curve into Photomatix, 
>>     
> This is because digital cameras do not have a response curve. The camera's raw
> sensor data are linear relative to the scene luminance in the useable tone
> range (i.e. above noise and before saturation). And linear means that the
> response curve is a straight line, i.e. there is no curve. 
>
> Then, the camera firmware processes the linear raw data in order to produce an
> image that looks good on your LDR monitor. If you are sure that this
> processing always corresponds to applying the same tone curve (which I doubt
> in the case of processing the extended dynamic range captured by the Fuji
> Super CCD SR as the firmware will probably try to adjust how much it
> compresses the highlights depending on the overall brightness of the image)
> then use Photoshop CS3beta as it allows to save and import a response curve
> when merging to HDR.
>   
Thank you Geraldine for pointing out. The camera itself has a linear 
response curve as long as we talk about RAW images. HDRShop can't read 
RAW images, so in this case i am talking about, that the camera JPEG 
depicts a response curve which is measured by HDRShop's camera 
calibration tool.
>   
>> In the first place i expected that camera curve calibration won't 
>> touch the "medium brightness" but in fact it does. 
>>     
> What do you mean by touching the "medium brightness" exactly?
>   
Again, thank you for reading my mails that carefully. I have re-read my 
own words and they are certainly completely mis-understood: The 
resulting HDRs generated by Photomatix conform to each other (as long as 
you use one of Fuji's "fixed" DR settings, see below), but the 
tonemapping results will differ because the mapped DR information is 
different (i didn't mention the additional step in my explanations). You 
may say, that using a standard response curve for the Fuji 
"pre-flattens" the HDR, and it is easier for the TMO to map this reduced 
range.
>   
>> Maybe Geraldine 
>> listens and can explain some basics about response curve 
>> calibration? 
>>     
> All camera calibration techniques that I am aware of rely on the assumption
> that the response curve does not change depending on the exposure or the image
> content. This is because these techniques were originally intended for
> recovering the response curve of films where this assumption is valid. When
> this is not the case, calibrating won't really help.
>   
This is the case for some of Fuji's "extended range" settings. 
Especially noticeable with the "auto DR" settings. This also impacts 
above assumptions and is the reason why i always capture the images by 
using the "full DR" settings.

Best regards
Bernhard