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To Process RAW Or Not

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#1 vidrazor

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Posted 13 October 2019 - 07:40 PM

I've read some folks feel it's better to pre-process light frame RAW data in a program like Lightroom or Capture One before bringing them into a program like DSS. What's the general consensus on this? On the one hand it can be handy in dealing with stuff like chromatic aberration, etc., but does it offer any advantage in extracting the data from it, or should you go straight to RAW?
Thanks.



#2 pfile

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Posted 13 October 2019 - 07:56 PM

hm, well you lose the ability to calibrate the frames properly. and isn't lightroom going to stretch the images?

 

i know tony hallas recommended this as the adobe camera raw program can correct lens shading, which i guess in theory obviates the need for flats (unless you have dust bunnies.) there might be a way to get ACR to not stretch the data, but for sure it's going to debayer it.

 

rob



#3 17.5Dob

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Posted 13 October 2019 - 08:06 PM

I've read some folks feel it's better to pre-process light frame RAW data in a program like Lightroom or Capture One before bringing them into a program like DSS. What's the general consensus on this? On the one hand it can be handy in dealing with stuff like chromatic aberration, etc., but does it offer any advantage in extracting the data from it, or should you go straight to RAW?
Thanks.

Only two folks out of several 1,000...

Tony Hallas and Roger Clark.

Can't be done without detrimental effects in linearity and accurate color .


Edited by 17.5Dob, 13 October 2019 - 08:10 PM.

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#4 vidrazor

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Posted 13 October 2019 - 08:14 PM

OK, well, I kinda figured that was the more logical approach and not mess with the RAW.
Thanks.



#5 calypsob

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Posted 13 October 2019 - 09:04 PM

Ive tried it before but honestly it destroys your data. You can launch camera at any time in ps so its much more beneficial to stack raw data first and deal with imperfections later. You can stretch data much more accurately with flats/darks/bias properly applied before tweaking anything else.

#6 whwang

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Posted 13 October 2019 - 09:41 PM

i know tony hallas recommended this as the adobe camera raw program can correct lens shading, which i guess in theory obviates the need for flats (unless you have dust bunnies.) 

 

My experience is that his is only good for daylight photography and perhaps some nightscapes, not for real deep-sky.  The lens profiles in ACR only have a small set of parameters.  This is not accurate enough to completely remove the lens vignetting if the images are to be strongly stretched later, which is the case for most deep-sky photos.



#7 ChristopherBeere

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Posted 14 October 2019 - 11:23 AM

RawTherapee enables you to apply darks and flats and has become my goto calibration software for RAW files.

 

It has excellent debayering options and a very well laid out interface for batch processing of large data sets.



#8 sharkmelley

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Posted 16 October 2019 - 12:29 AM

RawTherapee enables you to apply darks and flats and has become my goto calibration software for RAW files.

 

It has excellent debayering options and a very well laid out interface for batch processing of large data sets.

Interesting.

 

The RawTherapee documentation does indeed indicate it is possible to subtract an average of dark frames (effectively an on-the-fly master dark):

https://rawpedia.raw....com/Dark-Frame

 

However it also suggests that only a single flat frame can be used, not a average of flat frames:

https://rawpedia.raw....com/Flat-Field

 

How do you overcome that, because a single flat frame will inject additional unwanted noise into an image.  I see that RawTherapee allows you to apply a blur to the flat-field (to reduce noise) but then it is less effective at correcting for dust spots.

 

Mark


Edited by sharkmelley, 16 October 2019 - 12:35 AM.


#9 ChristopherBeere

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Posted 16 October 2019 - 07:24 AM

Hi Mark,

 

A single flat does indeed introduce a lot of noise so i use the Multiple Exposure function on my Canon 6D MKII to average 9 flats (the maximum it allows) in camera and that gives me an excellent low noise flat RAW file that i use to calibrate in RawTherapee.

 

I set the blur radius to zero (effectively disabling it) and that gives me a perfect subtraction of dust spots and corrects the vignetting.


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#10 sharkmelley

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Posted 17 October 2019 - 05:25 AM

Hi Mark,

 

A single flat does indeed introduce a lot of noise so i use the Multiple Exposure function on my Canon 6D MKII to average 9 flats (the maximum it allows) in camera and that gives me an excellent low noise flat RAW file that i use to calibrate in RawTherapee.

 

I set the blur radius to zero (effectively disabling it) and that gives me a perfect subtraction of dust spots and corrects the vignetting.

Very clever!

 

Mark


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#11 ChristopherBeere

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Posted 17 October 2019 - 07:28 AM

Thanks Mark smile.gif




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