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FORUMS Post Processing, Marketing & Presenting Photos RAW, Post Processing & Printing 
Thread started 23 Dec 2017 (Saturday) 15:26
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Command line: Manipulate DNG exposure

 
ShutterKlick
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Dec 23, 2017 15:26 |  #1

Dear friends,
I am running Windows7, and am looking for a command line utility to
modify the DNG's exposure and save to a new DNG, with the intent of
prepping for HDR processing.

For example, to make -2 and +2 EV modifications, Id like to do something such as:

converterapp "base.dng" -modifyexposure -2 "base-2.dng"
converterapp "base.dng" -modifyexposure +2 "base+2.dng"


I am hoping that whoever is reading this understand that the above is simply for
the sake of explanation.


My google fu is weak, I have searched for 4 weeks and turned up nothing.

May you be of assistance?

I am only interested in solutions that are command line, I can easily do this
with PS but that is not part of this project.

Thanks,
Andrew


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kirkt
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Dec 23, 2017 15:42 |  #2

Look at the dcraw “brightness” flag. Output 16 bit tiffs

For example:



dcraw -b 0.5 -T -6 <input file name.DNG>


The -b flag multiplies the white point, so “0.5” will half the exposure. Etc.

Kirk

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ShutterKlick
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Dec 23, 2017 16:37 |  #3

10-4, thanks!

It accomplishes what I want, and does it well! The previous version of DCRAW I had did not process my D5300 NEF very well, the colors were tinted. I downloaded the newest DCRAW and hacked together this script and it works great.. doing 8 bit TIFF on this one, but can add -6 to do 16 bit if I want..

for %%a in ("*.nef") do (

dcraw64 -b 0.25 -T -v "%%a"
rename "%%~na.tiff" "%%~na-minus2.tif"

dcraw64 -b 0.5 -T -v "%%a"
rename "%%~na.tiff" "%%~na-minus1.tif"

dcraw64 -T -v "%%a"
rename "%%~na.tiff" "%%~na-base.tif"

dcraw64 -b 1.5 -T -v "%%a"
rename "%%~na.tiff" "%%~na-plus1.tif"

dcraw64 -b 2 -T -v "%%a"
rename "%%~na.tiff" "%%~na-plus2.tif"

)

pause


Thanks for the tip on DCRAW, it doesnt output to DNG but I think 16bit TIFF should have the dynamic range I want for that frame to do good HDR.

Take care,
Andrew


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ShutterKlick
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Dec 23, 2017 16:49 |  #4

I am also looking at HDRTOOLS to exposure fusion the resulting TIFFs...
http://ttic.uchicago.e​du/~cotter/projects/hd​r_tools/ (external link)


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kirkt
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Dec 23, 2017 21:42 as a reply to  @ ShutterKlick's post |  #5

It seems like you might want to use the “-4” flag to create a linear 16-bit tiff for these tools.

Kirk


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ShutterKlick
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Dec 23, 2017 22:21 |  #6

kirkt wrote in post #18525127 (external link)
It seems like you might want to use the “-4” flag to create a linear 16-bit tiff for these tools.

Kirk

I will look into that flag, thanks!


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Stiga
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Post edited 6 months ago by Stiga.
     
Dec 24, 2017 04:29 |  #7

ShutterKlick wrote in post #18524868 (external link)
Dear friends,
I am running Windows7, and am looking for a command line utility to
modify the DNG's exposure and save to a new DNG, with the intent of
prepping for HDR processing.

For example, to make -2 and +2 EV modifications, Id like to do something such as:

...............

As I understand it, this process won't make any difference to your end procuct. Tonemapping the original DNG will produce exactly the same result. Think about it, the RAW file contains a dynamio range of at least 4 EVs in the first place. An HDR app will "see" this range and make use of it. Creating +2 and -2EVs so that you can feed 3 images into your app will make no difference.


Martin
I'm not a gear guy but I have a tons of software :-)

  
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ShutterKlick
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Dec 24, 2017 09:45 |  #8

Stiga wrote in post #18525214 (external link)
As I understand it, this process won't make any difference to your end procuct. Tonemapping the original DNG will produce exactly the same result. Think about it, the RAW file contains a dynamio range of at least 4 EVs in the first place. An HDR app will "see" this range and make use of it. Creating +2 and -2EVs so that you can feed 3 images into your app will make no difference.


Makes perfect sense, thanks for the follow up!!

SNS-HDR Lite will take a single RAW and do a fine job as I found, but since I started this project.. Ive discovered Nik collection for PS, and WOW.. it does a fantastic job, results do not look fake at all, VERY REAL.. the results that Nik yields are the results I have been in quest for! Now, Photomatix and Machinery do a fine job too.... its hard to describe, but the results Nik gives is to my eye more pleasing..

Thanks all!
Andrew


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ShutterKlick
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Dec 24, 2017 09:46 |  #9

Oh yeah, quick follow up.. the image created by HDRTOOLS is less than stellar, abandoned.

Andrew


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Command line: Manipulate DNG exposure
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