Measuring true value of shutter-speed overrides from average pixel luminance - page 2 - General Discussion and Assistance - CHDK Forum

Measuring true value of shutter-speed overrides from average pixel luminance

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With HDRShop I just get a completely black or white image.

I cannot see an option to display a histogram.


With HDRShop I just get a completely black or white image.
I cannot see an option to display a histogram.

The images shouldn't be black or white unless there is something else wrong.
What kind of image are you loading?  What I had done was shoot the images in  RAW DNG and converted the DNGs to 16bit TIFs using ImageMagick as outlined above.
"convert -depth 16 -type grayscale FILE.dng FILE.tif"

This is under Windows, I don't know if things are different under other OSes.

There is no histogram, I am just looking at the average/sum pixel values under the menu item [Image/Info->]


What kind of image are you loading? 

CHDK raw files converted to 16-bit with Reyalp's rawconvert tool.

They display with Image J.

With HDRShop, I 'Import raw Data file', set the width and height and gamma to 2.2, no header, monochrome, unsigned 16 bit and 'reverse byte order' unchecked.

All on Windows XP.

CHDK raw files converted to 16-bit with Reyalp's rawconvert tool.

They display with Image J.

With HDRShop, I 'Import raw Data file', set the width and height and gamma to 2.2, no header, monochrome, unsigned 16 bit and 'reverse byte order' unchecked.

All on Windows XP.
I haven't used rawconvert.  With HDRShop I just open the TIFs I created directly.  As they are 16bit, they don't ask for any other info.


This is getting very tedious ....

To follow the same procedure as yourself I installed CHDK on a spare 16 MB card.
I do not normally use CHDK but it is  required to create the DNG files.
Enabling DNG tells me to run badpixel.lua so I do and it fails because not enough memory.
So now I am using a 64MB card and it takes two photos and fails with :-

:38 attempt to index global 'os' a nil value.

I need to install the complete CHDK package.
« Last Edit: 17 / November / 2009, 16:20:55 by Microfunguy »

This is getting very tedious ....

To follow the same procedure as yourself I installed CHDK on a spare 16 MB card.
I do not normally use CHDK but it is  required to create the DNG files.
Enabling DNG tells me to run badpixel.lua so I do and it fails because not enough memory.
So now I am using a 64MB card and it takes two photos and fails with :-

:38 attempt to index global 'os' a nil value.

Sounds like you run out of space on the 64MB card for the DNGs (+JPGs).  The DNGs are over 15MB each plus the JPGs can average up to 5MB.  Unfortuneately you'll need a bigger card to collect more DNGs.

This is getting even more tedious ...

I type convert -depth 16 -type grayscale CRW_7090.dng CRW_7090.tif and get error message :-

unknown field with tag 37398 (0x9216) encountered.


« Last Edit: 17 / November / 2009, 16:45:38 by Microfunguy »

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Offline reyalp

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Why use dng ? rawconvert will take you directly from CRW to something you can easily convert to tiff, or analyze directly with many different programs.

If you convert with -noshift, the values will be the exact 10 or 12 bit values from the CHDK CRW. This means they only use a small part of the 16 bit dynamic range, so depending on what image program you use, you may have to adjust the contrast if you want to see anything.

Quote
:38 attempt to index global 'os' a nil value.
Did you build CHDK yourself ? sounds like the OS lib is not compiled in. badpixel.lua will not run without this. If you built using the default configuration, you would not have this problem.

How have you determined that "badpixel.lua" fails due to lack of memory ? It shouldn't, the lua part does very little.
Don't forget what the H stands for.


I converted to dng to try to follow barberofcivil's  procedure.

Certainly the file produced by your tool was extremely dark for the reasons you give.
I had difficulty with CS4 expanding the range to make it viewable.
The histogram split as the image posterised.

I used the latest autobuild CHDK, the full package.

Once the full package was loaded badpixel.lua ran OK.

If I load the file produced by your tool into ImageJ it is immediately viewable but looks posterised.
Not sure if I can use that for analysis even though ImageJ's histogram function also indicates average pixel value.

I have to assume that value is not based on the brightened screen image.

Sounds like you are having some difficulty, for some reason.

I've been using DNG as that is what I am already set up for on my camera and the SX10.
If you are doing everything correctly, there should be no issue:
-install full CHDK
-run badpixel.lua (click set to save at the end)
-enable RAW and DNG in RAW menu
The resulting DNGs should be correct.  Can you open them in other software?  They open correctly in several programs I have (irfanview, UFRaw for gimp, picasa, photomatix, etc.).

When I convert with imagemagick (using the command parameters you've used), the original DNGs are 15143kb, and the grayscale TIFs are 19881kb.
For some reason, the DNGs only show up as 128x96 thumbs in ImageJ.

I installed ImageJ and looked at the TIFs.  The information is virtually the same as I was getting in HDRShop, but with more information (However HDRShop evaluates pixels values on a scale of 0-1).  I may continue using this in the future as it gives more tools for analysis.

 

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