HDR Scanning is exposure controllable ?

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nurgle
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HDR Scanning is exposure controllable ?

Postby nurgle » Sun Jul 27, 2008 10:48 am

Hi, I have been trying to scan some old negs using Silverfast A1, using HDR.
The scans come back so light it is like they are two stops over exposed.
is there anyway to control the exposure is HDR..????
nurlge

LSI_Morales
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Re: HDR Scanning is exposure controllable ?

Postby LSI_Morales » Mon Jul 28, 2008 9:13 am

Dear Nurgle,

The scanning modes 48 bit HDR color or 16 bit HDR greyscale are available to create completely unmodified scans, in such cases you have to save the file as TIFF file so the entire Dynamic Range of your negative will be saved in a 16 bits RAW file.

This type of files have much more information than that a normal screen is capable of displaying (8 bit pictures), it means that after you have created the TIFF file, you still have to tell your editing program, which portion of the histogram should be displayed.

Alternatively you can tell SilverFast to use the gamma of your preview (a reduced gamma value) in the end file, in this way the resulting file will be displayed as you see it in the preview window in SilverFast.

Please open the "Options" dialog and select the "general" tab, there you will find an option named "Gamma-Gradation" and a checkbox next to it with the option "for HDR output". Please make sure you activate that option by marking the box and do NOT modify the value expressed there. See the next attachment.

Greetings
Attachments
GammaforHDR.jpg
Gamma-Gradation activation for HDR
GammaforHDR.jpg (61.12 KiB) Viewed 2057 times
Alejandro Morales

LaserSoft Imaging
Media manager, Software testing

owl
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Scanner: PowerSlide5000
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Re: HDR Scanning is exposure controllable ?

Postby owl » Fri Jan 22, 2016 6:37 am

Hi,

It has now been 8 years since the original post, but this seems like a good place for a follow-on question.

I can not get SF8 to use a gamma of something other than 1 when using 64 Bit HDRi RAW. Furthermore, I have read the Segal book section, which provides guidance, but which does not seem to work for me.

My setup
install from SF-8.8.0r1(AFL)_x64.exe
reset all preferences
reset software
take defaults initially, then
Kodachrome
64 Bit HDRi RAW
Gamma Gradation, 2.2
L*Gradation, unchecked
HDR RAW, checked
Profiles, input, SFprofK
Embed ICC Profile

here are my tests

image 01
kodachrome
1200 ppi
64 bit hdri raw
preferences, general, HDR raw (checked)
results: looks dark (under exposed) in
Lightroom
Irfanview
windows file explorer image (icons)

image 02
same but with
HDR raw UNCHECKED
results: looks dark (same)

03
L*Gradation checked, note: "internal color space has been set to EDI RGB v2"
HDR raw UNCHECKED (same as last time)
results: same

---
HDR

render all 3 images as full resolution jpgs
all three jpgs look the same
better (HDR is rendering with higher gamma), but not as good as the original slide projected on a screen, but that investigation, I will leave for another time.

---
So in summary, what settings do I need to use to have the HDR Raw scanner output from SilverFast 8.8 use a gamma consistent with what other programs would expect (e.g. 2.2)? Right now, I need to preview some images in HDR just to simply verify that I have used the right filenames.

Thanks.

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LSI_Ketelhohn
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Re: HDR Scanning is exposure controllable ?

Postby LSI_Ketelhohn » Wed Jan 27, 2016 2:01 pm

Dear customer,

HDR(i) and HDR(i) RAW images can only be saved with a gamma of 1.0. A gamma adjustment would contradict the statement that these images are saved unchanged.
HDR(i) RAW is a newer format than the previous HDR(i) formats and stores the settings data in its meta data. The image is the same.

If you want to store an adjusted image please use one of the regular 48->24 bit or 48 Bit images.


Kind regards,
Arne Ketelhohn.

owl
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Scanner: PowerSlide5000
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Re: HDR Scanning is exposure controllable ?

Postby owl » Wed Jan 27, 2016 9:25 pm

Hi,

In SilverFast 8.8, what purpose does the "HDR RAW" checkbox (in the General Tab of preferences) serve?

It seems to have no effect on anything I can observe.

Thanks.

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LSI_Ketelhohn
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Re: HDR Scanning is exposure controllable ?

Postby LSI_Ketelhohn » Tue Feb 09, 2016 3:47 pm

Dear customer,

It switches on/off the storage of the metadata and settings in the file instead of the HDR Studio database.
It does not have an "observable" effect. It only matters if HDR files are set up in HDR Studio software and then are transferred or a reset is made.

Kind regards,
Arne Ketelhohn.


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