Format of HDRi-images

SilverFast HDR Studio (48bit HDR processing)

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Format of HDRi-images

Postby Jossie » Fri Feb 08, 2013 7:31 pm

Good evening,

as a newcomer to the field I plan to use SilverFast AI Studio 8 to scan my slides and make the image processing with HDR Studio 8 and save the output as JPG. I plan to add metadata to the HDRi-files with EXIFtool for my needs. The HDRi-files are ment for archiving.

Now I have read in the forum, that one should not edit the HDRi-Files because they use a special format.

This worries me quite a bit, since "archiving" and "special format" contradict each other! What exactly is the format of these images and is editing the metadata safe?

Hermann-Josef Röser

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Re: Format of HDRi-images

Postby LSI_Ketelhohn » Tue Feb 12, 2013 4:42 pm

Dear Mr Röser,

This is correct the HDRi format stores unaltered image data and the infrared channel.
The Metadata contains important information about the images.
Altering them with another tool can damage this data or even destroy the infrared channel.
If you want to set metadata you should enter the IPTC data within SilverFast.

Kind regards,
Arne Ketelhohn.

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Re: Format of HDRi-images

Postby Jossie » Tue Feb 12, 2013 5:40 pm

Dear Mr. Ketelhohn,

the IPTC-data within SilverFast are incomplete and partly mis-interpreted (see Wikipedia for a definition of the tags).

In order to get a complete description of an image, tags like GPS-data, categorie, sub-location, peopleinimage, rating etc. are important (depending on the appliciation). In the end, it is the user who has to decide which tags are needed to fulfil his/her needs and not SilverFast. Thus restricting the format of the raw data prohibiting the modification / addition of metadata with an external tool is not very useful for archiving purposes.

Furthermore, a proprietary data format is not suitable for archiving to begin with, since x years from now nobody will know about SilverFast and the details of its format. Thus the data in the archive will be lost, unless a detailed documentation is made available. But is this really necessary? With well-defined image formats around, all supporting metadata in general, I do not see the needs for a proprietary format at all.

I think producing good scans is one thing and your software excells in doing that. But the archival point of view MUST never be neglected!

With kind regards

Hermann-Josef Röser

PS: Please note that (I hope due to a bug), no metadata at all (!) are currently transferred in HDR from the raw data to the output image!

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Re: Format of HDRi-images

Postby LSI_Ketelhohn » Fri Feb 15, 2013 7:32 pm

Dear Mr Röser,

Thank you for your feedback.
I will forward your information to our product management and we will check on the comments you made.

We will also check the HDR IPTC data handling.

Our file formats are not proprietary.
We use standard Tiff and JP2 containers.
However we require some additional information which is placed in free data fields.
There are no "standard" tags for this information.
These however are overwritten by some other softwares.

kind regards,
Arne Ketelhohn.

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Re: Format of HDRi-images

Postby Jossie » Sun Feb 17, 2013 5:02 pm

Dear Mr. Ketelhohn,

thank you for this additional information. So the formulation in the other thread, that " ... SilverFast uses a special format ... " is somewhat misleading.

Do I understand it correctly, that SilverFast uses its own tags to document the IR-Scan? I see tags unter ICC-header and ICC_Profile like RedTRC, ... , AToB2 if I look at all the metadata with EXIFtool after the scan, which I do not see if I look at EXIF, XMP or IPTC-tags separately. Are these the ones you mentioned?

In a test I just geotagged a file with EXIFtool. I can still see these special tags, but the image is destroyed: It had lost contrast when opened in HDR but iSRD can still be activated. Do you say that EXIFtool is destroying these other tags?

Sincerely yours

Hermann-Josef Röser

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Re: Format of HDRi-images

Postby LSI_Ketelhohn » Tue Feb 19, 2013 4:11 pm

Dear Mr Röser,

Sorry I do not know what the tags are called exactly.
But was maybe the creator tag changed?
We use that to determine if an image was created in SilverFast.

And can your tool handel multi layer Tiff files?
That would be necessary.


kind regards,
Arne Ketelhohn

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Re: Format of HDRi-images

Postby Jossie » Tue Feb 19, 2013 4:44 pm

Dear Mr. Ketelhohn,

as I had written, I just added the GPS information via EXIFtoolGUI.

In the meantime I contacted Phil Harvey, the author of EXIFtool, and sent him a test image (format 64BIT HDRi) to see, if EXIFtool does overwrite something in the TIF header if new tags are added. His reply was a firm no. However, existing tags can shift within the header due to the new information added. But this is in concordance with the TIF specification.

Does SilverFast assume that the information stored in the raw data files for later processing with HDR is at a fixed location in the header? This would explain the problem.

With kind regards

Hermann-Josef Röser

PS: I would assume that EXIFtool can handle multi-layer TIF data, since the metadata have nothing do do with the data themselves. But I will ask.

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Re: Format of HDRi-images

Postby Waterside » Wed Feb 20, 2013 3:50 am

ExifTool is a very common utility used by photographers, both amateur and professional: http://www.sno.phy.queensu.ca/~phil/exiftool/ There are also several commercial products, such as geo-taggers, that incorporate/bundle exiftool rather than develop this on their own. ExifTool is very reliable.

Rearranging or modifying EXIF tags should not disrupt the image data. Most manufacturers (EXIF writers) will write their private/proprietary details using the Makernotes field which is its intended purpose. Unfortunately some of these will use a binary format that is dependent upon its absolute location within the TIFF file which then makes it impossible to modify any other tags except by that writer (breaking all other EXIF tools). Most manufacturers are aware of this and will use an alternative format that uses relative dependencies within the Makernotes field, but are not dependent upon the location of this field itself. By doing this they help to ensure that the image data is not corrupted by any of the many EXIF utilities including ExifTool. None of the other EXIF tags may be location-dependent, nor should any of them be considered so.

Updating EXIF tags is a standard part of many photographer workflows, and the inability to do this with HDRi images scanned by SilverFast is a significant limitation.

Could correction of this issue be given consideration by LaserSoft?

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Re: Format of HDRi-images

Postby Jossie » Wed Feb 20, 2013 9:55 am

Good morning,

just a short addition:

I do not see the tag "Creator" in the file header. There is a tag "Software" under IFD0 and this holds "SilverFast 8.0.1 r20 (Feb 4 2013) 2535570 04.02." . Is that the one used for identification? The tag "ProfileCreator" is empty.

Hermann-Josef Röser

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Re: Format of HDRi-images

Postby LSI_Ketelhohn » Fri Feb 22, 2013 2:54 pm

Sehr geehrter Herr Röser,

Tritt dies mit der aktellen Version des ExifTools immernoch auf?
Phil Harvey hat diesbezüglich ja gerade einige Bugs im ExifTool behoben.


Mit freundlichen Grüssen,
Arne Ketelhohn.

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Re: Format of HDRi-images

Postby Jossie » Fri Feb 22, 2013 4:15 pm

Dear Mr. Ketelhohn,

I think we should stay with the English language.

As I told you yesterday on the phone, Phil Harvey kindly looked into the problem and detected a problem in EXIFtool, which he immediately corrected (see the EXIFtool forum). I made a test and the output of SilverFast HDR both from the original image, scanned by SilverFast Ai 8, and the one tagged with EXIFtool (Windows executable 9.20) and then processed by SilverFast HDR, now look identical and iSRD worked fine. The IRchannel was not destroyed.

So I conclude, that this problem is solved and one can use EXIFtool to tag scanned raw data before processing them with SilverFast HDR.
Thus the statement made in the forum, that one must not edit the metadata of raw images has to be corrected.

However, the bug I reported, that HDR fails to pass on the metadata to the poutput image altogether, was still there as of yesterday, as well as the mis-interpretation of the "by-line title" tag in the IPTC part of SilverFast. This tag does not hold the title of the image but the title of the photographer (like Dr.).

Sincerely yours

Hermann-Josef Röser

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Re: Format of HDRi-images

Postby LSI_Ketelhohn » Tue Feb 26, 2013 5:25 pm

Dear Mr Röser,

O.K. I just wanted to make sure.

I have forwarded the issue rgarding the Metadata in HDR to our developers.
This has not been fixed so far.
I will also check about the titel tag.

kind regards,
Arne Ketelhohn.


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