Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

0.9.9.2: Input File Type Correlated to Output Image Quality?

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univurshul
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0.9.9.2: Input File Type Correlated to Output Image Quality?

Post by univurshul » 30 Oct 2010, 19:55

After some testing, I've discovered that the input file-type is correlated (a direct result) to the image quality of the output TIFF.

For example, after exporting a RAW file from my image editor as an uncompressed TIFF for input to Scan Tailor, I noticed that is was noticeably less quality/resolution/detail than a basic JPEG-export (same image).

Not only did the JPEG process better in terms of detail/quality, it processed faster within Scan Tailor. (Important: all settings were identical when processed within Scan Tailor).

So, if one input file-type works better than another in Scan Tailor, which one works the very best?

Possibly someone can expand on why this is so. (I will post some examples later this evening.)

Tulon
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Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by Tulon » 30 Oct 2010, 20:19

Might be a DPI issue. There is a check box in the New Project dialog to force Scan Tailor into DPI fixing mode. You can check if they are the same in both cases.

Slower processing is expected, as it just takes longer to load a huge uncompressed image, though quality degradation is not.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

univurshul
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Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by univurshul » 30 Oct 2010, 20:23

Yeah, DPI was manually fixed at 180x180 for every file-type in a single project.

When I get back to my lab tonight I'll illustrate what I'm seeing. It's quite interesting. I have 3 separate image editors as well; I will double check one app isn't generating low quality TIFFs when it specifies it's fully uncompressed.

univurshul
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Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by univurshul » 31 Oct 2010, 00:51

It appears the issue is not Scan Tailor--it is a problem with the output feature of a particular image editor as noted below:
1.jpg
1.jpg (96.12 KiB) Viewed 4049 times
While I tested these different image-types within a single project, it appears ST auto-fields picture zones more accurately with properly exported TIFF files vs. other file formats:
2.jpg
2.jpg (72.95 KiB) Viewed 4049 times
I haven't placed any of the output images under a loupe because I can conclude that the fundamentals of large TIFF files still apply.

univurshul
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Joined: 04 Mar 2014, 00:53

Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by univurshul » 31 Oct 2010, 12:05

Tulon, I did have a question for you:

Scan Tailor output TIFFs are always 8 bit depth.

(All screens only use 8bit output, whether you set it to 8bit or 16bit. Almost all printers use 8bit output, whether you set it to 8bit or 16bit.)

Is there any benefit to export 16 bit images for input into Scan Tailor? Would a higher bit TIFF sent into ST render better results or is this unnecessary?

Tulon
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Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by Tulon » 31 Oct 2010, 12:22

univurshul wrote:Scan Tailor output TIFFs are always 8 bit depth.
Not entirely true. For B/W output mode it's 1 bit, for other modes it's either 8, 24 or even 32 bits if the original image had colors or maybe even transparency. It never goes beyond 8 bit per channel though.
univurshul wrote:Is there any benefit to export 16 bit images for input into Scan Tailor? Would a higher bit TIFF sent into ST render better results or is this unnecessary?
There is no benefit. As all internal processing is done in 8 bits per channel, the very first thing that's done to an input image is converting it to that format.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

univurshul
Posts: 496
Joined: 04 Mar 2014, 00:53

Re: 0.9.9.2: Input File Type Correlated to Output Image Qual

Post by univurshul » 31 Oct 2010, 12:24

Thanks. --Excellent to keep in mind.

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