Image quality (sharpness)

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  • romullus
    3Dflower
    • Jan 2019
    • 6

    Image quality (sharpness)

    Hi,
    New member and Zephyr free version user here. I'm relatively new to photogrametry world, although i have read and watched few tutorials here and there, so i know basic concepts. Recently i did small photogrametry exercise, i did shoot small figurine on a turntable with a camera on tripod on manual settings. Pictures came out in good quality, so i was expecting no issues from Zephyr. And indeed, apart the fact that i had to mask every image, Zephyr did a good job with the set (i used default settings and presets). Mesh was good, but somehow i felt that there isn't enough details in it. I thought - maybe my pictures aren't good enough? Then i noticed image quality index utility and decided to check the pictures in it. I got score from 0.05 to 0.01 for my set. That didn't seem like very big numbers, but i din't know what value is considered a good score, so i googled a bit and found that people are getting scores in range of 1's and 2's. My score clearly leaves alot to be desired. But my photos aren't blurry or featurless. I shot to RAW and feed ORF files directly to Zephyr without processing them. Then simply for comparison, i loaded one file into lightroom and exported it at default settings to TIFF. That image achieved 0.5 score in quality index utility, that's a order of magnitude improvement! How's that can be? I used default settings without additional sharpenning. Next i sharpened that photo in lightroom quite a bit (amount - 75, radius - 2) and there was another huge improvement in quality - score of 1.6! From tutorials i had impression that sharpening for photogrametry is not desirable, as it can introduce unwanted noise, but Zephyr utility tells another story. Could someone shed the light on this matter? Does using unprocessed RAW photos, is a bad idea? Do i need sharpen images when processing them? If so, then by how much?

    Here's a link to one RAW photo from my photoset, if that helps: https://www.dropbox.com/s/jfutdjf4o7...13710.ORF?dl=0
  • Andrea Alessi
    3Dflow Staff
    • Oct 2013
    • 1304

    #2
    Hi romullus,

    welcome to the forum!

    The quality index is just a relative tool - you should use it only to compare photos in the same set, to quickly see what are the potential best and worse.

    A 1.0 in a dataset might be much, much worse, than a 0.1 in another set - all scores are relative and does not mean that a low score is a bad photo

    When you're dealing with few images, it isn't probably that much useful - you can just browse your photos and notice which are blurry and quickly discard them. On the other hand, when you have dataset composed by 2000-3000 photos, that tool becomes a little more helpful in identifying possible problems.

    I wouldn't worry too much - the image looks good and you're correct - it's better to not modify the images when possible (although just a little bit of color correction won't hurt).

    Comment

    • romullus
      3Dflower
      • Jan 2019
      • 6

      #3
      Thank you for the answer!

      Comment

      • Robin Grice
        Blossoming 3Dflower
        • May 2023
        • 2

        #4
        Hello.

        I too am a relative newbie to the 3D scanning world and I have also been watching tutorials regarding this subject but so far my project has not benefited much from this information overload!

        My problem is also regarding the low quality figures given by 3DFZ in regard to my numerous sets of images I have tried, nomatter what lighting (indoor and outdoor bright n cloudy) I use, or which of five cameras I use (2 old dslr and 3 mobile phone) I still struggle to get above 0.09*** and, although they look pretty good to the eye, ?when the photos are process through 3DFZ they are mostly unuseable due to the low index no.

        I have enclosed a pic of the object I'm trying to scan, is it possible that it is just an impossible item to scan?. I have taken '000's of photos, and have achieved some sucsess but nowhere near the quality I need to be able to export as an STL for printing.

        I'm using the standard settings so as to keep things as simple as possible but now after a couple of weeks trying I'm starting to think this thing is not going to scan.

        Any tips would be greatly apreciated!

        Robin.

        Comment

        • cam3d
          3Dflover
          • Sep 2017
          • 661

          #5
          Hi Robin Grice - Welcome to the forum :-)

          It's not impossible to scan subjects like this, but they are inherently difficult to processing using photogrammetry as they have homogeneous smooth surfaces with very few features to match from image to image.

          Try a light sprinkling of talcum powder or similar to add a ton of random small features to help with the camera matching and ultimately improve the end result.

          For professional applications I'd recommend looking into a product like AESUB which sublimates (minimal cleanup).

          Comment

          • Robin Grice
            Blossoming 3Dflower
            • May 2023
            • 2

            #6
            Thanks cam3d

            Tried painting it matt white, grey, black and now filler primer, also tried talcum powder still nothing I will battle on, I will not be beaten.

            Comment

            • cam3d
              3Dflover
              • Sep 2017
              • 661

              #7
              Originally posted by Robin Grice
              Thanks cam3d

              Tried painting it matt white, grey, black and now filler primer, also tried talcum powder still nothing I will battle on, I will not be beaten.

              Happy to review your images if you send them to support@3dflow.net - Google Drive folder or WeTransfer link work well for sending lots of image files :-)

              Comment

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