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I am working on my bachelors thesis, where one part of it is to find width of vein in fingertip. I use database images and extract vein patterns from it, but i have to calculate the width of vein and I have no comparison of how many pixels in pic refers to how many milimeters in real.

I would like to ask how wide is the vein approximately in fingertip or in finger.

Thanks a lot, it would be really helpful.

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Here is an image. My best guess is its in the order of 1-3mm. The challenge you face is, absent any other features that provide scale, you don't know the size of each hand in those stock images. So you have two (too many) variables..(i) hand/finger size and (ii) vein width as a proportion of finger size. I don't see how it can be done. Imho, safest would be to image your classmates hands, beside a scale, and choose illumination that shows veins. –  PlaysDice Apr 20 at 14:26
    
"Database images". Provided these were acquired systematically in a lab using fixed imaging conditions (eg camera distance) then you can stick with pixels as your size unit for computation. If you have access to the imaging setup, go ahead and image a scale. I'd also just make a plot of your complete dataset for finger length and width and look for a 'biological' -type distribution without skew or bumps. And the image files themselves may have camera meta-data such as aperture and exposure, also useful for quality assurance. But images without scale, not ideal, for sure... –  PlaysDice Apr 20 at 14:51
    
Thank you for your answer @PlaysDice.Unfortunately, I dont have access to image setup or the sensor, I used the database I found on the internet.Neither I have device capable of providing images link.I tried to build one, but didnt have proper LEDs(couldnt shine through the finger with my LEDs). My results are between 1.2mm to 1.8mm and i used my finger as ethalon taken as normal image from approx. same heigh as in databse. Its not as good as it could be, but didnt come up with anything better. Thx for post –  Daniel Javorský Apr 20 at 19:28
    
Venous anatomy is highly variable from the start, there will also be changes with age and activity - I think this will b to calculate –  Rory M Apr 20 at 22:10

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