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  1. #31
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    Quote Originally Posted by justonething View Post
    Interested in knowing more about this but have no idea the scopes that you're referring to are what I was think about.
    So I'll just include 2 different types of scopes from Amazon and seeking some opinions
    1.Amazon.com
    2. Amazon.com
    Your evaluation would be most welcome.
    40x is enough to be helpful (on the second of those - the dissection scope - it'll certainly tell you what stone is actually polishing vs. not. E.g., I was able to use a 25x dissection scope to tell that a japanese waterstone sold here by a retailer wasn't as fine as the retailer said - it left a very visible scratch pattern that looked like a polish to the naked eye, but was well short of higher end synthetic stones under the dissection scope).

    But it'll fall short if you're comparing fine stones to each other and trying to establish a process, or if you get into something like sharpening razors. What would be interesting with a setup like that is an adapter to use a digital phone, as you could use a high resolution picture to make 25x or 40x look like 100-150. I've tried hovering my camera over the eyepiece on my dissection scope but it's too much to coordinate.

    The first scope looks like a blinged up $20 scope. IT may actually work well, but I don't have experience with that type. The screen and setup could be handy in-shop - I can use my metallurgical scope standalone, but it needs to be hooked to a computer to record pictures, so I can't keep it in the shop (I grind metal in the shop, so leaving it there would be out, anyway). I can't really offer any advice on whether or not that setup is worth the extra money over just getting a hand held scope and the stand, though. If it works at all, I'm sure it would see everything you need to see, but at very very close viewing, it'll be hard to adjust an item (e.g., if you're trying to move the edge to the center of an image, it'll be far easier to knock the edge off of the image one way or another).

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  3. #32
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    Quote Originally Posted by D.W. View Post
    I don't know what the max res is - it's either 3mp or 5mp - the scope doesn't say anything on it, but I use 1920x1080 as the default res. It's plenty big enough...
    OK, if 2MP with the right CMOS matrix configuration can give 1920x1080 resolution, 3MP to 5MP units should be more than adequate, at least at the CMOS end of the setup. But, if the optical components in the scope are inadequate the CMOS will just be capturing more blurry detail beyond the optical capacity of the scope.

    If a good human eye can see detail down to 200μm, unaided, it is assumed that the magnification needed to see 1μm is 200x. By my calculations, my two digital scopes top out at optical 120x and 125x, respectively. The 75μm wide line calibration line shown in my #26 post confirms that I would need about twice the optical magnification that I have in those scopes to see what is happening at 1μm resolution. I think the CMOS on my two scopes (one is at least 5MP) have more than enough sensors to capture a higher resolution image beyond what their optics can deliver to them. The digital zoom function adds nothing by way of usable higher resolution, at least on mine.

    As with most consumer electronic componentry, the cost of MP is coming down and the power is going up, as we have seen with the cameras in mobile phones. I expect the cost/performance curve on the optical components flattened out a long time ago and is the limiting factor in these consumer scopes.

    The fact that the lower end scopes don't quote a micron resolution, unlike the more expensive scopes do, probably indicates that it is the more expensive optical components that deliver that higher performance.

    Having come to that conclusion, I'm not about to lash out and upgrade to anything with a better resolution. What I currently have meets most of my needs, which primarily relates to woodturning where we don't grind/polish anywhere near where a higher resolution might be significant. Although, I may do some experimenting there, as I'm prone to do.

    If I was to ever do any upgrading it would probably be to add a digital eye piece and associated image capture to one of my microscopes of known optical quality.

    A higher resolution would be an advantage with my Japanese knives, but I settled on what works for me there a long time ago.
    Stay sharp and stay safe!

    Neil



  4. #33
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    As an alternative to loupes in the lower mag range, these new mobile phone attachments could be an option. Here are a few examples currently on you know where...

    313352537105

    383806609221

    363167053914

    Some options offer more magnification than most standard loupes.

    233854761878

    373437190354

    And this one even claims a resolution down to 2μm.

    114166840963

    Whether any of those could be tamed to use as an eye piece on an optical microscope is an interesting question. The focal point on optical scope might be the issue.
    Stay sharp and stay safe!

    Neil



  5. #34
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    Quote Originally Posted by NeilS View Post

    If a good human eye can see detail down to 200μm, unaided, it is assumed that the magnification needed to see 1μm is 200x.
    I was looking for the following information, which had alluded me, but having now found this it looks like I was way off with my 200x.

    "Under a sufficiently high power (500 times magnification), you should be able to measure objects that are approximately 1 micron and greater."

    From:
    How to Measure a Micron

    Hmm.....
    Stay sharp and stay safe!

    Neil



  6. #35
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    Top optical glass and lens technology will always be superior to phone camera lenses for resolution.
    A typical light microscope in a microbiology lab will be equipped with a 100X oil immersion objective lens.
    The oil (n= 1.515) changes the Numerical Aperture such that you can measure distance between bacteria
    in the order of 0.3 microns. That's resolution.
    Together with the common place 10X ocular lenses, that's an honest 1,000X.

    In wood carving, I find that the 10X loupe is adequate for the determination of edge damage, whatever the cause(s).
    More and more, I'm looking for the answer to begin with 600 or to begin with 800?
    I never test cutting hair as I don't as a rule carve hair.
    Instead, I test the result of my sharpening process in the wood being carved.
    I'm confident in my freehand sharpening skills as I can feel it and see the results.
    Sharpen every time to a consistent bevel angle. That matters.

  7. #36
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    Quote Originally Posted by NeilS View Post


    As with most consumer electronic componentry, the cost of MP is coming down and the power is going up, as we have seen with the cameras in mobile phones. I expect the cost/performance curve on the optical components flattened out a long time ago and is the limiting factor in these consumer scopes.

    I've done a bit more searching around for something that I might understand and getting further confirmation that many of the current economy/consumer digital scopes might have the necessary sensor size to capture down to 1 micron, but not the optical power/quality to match that.

    Because I acknowledge DW's expertise on 'sharpness', my search for affordable 1μm digital resolution is based on his advice that a cutting edge needs to go down to that level of abrasion to optimise cutting performance in the context he is applying it to; viz. plane blades, chisels, razors, etc.

    The following article, that is over a decade old now, raises the issue of mismatched sensors and lenses. I expect that this is even more of an issue now.

    ... sensor manufacturers have failed to communicate with lens manufacturers. This has resulted in a mismatch between the advertised sensor resolution and the resolution that is attainable from a sensor/lens combination. To address the problem, lens manufacturers now need to produce lenses that employ higher optical performance, lower f-numbers (f/#s), and significantly tightened manufacturing tolerances so that these lenses can take advantage of new sensors. (bold added to text by me)

    Source: Matching Lenses and Sensors

    I found the term "empty magnification" in an article that had a lot of techy talk in it (don't go there if that is not your thing)... Guidelines for Understanding Magnification in the Modern Digital Microscope Era.

    I think that might summarise what is happening with some economy/consumer digital scopes and is the case with at least the two that I have. They specify an upper magnification level, of which the upper range is empty magnification.

    And, of course, magnification is different from resolution, although the two get muddled up in some promo material. As the above article states, "magnification serves a useful purpose only when the resolution of the microscope makes it possible to see more details of an object".

    Does anyone having a different experience with their economy/consumer digital scope?
    Stay sharp and stay safe!

    Neil



  8. #37
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    I'd like to add based on what I've mentioned earlier I'm not sure that it's necessary to see around 1 micron clearly. The scratches at the tip of my "polished" irons are from 1 micron diamonds working their way around the edge - the graded diamonds are extremely uniform. I don't know if the grooves are actually a micron, but an approximation could be made trying to count them in a blown up picture as the height of the images is a known thing.

    All that said, I tried my dissection scope (supposedly 25x including a 10x eyepiece) with the phone camera and it could be rigged to work, but it fits the comments above - the lenses seem to create empty magnification. I can't really tell what's going on.

    I do think that even if you can't see 1 micron scratches, you can see when something has that uniform polish and nothing visible (even if visible stuff would be blurry).

    So for my purposes (with razors and very fine stone) seeing those tiny scratches clearly allowed me to sell graded japanese stones confidently, but I could've guessed pretty well with less resolution.

    I was surprised that 1 micron patterns performed that much better than coarser edges when it came to wear, though, but I'm guessing how uniformly the apex starts gives a bit of a head start vs. coarser abrasives.

    So, long story short, I hope it doesn't sound like I'm recommending that someone should be able to see 1 micron clearly. Any magnification at all is better than none and even my pukey old scope provides a whole lot of help, even though the image is blurry - we're just looking more for generalities with it.

    I'd love to be able to talk at length about $100 options that will match my metallurgical scope, but I just don't have experience with them. None of this super fineness is really really necessary unless you're sorting out small differences (and hopefully that's only done for some real potential gain).

    Love this topic, though - wish I had better advice middle of the road. The white scope (my trashy one) really taught me a lot just by itself, though, early on. Any time I thought there might be some kind of mystery cause, it was clear enough usually to show me that I just hadn't finished the edge. And that kind of simplicity is valuable, especially when on some forums, all kinds of hokey suggestions are made "that stone is causing deep damage to the edge and causing it to crumble" kinds of things. Sounds fanciful, but it's usually "no, you actually just didn't finish the job" was what I had to say to myself. The number of times that I had an edge actually crumble from coarse abrasives is probably less than half a dozen and I'd imagine I've set up near half a thousand old chisels (the ones that crumble are overhard).

  9. #38
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    Quote Originally Posted by D.W. View Post

    So, long story short, I hope it doesn't sound like I'm recommending that someone should be able to see 1 micron clearly. Any magnification at all is better than none and even my pukey old scope provides a whole lot of help, even though the image is blurry...
    OK, got that, DW. You never recommended the 1 micron resolution, it was me who extrapolated that from your findings on the grit sizes in the honing compounds that gave you the best results.

    You did in an earlier post (#30) indicate the level of resolution that has worked for you...

    Quote Originally Posted by D.W. View Post
    I use 1920x1080 as the default res. It's plenty big enough - as mentioned above, I kind of settled on it just based on what I can see and how much of the edge I can see.
    So, for a 1920x1080 resolution you would need at least a 2MP sensor that is capable of that aspect ratio. I think the challenge is to find adequate optics in an economy digital m-scope that can fully utilise that 2MP.

    Looking for 2MP offerings I came across this one that claims 1920x1080 resolution:

    333870125773

    Some specifications are saying things like; CMOS sensor, 2M pixel (hardware, no interpolation) and Sensor: 2.0 MP (true hardware). I think that interpolation (or digital zoom) is the thing to watch out for in these economy offerings and one of the areas in which 'empty magnification' is happening.

    Here is another specification that might be an indication of digital enhancement that is nothing more than filling up more pixels with less information...
    Specifications:
    Image Sensor: 0.3M CMOS Sensor (Digital 2M)

    So, looking for a resolution of 1920x1080 is a starting point, but also check to see if that resolution is coming from 2MP of 'hardware'. The other way of validating that you are getting a real 2MP of resolution is to see a micron rating, however, I'm only seeing that specification given on higher end digital m-scopes. For example, here is a camera that replaces the eye piece on a standard microscope that specifies its micron resolution, in this case 2.2μm x2.2μm. I don't see many offerings that specify above about 3.4μm, so I'm not sure if that metric is going to be available in economy m-scopes.

    I'm not sure having gone down this rabbit hole I'm coming up anywhere that is both useful and economical for most of us that are regularly sharpening blades!

    Having said that, this thread has had a lot of valuable input from DW on sharpness that we might not have got otherwise. Also, from RV on carving tools. Thanks to both of you.

    Perhaps a more useful level of resolution for most of us is more at the level where we can see that the edge finish is uniform right at the very apex and also intact. I think that is what you have been pointing us at DW.
    I for one have found the increased resolution from an economy digital m-scope beyond what is available from a hand loupe to be invaluable in understanding what is happening with my sharpening.

    At this stage I can't suggest any options that might be better at a reasonable cost, but at least we now have a thread with some information in it that can be added to if anyone comes up with anything new.
    Stay sharp and stay safe!

    Neil



  10. #39
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    Picture size in pixels is not resolution. It is picture size.
    Now with only those pixels, can you see the gap 'd' to discriminate between two objects or are they joined?
    I imagine that 1 pixel? would be visible to provide the correct answer.
    So if 1 pixel = d, in microns, how big is a pixel?

  11. #40
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    Quote Originally Posted by Robson Valley View Post
    Picture size in pixels is not resolution. It is picture size.
    Now with only those pixels, can you see the gap 'd' to discriminate between two objects or are they joined?
    I imagine that 1 pixel? would be visible to provide the correct answer.
    So if 1 pixel = d, in microns, how big is a pixel?
    Not that I understand any of this, RV, but I think it is only in the upper end units where they have sufficient optical/digital power to see any of that they quote a pixel resolution, eg. in the following one where it is 2.2μm x2.2μm.

    373369498491


    One thing I do understand is that magnification is not the same as resolution. I think I quoted from the following article from Cambridge University in an earlier posting.

    "For optical instruments in general, resolution or resolving power is the ability to see fine details in an image. More specifically, resolving power is the ability to distinguish in an image adjacent points or lines of the object that are closely spaced. Sometimes the terms magnification and resolution are used synonymously, but this is incorrect. Only resolution determines the limit of the smallest object that can be resolved. Magnification denotes the size of the resolved object. In light microscopy, resolution is typically expressed in line pairs per millimeter observed when lines of various separations are used as the object. In other words, at a given level of resolution pairs of black and white lines with equal line thickness and spacing can be distinguished. High magnification without sufficient resolution leads to empty magnification."
    Guidelines for Understanding Magnification in the Modern Digital Microscope Era,
    Published online by Cambridge University Press: 06 July 2018.


    The issue with most digital scopes, and especially the economy models, is that they are described by their maximum number of pixels and/or image sizes, but without any indication of their optical resolution.

    The same article above also goes into Useful Magnification for Digital Microscopy that may explain the limitations of the digital sensors on economy m-scopes, ie, if you can get your head around things like Nyquist's sampling theorem. I expect, if I could get my head around stuff like that, the article would be telling me that I couldn't afford an m-scope that could do what I want to do, anyway!
    Stay sharp and stay safe!

    Neil



  12. #41
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    Neil don't be hard on yourself, you do understand this.

    resolution as defined by Abbe' s equation is a distance called 'd'. Practically, wavelength/2 is about all you will get.
    That's the visible separation of two objects such that you can see that they are separate and distinct.
    There are a few things that you can do in the lab to fart around and pick up a little improvement (make 'd' smaller).

    The deal is that the wavelength of a beam of electrons is so much shorter than light photons.
    The Numerical Aperture is the shirts in a vacuum but wavelength makes up for it. So 'd' crawls down to 1 nm or less.

    In other words: are they far enough apart that you can see the gap or not?
    Read about "circles of confusion" in image construction. Jack up the magnification from small and fuzzy to big and fuzzy.
    I left the business long before digital became the fashion. Somehow, 'd' has to be related to the size of a pixel.

  13. #42
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    Quote Originally Posted by Robson Valley View Post

    Read about "circles of confusion"...
    RV, that sounds like a description of my understanding of this topic....

    However, without fully understanding all of the intricacies, I do know that there are m-scopes that can resolve down to the level of detail that provides the required level of feedback on what is happening at the very edge of a blade when it is sharpened and used, BUT few of us could afford one of them, even if we were obsessive enough to want one.

    For example, see the micron level images in the posts in this thread from Wickededge...

    Microscope Test aka the Scope Showdown! – Wicked Edge Precision Knife Sharpener

    But, getting the same performance from an economy digital scope is like trying to get a F1 racing car performance from a stock entry level sedan. The challenge is to find a part-way point that both delivers enough detail to be useful and is affordable.

    The following posting caught my attention in another discussion thread; see post 31...

    USB microscope is a game-changer. | Page 2 | Badger & Blade

    ... in which the author has modified his economy scope, "by increasing the distance between the lens and sensor. This gives a higher magnification but causes loss of lower end magnification".

    I've had a look at my two and both are made of fully sealed moulded plastic with no obvious way of readily pulling them apart to alter, but it would be interesting to experiment with that idea.
    Stay sharp and stay safe!

    Neil



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