Looking for a new microscope
- This topic has 17 replies, 6 voices, and was last updated 04/13/2018 at 9:07 pm by
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Hi Mark, I think you mean Depth of Field rather than depth of focus (see: https://www.videomaker.com/article/d2/13086-the-difference-between-depth-of-field-and-depth-of-focus they define the practical aspects of these terms like this: “In common English, Depth of Field is what the photographer is interested in; it is what is in acceptable focus in front of the lens. Depth of Focus is what only a technician is interested in; it is what is in focus behind the rear lens element which the film or image sensor “sees.” ”
At 200x, the DOF is going to be very small (a fraction of a mm) no matter which microscope you’d choose. You can do focus stacking (where you have a 3rd-party software package combine multiple images that are incrementally focused at deeper depths). Or some of the Dino-Lite models have built-in “EDOF” (extended depth of field). Dino-lite has videos on how that works and what it does for the image.
While you’re looking at Dino-Lite videos, some models also have a polarizer function (to reduce reflections from reflective objects) and an extended dynamic range function. They have videos showing how those work. I’ve found them to be useful for photos of knives and stones.
I didn’t find anything besides some of the Dino-Lite line of microscopes that have these functions. They charge quite a premium for them, but when there aren’t any other choices, I guess they can charge what they want.
One nice thing I just tried out with my Dino-Lite is that they have an Android app (no cost) where you can plug the microscope directly into your Android smartphone and get a live display on your smartphone screen, and you can take still images and video. That will probably be more convenient that having to have a laptop computer near your sharpening rig if you want to look at the knife edges and scratch patterns while sharpening.
The DinoCapture software that you install on a Windows PC has more features (including measurements) than the Android viewing software.
I don’t think there’s a way to get accurate depth measurements (especially minuscule things like the depth of scratches), but with the EDOF models you can get ballpark figures as shown in this video: https://www.youtube.com/watch?v=cje-m6Ib_PY
I’m not sure what you mean re: dual axis microscopes.
Dino-lite also has a model (for more money of course) that allows you to control which of the built-in LEDs are lit up. I can definitely see where that would be useful, since it would give you more “knobs” to adjust as you try to minimize overexposed areas while you are simultaneously displaying something that is exposed with just the right lighting (for example, in 200x photos of diamond stones).
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In all seriousness, for the beginner just starting to use a USB Microscope these two are good entry level devices:
Carson eFlex and the Plugable 2.0
Marc
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I have purchased 5 or 6 different scopes over the last several years. I think the most I spent was still <$100. I continue to use the first model I ever purchased and it’s my favorite still; Plugable 2.0. It is described as 60x up to 250X. I have no way or desire to really prove or disprove the magnification.
I prefer to use it set at high power. Others, in particular, TCMeyer, says he works with low power. The lower power gives a broader wider view with less detail. Whereas, high power gives me a pretty detailed but small field of view. I usually spot check along the knife edge at 5 or 6 positions and the tip, then switch around to the opposite knife side, and repeat. I hold the scope’s plastic shroud flat on the knife bevel then focus the outer ring to obtain a sharply focused image. I then applied masking tape over the focus knob to hold it in place. Then as I move along the blade I keep the USB scope steady with light physical contact against the side of the blade. If the image is slightly out of focus I can sharpen up the image by ever so slightly rocking the shroud up/down or side/to side against the knife. Over time and with experience I have set the focus ring to the position that best allows for the use of this method. I have adjusted the LED light brightness to a level I found works best for almost every situation.
From the recommendation of TCMeyer I purchase a silicone slippery tape that I have applied to the scopes plastic shroud to allow it to more easily slide along the knife’s blade. The thickness of the tape was allowed for to get proper focus of the knife’s bevel as the scope rests on the knife. Also I clean off the scopes edge and the tape where it contacts the steel to limit any possible scratches by sharpening debris.
I almost always view the knife’s bevel from the side. Once in a while I will view straight down on the knife edge. I have learned through time and experience how the scratch pattern appears when I have apexed the edge. That is when I have the bevel angle carried straight and evenly from the knife’s shoulder to the knife’s edge. This allows me to sharpen a knife without the need to create a large burr detectable by finger touch. It may save some blade metal over the life of the knife.
By visually monitoring the scratch pattern I am able to see exactly how finger placement, position and pressure on the plastic paddles affects how the stones abrade the steel. It has removed a lot of the guess work and stroke counting from the sharpening process. I use the scope strictly qualitatively. That is just to monitor the quality of my work. I only looking for the presence or absence of scratches and their consistency and direction. I don’t use it quantitatively, that is to measure scratches or scratch length or depth.
I work with a moderate powered small laptop, always on, with the scope software open and on. Before I start sharpening, using Windows OS, I create a folder tree for the sharpening process for the knife I’m working on, in the drive placement of my preference. This allows me to assign photos to their designated grit folder for future reference, as I take the photos along the grit progression. For example the folder tree will be titled by knife with recognizable description:
Main folder: (e.g., Shun Santoku 7″ VG-10), inside this folder I create and save a “Note pad” or “word pad” doc. with descriptive clamping position settings, bevel angle, key depth setting, and any other more descriptive information needed to replicate the edge.
Also in the main folder I’ll have photo, jpeg, folders labeled: (before sharpening- (initial inspection USB Mscope shots)), (100 grit D), (200 grit D), (400 grit D), (600 grit D), (8oo grit D), (1000 grit D), (1500 grit D), (4µ strop), then (2µ strop).
As I follow this process I designate through the USB Microscope software to save the jpegs to their proper labeled folder according to where I am in the progression. This allows me to keep everything sorted so I can tell by the photos taken during visual inspection during the sharpening process just when I first observed a situation needing attention. Of course the folder tree is specific for each specific knife depending on the process and stones used; diamond, Shaptons, diamond lapping film, strops, whatever. It took a little getting use to the organizing but now I have “template folder trees” of my three most common progressions, to copy and paste to speed up the organization process.
I do not take a photo every step-of-the-way along the sharpening process. I mostly visually inspect my work, in-real-time, like watching a TV. I do snap photos by depressing the scopes shoot button at various positions along the knife’s blade, heel and tip, several times during each grits progress to document the changes and save the results of a finished scratch pattern ready to move on to the next grit.
Marc
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My 5MP Celestron only does approximately 50X and 157X, using the face of the clear plastic shroud as the focal plane. My first USB ‘scope was supposed to do 800X, but I never got more than about 400X when in hand-held mode, and it really wasn’t workable then, as the DOF was so short it drove me nuts trying to get a clear image. This is still a problem with my Celestron at 157X. My main use for a ‘scope is to slide along the edge, checking for damage or a fine apex. At the higher magnification, you can’t really do that, as the point of focus jumps around way too much, so for 99.8% of my usage, it’s at 50X and works just fine.
Am I wrong, or is EDOF capability really only usable in image capture mode and not in real-time video? So you have to take a series of images of the same position, then process those images to extract one composite image? Doesn’t sound workable in hand-held mode. Or is it?
I use the higher magnification only when I really need to examine the very edge for roughness – probably only when I want something better than HHT2. Even then, I’ll immediately roll it back down to 50X as soon as I’ve seen what I want. I’d avoid magnifications higher than 200X, unless I intended to use it frequently with the ‘scope mounted on a solid stand with a fine focus adjustment that doesn’t disturb the ‘scope’s internal setting.
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Mark76: Here’s a photo at 165x of a pencil lead sharpened with a knife (no EDOF, no EDR):
Note that only the highest spot is in focus. And here’s the same still image with EDR:
Next, I did EDOF at 4 focus levels. Here’s the sequence of images with a focus that moves down in depth:
And this is the composite image the dino-lite created by merging the above 4 images:
Just to give you some idea of the depth of field at 165x and that it took 4 images to construct one that had the full pencil tip reasonably in focus. This narrow depth of field at higher magnification isn’t particular to the dino-lite and it holds for all these microscopes.
…and here’s a knife edge using EDOF. This is I think at around 150x magnification, after using Trizact A35 and A20 (I bought some aluminum blanks and cut some self-adhesive Trizact sheets to fit on the WE blanks).
In this case I only needed 2 levels of EDOF to focus the blade edge and body:
And here’s the combined image of the above 2:
But keep in mind I just got this microscope, so I hope I’m using this EDOF and the various other settings to their best extent. The dino-lite website videos will give a better idea of what someone who actually knows what they are doing can achieve ;o).
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