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Thread: Loupe project -- cheap and easy for the handy and thrifty

  1. #1

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    Loupe project -- cheap and easy for the handy and thrifty

    Loupes are expensive and very personal. Every “Which loupe should I buy” thread contains a huge range of options. A good loupe is an essential tool, so by all means splash out lots of money if you like. I tried a Toyo 4x loupe, which is highly recommended, and wasn’t happy. After that experience, I wanted to avoid the cycle of “buy, try, sell, buy again”, so I decided to make my own.

    If you search for “loupe” in the DIY forum you’ll find a few threads that describe ways you can make your own loupe.

    In this thread, I explain how to use a pair of inexpensive lenses to build a "roll-up" loupe. This is a difference approach than other threads, which fit lenses inside tubes. The final product is bright, clear, and sharp from side-to-side. It’s also cheap and very easy to make. It took me a bit over 90 minutes to put this one together because I was making pictures for this thread as I went.

    Click image for larger version. 

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    MATERIALS

    You’ll need the following to make this loupe:

    1. A pair of cemented achromatic doublet lenses from Surplus Shed. Of course you can use whatever lenses you want, but these instructions assume these ones. They’re $7.50 each. I found that two together gave me about 4x magnification in a nice long tube. Here’s the link: https://www.surplusshed.com/pages/item/%20L13517.html (Thanks to forum member Paul Kinzer who pointed me to these.)

    2. Two plastic report covers or section dividers. You probably have these on a shelf somewhere in your house already… If you don’t, you can get them for pennies at your office supply store. Make sure one is the colour you want your finished loupe to be.

    3. Good quality, thin two-sided tape. I used a 3M product. You can also use contact cement or another adhesive, but that’s messier and the tape works fine.

    4. (a) self-adhesive telescope flocking from Edmunds Scientific, or (b) some other matte black material you can glue to the plastic. I had a sheet of the telescope flocking material on hand already so I used that. A piece of black cloth would have worked too. If you want to buy the self-adheisve flocking material, it's relatively inexpensive and you'll have enough to start a loupe-making business! https://www.edmundoptics.com/p/55-20...k-paper/11273/

    5. Heavy duty tape like Gorilla Tape (a kind of duct tape). Anything similar will do.

    6. Ring, hook and lanyard.

    7. Tie wrap in the colour of your choice.

  2. #2

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    PROCEDURE

    1. Cut the plastic report covers into two strips 13.5 cm wide. Leave them the length of the material (mine were sized to 8.5” x 11” – so 11” long). One will be inner and one outer; in the picture, below, I started with a gray one for the inside.

    2. Cut the flocking material to 13.5 cm by 12 cm.

    Click image for larger version. 

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    3. Attach the flocking material to one end of the inner plastic sheet. In the picture you can see it attached to the end. If you use the telescope flocking material, it’s peel and stick. If you use a piece of black fabric, you can stick it down with the two-sided tape.

    Click image for larger version. 

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    4. Use strips of the double-sided tape to cover the exposed plastic end. Start at the edge opposite the flocking material and work towards it. It’s important that you start right at the edge so that the tube stays together better when you roll it up.

    Click image for larger version. 

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    Click image for larger version. 

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  3. #3

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    5. Stick a piece of the double-sided tape across the flocking material with the edge 75mm from what will be side of the loupe against the ground glass. In this picture the eye side is on the left and the ground glass side is on the right. This picture actually shows my first attempt. Notice how the tape is wider than the width of the two lenses together. You don’t want that because the tape sticks out messily when you’re done.

    Click image for larger version. 

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    6. Remove the paper from the tape and carefully position your lenses. In this picture I’ve trimmed the tape so that it doesn’t go past the edge of the left-hand lens. I positioned the right-hand lens first on the very edge of the tape, and then lined up the second lens leaving a tiny gap between them. Make sure the lens are lined up parallel to what will be the top and bottom of the loupe, and to each other. (You can do this by eye – they’re quite forgiving of slight misalignment.) I found it important to have the lenses oriented the same way. In my loupe, the thin part of each cement doublet is on the ground glass side of the loupe.

    Click image for larger version. 

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    7. Now for the tricky part: you have to roll the plastic around the lenses without moving them out of position. And you have to ensure that when you get all the way around the lenses, they’re snug and tight in the tube you’ve formed, and that you’ve lined up the edges of the plastic so it rolls neatly.

    Click image for larger version. 

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    If you did it properly you’ll have a nice tight tube with the lenses lined up straight inside. This is the time to check!

    EDIT (Corrected information for focus testing): Test it out on your ground glass. You need to focus on the grain of the ground glass. Good quality loupes allow for adjustments. Your home made loupe will not. If the grain never comes sharply into focus even when you pull it off the glass a bit, then it's a bit long and you'll have to trim a bit off. Make very small adjustments! If you achieve focus on the ground glass grain by pull it back from the glass, then it's too short. One easy solution that allows for future adjustments is to make a small collar out of a 1" wide strip of the plastic sheet. Mount this collar snugly on the bottom of the too-short loupe and slide it out until you get the ground glass grain in sharp focus. Tape it down rather than gluing so that you can make adjustments in future.

    Importantly, the length of the loupe (13.5 cm) is based on my preferences. It’s probably going to be fine because my eyes are “correct” when I wear my glasses.

    Click image for larger version. 

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    Last edited by rdeloe; 20-Apr-2019 at 19:39. Reason: Corrected focus testing information

  4. #4

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    8. With one sheet of plastic report cover material, the tube is too soft for my taste. It will deform if squished. To strengthen your loupe, add one more layer of report cover plastic. I used black. Cover the whole sheet with double-sided tape and roll your loupe over it. Be careful to line the loupe up very precisely before you start rolling.

    Click image for larger version. 

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    9. The double-sided tape I used wasn’t strong enough on its own to hold the seam down, so I finished off the loupe by running a strip of Gorilla Tape up the seam, and then wrapping each end with two layers of Gorilla Tape.

    Click image for larger version. 

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    10. There are lots of ways to hang the loupe around your neck. I went with simple and cheap. I used a name badge lanyard, a key ring, and a tie wrap to hold it all together.

    Click image for larger version. 

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  5. #5

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    Neat project! Well illustrated and explained.
    Philip U.

    Sine scientia ars nihil est. (Without science/knowledge, art is nothing.)
    https://www.flickr.com/photos/156933346@N07/

  6. #6

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    So, is your loupe properly focused on the grain side of the gg or on the top side of the gg?

  7. #7

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    Quote Originally Posted by Bob Salomon View Post
    So, is your loupe properly focused on the grain side of the gg or on the top side of the gg?
    Crap! Excellent catch -- I forgot to take that into account. Thanks Bob.

    Someone help me with my testing methodology please.

    I have a negative of a high resolution test chart. It's extremely detailed and properly focused.

    Would this approach let me make the needed adjustments?

    1. Tape the negative to the inside of the ground glass, with the emulsion facing towards the lens (so non-emulsion side is against the inside of the ground glass.
    2. Place a bright light in front of the camera (with no lens mounted -- so light is just for ease of viewing)
    3. Check for focus with the loupe.

    At the 75mm position described above, I'm definitely focusing on the front of the ground glass (oops). I flipped the loupe around so that I had room to move it back and forth and find focus. It looks like I just need to trim a bit off and I'll be focusing on the correct location. Does that sound correct? If so, I'll fix it and correct the original posts.

  8. #8

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    Quote Originally Posted by rdeloe View Post
    Crap! Excellent catch -- I forgot to take that into account. Thanks Bob.

    Someone help me with my testing methodology please.

    I have a negative of a high resolution test chart. It's extremely detailed and properly focused.

    Would this approach let me make the needed adjustments?

    1. Tape the negative to the inside of the ground glass, with the emulsion facing towards the lens (so non-emulsion side is against the inside of the ground glass.
    2. Place a bright light in front of the camera (with no lens mounted -- so light is just for ease of viewing)
    3. Check for focus with the loupe.

    At the 75mm position described above, I'm definitely focusing on the front of the ground glass (oops). I flipped the loupe around so that I had room to move it back and forth and find focus. It looks like I just need to trim a bit off and I'll be focusing on the correct location. Does that sound correct? If so, I'll fix it and correct the original posts.
    No, you take your lens off the camera, point the camera at any light source, adjust the position of the loupe till the grain of the gg is sharp.

    Then your loupe is focused on the grain of the gg and that position won’t change unless you change your gg or add a fresnel to the eye side of your gg.

    This is why adjustable eyepiece loupes are preferred for critical focusing.

    If you don’t do this then you will be out of focus by the position of the loupe to the grain side of the gg.

    If you have an asymmetric lens system then your loupe will be in focus from edge to edge, if not there will be a slight change from center to edge.

  9. #9

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    Quote Originally Posted by Bob Salomon View Post
    No, you take your lens off the camera, point the camera at any light source, adjust the position of the loupe till the grain of the gg is sharp.

    Then your loupe is focused on the grain of the gg and that position won’t change unless you change your gg or add a fresnel to the eye side of your gg.

    This is why adjustable eyepiece loupes are preferred for critical focusing.

    If you don’t do this then you will be out of focus by the position of the loupe to the grain side of the gg.

    If you have an asymmetric lens system then your loupe will be in focus from edge to edge, if not there will be a slight change from center to edge.

    I have a Fresnel lens installed on the inside surface of my ground glass (so lens side, not eye side). I trimmed 1 mm off the front of my loupe and now I'm focusing on the concentric rings in the plastic of the Fresnel lens. It's sharp across the viewing area.

    Adjustable would definitely be nice... but in this "thrifty" approach adjustable means razor blade!

    Thanks again for catching this Bob.

  10. #10

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    Re: Loupe project -- cheap and easy for the handy and thrifty

    Quote Originally Posted by rdeloe View Post
    I have a Fresnel lens installed on the inside surface of my ground glass (so lens side, not eye side). I trimmed 1 mm off the front of my loupe and now I'm focusing on the concentric rings in the plastic of the Fresnel lens. It's sharp across the viewing area.

    Adjustable would definitely be nice... but in this "thrifty" approach adjustable means razor blade!

    Thanks again for catching this Bob.
    You need to be focused on the grain of the gg, not the fresnel rings.

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