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Thread: what grit for ground glass

  1. #21

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    Re: what grit for ground glass

    You are reading Neal Stephenson upside down!

    Definitely a finer grind on the right, though.

    Neil

  2. #22

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    Re: what grit for ground glass

    And if you use Alum Oxide, it would look even better. I have a post somewhere that where I learned to just start with the .0002 Alum Oxide, and that's all you need. It makes a finer screen, with no divots.

  3. #23
    Peter De Smidt's Avatar
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    Re: what grit for ground glass

    I agree with Garrett.
    May tomorrow be a better day.

  4. #24
    Tim Meisburger's Avatar
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    Re: what grit for ground glass

    Okay. I still have not found .0002 aluminum oxide. Is this what I am looking for? https://www.willbell.com/ShoppingCar...M_Supplies.htm

  5. #25
    Peter De Smidt's Avatar
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    Re: what grit for ground glass

    It should be fine. I use this: #591-021 at http://www.lortone.com/abrasives_polish.html
    May tomorrow be a better day.

  6. #26
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    Re: what grit for ground glass

    I have heard that finer grinds reduce graininess, but also decrease brightness and increase apparent fall-off, but I haven't seen any disadvantage to the finer abrasives yet.

    If I can find them I will try installing the cheap page magnifier fresnels I bought too.
    Science is what we understand well enough to explain to a computer. Art is everything else we do.
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  7. #27
    Tin Can's Avatar
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    Re: what grit for ground glass

    Quote Originally Posted by goamules View Post
    And if you use Alum Oxide, it would look even better. I have a post somewhere that where I learned to just start with the .0002 Alum Oxide, and that's all you need. It makes a finer screen, with no divots.
    Ok, I eat Crow again! Tasty.

    I made an 11x14 GG last night using Garrett's way and used 3 micron aluminum oxide that Peter gave me. One step on Home Depot framing glass. Then I held it up next to my 2 year old 11x14 DIY GG on the same glass, but made with 2 steps of 320 then 500. !!!! I need a way to test this. I don't 'see' a huge difference, but I was tired late last night with bad light.

    Both methods took about the same time, One movie. So Garrett is correct that one step with the finest, which is darn fine, like soft mud, is all that is needed.

    This chart is handy. http://stellafane.org/tm/atm/mirror-...20Size%20Table


    So I propose using 51 USAF target under good light in a dark room, interchange the GG, take a look see and take spot meter readings.

    Any better suggestions for testing and comparing GG?



    Scratching my fingernail across both felt very similar. Too similar!
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    focus


    In Time

  8. #28
    Peter De Smidt's Avatar
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    Re: what grit for ground glass

    Did you use a loupe, and, if so, what power?
    May tomorrow be a better day.

  9. #29
    Tin Can's Avatar
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    Re: what grit for ground glass

    Quote Originally Posted by Peter De Smidt View Post
    Did you use a loupe, and, if so, what power?
    Not yet, that is for tonight during the rain.

    As soon as I finish breakfast, I am out into the Sun and shooting 35mm.
    Images vastly preferred

    not game trying to


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    In Time

  10. #30
    Tin Can's Avatar
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    Re: what grit for ground glass

    First is 2 step 320-500 grit. Second is one step 3 Micron. Second is one stop brighter as measured by Sekonic spot meter.

    Ipod shots of 11X14 GG of USAF '51 at 1 to 1 with 10X loupe focus of Nikkor 610mm at f22. Unfortunately the flash fired and made both exposures the same. I am not redoing it. Check exif and notice flash off glass.

    I prefer the new finer 3 micron grind.

    GG by moe.randy, on Flickr Untitled by moe.randy, on Flickr
    Images vastly preferred

    not game trying to


    focus


    In Time

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