1870 RPD-002 S8

1870 RPD-002 S8 2015-01-13T18:29:52+00:00
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  • DVCollectorDVCollector
    Moderator
    Post count: 103
    #6331 |

    I did a focus-stacked shot of this variety so I could generate a new 3D simulation for study.

    First, the stacked photo. The coin was shot at an angle to the lens to capture a lot of depth map data (cropped down from the original)

    1870 RPD-002

    From the focus-stacking, I generated a depth map and a 3D simulation. I think 3D is a really interesting way to study all the MPDs in the denticles. I think it’s the first time it’s been done for this variety. 🙂 Interesting to see how much the fields of the die shifted along that break.

    Note: the distortion along the edges of the video is due to scaling changes between focus steps. It could be cleaned up in post-processing if you wanted to spend the time.


    • This topic was modified 2 years, 9 months ago by DVCollector DVCollector.
    RussRuss
    Keymaster
    Post count: 117

    Damn, that is sick. Very awesome! Are you shooting strait on, with the coin face parallel to the lens? Does it create a better image map if you photograph the coin at an angle, facing the light source for an axial lighting effect? Just curious.


    Collecting Flying Eagle and Indian Head pennies never made more cents!

    DVCollectorDVCollector
    Moderator
    Post count: 103

    Thanks, yeah–I’m pretty darn pleased with the results. I think I see relief in the denticles and MPDs as the coin is turned.

    This was sorta an accident from shooting with my lighting technique, but I noticed an improvement in relief doing it this way. IHCs have such low relief that normally only a few focus steps would capture much relief at all. But, when you angle the coin, you are effectively spreading the details of the coin over a greater amount of steps, so more detail is captured. You take more shots, but you also collect more relief data–a rough diagram of what’s happening.

    flat coin vs. angled coin in focus steps


    • This reply was modified 2 years, 9 months ago by DVCollector DVCollector.
    RussRuss
    Keymaster
    Post count: 117

    Righteous! the camera is actually capturing more surface area. Cool diagram that is very helpful. Is the tilt usually 45 degrees?


    Collecting Flying Eagle and Indian Head pennies never made more cents!

    DVCollectorDVCollector
    Moderator
    Post count: 103

    More surface area–good way to put it! 🙂 The diagram is exaggerated to make it clearer. It’s more like 15-30 degrees, depending on the coin. Lower relief coins can take a steeper angle/more steps because of less distortion. The steeper you go, the more you’re focusing on detail on one side. Which is why I’ll tilt the most interesting side of the coin towards the lens, such as doubling of an RPD or denticles for an MPD.


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