HD keychain cam



  • edited January 2013
    Hi David
    I believe the front IR-block coating only applies to the #16 V2-B (it looks red instead of blue)
    To have it removed from the #16D would be amazing and make the camera one of the cheapest archaeological prospection tools.
    The 'no change in focus' should apply to both front and also the rear lens coated versions. I tried to get a professional to remove the rear coating..to no avail. Maybe it is a sealed unit. I have even contacted the supplier...with no response.
  • John, in the video it looks like all the movement is in the "roll" plane, with no pitch or yaw. That would mean the rig is just rolling back and forth around the kite line. Does that sound right?

    What would happen if you put the 808 at the end of the long arm?

  • Fundamental problem for light rigs in KAP is the amount of movement, particularly with a rig as light as this. For such light rigs, slack-lining is a great way to go, you need much less kite and less wind than most. KAPpers are comfortable with. Either that or add a bit more weight to stabilise the rig.
  • edited January 2013
    Hi wayback
    That is correct.
    Theoretically, adding this camera to the long arm should make little difference to the pendulum component of the motion. The camera is light, so it would not significantly move the centre of gravity of the system and therefore change the effective length of the pendulum.
    To increase the natural period of the swing, lengthening the long arm should be the way to go. So, my next attempt will be with a long piece of wire from a coat hanger, as mentioned above, which will also add weight. Adding overall weight to a free moving 'pivot' assembly should increase inertia as pointed out by Simon and a slack line should further dampen movement (although, I must admit, I did not think of doing that - thanks Simon).

    With a light camera like this, a counterbalanced steadicam approach should work too, but for use with kids, I need something very simple.

  • Hi John.

    Removal of any rear IR filter or coating WILL affect focus, that is the law of optics.
    The focus distance will change by about 1/3 the filter thickness.
    For these sorts of cameras that is a tiny amount.
    Whether it is noticeable is another matter.
    In addition, because of the small sensor size and very short focal lengths, the depth-of-field is huge anyway.

    Are you not bothered by the distortions of the 'D' lens or can they be adequately corrected ?
  • edited January 2013
    Seems like you could put a fishing weight on the long end of the tent stake, and leave the camera where it is. Just don't tape the weight to the stake, but put a length of string between the stake and the weight so it dampens any possible pendulum like resonance with the kite string.

    I just got one of these too so maybe I'll post a video as well, off to the camping store!
  • edited January 2013
    Hi David
    You are correct.
    The older version of the 808#16 does not have a rear filter according to the professional that I asked to remove it!
    It is simply a coating on the rear surface of the lens, so removal of the coating should not affect focussing as the thickness should be negligible. I assume that it is coated by vacuum deposition.

    The distortion is marked as with the GoPro:
    Most of this can be quickly removed using the free program GIMP http://getgimp.com/lp/index.php?pk=4769 by sliding the main lens distortion filter slider to the left, via menus:
    Filters > Distorts >Lens Distortion
    There is a rough-and-ready example here on our balloon page:
    Alternatively, you could carefully correct an image of a brick wall (or chart) and apply the corrections to your other images.

    The camera and simple rig are intended for use by kids, so the wide angle is useful for limiting height. The weight and cost also reduce the concerns of their teachers etc. Educationally, older or more able students can try GIMP.
    Despite its limitations, the camera can be useful as a broad sweep auxiliary camera which can also be attached to the main one, when carrying out our archaeological surveys - note the ground detail in the snow image.
    Above all, this simple approach is intended as a hook for those who have not done KAP - once caught, it is easy to move onto better things ;o)
  • edited January 2013
    String theory ;o)
    That is one less technique for me to try!
    I hope that you are having better weather than us.
    We currently have wind gusts of 45mph and rain
  • John, look at first item in Section 4 here :-


    It would seem to be a mechanically and optically suitable lens with no IR coating.

    Too bad you cannot obtain them.

  • edited January 2013
    Hi David, I think that I should try again with Eletoponline to see if they can get an appropriate lens for IR. It should be a simple processes of not coating some in a production batch...unless it is part of an automated line?!

    More on the above tent peg transverse pendulum rig:
    I will be trying a longer coat hanger wire next, as this is what most people will have to hand, or can easily obtain.

    However, if a wire is chosen that is the same diameter as the screw that holds on the legs of a mini-tripod, a thread could be added to the short arm and, with the legs removed, the tripod head can be screwed onto the wire. The thumb wheel of the tripod head can be glued so that it does not turn on its own thread and velcro added to its surface for attaching the camera, albeit upside down.
    If the thread on the wire is long enough, it alone is enough to lock the gimbal into a desired position. The metal mini-tripod heads are the most versatile, as the section with the gimbal notch can be rotated.
  • edited January 2013
    I have been informed that the lens for the 808#16D can be supplied without the IR block coating ;o)
    I have asked for more details in terms of the minimum number that I can order.
    ('There have been a couple of posts about how easy it is to separate the filter from the lens unintentionally if the lens is removed and handled' See: http://www.rcgroups.com/forums/showthread.php?t=1820193). So, possibly not a coating!?

    I then have to find a small R72 IR pass filter, rather than use processed, unexposed transparency film.
    This could mean cheap near infra-red KAP for everyone!

    If the weather forecast holds true, we hope to have flown 808#16D coat hanger cam ver.1 before last light on Friday of this week.
    A soft weight will be added to the end of the long arm.
  • Who did you contact at Eletoponline ?

    I would prefer the 'A' lens for my work.

    I will let you know if the 'B' lens has a filter or coating.

  • Peter (xinrong zhang)
  • We played around with the SD version of these cameras a while ago, perhaps the mounts on the linked page might give someone an idea, providing the kite does not flap too much attaching directly to the kite works well.
  • John, I'd like to revisit how the 808 is suspended from the kite line. In another thread on reducing camera vibrations, or perhaps something similar, someone put forth the idea of using a pendulum-style rig, but instead of increasing the length of the pendulum to reduce its period, you would place a nearly equal weight ABOVE the line. With this method, the period is reduced so much that the camera only follows absolute movements of the line, but almost no pendulum motion is induced.

    So for example, if you mounted the 808 at the end of a wooden yardstick, the balance point of that rig would be moved from the 18-inch point for a bare yardstick down to about 14.25 inches with the 808 mounted. Then you would attach this rig to the kite line at the 15-inch point, with 21 inches of bare yardstick sticking up above the line. It needs to be a little above the balance point so the rig will be biased to hanging vertically with the camera at the bottom.

    I did a quick test with my 808 taped to the end of a yardstick, but instead of mounting the rig on a kite line, I just gripped the yardstck between my thumb and forefinger at the 15-inch point, and moved the yardstick around to simulate how the line might move. I found that even if I do large movements from side to side, the camera simply matches those movements, but does NOT swing pendulum-style. By contrast, if I grip the yardstick at the 35-inch point, any movement produces large pendulum swings. The damping effect of the near-midpoint mount is quite pronounced.

    With the complication that part of the rig extends above the line, it's not clear how one would actually build it in practice, but whoever had the original idea can no doubt provide the method - since he actually built it. I wish I could remember who it was, but it just escapes me. Perhaps someone else will remember that thread. Of course the original idea was for mounting a regular camera - instead of using a picavet - but it seems to me that it should work particularly well for video, including your 808 stuff.

  • edited January 2013
    David, Eletoponline has responded without answering my questions about the nature of the filter:

    Yes, we can remove the IR filter for you, if the running qty is ok for

    However, as I posted above, the rear filter on the D lens can easily be removed.
    As the lens costs less than £8, I may have a look later but it would be a pain to find some plane glass to replace it.
    Removing the filter/coating from the front element of the #16 V2-B would be a better option.

    Wayback, Confused at the first read...will have a think.

    Bruce too, Great! Thanks, I have added the link to http://www.armadale.org.uk/aerialtechniquesforchildren.htm

  • John, regarding the 'B' lens, here is one (of two) that I did earlier :-

  • edited February 2013
    David, Please explain.
    Is that the hot mirror removed?
    From the front of the lens?
  • edited February 2013
    Yes it is.

    Using a brand new Swann Morton scalpel number 11 blade, place the module on a polypropylene cutting board so that the flat flexible connector is vertical.
    Hold the module very firmly (not easy because of its size) and using a see-saw motion rather than slicing action, cut into the lens mount.
    Press the scalpel against the underside of the raised ridge formed by the outer part of the lens mount.
    Turn over and cut the other side.
    Finally, cut the third side that is away from the connector.
    Carefully cut through any remaining bits and lever-up the top sufficiently for the filter to drop out.

    Weld the plastic back together with something like Polyweld.

    Fit the hot mirror into a tiny, push-on holder so that the camera can also be used for normal photography.
  • Oooooh!
    What are the images like without the hot mirror?
  • edited February 2013
    HD 808#16D coat hanger cam video:
    http://www.youtube.com/watch?v=92XZHEX8rPg&feature=youtu.be (not stabilised, wysiwyg)
    Remember to click on the YouTube cogwheel icon to view in HD
    This technique is perfect for extracting or taking stills.

    The videos can be improved, by reducing the wobble, using a larger gauge coat hanger wire, or something rigid.

    rdbeales - There may be something to be said for replacing the entire long arm with a weighted line. Let me know how you get on. I like the idea of the system being very compact with a telescopic arm or string.
  • John, at the moment the two circuit boards are on the bench wired together for testing the degree of synchronisation for stereo.

    When that work is completed I will take some IR images.
  • edited February 2013
    David, Interesting!
    Why stereo?
    You get better 3D by going for a wider base and merging images in Photoscan.

    We constructed a virtual 3D model in the near IR for a site we visited in 2011:
    but there was no real advantage in this case as the site was excavated:
    Near infra-red, 3D model: http://www.armadale.org.uk/archeoscanir02.pdf
    The images taken were near verticals, so the vertical faces are a bit smeared.
  • It is what I do :-


    and I write the documentation for this and other programmes :-

  • And what's the thickness of the hot mirror? It looks like it's on par with the thickness of a microscope slide.

    Dicing glass into squares that small isn't easy, but with some patience it should be possible to make a replacement that would get you back to about the same optical depth as the hot mirror. Microscope slides aren't AR coated or anything, but it might help get the camera back in focus.

    David, this is a really really cool development. I hadn't even thought of these cameras for NIR imaging.

  • edited February 2013
    David, Even more interesting ;o)

    Tom, I believe this is the #16 V2-B http://www.ebay.co.uk/itm/180962539554?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 so the hot mirror is in front of the lens, so no plane glass replacement is necessary for focusing. That is what makes it special. David has not mentioned if the lens is stable without the hot mirror....I assume it is.
    See also: http://www.chucklohr.com/808/C16/index.html#111126C16

    As I mentioned on the community thread, the camera is 'perfectly OK for first sweep archaeological prospection' and even more so in the near IR. However, if the #16 V2-B lens is like its predecessor (808#16), there may be a problem with a 'hot' spot.
    HD 808#16 with transparency film, near IR filter, see foot of:
    However, the #16 V2-B has a completely different lens, with a slighly wider angle of view. I have one but have not tried it out in the IR.
  • Aha! COOL!

    Yeah, I know what you mean about the hot spot. That used to be typical of large format lenses made about a hundred years ago. I can't remember which manufacturers tried this, but Voightlander, at least, included an apodizing filter with some of their lenses. These were neutral density filters with a radial gradient - dense in the middle, transparent at the edges. Made just right, they balanced out the hot spot at the center of the image.

    Of course the Voightlander filters were all 1" and bigger. You'd need something pretty tiny for the 808 cameras. To work well an apodizing filter needs to go as close to the pupil as possible, so sticking a larger one in front of the lens doesn't work as well. But I wonder if there's some way to make one out of film using an out of focus pinpoint light source.

  • The thickness of the filter is 0.72mm.
  • edited February 2013
    If I have time, I will have a look tomorrow to see if the #16 V2-B has a similar hot spot.
  • edited February 2013
    No hot spot ;o)
    This is unconverted with a transparency film IR filter.
    So, it is looking really promising for the converted 16 V2-B.
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