Playing with an action cam

[LordV]

Bought one of those tiny gopro clones on amazon on offer and have been having a play. As is, it does not focus very close (it's a fixed focus lens) but adding a Raynox DCR-250 to it enables it to focus down to about 3" away. A 14mp sensor and lots of built in capabilities such as interval shooting both in still and video modes plus WIFI remote control.

Initial shots below- just about claim it does close ups

Brian V.
As is


Plus Raynox DCR-250


WIFI remote control

[enricosavazzi]

There are a few more interesting things about these action cameras (or at least some of them, I know from direct experience that the following applies to some of the Gopro models, and it may or may not apply to other brands and models):

• The NIR- and UV-cut filter is stuck at the rear of the lens, not on the sensor. Just change the lens and you got a "full-spectrum" camera. Add a suitable filter in front of or at the rear of the lens to get NIR or NUV imaging.
  
  There are third-party modifications that allow the use of C and CS lenses on these cameras (in addition to the built-in D mount). You can get C/CS adapters for almost any legacy lens or mirrorless system lens.
  
  The original lens is glued into its D threaded mount, but it is usually possible to twist it free, and then use the D thread as a focusing helicoid.
  
  The HDMI output usually allows a portable field monitor to be connected as a live-view viewfinder. Especially useful for the models without a built-in screen like some Gopro Black.

[LordV]

There are a few more interesting things about these action cameras (or at least some of them, I know from direct experience that the following applies to some of the Gopro models, and it may or may not apply to other brands and models):

• The NIR- and UV-cut filter is stuck at the rear of the lens, not on the sensor. Just change the lens and you got a "full-spectrum" camera. Add a suitable filter in front of or at the rear of the lens to get NIR or NUV imaging.
  
  There are third-party modifications that allow the use of C and CS lenses on these cameras (in addition to the built-in D mount). You can get C/CS adapters for almost any legacy lens or mirrorless system lens.
  
  The original lens is glued into its D threaded mount, but it is usually possible to twist it free, and then use the D thread as a focusing helicoid.
  
  The HDMI output usually allows a portable field monitor to be connected as a live-view viewfinder. Especially useful for the models without a built-in screen like some Gopro Black.

Yes I'm getting an M12 (d-mount?) to C-mount adapter.
I've been looking for some reasonable way of sticking a longish tube on the m12 to allow an RMS 160mm lens to be used on it. Was thinking of c- mount tube and then a c-mount to rms adapter.
In the mean time i'm getting one of these to play with
https://www.amazon.co.uk/gp/product/B01 ... UTF8&psc=1
Not sure if it will work.

Brian V.

[enricosavazzi]

For photomacrography, you need a relatively large distance between sensor and lens, so all you may need is a mechanical connection between camera body and lens, via some sort of extension tube.

If you want to keep infinity focus with C and CS lenses, then things get more complicated. The modification I mentioned in my earlier post involves moving the sensor from deep within the camera body (where the M12 lens screws in) to a position flush with the external surface of the camera front. The modification also completely replaces the plastic front of the camera body with a two-layer machined aluminum part, removes the original sensor support and replaces/extends the internal cable between sensor board and "motherboard", among other things. A C/CS mount is then attached at the front of the camera. See https://www.back-bone.ca/ .

Without changing the sensor position, there is no way to bring a C (or especially CS) lens close enough to the sensor to achieve infinity focus.

[LordV]

Still playing with the camera. Having purchased a spare lens I have removed the IR/UV filter from the first lens and now have an IR set up.
Example shot below. I have temporarily fitted an industrial C mount macro lens and it gives a mag range of around 1cm to 3.5mm across the frame but I need an extension tube to get it to fit properly which is coming from China (hopefully).

Having marked the normal and close focus positions it's possible to get close focus just by unscrewing the lens about 1/4 to 1/2 turn - example of this in the soap film video below. Click on the picture to see the video

Brian v.

With 760nm cut off filter on the front.




soapfilm by Brian Valentine, on Flickr