Here's a challenge for you photo bugs

By: Pdoug 2473 days ago
I am attempting to photograph the first 2-3 inches inside of a 1/2" ID tube with approximately a 3" depth of field.
I can just about get enough flash up the opposite end of the tube to with a flash unit, but can not push enough light into the front end.
Have the camera at an angle so that the opposite end flash is not firing directly into the camera. This angle will work, but I am having real trouble getting the focus I want.
Have tried all types of different lenses and a macro zoom, which is the only macro I have. 35-100 w macro.
Nikon D100.
Any suggestions??
Thanks
By: johnriley 2472 days ago
Tricky, as I'm not sure anyway what you are trying to show.

Assuming it is the interior structure of the tube I would attempt to light it with natural or continuous artificial light rather than flash. A white card under the tube and a high level of ambient lighting might throw sifficient illumination.

Then you need the smallest aperture you can get, maybe f22, maybe f32. Focusing point should be one third down the tube that is required to be within the depth of field. A tripod would be essential, plus a suitable clamp to hold the tube as well.

This gives a starting point, after which you will need trial and error to refine the process.

Hope that helps!

John
By: twinsemi 2394 days ago
Have you tried using light sticks? They might fit inside the tube, and would allow a slower shutter speed than flash.
By: cashierx 2325 days ago
Try using a Maglight hand torch set to a pinpoint focus circle. This will be sufficient to throw the necessary light into the small diameter tube.

There is always light fibres you could experiment with as well.

Robbie
By: EricD 2309 days ago
Not sure about illumination, but there is a kind of lens designed just for this task:
http://www.opto-engineering.com/pericentric.htm

The 'pericentric' (aka hypercentric) lens images the outside of a cylinder onto a plane. The 'hole inspector' seems to be mostly a large ball-bearing - maybe DIY - or is it a parabola ?

http://www.schneiderkreuznach.com/pdf/div/optical_measurement_techniques_with_telecentric_lenses.pdf
is Schneider's course on optics - 'hypercentric' is beyond 'telecentric'.

Another couple of important questions - is it a shiny or difffuse surface ? Are you looking for shape or colour features ?

Maybe a ring-light or something shone through a 50% mirror at 45 degrees ?

Eric

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