Now that's more like it! Thanks for a healthy counter-argument, Leon! :-) I did some experiments a couple of days ago with a set of 40 cm long, Ø 8 mm acrylic rods (aka plexiglass) and gaffer tape. In the first attempt i just cut the rods with a hacksaw, taped them onto the 540 flash and did some sample exposures. With 4 rods glued together, I got exposures in the range of 1/125 at f/4 with the tip of the rods 5-6 cm away from the subject. Then I used some very fine-grained sandpaper, and smoothened them further with a polishing disk. This increased light transmission with about 1.5-2 stops, judging from the histograms.
But it's a pretty crude experiment anyway. The main point is that you're very much right about the light loss, but that it's possible to minimise the loss by careful polishing of the ends. When a large number of small fibres are involved, they should probably be embedded in some kind of resin like epoxy or even harder stuff, and then polished as a bundle. I'm very curious to see how much light can be retained in this way, and there seems to be only one way of finding out...:-) Thin fibres is a must for flexibility. According to what I've gathered, it is possible to bend a Ø 5 mm bundle of Ø 0.13mm fibres into an S even at such short lenghts as 50 cm. So what I had in mind was a medusa-like device, with a big bundle in one end and lots of 5 mm strands in the other. Rushing into things as I often am, I've gone and ordered just that. >From your arguments I realise I may have acted prematurely. :-( Anyway, the bundled end will be Ø 30mm and consist of ca 20 strands of Ø 5 mm insulated fibre-bundles as described above. The vendor will polish the bundled end for me to high-gloss quality, and I will provide attachment to the flash and lens front. It will be ready for testing by the end of next week, I think, give or take.. I'm impressed by your flash mod. Is it actually made so that the capacitor in the 360 power both strobes? Where did you scavenge the second strobe from? Cheers, Jostein 2007/8/23, Leon Altoff <[EMAIL PROTECTED]>: > Hi Jostein, > > You will loose a lot of light if you use a bundle of fiber optics, > particularly if you don't prepare the ends of each fiber individually. > It will also be very defused once the light exits the fibre. There are > limitations to the angle you can bend them and a bundle will not bend > well anyway. If fiber optics worked for flash photography then everyone > would be selling them. > > The answer to macro lighting is to get the actual light source close to > the subject. I use an AF360 with a second head grafted on to it so I > get balanced light from both sides of the subject. It works fine PTTL > and also wireless if I'm not photographing into water (I do this a lot). > > These are some quick and dirty photos of my franken-flash. (apologies to > those who have already seen these). > From above > http://www.bluering.org.au/leon/flash/FrankenFlash4259.jpg > > From the front > http://www.bluering.org.au/leon/flash/FrankenFlash4260.jpg > > The socket on the flash > http://www.bluering.org.au/leon/flash/FrankenFlash4263.jpg > > Folded up > http://www.bluering.org.au/leon/flash/FrankenFlash4264.jpg > > -- > Leon > > http://www.bluering.org.au > http://www.bluering.org.au/leon > > AlunFoto wrote: > > Here's a question for the technically curious. > > > > Do you think it will be worthwhile to use fibre optics to lead light > > from an ordinary flash (eg. Pentax 540 FGZ) into various > > configurations for macro flash purposes? > > > > I can't get the idea out of my mind, and probably need some healthy > > counter-arguments... :-) > > > > The pros I can see are: > > > > There is no P-TTL-enabled macro flash for Pentax. Using fibre optics > > with an ordinary flash could provide this. > > > > Theoretically, one should lose far less light per distance through > > fibres than the inverse square law that applies through air. So > > leading the light to where the motif is could allow for flash light > > with a very reasonable GN. > > > > Using thin fibres in slim cables, eg. 20 fibres in Ø 5mm cables, the > > individual cables are flexible and can be arranged in many > > configurations. Ring flash can be simulated, as well as setups more > > weighted to the sides. > > > > Optic fibres are lightweight, and will not place much extra weight or > > bulk at the front of the lens. Contraptions for attaching the fibres > > not considered, of course, but how bulky can they get? > > > > On the con side, I see that the 5mm cables probably have to be bundled > > by a professional towards the flash. I believe it's only possible to > > construct circular bundles, so a part of the flash output may not be > > shunted into the optic fibre. But at the moment, this is not at all > > enough to stop me from thinking about this...:-) > > > > Anyone have better counter-arguments? > > > > Please? :-) > > > > Btw, I know that Novoflex has a fibre optic solution for macro flash, > > but that's not what I'm thinking of. The Novoflex unit is a large, > > bulky adaptor that looks more like a microscope light source for the > > lab than a portable field solution. > > > > Cheers, > > Jostein > > > > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > -- http://www.alunfoto.no/galleri/ http://alunfoto.blogspot.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
