Thanks!Quote:
Originally Posted by RalphLambrecht
I should have mentioned that I submitted that to WPPD. I'm not sure what year. It was a 9 hour exposure in my dark bathroom. It was nothing but lightning and rain all that day....
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Thanks!Quote:
Originally Posted by RalphLambrecht
I should have mentioned that I submitted that to WPPD. I'm not sure what year. It was a 9 hour exposure in my dark bathroom. It was nothing but lightning and rain all that day....
I have been really happy with the 4x5 pinhole camera I made....Quote:
Originally Posted by m1tch
For determining pinhole designer, I prefer PinholeDesigner from http://www.pinhole.cz/en/pinholedesigner/. A user constant of 1.4 seems to work better than the default 1.9 Lord Rayleigh constant. Lord Rayleigh may have calculated pinholes on a basis of scientific theory, not photographic results. Contrary to some photographers, the accuracy required for optimum performance is fairly critical. It seems counter-intuitive, but an optimum sized pinhole can actually resolve line pairs on a resolution chart with a spacing finer than the pinhole diameter. When comparing lens resolution charts photographed through pinholes, a deviation from optimum diameter by maybe 10% starts to become noticable. However, lens resolution charts don't make the most pleasing subject for pinhole photography. If detailed pinhole images are the goal, large film with short focal lengths gives the best results in the center of the image. Resolution and illumination fall off towards the corners. For a comprehensive book on pinhole photography, get Pinhole Photography by Eric Renner. For much online information, google for Jon Grepstad
I've used a user constant of 1.562 I don't remember exactly where I found this number but I do remember someone had done a pretty convincing analysis about it.
Attachment 60577
I built one out of foam core with my son. That was fun and pretty easy to do. Recently, I bought a Ilford Harmon Titan pinhole camera from Badger Graphic. I highly recommend the Harmon Titan.
I made a couple of wooden pinhole cameras, based on Zero Image design, and used a laser-drilled (EMS) pinhole, purchased from USA. FL is 30mm, which is about right according to Pinhole Designer software (link in one of the previus posts), with the constant of 1.5 (instead of the default 1.9).
I'm pretty happy with the results: one camera is 6x6 format, and the bigger one is a combo 6x6 - 6x9 camera, and that one uses the same FL and pinhole size (0.2 mm, i.e. 200 microns and 30mm focal length).
Attached are a few results.
Selenium toner also works quite well for blackening brass, as does sulphide toners.Quote:
Originally Posted by DWThomas
Great images! What do u use to make a pinhole the exact size?
Yes, I've heard this but my attempts to do it weren't very successful. I don't know if it was an issue of concentration or pH or what. The model RR stuff is able to easily do a weathered black railroad locomotive finish on brass. It is a tad pricey, but so is toner!Quote:
Originally Posted by paul_c5x4
In my case 'exact' is a relative term! As I mention my process is iterative, I go a ways and then measure. If the hole is too small, I do a little more. If too big, enh, start another one. But in the end, the dimension is important, but not all that critical, it's just nice to know what it is for exposure calculations. A very gentle teasing with a spinning motion of the needle can also help round the hole.Quote:
Originally Posted by ezwriter
I assume with the laser drilled holes some sort of industrial numerically controlled machinery comes into play.
