Archived posting to the Leica Users Group, 2011/04/28
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]A pinhole really doesn't have a "focal length"; the location of the pinhole establishes the perspective. There can be no formula for determination of the size of the image circle that covers everybody because all pinholes are not the same. The typical drilled ones (laser, mechanical, makes no difference) are actually small tubes, which limits their coverage. The best pinholes are made in extremely thin material and have knife-sharp edges, or the closest approximation to that possible. The various sites that George mentions will give you formulae for the size of the hole needed, but it might be important to note that each formula is predicated upon certain assumptions. These include the tradeoff between resolution and diffraction, and the particular wavelength that one accepts as a standard. Generally, the wavelength is assumed to be in the green range. As for resolution/diffraction, unless you want something unusual, like enhanced diffraction colors, a published formula ought to work fine for you. Now, MAKING the hole to spec - that's another issue! If you buy one, you get a tube. > Date: Wed, 27 Apr 2011 20:26:54 -0700 > From: Richard Man <richard at imagecraft.com> > Subject: Re: [Leica] Digital Pinhole for Micro 4/3 > To: Leica Users Group <lug at leica-users.org> > Message-ID: <BANLkTikApUO4=AwX4Ww0pHCDNzsvzGcsdQ at mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > How does one calculate the effective length of a pinhole? Is the "body cap" > distance the "normal" distance for most format? e.g. 50mm for SLR? And how > is the size of image circle calculated? > > On Wed, Apr 27, 2011 at 8:10 PM, Jayanand Govindaraj <jayanand at > gmail.com>wrote: > >> > Ken, >> > Nice shots. I was also thinking of buying this - it is inexpensive >> > enough >> > for an experiment! >> > Cheers >> > Jayanand >> > >> > On Thu, Apr 28, 2011 at 5:19 AM, Ken Carney <kcarney1 at cox.net> wrote: >> > >>> > > Jayanand, >>> > > >>> > > Thanks for posting, I may give this one a try. I like pinhole, but >>> > > only >>> > > wide angle pinhole. My favorite pinhole camera is a Leonardo 4x5" >>> > > with >> > a >>> > > 1.5" focal length, which is roughly 15mm in 35mm terms. I have an >>> > > 8x10" >>> > > pinhole with the same approximate equivalent. 22mm is not as good >>> > > as >> > 15mm, >>> > > but a whole lot better than 50mm, which is what you get with the SLR >> > pinhole >>> > > caps. >>> > > >>> > > Here is an 8x10 "super" wide angle image: >>> > > http://www.kencarney.com/Places/tif_0025_std.html >>> > > And one with the Leonardo 4x5: >>> > > http://www.kencarney.com/Nature/psd_0041_std.html >>> > > >>> > > Best, >>> > > >>> > > Ken >>> > > >>> > > >>> > > >>> > > On 4/27/2011 12:07 AM, Jayanand Govindaraj wrote: >>> > > >>>> > >> Looks interesting: >>>> > >> >>>> > >> >>>> > >> >> > http://theonlinephotographer.typepad.com/the_online_photographer/2011/04/pinwide.html >>>> > >> >>>> > >> http://wanderlustcameras.com/ >>>> > >> >>>> > >> Cheers >>>> > >> Jayanand >>>> > >> >>>> > >> _______________________________________________ >>>> > >> Leica Users Group. >>>> > >> See http://leica-users.org/mailman/listinfo/lug for more >>>> > >> information >>>> > >> >>>> > >> >>> > > >>> > > _______________________________________________ >>> > > Leica Users Group. >>> > > See http://leica-users.org/mailman/listinfo/lug for more information >>> > > >> > >> > _______________________________________________ >> > Leica Users Group. >> > See http://leica-users.org/mailman/listinfo/lug for more information >> > > > > -- // richard <http://www.imagecraft.com/> // icc blog: > <http://imagecraft.com/blog/> // photo blog: <http://www.5pmlight.com> [ > For technical support on ImageCraft products, please include all previous > replies in your msgs. ]