John, I'm sorry my Cosina is not living up to your expectations...but seeing your rig I'm wondering about how insanely high your expectations might be :-D
Your link to Abraham's nose takes me to your pile o' extension tubes & stuff , and when I look at the complete album I can see you drinking out of a lens, for example, but no Lincoln penny to be found. You can calculate the magnification power of your set up with a ruler. Take a photo of it as close as you can, parallel to the ruler, and the ruler running from side to side of the frame. Look at the image and count how much of the ruler you've photographed. If you're using millimeters, let's say your picture shows 12mm of the ruler. An APS-C sensor is 24mm wide, so your magnification ratio is 12/24 = 0.5, so you can say your macro capability is 1:0.5 (or 2:1 if you prefer). If the image you'd taken was 24mm across, then your macro ratio would be 1:1, or "life size", which is what macro lenses (such as your 100mm f/2.8) typically reach. You might find these articles on my site useful: http://enticingthelight.com/2009/02/02/shooting-macros-section-1-equipment/ http://enticingthelight.com/2009/02/07/shooting-macros-section-2-the-small-world/ http://enticingthelight.com/2009/02/26/shooting-macros-section-3-the-math/ Cheers, —M. \/\/o/\/\ --> http://WorldOfMiserere.com http://EnticingTheLight.com A Quest for Photographic Enlightenment On 12 December 2012 13:14, John Celio <[email protected]> wrote: > I recently bought an inexpensive Cosina 28mm lens from Miserere with > the intention of reverse-mounting it on my pile o' extension tubes & > stuff (illustrated with a different lens here: http://goo.gl/WcvoZ) to > see what could be done with such immense magnification powers. For my > first subject, I picked a penny. > > As luck would have it, Abe's nose was the first thing I saw in my > viewfinder: http://goo.gl/Xi8vs > > That's some serious magnification there. I have no clue how to > calculate what the macro ratio is, but there's not much point to it at > the moment. I appear to have gone beyond the resolving power of the > lens. All the photos I took are very soft, regardless of the aperture > I used. This one looks a teeny bit sharp on the nose, but I think > that's an illusion. > > (Reference for those who don't know what a US penny looks like: > http://en.wikipedia.org/wiki/US_penny. Note that the article also > mentions the size of the coin if you want to try to figure out the > scale here.) > > I'm going to keep playing with this setup, but in the meantime I'll > save up for a sharper lens. I wish I could use the lenses I already > own, but this experiment has taught me the one downside of DA lenses: > not having an aperture ring makes extension ring/bellows shooting very > difficult. > > John > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
