Brings up all sorts of questions: deliberate misleading to reduce commercial competition? typo/missed word?
I assume the reversed lens needs to be open for focusing ease? > On 04 September 2016 at 11:38 Jostein <[email protected]> wrote: > > > We have tradition for calling new gear aquisitions for enablement, but > since this is about knowledge aquisition, it didn't seem right even if > it feels like enablement. > > The 645D is a bit cumbersome to work with for macro, because of its > sheer size. The motivation to do so is of course image quality, like > when using the 645FA 120mm f/4 macro. However with so much CCD real > estate, it's tempting to seek more magnification with extension tubes, > reversed lenses or most of all; stacked lenses. > > I've used the optics involved before, with a K-mount adapter and various > APS-C cameras. So I know the drill, and I have had high expectations > based on earlier results with subjects as different as snow crystals and > freshwater plankton. One of the best combinations seems to be a 645FA > 150mm f/2.8 with a reversed 75mm f/2.8 stacked in front, giving 2X > lifesize magnification. > > But not on the 645D. All sorts of weird colour fringing popped up, it > was like watching an old 3D film without the coloured glasses. > > My guide to the chaos of macro photography has always been the venerable > book "Closeups in nature" by John Shaw. It's nearly fourty years old, > but still relevant and with many wonderful images to illustrate his > text. On the subject of stacked lenses he explicitly states that the > reversed lens should be used wide open. > > It shouldn't. That's my enlightenment. With the camera-mounted lens on > full aperture and the reversed lens stopped down, all the weird fringing > disappeared. I tested the same with K-mount lenses too, of course, and > with the same eye-opening and jaw-dropping result. > > So, that's my little eureka moment for the week and I'm proud of it. > > Carry on. :-) > > Jostein > > -- > 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.
