Nah. I'll skip on the bathtub so no Archi. Jostein Den 5. september 2016 07.36.06 CEST, skrev Alan C <[email protected]>: >Interesting. So must we call you Archi now? I tried sourcing John >Shaw's >book locally - you won't believe how much they want. > >Alan C > >-----Original Message----- >From: Jostein >Sent: Sunday, September 04, 2016 12:38 PM >To: Pentax-Discuss Mail List >Subject: Enlightenment > >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
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