On 11 Oct 2005 at 18:23, Godfrey DiGiorgi wrote: > I find the A50/2.8 Macro OOF rendering a little less than perfect for > general pictorial use, but it's a very good lens for a lot of work > and a fine macro performer.
It's bokeh has never really bothered me but maybe it's the type of shots I tend to make with it? > Question: I have a set of extension tubes, a 2x-S teleconverter, and > the A50 Macro. I'm trying to make the greatest magnification possible > out of the set. I presume the way to do this is to assemble > Camera->Tubes->Converter->Lens > ... eh? > > I'll be experimenting, but if someone's already done it I'd like to > know. >From the distant past: On 13 Jan 2004 at 6:58, Christian Skofteland wrote: > Rob, John Shaw in "Closeups in Nature" says to put the TC on the camera > body, the tubes in front of it and the lens in front of that. This way you > multiply your extension, thereby allowing you to focus closer and increase > your magnification. > > If you put the tubes on the body and the TC in front of the tube you are > multiplying the lens focal length but the extension is the same. Therefore > your magnification would be lower than using just the tubes. OK I performed some practical tests with various combinations of lens TC and tubes. In all cases I used the full 57mm 3 tube set with the lens set wide open and set at its minimum focus distance, the AF TC was set at its infinity focus position. The exposure factor quoted below is relative to 200mm at minimum focus distance. The 200 alone gave me 1:1 (23.5x15.7) on the sensor. The 200 +1.7AF gave me 1.75:1 (13.4x9mm), exposure -1.58 stops The 200 +1.7AF+tubes gave me 2.85:1 (8.2x5.5mm), exposure -2.74 stops The 200 +tubes +1.7AF gave me 2.42:1 (9.7x6.5mm), exposure -1.77 stops I hope that helps Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
