Hello, I have promissed to share my impressions of the Tamron SP 17/3.5 lens that I have just aquired. I compare it with Carl Zeiss Jena Flektogon 20/2.8 because I use it and I have not a comparable pentax lens (18mm ot 20mm).
So, first the feeling of handling it. It is a metal barrel that has a solid feeling. The focusing ring is a little bit narrow but it is not such a pain like the one of Mir-20 lens I have put my hands on yesterday. I traded the nikon mount Adaptall adapter with which the lens have came for a Pentax K adapter. I had any problem with it. It focuses just to infinity not like the Flektogon that with M42 to K mount adapter focuses beyond infinity. On the other hand, the focusing run ot the Tamron lens is too short - it is 1/4 of the full turnover versus 3/4 of the Flektogon lens. The front lens is 67mm in diameter but there is no screw mount for putting filter in front of it, Flektogon has and I have recently got a cokin filters holder that do not cause vignetting with it. The pictures that I will discuss could be found here: http://flickr.com/photos/karavelov/sets/1360481/ Abberations: I could not say anything about CA because I shoot B&W. There is not noticeable barrel distortion in either of the lens. Howerver there is some coma distortion that I could notice with both lens that is stronger with the Tamron. I have not checked yet the flare resistance of the Tamrom lens, but the images seems not so contrasty as the Fleftogon ones. Light falloff - it is realy a problem of tamron lens. I could see some vignetting even on pictures that have been taken at f8 (see the pictures). Flektogon shines here. Resolution: Both lens have poor resolution at the edges but my feeling is that Flektogon is more sharp. At the center I think that also Flektogon is sharper. (see the crops - I do not know if am not hitting the grain of the film with the Tamron lens here). The flektogon has also better edge definiton that Tamron 17mm lens. Nevertheless 17mm makes really difference of the field of view. With all its limitations it may be the choice for some situations: http://flickr.com/photos/karavelov/62990960/ Best regards & I hope it was useful for you luben -- "Computers are useless. They can only give answers." - Pablo Picasso
