From gnu.mat.uc.pt!news.rccn.net!Portugal.EU.net!EU.net!newsfeed.internetmci.com!in1.uu.net!tandem!news.mpd.tandem.com!usenet Mon Nov 13 12:18:02 1995 Path: gnu.mat.uc.pt!news.rccn.net!Portugal.EU.net!EU.net!newsfeed.internetmci.com!in1.uu.net!tandem!news.mpd.tandem.com!usenet From: Bert van Es Newsgroups: rec.photo.equipment.35mm,rec.photo.misc Subject: Re: Pentax lenses designations Date: 10 Nov 1995 18:21:05 GMT Organization: Tandem Computers Lines: 52 Message-ID: <48056h$d6i@news.mpd.tandem.com> References: <47ophj$6gt@s3.iway.fr> NNTP-Posting-Host: 168.87.14.68 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 1.22 (Windows; I; 16bit) To: nguillem@pratique.fr Nicolas, It is very simple. The first Pentax bayonet lens serie was the SMC-K serie. Most of the are simular or the same lenses as the last P screw mount lenses, only with bayonet. Examples are the 3.5/24, the 2.5/135, the 1,8/55 etc. Lateron there were new lenses introduced like the 2.8/24 (still SMC-K series) Then shortly after that Pentax brought out the SMC-M series. One of the goals was to make the lenses smaller (for the smaller M series cameras) and an other was to stardardize on 49 mm filter thread for as many lenses as possible. So the 1.8/85 SMC-K serie lens became the 2/85 SMC-M serie lens and the 1.8/55 became the 1.7/50 etc. All exept a few of the SMC-K and SMC-M series lenses had automatic diafragm (it closes just before the exposure). But no automatic aperture mode was possible.(you have to set the aperture to a certain predefined value) The A series are a further development in that with the A series you can use the automatic aperture or program mode. The camera is capable of setting the aperture during exposure. Many lenses are the same as the M lenses, same are just a bit better corrected. But also many new lenses are developed, (like the 2.8/20, the 1.4/85 etc.) Pentax had in mind that these new lenses should be used by professionals, so they did not care to make the lenses a bit heavier than the SMC-M serie lenses. So the Pentax 4.0/20 mm M became the 2.8/20 mm A. Now about your suggestion about the lenses. The 2.8/24 K lens is a good lens (I have it my self). There has never been a SMC-M version of that. (they probably could not make it fit in a 49 mm filter thread) The SMC-A serie 2.8/24 is exactly the same ( as far as I know) only with the "A" contact for the automatic aperture mode. The SMC-K 1.2/50 has never been changed optically in the K,M and A series. So if you have to buy a 1.2 lens buy the cheapest you can get. But why don't you buy a 1.4? These are optically better and a lot lighter and much cheaper! (I had a SMC-A 1.2/50 and had it exchanged for a FA 1.4/50 for that matter) The 2.5/135 is ok. There is a SMC-M 135/3.5 and a SMC-A 135/2,8 but these seem to optically less that the 2.5 K series. Watch out that you don't buy a 2.5/135 TAKUMAR lens. These are not multi coated as the SMC-K version. The SMC-F or SMC-FA 135/2.8 are optically the best, but they are hardly to find (and expensive). Best regards, Bert van Es (vanes_bert@tandem.com)