Pentax-M/Pentax-A

Having had my Pentax ME Super for aeons, I've recently picked it up again more seriously.

When I bought it second-hand in 1988, it came with a SMC Pentax-A 1:1.7 50mm lens. Now I'm looking at the depth-of-field table in the manual, and I see the data it gives relates to a SMC Pentax-M 50mm lens.

What is the difference please between a Pentax-A and a Pentax-M lens (sorry if this is a kindergarten question) and can I use the table for Pentax-M lens with my Pentax-A lens?

Thanks for any help on this.
D Kendall

The only difference between the Pentax-M and Pentax-A lenses is that the A lenses have an 'A' setting on the aperture ring. This enables them to be used in program and shutter priority modes with A series and later camera bodies. The depth of field tables will be the same.

If you use an A series lens on a K or M camera body, the 'A' setting on the lens cannot be used.

Thank you for that - couldn't find the info anywhere else.

Pentax has the best compatability with its older K lenses. There are a few exceptions though. The M lenses can not be used on the *ist cameras (including the *ist D) . FAJ lenses won't work with cameras that can't use the A feature of the KA lenses and the DA lenses are only for the *ist D.

M lenses are easily usable on the *ist D with firmware 1.10 or higher. All my best lenses are 'M' and I rarely use anything else on my * ist D.

Yea, try that with ANY OTHER camera brand!

(Does Pentax ROCK, OR WHAT! )

As above.

Slip your M 50mm 1.7 on an ist D and enjoy.

Jayson

YES, many Sigma SD 9/10-user are using this lens too (because Sigma doesn't have a comparable 50mm lens - only a 2.8/50 macro lens).
The Sigma mount is somewaht comparable to the K-mount. You "only" have to remove a small part of the rear lens side that mechanically informs the body about the open aperture.
In the german "fotocommunity" someone posted how to do that :
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also mal vorab........

es gehen an der SD9/10 nur manuelle PK-Scherben, AF und Blendenautomatik geht garantiert nicht!!

Zu den PK Objektiven:

Das PK Bajonett ist fast gleich dem der Sigma, lediglich sind die Nasen an den PK-Objektiven kleiner, was dem Nutzen keinen Abbruch tut.

Da die älteren PK-Objektive zumindest eine Blendenautomatik hatten, bzw. die Blende von der Pentax gesteuert wurde, muss diese nun leider "demoliert" werden.

Der Vorgang klingt banal, ist er auch.

Vorgehensweise:

Die brutale Methode:
Mit dem Dremel oder sonstigen Schneidwerkzeugen.
Das Objektiv hat nicht nur den Nippel für die Blende, sondern auch eine Erhebung aus Plastik.
Beides muss zwingen entfernt werden. Die Plastikerhebung ist mittels Drehmel (das Ding vom Aldi tut es auch *gg*) einfach nur runterzuschleifen - dauert zwei, drei Sekunden. jetzt geht es aber ans Eingemachte. Der Nippel für die Blende ist aus Metal. Dieser lässt sich mit einer Drehmeltrennscheibe recht gut absägen. Immer schön drauf achten, dass möglichst keine Späne "ins Objektive" gelangen können! Nach der Aktion alles schön mit Luft freiblasen - fertig!

Das Objektiv lässt sich jetzt normal an die SD9 anbringen. Die Markierungspunkte stimmen zwar nicht mehr - macht man sich halt neue!
Die Blende muss jetzt von hand gewählt werden - Fokus - klar, natürlich auch!
Die Schärfemessung funktioniert mit der SD wunderbar. Wenn der "Beep" in der CAM eingestellt ist, piepst die CAM bei korrektem Fokus - und die Aufnahmen werden TOP (in Anhängigkeit des Objektives - logisch)

Die sanfte Methode:

Den Bajonettring mittels Lösen der 4 Schrauben entfernen. Achtung, es sitzt in der Regel noch ein Ring drunter - die Lage merken!
Nun kann man das Plastikteil komplett entfernen - das Schleifen fällt flach!!!
Lediglich der Blendennippel - der stört noch. Ziehen kann man das Teil nicht (soll aber bei einigen gehen) also nimmt man einen Seitenschneider oder Kneifzange und kneift das Teil ab. Unbedingt darauf achten dass der Nippel nicht verbogen wird, sonst hakelt die Blende!!
Bajonettring wieder drauf - fertig!

Das Objektiv hat ein ganz wenig Spiel - sitzt also nicht bombenfest! Ein horizontales und vertikales Spiel von einem halben Millimeter ist leider nun mal, weil der Pentaxverschluss kleiner ist. Tut dem aber kein Abbruch!
Ich würde zunächst versuchen, irgendwo auf dem Trödel ein Objektiv für ganz kleines Geld zu ergattern - ein schönes Lehrstück - und ihr werdet sehen, dass das klappt!
Ich habe mir jetzt drei Objektive umgebaut - Bingo!


Was es noch gibt:

Es gibt - zwar selten - Adapter von K auf Sigma!! Ebenso von M42 auf Sigma. Der Preis liegt um die 20 Euronen - beim M42 gut angelegt, sonst bekommst Du die Scherben nicht an die CAM, beim K-Adapter halte ich es für unnötig!

Achtung:
Nie versuchen, das K an die Sigma zu bringen, bevor der Blendennippel entfernt wurde!!!!!

Noch Fragen?
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Here is the complete Thread :
http://www.fotocommunity.de/forum/read.php?f=1&i=95257&t=94864#reply_952...
There you can find the possibilty to send an e-mail to the original poster.
Good luck !
Paul

Hi,

I am a newbie from Hong Kong and just found this thread. Can someone please repeat the procedures in english. Cant read german.

Thx.

since we are talking KA lenses, does anybody know whether there was ever a f1.4 50mm produced with this set-up?
i've a standard f2 on a super program, and have seen some f1.7 advertised for sale, but i don't know whether they are worth investing in...
i've tried all sort of searches on the net, but can't seem to find a reply.
even better, what was the full range of KA mount lenses available?
thanks a million!

I've just found all the info i need for pentax k- mount cameras on this fantastic site....

http://kmp.bdimitrov.de

apparently, not only there was there a f1.4 made, but also an f1.2 (!)..
the site seems to contain all you need to know about these classic cameras...

I recentley came across an interesting article i found in a box of photographic goodies from a deceased photographer, apparently he even got a couple of photos in National geographic. In the box were two very used XR Ricoh Rikenon F2 lens along with leather box for a pentax SMC 100 F2.8 lens that somebody before me had cherry picked, B******.

The article in this mag explained that manufactures of F1.7s or 1.8s lenses were often streched versions of the F2 model. Any imperfections in the F1.7 are consequently exaggrated, probably not noticable to the layman. They concluded that you were better off with the F2 if you didn't need that extra half a stop. The F1.4s, on the other hand, are not further streches of the F2 but designed from the start as unique from other lens in there line up.

So, whats the deceased photograher doing with two Ricoh 50mm F2s and the Pentax SMC 100mm. I think he knew long before what the article stated, that F2s were better than the faster F1.7s/F1.8, from the same manufacturer. Unfortunatly for me one Ricoh F2 has dodgy aperture blades and the other i sold on ebay before i realised what a gem of lens it was.

Just to add slightly to that, it's important to know what a lens has been designed for, and this avoids disappointment should our requirements be different.

The SMC Pentax-M 50mm f2 and 50mm f1.7 lenses are essentially the same and are exceptionally good. The 50mm f1.4 design appears to be designed for maximum contrast at the expense of fine resolution, and thus is probably intended for low light use and reportage, perhaps unsurprisingly....This is not to my taste, but might be just what someone else requires. The 50mm f1.2 has excellent control of point light sources (great for night shots) but its best performance comes in arounf f5.6-f8, which is where it may well be used most of the time for general purposes. Looks like another deliberate design choice.

Don't forget the SMC Pentax-M 40mm f2.8, which is also excellent!

Yes, i'm in full agreement that lens are designed for a particular situation.

I've read on the internet that there is a difference between the Pentax-M 28mm F2.8 and F3.5. The F3.5 is supposed to have better edge definition than the F2.8 which would lead to think this would be a better lens for landscape photography.

This morning after the previous posting, i've managed to find the article. In the old days it seems like they really tested the lens assigning lpm scores rather than todays rather than subjective opinion. My view on lpm ratings is that so long as one person has done all the analysis, then results are comparable between lens and manfacturers done by that individual tester. lpm aside, as this varies between depending on the tester's method, the Pentax 50mm F2 should be relatively sharper than the F1.7, see below.

Here's some ratings for 50mm pentax lens from that article.
In all cases maximum lpm peaks around f6.7 and edge around f8.

F2, centre 130 lpm, edge 112 lpm.
F1.7, centre 115 lpm, edge 97 lpm.
F1.4, centre 127 lpm, edge 112 lpm


For those interested, the source;
What camera weekly, pages 46-50, April 10, 1982.

So the original point of teh thread about Pentax M and A mount lens. People tend to rate A series lens with higher LPM scores. My view on this is that the improvement in performance is marginal at best. People agonise too much over the glass on their camera judgeing by the number of forums on the subuject, but not on their enlarger/projector. Bad projector lens, poor quality print. Which leads me to a question,

Why doesn't pentax make enlarger lenses? Supid question really, people are going digital.

Dominic

I think those lpm readings are within the bounds of experimental error, as well as being from just one example of each lens. This has always been a problem, and although getting hung up on such data is meaningless, these days the effort has been completely abandoned by testers, which I don't think is good either. Modern lens and camera tests are too often more user reviews than tests.