Many people seem to think that the Sigma-made, Sigmatel \"Multi Scalematic\" 135mm f1.8, is exactly the same lens as the Spiratone, Porst, Soligor and all the other versions out there.
This has probably come about because some have speculated that the Spiratone, in particular, was apparently be made by Sigma too.
However after conducting some research I have discovered that there are actually two different Spiratone versions, which have different optics from each other, and there is the Soligor version too, again with different optics. Note how the The Pentax-A version is almost the same as the Sigmatel (I wonder who copied who? ).
So there are at least 6 different optical designs used for 135mm f1.8 lenses and there are probably still more I dont know about yet. If you know any with different optics to the ones shown in the diagrams below please post them in this thread.
But its not just optically where they differ...Both Spiratones, the Porst version and the Soligor versions all have an 82mm filter thread but the Sigmatel is a physically smaller lens and only has a 77mm filter thread.
Their MFD\'s are different too...The Spiratone, Porst and Soligor versions all have an MFD of about 6 foot (1.83m) but the Sigmatels MFD is only 4 foot 3 inches (1.33m).
Because of these findings, I decided to post a review for the Sigmatel on the Pentax Forums website: http://www.pentaxforums.com/userreviews/showproduct.php?product=991
Many people seem to think that the Sigma-made, Sigmatel \"Multi Scalematic\" 135mm f1.8, is exactly the same lens as the Spiratone, Porst and Soligor versions.
This has probably come about because some have speculated that the Spiratone, in particular, was apparently be made by Sigma too.
However after conducting some research I have discovered that there are actually two different Spiratone versions, which have different optics from each other, and there is the Soligor version too, again with different optics. I cant be 100% sure of this but going simply by external appearance I would hazzard a guess that Porst version is made by Sun optical and follows the samne optical scheme as the Spiratone which is made by them too.
Here are their optical diagrams:
But its not just optically where they differ...Both Spiratones, the Porst version and the Soligor versions all have an 82mm filter thread but the Sigmatel is a physically smaller lens and only has a 77mm filter thread.
Their MFD\'s are different too...The Spiratone, Porst and Soligor versions all have an MFD of about 6 foot (1.83m) but the Sigmatels MFD is only 4 foot 3 inches (1.33m).
Because of these findings, I decided to post a review for the Sigmatel on the Pentax Forums website: http://www.pentaxforums.com/userreviews/showproduct.php?product=991
).
