[Sorver]

Just wondering if the Cosmo aps auto teleplus 2x that fit the screw mount pentax may fit my pentax lenses without doing any damage. I know the simplest thing would be to give it a go but I am a big chicken and don't want to break my new toy just wondering if anyone knows Sorry should mention I have a k-50 K mount obviously.
Thanks in advance.

[tibbitts]

If you mean fit without a screw-mount adapter, no. With an adapter, probably yes. But you might want to specify what lens it would be used with to get a better idea of whether using a 2x converter would be worthwhile. Also, even in the somewhat rare cases where using a 2x converter might make sense, generic 2x converters in K-mount are just not that expensive, so it might we worthwhile to get one that doesn't require an adapter and would provide more convenient operation.

[Sorver]

If you mean fit without a screw-mount adapter, no. With an adapter, probably yes. But you might want to specify what lens it would be used with to get a better idea of whether using a 2x converter would be worthwhile. Also, even in the somewhat rare cases where using a 2x converter might make sense, generic 2x converters in K-mount are just not that expensive, so it might we worthwhile to get one that doesn't require an adapter and would provide more convenient operation.

Thank you so much for replying after spending today in the camera shop I realise I could of asked you how long is a piece of string and it would of been easier lol I agree probably better off buying a new one and just enjoy looking at the old one still looking for a lense with a low f below 3 and adding a converter on. I would love the tamron 16-600 but think it will be awhile before they bring out the k mount for it. Basically after distance with lightness and easiness to carry.

[tibbitts]

If you mean the Tamron 16-300 plus a converter, all the superzooms are very slow at the long end (which is the only place you'd use the converter), such that they would be almost unusable for typical photography with a 2x. In terms of overall image quality with current sensors, you might be better off just cropping for that 2x vs. using a converter. I'm guessing that, barring major marketplace developments, Tamron won't make any new Pentax-mount lenses, except any that Pentax chooses to rebrand and offer at a considerably higher price (like the 18-270.)

[Sorver]

If you mean the Tamron 16-300 plus a converter, all the superzooms are very slow at the long end (which is the only place you'd use the converter), such that they would be almost unusable for typical photography with a 2x. In terms of overall image quality with current sensors, you might be better off just cropping for that 2x vs. using a converter. I'm guessing that, barring major marketplace developments, Tamron won't make any new Pentax-mount lenses, except any that Pentax chooses to rebrand and offer at a considerably higher price (like the 18-270.)

No no converter with the 16-300 just straight up i was told could be wrong that a pentax mount was coming for it. Handy to know that they are slow on the long end though. I would only use a 2x on a prime probably a straight 300. I agree probably better just cropping. Sorry tend to type as my thoughts go and don't put them into separate ideas very confusing for everyone.