Zoom or teleconverter?

I have a 50-135 zoom, but on occasion need a longer reach lens. The 300mm Prime is now far too expensive for occasional use - so I am considering the 55 - 300 zoom but am concerned that it overlaps with my 50 -135 and predict lots of indecision as to which lens to pack!

Would a teleconverter be the answer - similar cost but much more portable and compact.
Any suggestions? Has anyone got experience of a teleconverter with the 50 - 135 - or would the 55-300 deliver better quality.

My main interest is landscape / architectural

From my experience with a Tamron teleconverter, I would say that IQ is significantly better without. I have compared a 135 mm prime and (2X) teleconverter against a Tamron 70-300 zoom, and IMHO the zoom IQ is much better. With the teleconverter, colours also seem to go 'cartoon like' (can't think of a better way of describing the effect) and contrast drops off.

I also tried the teleconverter on the Tamron zoom, and the IQ drops dramatically.

Maybe I've got a 'bad' one (teleconverter)? Otherwise I would recommend going with the zoom.

Thanks El Dingo

Do you think the effective reduced aperture on the prime / converter combo was the main cause for your reduced quality. I was wondering whether a 2x teleconverter on the f2.8 DA 50-135 would work relatively well compared to the lesser light gathering capability of the f4 -5.6 DA50-300 - or is that just naive thinking!

Yes it is, remember the tele-converter will reduce the light transmission by 2 stops anyway. So apart from reduced IQ because of the extra glass, your 2.8 would become a 5.6 at best. Much better to get a cheaper zoom; have you tried the Tammy 70-300, much better than comprimising the DA 50-135.

Davex.

editted, stupid remarks

Thanks Davex

I was hoping a teleconverter would help me avoid the difficult decision of buying an additional lens thereby increasingl bag weight and duplicating of the focal length of my DA 50-135 - however it would seem from the current responses that the loss in quality is quite noticeable.

The Pentax 1.7x teleconverter is actually very good and work well with my 50-135mm but for the money they are going for on Ebay (when you can find one) you could buy a Pentax DA 55-300mm.

Just to throw a spanner in the works, have you thought about replacing your lens with a 18-200 or 18-250 zoom?

One lens many uses!

Most of what you said Davex is half true.
The F-number is en ratio number of the diameter of the entrance pupil devided through the lens focal length. When you use a 2x converter you double the focal length while the entrance pupil stays the same that's why the f-number is two stops higher. The extra glass of the TC slows it down a tiny bit more but not that much.

The DA*50-135 has SDM and SDM only works good with one type of Tamron 1.4x TC. The Pentax 1.7x talked above has his own AF so that means that any lens mounted on it has AF.

If a lens of 70-200 is long enough then one of the TC above might preform quite or else I would go for the zoom.

To be totally accurate it is the MC4 version of the 1.4x teleconverter that works with the 50-135mm (there are 2 types, one with the required contacts and one without).

Thank you Mike I forgot the type
The MC4 PZ it was I believe or not?