I use the x1.4 converter with my K3II and PENTAX-D FA 100mm F2.8 MACRO all the time - it's a great combination giving additional stand-off distance that's very useful for butterflies.
I don't know if the camera recognises the converter for distortion correction (I usually shoot RAW) but the results are first class. See my Flickr pages at https://www.flickr.com/gp/darrelphoto/05N75s
Best
Darrel

I'm not planning a switch to FF, just wanted to know how well suited the x1.4 converter is to the 150-450 zoom lens.

I've been using the Pentax DA* 300mm f4 with the Pentax-DA AF Rear Converter 1.4x converter on my K3II for wildlife shots and I've been pleased with the results. Recently though I've been thinking of investing in the Pentax 150-450mm F4.5-5.6 lens to bring more possibilities into view and was wondering how the lens performs with the converter. Any thoughts?

Hi All - thanks for taking the time to reply to my post - all very interesting! Ideally, Pentax would have redesigned and retro-fitted free of charge via a recall. Back in the real world, that was never going to happen but by ignoring the issue Pentax haven't done themselves any favours. What I'd like to see is for Pentax to acknowledge that there is a problem and to "legitimise" the reversion to screwdriver mode for those of us that do not want to carry on with SDM. Whilst they were at it, they could also reinstate the full suit of options in the K3II and future camera's debug menu. I wonder why dealers won't carry out the software fix. Given that they are in place, we are only talking about a very small marginal cost. It would probably take longer to open the returned packaged body than to do the work itself! That said, I would have happily have paid £30 or so, although maybe not now I know how simple the fix is to implement, unless you only have a K3II. Best regards, Darrel

I bought my DA*16-50 back in 2011. Its optics are excellent but the autofocus started to become unreliable around 18 months ago and just before Christmas it packed up altogether. Johnsons advised that a repair would be in the region of £180 to £220. Having read of others having multiple failures that didn't seem a good option to me. I'd read of software hacks to get the lens to revert to screwdriver mode but that required a Windows computer (I have a Mac) and my K3II wouldn't allow access to the necessary options in debug mode. So, what to do? Happily, I came across a hack that I could use with my Mac and so I decided to buy an older body, a K5II to reprogram the lens. The work took 3 minutes and now the lens is back in business, albeit a little noisier than before. I'll probably keep the K5II as a second body - maybe I'll need it again if/when my DA*50-135 packs up. I'm pretty pleased with this outcome but not so pleased with Pentax, who appear to have a head-in-the-sand attitude to this well documented problem. I've been using Pentax cameras for over 40 years and feel that I've shown them more loyalty than I've received from them. Why they can't get their dealers to offer this solution for a nominal cost - or for free? Anyway, I'm up and running again and looking forward to putting the lens to good use as the winter steam railway galas get underway.

DA17-70 (9mths) and DA*300 (14mths) - both fine...

great shots Clarky - wonderful colours!

OK - I forgot that. It's simple to register, you'll not be hassled!

The DA*300 is a corker for wildlife. I use it with my K10D for bird shots where, although 300 is a bit short, the sheer resolving power of the lens means that every pixel counts - that is, the images can be cropped quite hard whilst maintaining quality. A bonus for me is its close focussing capability that makes it very useful for butterfly shots too. Checkout my shots at link
Go for it!!

Just like to add my voice in support of SRS. Very friendly, efficient & great prices too.
Really good service!

Regards
Darrel