HD PENTAX DA AF 1.4X AW Rear Converter

Oops, Sorry Dave's Mrs

No need to apologise Steve, I will just have to pluck up courage and take it on he chin when I tell her!

Cheers
David

Here is a comparison shot taken with the DA* 300mm ... 1st is a straight 100% no TC crop, second is with the TC and third is the Sigma 50-500mm OS.

All were handheld and shot wide open so there may be a little variance but I think this gives a pretty good idea of IQ. No processing, straight raw to jpeg conversion.

[IMG]http://img.photobucket.com/albums/v188/Sockpuppetuk/DA300mm_cr_zpscf7e5a00.jpg[/IMG]

[IMG]http://img.photobucket.com/albums/v188/Sockpuppetuk/DA300mmTC_cr_zps23e4efc4.jpg[/IMG]

[IMG]http://img.photobucket.com/albums/v188/Sockpuppetuk/50500mm500mm_cr_zpsca08ea99.jpg[/IMG]

Interesting Mike. How did you do the focussing on the three? I'm just wondering if you used live-view for the test since it should get rid of any small focus errors in the different lens/combinations.

Thanks for taking the time to put some comparisons up though.

Interesting indeed Mike. To my eyes the shot with TC looks sharper than the DA*300 on its own - which I didn't expect. From these images the Sigma to me looks pretty much as sharp as the 300 despite what most folks say.

No live-view used, just the normal viewfinder. My lenses are pretty much on the button focus wise with my K-5II so any variation in that respect would only be + or -1 either side.


It has been said on the other forum that the shots taken with the TC have been sharper than without on quite a few occasions. As for the Sigma being pretty much as sharp there is a definite drop off in my eyes but that is more than made up for by way of zoom usefulness (especially at airshows and suchlike).

I did actually send the TC back just before I went on holiday last week (precisely because of the 50-500mm) but bought another this morning which should be with me tomorrow hopefully.

This was through dirty double glazing and 40 feet away
link

My edit

that's how it looks to me. Back focussing a bit?

I agree with Smeggy's observation on this one, it does look as though the DA*300 shot is a tiny bit back-focussed. Look on the right of the fairy bottle, at the marks on the plastic of the bottle. These are definitely sharper in the first image and if this was focussed 100% I think it would be at least as good as the TC shot. The Sigma is the softest of the three, but still pretty good.

Regardless of the relative sharpness of all three images, this is still an impressive showing for the TC.

Regards
David

The 300mm is set exactly the same with and without the TC on the K-5II so if it were back focusing then surely it would be doing the same with the TC attached? The same focus point was used on exactly the same part of the bottle so maybe the focus point used was picking up a different target the first time .... which has always been my main gripe with Pentax.

Presumably the K-3 would be a better test due to the abundance of points.

Interestingly I could not get anywhere near as good results with the 60-250mm and teleconverter,

not necessarily. the addition of the TC could easily change the AF adjustment. I wouldn't trust the TC to be nuetral in this regard. It adds glass remember.


The reason I suggested "backfocussing" is that the right hand side of the bottle, which curves backwards appears slightly sharper in the first shot

.

I think it's more likely that the camera was moving slightly as the shots were made. A back and forwards movement of only a tiny amount would be enough to change the point of focus after focus was locked.

A tripod is really essential in any kind of lens test, even a simple one.

Yes, this is not rigorous enough IMO. Sorry Mike. Far too many variables unaccounted for. All of them look soft to me. None of the lenses have been given a fair shot.
But thanks for posting them; it all adds up and they have a certain real-world use. Essentially, there's not much in it in the real world, but I'm willing to bet the 300* would be a clear winner normally, not least because it would be faster, brighter in the viewfinder and the easiest to hold.
We really need tripod, mirror up, preferably best of 3 and original images to peruse.

No need to apologize, I did say in the original post there could be some variance due to the shots being handheld. But at the end of the day that is how I shoot, I have used a tripod precisely once in all the years I have been taking photo's (the day I bought it) so it was a legitimate test for my style

Incidentally, here's an example of using a cheap 2x convertor versus cropping a 300*.
Mirror up, tripod, manual focus, live view x 2, no sharpening.
300 cropped to 800px


300 with 2x convertor, cropped to 800px


This image sharpens-up really nicely with 50/1/0 USM