[stormtech]

I'm kind of jumping in here, but want to thank you Scott for your analysis of the TC's. And apologies to the OP - I am not trying to off-track you post - just a comment about how Scott's post just shed some light for me.

My go-to lens for birding and wildlife is my presently longest lens - the FA* 300 4.5. I also yearn for something longer toward the 500mm range, but like you say, I just don't have that 5K for the Sigma 500 4.5 lens.

I have tried the Pentax F AF 1.7x TC on my FA* lens. While the IQ was acceptable, I found with practice that I could get the same or slightly better results with cropping the native 300mm image to the same FL as with the 1.7x TC. So I abandoned that TC. I am thinking of trying the readily available Vivitar 1.4x TC as it is supposed to be equal to the Tamron 1.4x PZ TC. But again, I feel that I can do the same or better with just cropping my images instead of using the TC.

But one thing you said might have struck a chord with me - that with the TC installed, you will have a better chance with AF than without at longer distances since the subject will fill the frame that much more.

Very interesting development for me - I will have to ponder this for a bit. Thanks for making me think Scott!

[AdrianM]

As an alternative, try the Sigma 150-500, if the 500 f4.5 is too pricey. There are a number of Pentax bird photographers that I know in Australia who have this lens and it is delightfully sharp.

By the way, before I bought the 500 f4.5, I used a DA*300 with a Kenko 1.5x TC. For most circumstances, I had to use 'catch in focus' to get the combination to work, but it was deligtfully sharp, and it is a combination that I still use when trying to save on weight. I also have Sigma 100-300 f4 and that takes a TC quite well and achieves autofocus better than the DA*300 with TC.

[audiobomber]

As an alternative, try the Sigma 150-500, if the 500 f4.5 is too pricey. There are a number of Pentax bird photographers that I know in Australia who have this lens and it is delightfully sharp.

Some people are satisfied with the Sigma 150-500mm, some are not. My definition of sharp is that the image is still sharp at pixel level (i.e. cropped to 100%). The Sigma 150-500 did not meet my standard at the long end so I returned it. This review is accurate IME: Sigma 150-500 mm f/5.0-6.3 APO DG OS HSM review - Introduction - Lenstip.com

The Sigma 50-500 is sharper at the long end: Sigma 50-500 mm f/4.5-6.3 APO DG OS HSM review - Introduction - Lenstip.com

Both my Pentax A*300mm f4 and DA*300mm are sharp enough, used with a Kenko PZ 1.5X. The A*300 is more prone to CA in high contrast conditions. Auto focus with the Kenko is not very reliable, but this is supposedly ameliorated if you pre-focus manually.

[Shanti]

Some people are satisfied with the Sigma 150-500mm, some are not. My definition of sharp is that the image is still sharp at pixel level (i.e. cropped to 100%). The Sigma 150-500 did not meet my standard at the long end so I returned it. This review is accurate IME: Sigma 150-500 mm f/5.0-6.3 APO DG OS HSM review - Introduction - Lenstip.com

The Sigma 50-500 is sharper at the long end: Sigma 50-500 mm f/4.5-6.3 APO DG OS HSM review - Introduction - Lenstip.com

Both my Pentax A*300mm f4 and DA*300mm are sharp enough, used with a Kenko PZ 1.5X. The A*300 is more prone to CA in high contrast conditions. Auto focus with the Kenko is not very reliable, but this is supposedly ameliorated if you pre-focus manually.

would you say then the DA 300 is sharper than the Sigma 50-500? then, the samples at lenstip at 500mm are not so impressive,to me at least

[rawr]

the samples at lenstip at 500mm are not so impressive

By all accounts the Sigma 50-500, particularly the OS version, does well at 500mm, and even the Lenstip test shows it performing quite decently at 500mm @ f8.

I'm pretty sure that the DA*300 is a much sharper lens than the Sigma 50-500. But add a 1.5 or 1.7 teleconvertor to the f4 DA*300, and it may perform a lot like the Sigma.

However, of course, when you are getting out to 500mm, while lens sharpness of course should be a priority, good technique becomes more important than ever, since even the slightest bump or vibration can make even the highest quality lens at that focal length look soft.

[ramiot]

And natuturally there are other options in the Pentax world, I own a Pentax A*600mm with a Pentax 1.4X-L TC and I am very happy withe results. Yes it means doing your focus manualy and it is a heavy set-up but it delivers pretty well. here are some photos :





I've owned a Bigma 50-500mm a few years back but I prefer this set-up because of the fixed prime lens . It is a affordable solution.