[HawaiianOnline]

What are the best K-Mount teleconverters you've used? I am aware that some TCs work better with some lenses, while others that are rubbish with those same lenses work very well with yet other lenses. So, please feel free to note what lenses work well with a particular converter. For example, I have a Sigma 300mm f2.8 and a Tamron 1.4 TC. I bought the Tamron 1.4 from a local shop that was going out of business some time before I got the 300mm The two work very well together, but I've always wondered if maybe Sigma's own 1.4 TC would be a better fit. I also have a sigma 2x that is utter rubbish on the 300mm IMHO. While the general feeling seems to be that any 2X TC is rubbish, would a TC like the Kenko MC7 work better?

[Jewelltrail]

I recently shot with the Tamron F SP TC 2X KR BBar MC7 and am very pleased with the results. I use it on some MF glass and especially on my Tamron 90 2.8. Here are some shots with the TC. The sparrow is with a Pentax 67 165mm f 2.8, the other pics are with the Tamron 90.

[Ben_Edict]

What are the best K-Mount teleconverters you've used? I am aware that some TCs work better with some lenses, while others that are rubbish with those same lenses work very well with yet other lenses. So, please feel free to note what lenses work well with a particular converter. For example, I have a Sigma 300mm f2.8 and a Tamron 1.4 TC. I bought the Tamron 1.4 from a local shop that was going out of business some time before I got the 300mm The two work very well together, but I've always wondered if maybe Sigma's own 1.4 TC would be a better fit. I also have a sigma 2x that is utter rubbish on the 300mm IMHO. While the general feeling seems to be that any 2X TC is rubbish, would a TC like the Kenko MC7 work better?

The performance of TCs is largely dependend on the lens and can hardly be generalized. Though the Sigma Apo TCs are a very good match to the Sigma lenses, specified to work with the lens. The 1.4x TC is really excellent and with my 70-200/2.8 I cannot detect any noticeable image degradation. The 2x Apo TC is visibly poorer - at least my copy - but still useful. Lowell has a 2x Apo which works extremely well with his Sigma 70-200/2.8, so the 2x Apo TC can be a very good match.

Nevertheless the very best TCs I have used so far are the Pentax 1.4x-L and 2x-L A-series TCs. The 1.4x-L is simply stunning and the 2x (though with a slight loss of IQ) is the best 2x TC I have used so far, much better than the Kenko MC7 or even the Pentax 2x-S version. At least the Kenko MC7 is better than the old Pentax K T6-2x.

Generally I would say, that not all 2x TCs are rubbish, but you should stick with those dedicated to special lenses (which is the Sigma policy). Any other combination is just hit and miss. 1.4x TCs offer higher IQ up to a standard, where you cannot discern any IQ difference to the lens itself.

Ben

[Jewelltrail]

What Ben says makes a lot of sense. I believe the "matching" of a TC to a lens is the essential part of the equation. I had been shooting with the Tamron 1.4X Pz-AF MC4 and my Tammy 90mm 2.8 but wanted more reach. When I picked up the Tamron F SP TC 2X KR BBar MC7 converter I was fearful image quality was going to take too much of a hit. But I tried it and liked the results; IQ is amazingly good. So much so, in fact, that I sold the 1.4x TC since with Macro I do not use AF. Here is a shot, along with a %100 crop of my current setup. My advice for you would be to seek out images with different setups, until you see one to your liking.

Tamron 90mm w 2X TC @ f5--500 ISO--1/1250th--spot metered--no Post Processing--shot Raw and resampled only

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Last edited by Jewelltrail; 09-25-2009 at 09:08 AM.

[pcarfan]

Sigma 100-300 F4 and the Bower 2X TC AF, had the TC for less than two days...

PP in CS2

[F16]

That's an impressive result for a zoom + 2x TC, pcarfan. I don't know what focal length or aperture you used, but certainly a good, usable result considering the setup. Who makes the Bower TC, Kenko maybe?

[Ben_Edict]

I recently shot with the Tamron F SP TC 2X KR BBar MC7 and am very pleased with the results. I use it on some MF glass and especially on my Tamron 90 2.8. Here are some shots with the TC. The sparrow is with a Pentax 67 165mm f 2.8, the other pics are with the Tamron 90.

Your images certainly show the potential of that combo - and your patience. I never got a sparrow that sharp or in such a nice composition. Sparrows are so nervous, always hopping around or just zipping by...

Ben

[Squier]

I have used the Tamron SP BBAR MC Flat Field 2X TC with a Tamron 70-350mm Zoom, and i reckon its a brilliant piece of kit. Having said that, its a dedicated TC for Tamrons and not just a generic TC

700mm @ F8

[pcarfan]

That's an impressive result for a zoom + 2x TC, pcarfan. I don't know what focal length or aperture you used, but certainly a good, usable result considering the setup. Who makes the Bower TC, Kenko maybe?

Focal length was 300mm X 2 for 600mm, but being indoors is not true 600. Aperture wide open at F4 X 2 for F8.

It is PP, for sharpness and contrast.

I bought the TC from a forum member to remove the lens element and use as an AF ext. tube. But just wanted to try it on my sigma prior to doing that to see how it compares to the 1.7 AFA I had, and the results are equal to or better than with the sigma 1.4 TC and it blows away the 1.7 AFA. The sigma 1.4 TC + sigma 100-300 got high praise in photozone (nikon mount). Needless to say, I am shocked.

Focusing is dead slow in room light (even with my FA77 1.8, so it's just the TC, and not the aperture), but F8 will not be usable in dim light anyways. I don't like TC's, but this combo is giving me hopes as I am willing to compromise to get 600mm...we'll see how it does in real life.....if the K-7 gains a two stop advantage in iso performance (iso 800 = K10D iso 200), then I will be thrilled, as I'll be able to get decent shutter speeds for 600mm even at F8.....

[Jewelltrail]

Ben Edict: Your images certainly show the potential of that combo - and your patience. I never got a sparrow that sharp or in such a nice composition. Sparrows are so nervous, always hopping around or just zipping by...

Ben

Thank you Ben for your generous words, but I can not take all the credit. I shot that on a tri-pod, with a setup. The bird feeder is not too far from the house and my setup was already pre-focused on the spot where the birds feed. Also, I have a remote control and can watch the birds from further away, but from an angle which allows me to know when is the best moment to push the remote.

Finally, the shot of the sparrow is a crop. But the Pentax Medium Format glass continues to impress me with IQ, with an without a tele. It really is beautiful glass, so Pentax deserves the credit here more than I do, along with the remote and tri-pod. I really look forward to getting more experience with MF glass on my crop sensor.

[HermanLee]

Vivitar 2x Macro TC with electronic contact.
This one is a very good TC for macro work.

Here some sample of Vivitar 2x MFTC + Pentax A 50mm/1.7:




It works well with FA 43 Ltd too:

[F16]

Focal length was 300mm X 2 for 600mm, but being indoors is not true 600. Aperture wide open at F4 X 2 for F8.

It is PP, for sharpness and contrast.

I bought the TC from a forum member to remove the lens element and use as an AF ext. tube. But just wanted to try it on my sigma prior to doing that to see how it compares to the 1.7 AFA I had, and the results are equal to or better than with the sigma 1.4 TC and it blows away the 1.7 AFA. The sigma 1.4 TC + sigma 100-300 got high praise in photozone (nikon mount). Needless to say, I am shocked.

Focusing is dead slow in room light (even with my FA77 1.8, so it's just the TC, and not the aperture), but F8 will not be usable in dim light anyways. I don't like TC's, but this combo is giving me hopes as I am willing to compromise to get 600mm...we'll see how it does in real life.....if the K-7 gains a two stop advantage in iso performance (iso 800 = K10D iso 200), then I will be thrilled, as I'll be able to get decent shutter speeds for 600mm even at F8.....

I figured you were probably using it wide open at 300mm, but wanted to confirm since the result is so good under those circumstances. Again, really impressive, I don't know much about that zoom but it must be a really good performer on its own, would be interesting to see how it compares to a decent 300/4 prime or 300/4.5 prime. Do you have a photo of that Bower TC & have you researched who makes it? Too bad it does poorly in AF even with fast lenses, hopefully it is more useful outdoors.

[pcarfan]

I figured you were probably using it wide open at 300mm, but wanted to confirm since the result is so good under those circumstances. Again, really impressive, I don't know much about that zoom but it must be a really good performer on its own, would be interesting to see how it compares to a decent 300/4 prime or 300/4.5 prime. Do you have a photo of that Bower TC & have you researched who makes it? Too bad it does poorly in AF even with fast lenses, hopefully it is more useful outdoors.

The sigma 100-300 is one of the best zooms out there....I rated it a 10/10 and only the FA43 fetched the same rating from me. (I haven't had the FA77 long enough to rate it yet). Sigma 100-300 has been tested against many Nikon and Canon primes and have come out almost in par with them.

This is the Bower TC I bought,
https://www.pentaxforums.com/forums/sold-items/58178-sale-sold-2x-pz-af-telecoverter.html
and at that time I did a Google search and was able to find many new ones for sale for ~$80, but i can't seem to find any now ???

The TC looks crap with the FA77...so, to my knowledge from these very early TEST shots only, it works only with the sigma 100-300 F4.

The following is a ~50% of the image...The bokeh is not messed up, which is just awesome....I cannot get good shutter speeds for 600mm at any suitable iso's from the K10d.......it will be a good combo for the K-7 (assuming iso improvement even over the k20d)...AF is fast in bright light.




This is a whole image. sharpened. Bokeh is still nice. The images do lose contrast and sharpness, but seems acceptable.


P.S: This time the bird was a bit closer, still a 50% crop...


The whole image


Only got two shots of this bird, looks similar to the ones posted earlier in this thread...heavily cropped.

[F16]

Thanks for the info & photos. Certainly looks like a worthwhile combination when you need a ton of reach without going out and getting another lens. I don't see major color fringing which is common with a TC & longer lenses. And I'm not sure that you'd see any major improvement with a 3rd party 400/5.6 + 1.4 TC over what you're using now.

[Squier]

I agree, that Sigma lens takes great shots - which model 100-300 is it ?