Question related to Teleconvertors

[tvanand]

Hi,

I have a question related to teleconvertors.

Currently i own 70-300G lens and 28-135 F4-4.5 lens, Is there any teleconvertor available which can be used on both these lenses (2x Teleconvertor). does the teleconvertor from sony support this.

thanks in advance

[harveyzone]

Currently i own 70-300G lens and 28-135 F4-4.5 lens, Is there any teleconvertor available which can be used on both these lenses (2x Teleconvertor). does the teleconvertor from sony support this.

I am pretty sure that the Sony teleconvertor will not work with either so you need to look for third party ones.

Any 2x teleconvertor used with these lenses will struggle with A/F, which will not work (or at best, will spend a long time hunting) at the long end, due to reduced light associated with it (2 stops lost with a 2x, 1 stop with a 1.4x). Also, the 70-300G is not screw driven, but uses SSM, so will not work with 5 pin convertors, and, I understand, is pretty poor even with many of the 8 pin ones. There is no reason that one cannot be used with manual focus though.

Be aware, however, that you can sometimes get better results by interpolating (up-sizing) a file and cropping than you can with a poor quality teleconvertor.

Personnaly I would not bother, unless you get a very good deal on one, in which case it may be worth picking one up to experiment with.

Some good information here... http://www.dyxum.com/dforum/forum_posts.asp?TID=2100.

[David Kilpatrick]

The Minolta/Sony converters can not be fitted at all to the lenses involved. The best standard choice would be a 4-element Kenko 1.4X converter, since this has eight pins and AF is retained. The Sony AF system will handle lenses of f6.3 and f8 nominal aperture, unlike the Canon AF which requires all lenses to be f5.6 or faster - which is why Canon don't make anything like an 18-200mm f3.5-6.3. I have actually got higher end 1D series Canons to work with slower lenses (the Tamron 28-300mm f3.5-6.3 VC stabilised lens for example). But all KM and Sony digital bodies will AF at f8. I used to have a 1.4X when I had the 28-135mm on film, and the real problem was that it lost the engraving-like sharpness which characterises that lens, along with boosting the slight pincushion distortion at the tele end to a more visible level.

David

[01af]

Be aware, however, that you can sometimes get better results by interpolating (up-sizing) a file and cropping than you can with a poor-quality teleconvertor.

Actually, I have never come across a case so far where cropping yielded a better result than a tele converter. Even mediocre ones usually give better results than cropping. That said, a really bad one might indeed be worse than cropping ... but so far I never saw one that bad.

Anyway---this kind of zoom lenses (i. e. AF 28-135 mm 1:4-4.5 and SAL 70-300 mm 1:4.5-5.6 G SSM as well as similar ones) generally don't go well with tele converters. While you can use them with 3rd-party TCs (like those offered by Kenko or Soligor, to mention a few), auto-focus won't work and image quality will be low. A lens-converter combination's performance depends on three factors: (1) quality of converter, (2) quality of lens, (3) and how well the two go with each other. So even when points (1) and (2) are fine, point (3) may still be dodgy---and with wide-angles and slow-speed zoom lenses, it usually is.

So rather than extending your zoom lenses with a tele converter, I'd rather go for a longer lens, e. g. the AF Reflex 500 mm 1:8 or a 200-500 mm (or thereabouts) zoom lens.

The best standard choice would be a 4-element Kenko 1.4X converter, since this has eight pins and AF is retained.

David, do you positively know that 3rd-party tele converters (or extension rings) will retain auto-focus with SSM lenses when they just have eight pins? Or are you just assuming so? The reason I'm asking is because I've been told that providing eight pins is not enough; in order to retain SSM auto-focus the converter also has to support the SSM protocol actively. However I am not sure my information is correct or not.

The Sony AF system will handle lenses of f6.3 and f8 nominal aperture ...

The limit for the Minolta/Sony AF system is a nominal aperture of 1:6.7 ... which is half an f-stop less than 1:5.6. The AF Reflex 500 mm 1:8 mirror lens is the exception that confirms the rule because the entry pupil's outer diameter is approximately that of a 1:6.7 regular lens. Regular lenses with a nominal speed of 1:8 won't auto-focus ... or if they do then inaccurately so and out-of-spec.


-- Olaf

[David Kilpatrick]

The current 8-pin extension tube set works fine on the 70-300mm SSM up to a point. With all three tubes on, it simply hunts, though it operates and apparently tries to hit the focus mark. The action is much too fast. With a single tube on, it's OK; with two tubes, it still works using the longest and the shortest, but it begins to hunt too fast using the longest and the middle.

I have no teleconverter to test. In my past experience, tele converters plus lenses would AF to f8, not f6.7 - that is, an f5.6 lens with a 1.4X converter was still functional.

David

[01af]

In my past experience, tele converters plus lenses would AF to f8, not f6.7 - that is, an f5.6 lens with a 1.4X converter was still functional.

Well---I even got a Minolta f/5.6 lens with a Soligor C/D 2× tele converter auto-focusing, i. e. at f/11 ... albeit on the Dynax 7D, this would only work with the four AF sensors at the corners, in bright sunlight. And it's neither fast nor accurate. And it will work with 3rd-party tele converters only. With a Minolta or Sony lens tele converter on a Minolta or Sony tele converter, auto-focus will get disabled whenever the lens speed drops below 1:6.7. For example, the Minolta AF Apo HS 300 mm 1:4 G lens on a 2× TC Apo-II won't auto-focus. The Minolta AF Apo HS 400 mm 1:4.5 G lens on a 1.4× TC Apo-II will.

There is a certain transition zone between where AF works as designed and where it will cease working entirely. 3rd-party equiment sometimes can, and will, take advantage of that grey zone ... but generally it's not a good idea to rely on the results.

-- Olaf

[01af]

I even got a Minolta f/5.6 lens with a Soligor C/D 2× tele converter auto-focusing, i. e. at f/11 ... albeit on the Dynax 7D, this would only work with the four AF sensors at the corners, in bright sunlight.

Regarding the question how this is possible technically ... I guess the off-center AF sensors can see, and use, some scattered stray light for focusing if it only is bright enough. Just speculating ...

-- Olaf

[Greg Beetham]

Hey guys I thought you might be interested in this, it might help with this converter discussion...David, you might already have this stuff anyway..
I've got some half doz pages of info on Minolta lenses and I've photographed a couple of relevant sections on the converters and the lenses they fit onto (or not) and if AF is enabled (or not).... it takes a bit of sifting through too get an answer to a specific question as the various lens models and the various converters have different status depending on which converter/model is fitted to which lens/model etc.
Greg

[tvanand]

Thanks for your replies. btw i was looking at the Kenko Teleplus model, from what i understand based on the comments is that the AF cannot be used in 70-300 G Lens if i am using a teleconverter (correct me if i am wrong).

Comparatively the Kenko brand looks cheaper than others models, but there are 2 types available the Kenko Teleplus PRO 300 DG and the teleplus mc7 DG (sorry, i was not able to find much information about this brand and also comparision between these 2 models), what is the difference between those. which one do you recommend

[01af]

... from what I understand based on the comments is that the AF cannot be used in 70-300 G lens if I am using a teleconverter ...

Umm ... yes and no. On a 2× tele converter, the 70-300 mm G SSM lens' speed will drop to 1:9-11 which is far below the official limit of 1:6.7. However, as said before, with many 3rd-party tele converters AF will still be functional, or will try to be. So you may get auto-focus ... but if it works in the first place (try it out!) then it will be inaccurate and not very reliable.

On a 1.4× tele converter, that lens' speed will drop to 1:6.3-8---which is better than the official limit of 1:6.7 at the short end but below the limit at the middle and longer part of the focal range.

Anyway, whether AF will be functional or not---image quality won't be the best. Zoom lenses of this kind generally don't go in harmony with tele converters. And the slow effective lens speed will render the lens-converter combination hardly usable.

... there are two types available, the Kenko Teleplus PRO 300 DG and the Teleplus MC7 DG [...], what is the difference between those?.Which one do you recommend?

The PRO 300 series is Kenko's top line of tele converters and the best you can get short of the original Minolta/Sony converters (which however won't work with the 70-300 G SSM). The MC7 also is pretty good. You can't go wrong with any but if your wallet permits then you should prefer the PRO 300. Still, the 70-300 G SSM lens is not really recommended to be combined with any kind of tele converters. They work best with fast tele zooms and prime telephoto lenses.

-- Olaf

[PhotoTraveler]

This is the compromise with such lenses as the 70-300G, same as the 100-300APO D it replaces.

With such lenses, you get more zoom than a lens such as a 2.8/70-200. But the price you pay is the high end constant aperture lenses tend to work with TCs, where the vari-aperture lenses do not. If you give up that initial zoom for a lens like the 70-200, you can later get it back with a TC and get up to 400mm with the 2X TC. So it's a trade off.

An important thing to remember is that TCs are really meant to be used on big Telephoto Primes. ~200mm and up. This is why all 4 brands have TCs that are matched and only work on those lenses. This gives you flexibility and the best optical quality you can. Consumer lenses and vari-aperture zooms just aren't meant for TCs. Nor are lenses in the standard to wide angle range.

It wasn't till brands went and re-did their 2.8 tele zooms that they put TC support in them. In the case of Nikon and Minolta, both their 80-200s did not work with the matched TC's the replacements do. There are very few zooms in all the systems that support the Matched TCs made by the system maker. For Minolta-Sony, only the 2.8/70-200 supports them. For Nikon only the 2.8/70-200 and 4/200-400 work with their TCs. For Canon, only the 2.8 and 4 70-200 Lenses. Getting TCs on anything else is pretty much a 3rd party route, and then the results could be not very good. And even the 3rd parties have matched TCs for their Teles, and those matched TCs don't work on the Sony, Nikon, Canon stuff.

Of course there are those odd exceptions. The 135 STF works with the TCs. Don't know if I have ever seen anyone try, and don't know why it supports them, but it does. Canon has some similar oddities. I've heard the new Nikon Tilt Shift lenses work with the matched TCs. Still, it remains that TCs are for big Tele Primes and zoom support is rare.

When you go for such a zoom, you are locked into that FL. This is why I think Canon has done a very good thing with the 4/70-200. It's a cheaper and slower tele zoom. But very good quality. So it's a great lens for those not needing the 2.8 or can't afford it. But it accepts the TCs, so you can make it a 280mm lens with a small TC and have AF, or a 400mm lens in manual focus. A nice high quality option that gives you a cheap yet fast high end lens most the time, but with a small add on gets you that extra reach when needed. No different than carrying a 1.4 or 1.7/50 in your pocket just incase you need something fast, you can carry the TC in case you need something long.

This is why I would very much like to see a 4/70-200G from Sony. I suspect the 70-400G will be as big as such a package, but it will always be a slow lens, not just when you need the big tele. It will probably cost more than what the 4/70-200G path would cost (1000+500 verses 1500+ for the 70-400). But more I would love to see them kick it up a bit and go for a 4.5/70-250G. Would work out to be about the same size and cost, but get you a bit more but still gives you AF with the 1.4x (just like the 4.5/400G took advantage of this). This would be a 6.3/350 at the long end and still have AF. I'd even accept it being a 4.5/100-250 if need be. And in manual focus you could get a 9/500 which isn't to bad, and no worse than the 8/500 Reflex. Of course the 8/500 breaks the F6.3 rule due to being a reflex.

The shear size and weight of the 70-300G or 70-400G make a 4/70-200G with TC support look pretty good in my book.

[Dr. Harout]

I noticed PhotoTraveler has joined us and just wanted to say a big hello and welcome.
I always read his treads and comments with great interest.
Welcome

[David Kilpatrick]

Seconded - these are useful contributions, and they won't disappear into the far distance quite as easily as threads on some very large forums can!

David

[Greg Beetham]

Hi PT, great post, good too hear from you again.
Greg