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Cameras, Lenses and Accessories: Discuss Kenko TeleConverters...Will the AF on my Nikon D90 work on the Kenko Pro 2x & 3x conveters for digital cameras? I ...
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Old 15-08-2011, 04:57   #1 (permalink)
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Kenko TeleConverters

Will the AF on my Nikon D90 work on the Kenko Pro 2x & 3x conveters for digital cameras? I have a Nikon D90 & use a Nikon AF-S DX 18-200 VR 3.5-5.6 G ED lens. The Proo 300 3x needs max apeture of f/2.8 or brighter and the Pro 2x needs f/4 or brighter. Can I adjust the ASA value so that my D90 will function (AutoFocus) in the max apeture required light situations? ie 2 stop light reduction & 3 stop reduction?

Or will I need to manually focus, etc. to use them.

Greg Mc

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Old 15-08-2011, 09:07   #2 (permalink)
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Re: Kenko TeleConverters

Welcome to Pixalo Gemac

Kenko have a good reputation and are a popular choice. However, you are right to be cautious. My guess is that your lens will not accept a TC.

First, I have no experience with these converters, but I have used Sigma and Nikon TCs. I had a Sigma 1,4x TC to use with my Sigma 70-200 f2.8 and it worked very well. However, when I bought a Nikkor 80-200 f2.8, it would not allow any auto functions. Now, I don't know if that was just a one off thing that affected just me, but changing to a Nikkor TC cured the issue.

On their web site Sigma list the combinations of lenses and TCs that work. Not every lens will accept a TC if the rear elements of the lens will come into contact with the TC. Not good! You will have to ensure that the combination you want is compatible. This will also probably change with the power of the TC. For instance, a 1.4x might work with a lens, but not the 2x TC. The Sigma web site does not have their 18-200 listed in the TC compatibility chart.

I would be very cautious about using a 3x TC. I have never read a review that gives a good quality report at this power.

You are right to think that autofocus will be affected by using a TC. A 1.4x will loose 1 stop, a 2x will loose 2 stops and a 3x will loose 3 stops. As the lens needs light to autofocus, upping the ISO will have no effect. I'm only familiar with the Sigma web site and they also have a chart that gives lens and TC combinations and if AF will work or not. The Sigma 18-200 does not appear in this chart.
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Old 15-08-2011, 09:15   #3 (permalink)
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Re: Kenko TeleConverters

Found this compatibility chart on the Nikon web site. Looks like I was right in saying that your lens will not accept any TC

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Old 15-08-2011, 10:47   #4 (permalink)
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Re: Kenko TeleConverters

Welcome to Pixalo Greg

Quote:
Originally Posted by gemac View Post
Can I adjust the ASA value so that my D90 will function (AutoFocus) in the max apeture required light situations?Greg Mc
No. f/stops are a physical adjustment which constrain the operation of the lens. ISO is the perception that the camera has of the light arriving at the sensor and can be changed to react to different light. The camera's metering needs the amount of light that physically passes throught the lens in order to meter and focus. Nikons generally require lenses faster than f/5.6 (smaller f/stop numbers) in order to auto focus. Adding a teleconverter increases the f/stop number and will then usually require manual focus.


Graham, I have been looking at these converters because they have the reputation of fitting all Nikon lenses, even those with the rear element closer to the camera. There are a number of reports on various web sites of possible couplings.

On the plus side
They are deeper recessed and the Pro 300 DGX range is reckoned to be excellent quality with top glass and coatings, and equal to any Nikon / Canon with full automation. The DGX is important as it has full electronic coupling with its own (CP?)U that translates the distance information and f/stop so that you get full 3D matrix metering. The earlier DG range does not do this. The 2x and 3x have good reports of their sharpness.

On the negative side
Kenko recommend their converters with fast prime lenses with a longer focal length than 50mm, although users have reported good auto-focussing results in strong lighting with zoom lenses only giving a maximum of f/5.6. coupled with the "Kenko Pro 300 DGX 1.4x".
As this lens has a minimum focal length of less that 50mm and a maximum aperture of f/5.6 at 200mm, it would not be recommend to use any teleconverter with it, even though they look attractive alternatives for a longer reach.
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Old 15-08-2011, 11:41   #5 (permalink)
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Re: Kenko TeleConverters

Quote:
Originally Posted by grease spot View Post
Kenko recommend their converters with fast prime lenses with a longer focal length than 50mm,
Both the Sigma and Nikon compatibility charts do not have any TC compatibility with zoom lenses under 50mm at the short end. I think that this is because of the physical construction of these lenses brings the rear group of elements too close to the rear of the lens to accommodate a TC.
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Old 18-08-2011, 21:35   #6 (permalink)
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Re: Kenko TeleConverters

Never found a lens my Kenko 1.4x TC won't fit (but Canon/Sigma lenses not Nikon) - but then I've never tried it on anything under 105mm (but I will over the weekend!). Of course, AF suffers if the aperture is above f/5.6 but I've successfully stacked 2 x 1.4x on a 500mm f/4.5 lens (but had to resort to the taping trick to fool the camera electronics)
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Old 18-08-2011, 22:47   #7 (permalink)
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Re: Kenko TeleConverters

Quote:
Originally Posted by grease spot View Post
On the plus side
They are deeper recessed and the Pro 300 DGX range is reckoned to be excellent quality with top glass and coatings, and equal to any Nikon / Canon with full automation. The DGX is important as it has full electronic coupling with its own (CP?)U that translates the distance information and f/stop so that you get full 3D matrix metering. The earlier DG range does not do this. The 2x and 3x have good reports of their sharpness.
I have the 1.4x DGx as well as Nikon 1.7x and 1.4x and 2.0TCII and also a 2xTC III. I used to have the Kenko 2.0DGx like the 1.4 to occasionally work with 2 bodies but sold it when I got the TCIII. The Kenko are amazing value, versatile and have a lot going for them but are not equal to the Nikon equivalents in build quality, weather proofing (they have none) performance and, not quite, optically. 2.0X was always a last resort but with the arrival of the TCIII then it may get more use. I have never tried one of their 3.0x and can't see any circumstances where I would need one, it might have a use in astro photography.
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Old 18-08-2011, 23:36   #8 (permalink)
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Re: Kenko TeleConverters

Quote:
Originally Posted by VinnyP View Post
I have the 1.4x DGx as well as Nikon 1.7x and 1.4x and 2.0TCII and also a 2xTC III. I used to have the Kenko 2.0DGx like the 1.4 to occasionally work with 2 bodies but sold it when I got the TCIII. The Kenko are amazing value, versatile and have a lot going for them but are not equal to the Nikon equivalents in build quality, weather proofing (they have none) performance and, not quite, optically. 2.0X was always a last resort but with the arrival of the TCIII then it may get more use. I have never tried one of their 3.0x and can't see any circumstances where I would need one, it might have a use in astro photography.
Thanks for the very useful feedback. I had not considered build/weather proofing in my comments above but just what I had found with regard to optical performance.
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Old 21-08-2011, 04:55   #9 (permalink)
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Re: Kenko TeleConverters

If I only used my lens in the 100mm and above could I still use the TC in auto focus, exposure etc or would I still need to focus and get exposure info manually?
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Old 21-08-2011, 08:38   #10 (permalink)
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Re: Kenko TeleConverters

Using a longer focal length will move the rear elements away from the back of the lens, but you will risk causing damage to the lens should you forget you have a TC fitted in the heat of the moment. I think that you will still loose AF, but not sure about the exposure.

I believe that to prevent unsuitable lens/TC combinations that might cause damage to the lens and/or the TC Nikon have a peg on the mount that will not allow the TC to be fitted, so if you are still going to do this I would check before you buy.

My advice is don't do it.
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Old 21-08-2011, 09:53   #11 (permalink)
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Re: Kenko TeleConverters

It would auto expose and with a 1.4x will probably just about AF but not reliably especially on moving subjects. Anything higher than that won't even nearly AF and manual focusing with that dark an image on the D90s focus screen is not going to be easy. If you want a little more reach then think about replacing the 18-200 with a Tamron 18-270. But the best solution for longer than that is going to be ending up with 2 lenses.
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