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Pentax 2x Converters

Joshua Woolls , Jun 19, 2007; 04:58 p.m.

I have a Pentax K100D and I was looking at getting a 2x Converter. Pentax Rear Converter-A 2x-S is the one that I have found and I was wondering if it is a good choice or if I would be making a mistake picking it up. The price is about 60 dollars, which seems reasonable to me. Is there a better option? If there is, does it cost substantially more. What features would I not be able to use on my camera with this lens? Thanks for all the help.

Responses

Peter Zack , Jun 19, 2007; 05:56 p.m.

I would recommend a 1.4x converter if you are getting one, Tamron makes a good version as does Sigma (APO EX). Both will cost more but produce better results. These will multiply a 300mm to roughly a 420mm which has an effective focal length of 630mm on a DSLR and you only loose 1 stop (at f4 the lens becomes f5.6 etc). You may loose the auto focus though, unless the lens is below f4. Most converters are designed for faster lenses to retain the auto focus function. And that is also assuming you have enough available light for auto focus to begin with.

These converters do reduce the lenses image quality as well. Any converter will show a loss in the final image.

You may just want to save the money and wait to buy a better long lens and then you keep the AF as well as the image quality.

That being said I have a Vivitar 2x macro converter that I never use to extend the telephoto length but as a macro lens. It's convenient but still not as good as a dedicated macro lens like the 50mm f2,8 or 100mm f2.8 etc. It will convert a 50mm lens to a 100mm 1:1 macro. It basically works like a set of extension tubes with variable control to frame the shot. They usually sell for around $60-80 and there is a version with all the contacts so that the lens keeps full auto control again if it is faster than f4.

Godfrey DiGiorgi , Jun 20, 2007; 09:58 a.m.

I have a Pentax-A Rear Converter 2x-S. It is an excellent performer and poses minimum degradation of image quality with lenses that match it well. Fitted behind any A series or later Pentax lens, it allows full metering functionality on the Pentax DSLRs. It does not transmit focal length information, however: you have to set that manually with the K100D and K10D.

I find that it tends to exaggerate chromatic aberration with the DA50-200 and DA70 lenses. I use it mostly with the A50/2.8 Macro to provide a longer focal length for better working distance and 1:1 magnification: with this lens, there seems very little CA exaggeration and it doesn't degrade image quality by very much at all.

Overall, I haven't found any other teleconverters that performed better. I've tried a Vivitar and a Sigma, they produced similar results. $60 is quite inexpensive for a six to seven element teleconverter of this quality.

Godfrey

Peter Zack , Jun 20, 2007; 11:58 a.m.

I should qualify my comment. The Vivitar I was referring to sells for $60-80 as a used item. It was much more than that when new. Metering works just the AF is lost on a slower lens.

Douglas Stemke , Jun 20, 2007; 12:38 p.m.

I would parallel Godfrey's comments I have the 2X-S and 1.4X-S. The 1.4X is a better TC, but of the 2X TCs I've owned the 2X-S has been the best optic. Mine did loose a screw though and it has proven hard to find a good replacement.

Maurizio Maggiore , Jun 20, 2007; 05:56 p.m.

I have the 1,7 autofocus and it works well with the 300 FA* f4.5. However, I have to disable the lens's autofocus and set it to infinity.

I also have the dedicated 2x for the Sigma 80-200 2.8 and I reccommend the two wholehartedly. It all boils down to which lenses you need to use it with, I guess, as pointed out by others. Maurizio

Sonbou abc , Jun 29, 2007; 02:22 a.m.

Be very careful with duplicators. I have the sigma 2x (with AF and everything...) and I barely used because it takes a lot of light. For this reason, If you only need 1.4x don't get 2x. And if you can effort a new lenses don't use a duplicator (for sure). Exceptions: 1- You own really good lens; 2- For whatever reason, You don't have to mind for light; 3- Just experimenting.

George

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