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01-30-2011, 05:40 AM   #1
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I have a 2x teleconverter, what do people think about them would it be worth using?

01-30-2011, 06:34 AM   #2
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All teleconverters degrade picture quality to some degree, good ones can still produce acceptable results while bad ones, well that one goes without saying. Take a picture with your standard lens, then add the teleconverter and shoot the same picture. Look at both and decide for yourself if you're happy with the results. Cropping the standard shot to the same dimensions as the teleconverter shot will help bring out any differences.
01-30-2011, 06:45 AM   #3
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Teleconverters seem to be a real crap shoot. I have a couple, a Quanatray 2X and a Soligor 1.7X. They work, but are not as good as the lens alone. You have to experiment to find if it is better for you to just crop the image or use the TC. Try the TC with all of your tele lenses, some lenses are better with a TC than others. I don't have an explanation for this. You just need to find out what works for you.
01-30-2011, 07:05 AM   #4
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I suppose the generally accepted wisdom is that a lens' shortcomings in IQ are amplified by a TC; the "gain" factor is inversely propotional to the quality of the TC. Therefore using any TC on a consumer telezoom class lens will usually not be worthwhile, but using a high quality TC with a higher native IQ (prime, or pricey (= fast, usually) telezoom) can give fair results; indeed, a crop of the same area should be a reasonable baseline for comparison.

Inevitably, there is loss of light (intensity) as the image falling on the sensor/film is streched yet the amount of light in absolute terms (as in counting photons) remains the same: 1.4x = 1 stop (2x area = 1/2 intensity), 2x = 2 stops (4x area = 1/4 intensity); actually slighty more as some of the available light is absorbed by the TC optics enroute to the sensor/film. This means a smaller effective aperture; a practical consequence is a dimmer viewfinder (MF more difficult) and AF problems and/or complete loss of the latter. Also, it seems that there is a connection with IQ here: a lens giving best results stopped down will continue to do so only this might no longer be practical with the TC.

01-30-2011, 07:32 AM   #5
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When the question about using my teleconverter comes up I ask myself "Is it better to take the shot without the tc, then crop as necessary to get the image I want, or to add the teleconverter and then not crop so much?" When I have the time I take the photo at the maximum zoom, then add the teleconverter and try again. Sometimes cropping is better, sometimes the TC is better. The auto focus does not work well with the tc, and the lens is stopped down more, so I always take the photo without it first. I do carry the tc for times when any photo is better than no photo. My Kenko 2x was only $20 on Ebay so it is a cheap option.
01-30-2011, 07:35 AM   #6
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What TC & what lens?
01-30-2011, 11:55 AM   #7
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A few TC's have come my way. I very occasionally use a macro-variable TC. I just don't use the others, and they're not worth selling. Yet. Oh, I keep two each of 2x and 3x in M42, just in case I ever want to stretch my 1000/10 mirror into a 10000/100 spy-eye. Yeah, right.

Some TC's are made for specific (long) lenses and are just fine there. Every telephoto lens has a TC optical group built inside it. But generic TC's are NOT matched to specific lenses and generally DON'T give better image quality (IQ) than you'd get by cropping and enlarging. But they're probably OK where IQ doesn't matter, like for surveillance, blackmail, etc.

02-01-2011, 12:08 AM   #8
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QuoteOriginally posted by fourfivesix Quote
I have a 2x teleconverter, what do people think about them would it be worth using?
More information is needed to give you an informative answer. All teleconverters will make you lose stops in aperture which in essence makes your lenses slower. All teleconverters will degrade IQ, to a certain extent. The better the converter the less IQ loss. Some converters will cause the lens to lose its AF and auto-aperture capabilities. Again the more expensive converters will allow you to keep the AF and auto-aperture capabilities of the lens. All in all I would say a 2x converter is useful sometimes. I have one and use it on seldom occasions but I do definitely notice the loss in IQ and the loss in aperture. No one can really answer this question for you because everyone will have a differing opinion. The best way would be to actually use one for yourself then decide. Good Luck!
02-01-2011, 01:33 AM   #9
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I used a Tokina 2x with the M 200mm and it was terrible! Maybe if you stick with a dedicated 1.4x from Pentax with the apprirate tele lens, it will work, but otherwise, just buy a longer lens instead, would be my advice.
02-01-2011, 05:16 AM   #10
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I wouldn't use a teleconverter with any zoom lens because they degrade image quality and the designers go to a lot of trouble to hide zoom's faults.

Be careful that the lens you are using doesn't move the rear element back into the front element of the TC too. Note that matched TCs will have a list of compatable lenses.

If you must use a TC the Genuine Pentax 1.7 AF does have a reputation of being one of the best non matched TCs available. It also allows AF with manual lenses but it's pretty slow.
02-01-2011, 06:43 AM   #11
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QuoteOriginally posted by fourfivesix Quote
I have a 2x teleconverter, what do people think about them would it be worth using?
If you already have one that fits and you like the images it helps you produce you should keep and use it...

If you don't like what it does for you... Get it up on the marketplace or on ebay and don't worry about it...
02-01-2011, 07:28 AM   #12
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High-quality TCs on high-quality lenses are fine.

Pentax 2X-S TC + DA*300mm:


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