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Old Dec 7, 2005, 1:40 AM   #1
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When one uses a teleconverter lens, what is the downside?

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Old Dec 7, 2005, 2:36 AM   #2
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Using a teleconver lens will decrease image quality.A 2× teleconverter gives the effect ofdoubling the focal length. It also decreases the amount of light reaching the film or sensorbya factor of 4 as well as the decreasing the resolution bya factor of 2.
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Old Dec 7, 2005, 3:53 AM   #3
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Only if you use eBay's general El Cheapos whose best use is paperweight.

High quality converters designed for lens in question don't degrade quality or lower F-ratio, but those are big, heavy and costly.

Downside is that you can't use zoom with them, those are meant for use at full tele position of zoom. Otherwise you'll end up with lot of vignetting.
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Old Dec 7, 2005, 5:08 AM   #4
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Depends. Are you talking about a teleconvertor for an SLR, or an addon converter for a fixed lens camera?

If you get a good quality (tele)converter, there should be little or no loss in image quality. The addon fixed lens converters will not effect the f stop of the lens, but the SLR between the lens/body teleconverters will reduce the amount of light reaching the film/sensor.

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Old Dec 7, 2005, 9:14 AM   #5
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I am going to get the Canon S2 IS. What you are saying, then, is that I wont be able to use the camera"s zoom if I add the tetleconverter? I plan to get the Canon teleconverter. Thanks!
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Old Dec 7, 2005, 10:41 AM   #6
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amazingthailand wrote:
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Depends. Are you talking about a teleconvertor for an SLR, or an addon converter for a fixed lens camera?

If you get a good quality (tele)converter, there should be little or no loss in image quality. The addon fixed lens converters will not effect the f stop of the lens, but the SLR between the lens/body teleconverters will reduce the amount of light reaching the film/sensor.

Declan
On an SLR, a teleconverter will affect the f stop. The 1.4 will lose you One stop, the 2x, will cost you two.

The cheap converters are a waste of money. They will degrade the image in a noticable way. The better ones will have SOME effect - but not enough to do major harm.

They will have NO effect on zoom. If you have a 28-105, with a 2x, you will have 56-210

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Old Dec 7, 2005, 4:51 PM   #7
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Doctor Bob wrote:
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I am going to get the Canon S2 IS. What you are saying, then, is that I wont be able to use the camera"s zoom if I add the tetleconverter? I plan to get the Canon teleconverter. Thanks!
The teleconverter lens added on the front of the existing lens will have an exit pupil designed to work at the maximum focal length. If you zoom to a lower value, there will likely be vignetting, getting more severe with shorter focal lengths.

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Old Dec 8, 2005, 12:12 AM   #8
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Brian - Thanks! What you are saying, then, is I should have the lens at the maximum power and the add on the teleconverter. I should not adjust the zoom after that. Do I have it correct?
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Old Dec 8, 2005, 12:55 AM   #9
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Doctor Bob wrote:
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Brian - Thanks! What you are saying, then, is I should have the lens at the maximum power and the add on the teleconverter. I should not adjust the zoom after that. Do I have it correct?
Yes, unless you want the effect of looking through a hole, which can be used creatively at times. :evil:

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Old Dec 11, 2005, 7:59 AM   #10
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Gidday Dr Bob
I have the S2 and use an Oly Tcon17 - vigenetting will start just past 3X zoom giving you about 9X to play with. The Canon is not much different only not as much zoom and more expensive.

Check this site for comparisons

http://www.lensmateonline.com/newsite/S2tele.html


Also another lens i have just found out about with a 58mm thread is the Sony DH1758 or HDG1758 (not sure of the difference) not much price diff and will fit straight on to 58mm adapter - so no step rings.

Cheers Dom
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