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Old Sep 26, 2003, 8:09 AM   #1
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Default Teleconverter trade-offs


As I've said some posts before, I'm still deciding on either buying the new Minolta Z1 because of the 10x zoom or the Canon A70 (or some other for what matters) and a teleconverter for picture quality. I'm still waiting for some reviews to decide.

But then I was thinking that, using a teleconverter might have some trade-offs. Does anyone want to share some knowledge on what might be the disadvantages of using a teleconverter against an original big zoom?

Have fun.

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Old Sep 26, 2003, 8:25 AM   #2
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Originally Posted by psargaco
But then I was thinking that, using a teleconverter might have some trade-offs. Does anyone want to share some knowledge on what might be the disadvantages of using a teleconverter against an original big zoom?
- Optically there is always less light , so you loose a F few stop when you add a lense , but you must compare fairly , because a long integrated zoom may have a high F number as well. Nevertheless , the TCON-17 (which I use with my D7i) doesn’t make you loose any F stops (forgot where’s the details of this).

- Mechanically , an add on lense may make the whole camera-lense assembly less compact and more fragile , see my comments in my case at the end of this thread:
If your camera use an extension tube to hold the add on lense, you then don’t have my “discomfort”.
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Old Sep 26, 2003, 8:52 AM   #3
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Disadvantages of additional teleconverter (starting with a longer lens)

Good teleconverters are expensive, cheap ones may not give good pic quality -- like trouble with bad CA (distorting colors/vertical lines showing up as "rainbow" under magnification), loosing pic sharpness, and vignetting

Bulky -- the Oly TCON17 is like 2# and 6" (with adapter tube) stuck on the end of the cam -- and its only 1.7x.

Limited zoom capacity because of vignetting and CA -- without a scope and some complex mountings, you might only get another 1.5-2x on the end of your existing lens.

Advantages of a teleconverter:
Smaller lenses are lighter.

If you don't need it, you can leave it home.

Shorter lenses can give better up-close and wide angle performance than long zoom lenses.

Many times shorter lenses + big teleconverter = better performance than longer lens + smaller teleconverter.

Best regards

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Old Sep 27, 2003, 9:34 AM   #4
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All good points. Just a couple observations to add. First, remember that when you add a tele converter you apply the magnification factor to the entire existing system. For example, let's say you have a lens which produces a zoom range ending at 200mm and you add a 1.7x tele to the end. You end up with 340mm at the full zoom, but the limitation is that you will likely encounter vignetting at less than full zoom which increases in severity as you zoom back.

With the "built-in" long zoom, you have no vignetting (usually) as you zoom back. "Nearly" any digicam which provides filter threads will work well with the TCON-17 1.7x Olympus tele extender so you can still add this to the end of your 10X zoom.

Keep in mind that 10X doesn't relate to telephoto magnification, but rather to the relationship between full wide angle and full telephoto zoom. If you start with 28mm at the wide angle end and have a 10X zoom lens you end up with 280mm at the telephoto end. If you start with 38mm at wide angle, you end up with 380mm at the telephoto end. Add a 1.7x tele converter to 280 and you end up with 476mm. Add the same tele to 380 and you end up with 646mm. So if you spend more time at the longer end of the focal length then you may want to think about a camera which has less wide angle to start with.

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