How teleconverter work?


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Necroist

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#1
After some discussion with Aquarius this morning on teleconvertors, I decided it would be better to clear my doubts here.

Lets say there's this teleconvertor with rating of 2X

And I'm using a camera with 5X optic zoom.

Does it mean, my camera will have 10X optical zoom?
 

dbchoong

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#3
Here's some zoom power with my 2.7X teleconvertor on an A40.

Photo taken standing along Victoria Street opposite Bugis Junction (near 7-11 store).

First pic: Max 7.5X digital (3x optical and 2.5x digital)


This pic: Max 7.5X digital with 2.7X teleconvertor


;)
 

Goondu

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#5
Originally posted by dbchoong
Here's some zoom power with my 2.7X teleconvertor on an A40.

Photo taken standing along Victoria Street opposite Bugis Junction (near 7-11 store).

First pic: Max 7.5X digital (3x optical and 2.5x digital)

This pic: Max 7.5X digital with 2.7X teleconvertor

;)
Do you always shoot with digital together with the optical zoom? Your previous post on the 2.7x convertor has some degradation of quality near the edges of the pictures. Can it be due to your digital zoom?

:dunno:
 

dbchoong

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#6
Normally do not use digital zoom. I was just testing out how far the zoom can go. The previous post you mentioned, those pic were taken without digital zoom. Only 3X optical + 2.7X tele.

Yes, the teleconvertor degrades pic quality around the pic. The center is normally ok, but the sides normally can see some vignetting. The photos above are not cropped, just resized. A bit surprised that vignetting not so obvious in the pics. Wonder why?

:)

Originally posted by Goondu


Do you always shoot with digital together with the optical zoom? Your previous post on the 2.7x convertor has some degradation of quality near the edges of the pictures. Can it be due to your digital zoom?

:dunno:
 

Eugene

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#7
May i know the brand of this 2.7x teleconvertor?
How much is it?
Thanx

:what:
 

Necroist

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#8
Originally posted by dbchoong
Normally do not use digital zoom. I was just testing out how far the zoom can go. The previous post you mentioned, those pic were taken without digital zoom. Only 3X optical + 2.7X tele.

Yes, the teleconvertor degrades pic quality around the pic. The center is normally ok, but the sides normally can see some vignetting. The photos above are not cropped, just resized. A bit surprised that vignetting not so obvious in the pics. Wonder why?

:)

Its 3 + 2.7 meh?

I thought 3 X 2.7 heh...
 

Eugene

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erm... may i know the brand of this 1.9 TC?
Thanx
 

Goondu

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Originally posted by Eugene
erm... may i know the brand of this 1.9 TC?
Thanx
I think it is the SteinZeiser. Made in Japan. And your next question would be where to buy? I don't know. Check with dbchoong via pm.
 

Bean

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#14
Originally posted by Necroist

Lets say there's this teleconvertor with rating of 2X

And I'm using a camera with 5X optic zoom.

Does it mean, my camera will have 10X optical zoom?
Originally posted by mpenza
you can say that.

but this assumes that the "2x" teleconverter really is 2x.

Well, if the camera has a 5x optical zoom, let's say the variable focal length range of 20mm-100mm.

When you add a 2x teleconvertor, the varible focal length range will be changed to 40mm-200mm.

200 / 40 = 5x

Therefore, a 2x teleconvertor will not change your 5x optic zoom camera to a 10x optic zoom camera, but still remains as 5x.

;)
 

mervlam

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#15
Originally posted by Bean


Well, if the camera has a 5x optical zoom, let's say the variable focal length range of 20mm-100mm.

When you add a 2x teleconvertor, the varible focal length range will be changed to 40mm-200mm.

200 / 40 = 5x

Therefore, a 2x teleconvertor will not change your 5x optic zoom camera to a 10x optic zoom camera, but still remains as 5x.

;)
in summary, the 2x teleconverter only increases the focal length of your lens by a factor of 2. It does not increase the lens' optical zoom. ;p
 

roygoh

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#16
Not that simple.

For consumer digicams, the teleconverters are mounted in front of the main lens. Most teleconverters would cause vignetting when you zoom out, because it is not practical/cost effective to design the optics to provide 2X multiplication at wide angle. As such, your usable zoom range, with the teleconvertor mounted, and taking the 20~100mm original zoom range as example, may be 100 ~ 200 mm instead of 40~200mm. So you might end up with a 2X usable zoom range with the tele-convertor mounted. Of course, if you consider the entire zoom range with and without the teleconvertor, then your total available zoom range becomes 20~200mm, or 10X.

For SLRs, most teleconverters are mounted between the lens and the camera body. This design does not cause vigneting.
 

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