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DPChallenge Forums >> Hardware and Software >> About tele lens
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08/05/2003 09:02:32 AM · #1
I've decided to buy 5x tele lens for my Sony DSC-S70.
This cam has 3x optical zoom. What will be overall zooming? I've heard that tele lens should be used on maximum focal length otherwise vignette would appear. So, available zooms are 1x - 3x (build-in), then I mount external tele lens and zoom varies from 3x to 15x. Is that correct?
I'm new into this, so forgive me if the question is dump :)

Message edited by author 2003-08-05 09:11:04.
08/05/2003 09:15:10 AM · #2
Alexander,
You need to know the "power" of the tele lens. If the lens is 3x, then your maximum zoom would be 3x * 3x = 9x. Since you've been told that vignetting will occur at short focal lengths, it seems that the lower end of your focal range will not be useful. Just how much of the range is useful you will need to determine by trial. You may find, for instance, that only 10x-15x is obtainable.
Make sure you can return the lens if you are not satisfied, or if you can find it locally, try it before you purchase.
08/05/2003 09:32:27 AM · #3
I don't have one myself, but some tele lenses are multipliers. For example, there is a lense made for the Sony F717 which is a 1.7x. It multiplies the optical on cam 5x by 1.7 giving an effective 8.5x tele.

It sounds like the 5x tele has a fixed focal length. If the 5x is not a multiplier, then it is fixed. You might look into this to be sure. If you have to use your camera on maximum focal length 3x, then you would be using your camera zoomed all the way out to 3x and leave it there, and with the 5x tele on the camera, you would have 8x fixed focal length with no zooming or you could possibly zoom some at the longer focal lengths of your camera's lens, maybe from 1.5x to 3x, giving you a 6.5x to 8x zoom.

If the 5x is a multiplying lens, then what you are thinking is correct, but I haven't heard of 5x multiplying lenses before. 5x would multiply any lens you put it on by 5 times.

Message edited by author 2003-08-05 09:35:48.
08/05/2003 09:46:33 AM · #4
Thanks for your replies!
Here is the link I've meant:
//cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2944185686&category=30066

I've seen 3x (but i was looking for more strength ;) tele also:
//cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2944017838&category=30069

What would you say about these two? What are the lacks here, which one is better in which features and what are the disadvantages (besides the need of tripod) in using tele lense overall? I see only positive sides, but sure there are some negative ones... :)
08/05/2003 10:10:44 AM · #5
Don't know enough about those to recommend or not. Just remember, in lenses, like most things, you get what you pay for.
08/05/2003 06:17:14 PM · #6
This lens does multiply the focal length by 5, in other words, your max zoom becomes 5x*3x = 15x. You will certainly not be able to use your full zoom range with this lens, you will be strictly limited to near maximum zoom.
IMHO, this thing probably won't produce great results, and the limited zoom range further limits its utility.
08/05/2003 07:45:06 PM · #7
My best advise - Do a web search on Digiscoping. Look for other people that have YOUR camera and have already gone through the expensive trial and error purchases. It will pay off greatly.
The last three entries in my portfolio were done with a Celestron C-5 spotting scope mated to my Sony. In all three cases, the distances were enourmous....

Message edited by author 2003-08-05 19:46:48.
08/05/2003 09:03:26 PM · #8
You may want to check the following website..
//www.ckcpower.com/
I own the New CrystalVue LX Lens, and it is outstanding, very good quality and it produces a good quality image with my camera it is about 7x

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