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Just curious

 
 
carlazxz@yahoo.com
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      10-24-2005
I have a 10X optical digital camera c755 , a point and shoot mind you ,
not SLR
I ordered a 3X telephoto to add from Opteka
So that gives me a 30x optical . Does it not ?
What am I missing here ?
Are you saying this 3x attachment will suck ?

In fact I saw an 8X telephoto attachment with tripod and all for the
same digital camera
Are you saying it is a joke ?

 
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Dave Martindale
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      10-25-2005
http://www.velocityreviews.com/forums/(E-Mail Removed) writes:
>I have a 10X optical digital camera c755 , a point and shoot mind you ,
>not SLR


So far so good. The "10X" here means that the longest focal length
is 10 times the shortest focal length, so the total zoom range is 10:1.
It does *not* mean that the camera provides 10 times magnification
compared to the unaided eye - it's not the same as 10X50 binoculars,
where the "10X" is actual magnification.

>I ordered a 3X telephoto to add from Opteka
>So that gives me a 30x optical . Does it not ?
>What am I missing here ?


Well, no. The device you ordered is an "afocal adapter", a small
telescope that mounts in front of the existing lens. It's not a
telephoto lens on its own - in fact it probably doesn't form a real
image at all.

When you install it, and zoom the camera lens to its longest focal
length, you'll get 3X additional magnification. Effective focal length
will be 30X that of the lens set to its shortest FL, without the
adapter. But you won't have a 30X zoom.

You'll probably find that the adapter will be usable only near max
telephoto settings on the main lens - at shorter focal lengths you'll
get vignetting. If you're *lucky*, it will be usable for the longest
3:1 portion of the main lens range, so the zoom range with adapter will
extend down to the point where the main lens without adapter can take
over. But you may find that the two ranges don't overlap, and you end
up with a 10X range without the adapter, and then a small range
somewhere out beyond that. Unless you can test the combination of this
adapter with your camera's lens in advance, it's best to assume that the
adapter will simply give you an additional fixed focal length that's 3X
longer - but no zoom range at all with it attached.

>Are you saying this 3x attachment will suck ?


Maybe. It all depends on the quality of the adapter.

>In fact I saw an 8X telephoto attachment with tripod and all for the
>same digital camera
>Are you saying it is a joke ?


Now *that* was almost certainly an 8X monocular telescope with a mount
that places your camera lens at the eye position of the scope. How well
these work depends on the optical design of the scope and the camera
lens. But there's often some vignetting, and the effective f/number can
be pretty slow. Look up "digiscoping" on Google to find lots of
information on this option. But it's *not* the same as having a camera
lens of the same focal length.

Dave
 
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