A friend asked me a question and i need help with the answer.

[disco2td5]

He was looking at a catalog that had compact cameras with x40 optical zoom and dslr's with 18-55mm lens and was wonering if there is a formula for lens mm to x optical zoom. That way it would be easyer to compear zooms. He is trying to decide weather to go compact or dslr. Any help would be appreciated.

[Duane Pipe]

I cant help with the conversion Jeramy. I think we could offer more advice if we new what cameras they are thinking of buying or at least their budget. I think the most impotent question is What do they want the camera for, What is their main interest I mean:lol2:

[Lance B]

Need to know the size of the sensor on the compact he's looking at so as to compare actual mm or FOV equivalents. The 18-55 is a 3x optical zoom. 40x optical zoom? Seems like a huge zoom ratio and that would be akin to an 18-720 zoom on an APS C DSLR!

[Film Street]

18-55mm lens -

55 divided by 18 = 3.0555 optical zoom

18-200 lens -

200 divided by 18 = 11.11111 optical zoom


When comparing zooms pay attention to what focal length the zoom starts at eg:

16-200 lens -

200 divided by 16 = 12.5 optical zoom

some zoom lenses can sound longer much longer than others just by having only a couple of extra millimetres at the wide end.

[fotog]

As far as I know compacts don't go above 20x optical zoom. Anything above that would be impossible to hold steady unless you mount on a tripod. Then you might as well get an entry level dslr. Go online and check out reviews and comparisons of compacts, there are some really good ones.

[disco2td5]

I cant help with the conversion Jeramy. I think we could offer more advice if we new what cameras they are thinking of buying or at least their budget. I think the most impotent question is What do they want the camera for, What is their main interest I mean:lol2:
Thanks for replying.
He is looking for a camera for everyday eg happy snaps on camping trips and holidays and maybe geting into some landscapes in the futuer.
He also likes the idear of prime lenses on dslr's. hes looking at the nikon D3100 and im not sure what compack he was looking at.

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Need to know the size of the sensor on the compact he's looking at so as to compare actual mm or FOV equivalents. The 18-55 is a 3x optical zoom. 40x optical zoom? Seems like a huge zoom ratio and that would be akin to an 18-720 zoom on an APS C DSLR!
Thanks for the reply
He is looking at the nikon D3100 with the dx sensor . As for the x40 optical zoom i dont know what compact ha was looking at he may have given me the wrong number.

[Bennymiata]

Most compacts have very small sensors, so can use smaller lenses.
While a normal APSc DSLR has a sensor around 23X16mm, the average compact's or brige camera's sensor is only around 5X8mm (and many even smaller), so it's a lot easier to make a many X zoom lens for them than it would be for a DSLR, hence why you see lots of compacts with 20X zooms, and even up to 40X zooms.
They only have to go from a true 3mm up to 60mm to get 20X zoom, but the IQ of these lenses is in no way comparable to the lenses on DSLR's and the bigger the zoom ratio, the more they have to stick out at maximum zoom and the poorer the quality of the lens (in most cases).

[disco2td5]

18-55mm lens -

55 divided by 18 = 3.0555 optical zoom

18-200 lens -

200 divided by 18 = 11.11111 optical zoom


When comparing zooms pay attention to what focal length the zoom starts at eg:

16-200 lens -

200 divided by 16 = 12.5 optical zoom

some zoom lenses can sound longer much longer than others just by having only a couple of extra millimetres at the wide end.

Thanks for replying
This should satisfy him and also i have learnt something new my self from this:)

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As far as I know compacts don't go above 20x optical zoom. Anything above that would be impossible to hold steady unless you mount on a tripod. Then you might as well get an entry level dslr. Go online and check out reviews and comparisons of compacts, there are some really good ones.
Thanks for replying .
As for x40 optical zoom im only going bye what he told me. i didnt even thing of going online for some comparisons thank will have a look soon.

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Most compacts have very small sensors, so can use smaller lenses.
While a normal APSc DSLR has a sensor around 23X16mm, the average compact's or brige camera's sensor is only around 5X8mm (and many even smaller), so it's a lot easier to make a many X zoom lens for them than it would be for a DSLR, hence why you see lots of compacts with 20X zooms, and even up to 40X zooms.
They only have to go from a true 3mm up to 60mm to get 20X zoom, but the IQ of these lenses is in no way comparable to the lenses on DSLR's and the bigger the zoom ratio, the more they have to stick out at maximum zoom and the poorer the quality of the lens (in most cases).
Thanks for replying
Wow i did realize compacts have such small sensors. i thingk it might be best to show him this thread and let him make his decision.

[arthurking83]

smaller sensors with massive lens zoom ratios will generally give poorer image quality results than a much larger sensor with a smaller zoom ratio.

Also be careful with the specs on the 40x zoom of the camera, some of that multiplication could be 'sensor zoom' or digital zoom .. which on a small sensor is as useless as any number of other useless gadgets and accessories.

Some superzoom bridge cameras can perform quite well if the image size is kept to a minimum when compared to a dslr with a medium quality zoom lens.

[Mark L]

.... i thingk it might be best to show him this thread and let him make his decision.

And after he does that, suggest he also joins us here on AP. :th3::)

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Oh. If you do read this thread, g'day there, friend of Jeramy. :)

[ameerat42]

...Oh. If you do read this thread, g'day there, friend of Jeramy. :)...

There you are! A ready-made username:o