Confused about Zoom and "X" equivalent...

Nethawk

Nethawk

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Hi all,

Still a newb here but enjoying my time. For the time being I have a Canon S5IS (12 X zoom) and will be switching to a Nikon D60 soon with the standard 18-55 VR lens. My problem is that I don't know how to calculate how standard DSLR mm lens lengths translate into "6 X", "12X" power zooms etc. If say for instance I buy a 55mm - 200m zoom, then what's the "X" zoom equivalent? I read that it's like 11 or something but is that reliable? Is there a formula for figuring this out?

Thanks and appreciate the advice and help. :)

By the way, as long as this post is open, I might as well ask another question in regards to the 18-55m lens: is this lens capable of blurring a background and keeping my main focus subject sharp if I put the camera in aperture mode and zoom in? Or should I get a more powerful zoom for this?
 
the "X" ratio is simply the longest zoom divided by the smallest. So a 50-200 has 4x, the 18-55 has 3x.

However that figure is fairly meaningless as its only the ratio of the lenses minimum zoom to maximum - it says nothing about the initial zoom of the lens. for example a 50mm lens already has "twice the zoom" than a 25mm lens.
So my advice, get out of thinking of "X zoom" as its meaningless - just look at the focal length in mm instead. 200mm is twice 100mm which in itself is twice 50mm which is twice 25mm and so on.
Oh, and read up on crop factor as well.

Some more examples:

A 10-40mm lens has a "4X zoom"
A 50-200mm lens also has a "4x zoom". BUT this can see much further than the other lens even at its minimum.

Your current camera apparently has an equivalent of 36-432mm (432/36 is 12x) to convert roughly to SLR for comparison
 
The blurring effect your talking about is called bokeh, and is caused by opening up your aperture and shortening the DOF. Understanding DOF, Hyperfocal dist., and circle of confusion is very useful when getting into these techniques.
 
And is Bokeh achievable with a 55mm lens? I read somewhere that it's better to use a more powerful zoom. Here's a shot I took of an iguana last year with my Canon. But I forget what zoom factor I used to get it. I just want to make sure my first full DSLR lens is capable of getting a very good Bokeh.

site-ph6.jpg
 
You need to know the maximum aperture of your lens.

Bokeh is produced by using large apertures to shorten depth of field. Apertures are funny things because they work on a inversely proportional relationship but a very simplified explanation is that the smaller the f number, the larger the hole through which you take the pic and the shorter the depth of field. Small number, big hole, small DOF.

I'm not familiar with the Nikon range so I'm afraid I can't comment on the abilities of that particular lens, just that you want to be looking in the range of around f2.8 and below for cracking bokeh.

You are right in that the longer lenses do produce more in the way of bokeh.
 
it is possible to get bokeh with the kit lens, but it is dependant on how far the background is away from the subject. the higher the f stop(larger apperture) the smaller the DOF(bit in focus) and the closer the background can get but still be blurred(out of focus).

a 50mm prime is a cheap way to get large apperture for doing this, and the view is close to what you see with your eye
 
gnirtS said:
the "X" ratio is simply the longest zoom divided by the smallest. So a 50-200 has 4x, the 18-55 has 3x.

However that figure is fairly meaningless as its only the ratio of the lenses minimum zoom to maximum - it says nothing about the initial zoom of the lens. for example a 50mm lens already has "twice the zoom" than a 25mm lens.
So my advice, get out of thinking of "X zoom" as its meaningless - just look at the focal length in mm instead. 200mm is twice 100mm which in itself is twice 50mm which is twice 25mm and so on.
Oh, and read up on crop factor as well.

Some more examples:

A 10-40mm lens has a "4X zoom"
A 50-200mm lens also has a "4x zoom". BUT this can see much further than the other lens even at its minimum.

Your current camera apparently has an equivalent of 36-432mm (432/36 is 12x) to convert roughly to SLR for comparison
Click to expand...

Thanks, gnirtS!

Now I understand too! :)
 
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