Zoom Lens Clarification

[virtuoso90]

I already own a canon 18 - 200 IS lens.

I am considering the 70 - 200 f/4 L
I had a question whether the 70 - 200 gives me more zoom then the 18 - 200 ?? And if so whts the principle behind it ??

The fact that both lenses have a maximum of 200 mm focal length is a little confusing to me.

Also is there a major difference between image quality between the two lenses ??

Help is highly appreciated.

[OsmosisStudios]

You cant look at lenses as having a certain zoom ratio. Hell, prime lenses are, stricly speaking, a 0x zoom.

In SLR terms, the focal length "mm measurement" is an indication of how much magnification the lens provides. More simply: a smaller number means a wide-angle, a longer number is a more distant view.

Both those lenses provide the same magnification: 200mm is 200mm. The difference is that the 18-200 covers a range from wide-angle to telephoto: the 70-200 is a telephoto to telephoto. Your 18-200 will have a 70mm point to it.

The lenses also serve very different roles. The 18-200 is a versatile all-around lens, but the image quality is lacking compared to certain other lenses. The 70-200 is one of Canon's Sharpest lenses and is a telephoto only, so you'd be missing out on the wide end. That's where another lens would come into play.

My gear is a 10-24, an 18-70 and a 70-300. The 10-24 and 18-70 overlap (from 18-24) but otherwise I have to switch lenses to go any longer than 70mm.

[inkista]

What he said. Except...

Originally Posted by OsmosisStudios

You cant look at lenses as having a certain zoom ratio. Hell, prime lenses are, stricly speaking, a 0x zoom.

Nitpick: 1x zoom. (x-zoom = tele/wide-angle. So, 50mm/50mm = 1x).

So, while an 18-200 gives you 11x zoom, a 70-200 gives you 2.8x zoom, if you're going by the zoom factor. But typically, any lens with more than 3x zoom factor will be optically compromised in some way to provide that wide a zoom range. It's very very difficult to get optimal performance at every focal length along the way, which is why primes tend to be high image quality: it's a much easier design challenge to get optimal performance out of a single focal length.

The thing is, though, that those two lenses are quite different physically (the size and weight of the 70-200 is much larger and it's painted white and all metal) and--don't forget this--they differ on maximum aperture. With your 18-200, the 200mm end of the lens has a max. aperture of f/5.6. With the 70-200, it'll have one of f/4. Also, the 70-200 is an L lens. It has special glass in it to increase its CA performance and contrast. It's sharper and the colors richer, and the USM means that its autofocus performance is likely to be much faster than the 18-200. Also, it can be used on a full-frame body. The 18-200 is EF-S and cannot. But the 70-200 is a dedicated telephoto zoom, while the 18-200 is an all-rounder.

Both lenses are good at what they do--they just do different things. If you were going to shoot outdoor sports, the 70-200 would be a better tool, because it would autofocus more quickly and you'd have that extra stop at the long end. The 18-200 is a much better single-lens solution for travelling light. Different tools, different tasks.

[OsmosisStudios]

Originally Posted by inkista

What he said. Except...


Nitpick: 1x zoom. (x-zoom = tele/wide-angle. So, 50mm/50mm = 1x).

.

I thought the math made sense in my head. This is why im in design and not engineering.

[virtuoso90]

Thanks so much you guys !!

That Really Helped !!

Im definitely going to pick up a copy of the 70-200 f/4L !!