18mm-70mm lens versus 6mm-72mm?

Question

I'm looking at purchasing a digital SLR camera and I was wondering how the 18mm-70mm lens would compare to the one on my current fixed camera which is 6mm-72mm. I'd like to be able to zoom in as close as my current camera which works out as 12x, but the SLR kit lens is only 3.8x so doesn't sound as good despite the comparative large number. Am I getting this all wrong?

Answer 1

Point & Shoot cameras are marketed in reference to their zoom ratio, such as 12x with your camera.  SLR lenses are marketed by their focal lengths.   Your focal lengths are listed on your point and shoot, but until you start thinking in terms of focal length, it will be harder to understand.  In fact, you probably need to start thinking in terms of 35mm equivalent.  To do that, you need to know the sensor size of the camera as well as the focal lengths of the lens.

First you need to convert your point and shoot focal length to the 35mm equivalent.  I'm guessing you've got a camera like the S3 IS, which would be 36-432mm in 35mm equivalent.  (Sony H2 uses the same sensor size, so it's 35mm equivalent is the same.)

Next you need to convert the dSLR focal length to 35mm equivalent.  The 18-70mm sounds like a Nikon lens, so it would be 27-105mm in 35mm equivalent. (Sony A200 has the same 1.5 focal length magnifier, so the calculations are the same.)

Now you can compare the two lenses.

36-432mm vs 24-105mm.  The 18-70mm gives you more wide angle, but your point and shoot has much more in the way of telephoto.  The 18-70mm is mounted on a much better sensor, so for general walk-around shots, it's got a very usable focal length range and your image quality will be higher if you expose it properly and get it in focus.

Focal lengths greater than 400mm is considered super-telephoto.  If you want to get into this range, expect to buy a very expensive lens.  It will probably be a prime lens, which makes its zoom ratio 1x.  Another way people like to look at it is divide the focal length by 35.  So at 70mm, that lens would be a 3x power (70*1.5)/35.  At 72mm, your P&S camera would have a resolving power of 12.34x  (432/35).  I have a 600mm prime (1x zoom ratio) which has a resolving power of 17.14x.  If I mount my 600mm prime on my Canon 40D, it would have a resolving power of 27.43x (600*1.6)/35.

Answer 2

The 18 -72 will not give you the range that the other camera had. But while the range is smaller the optics will be much much better giving you a clearer better picture. At 18 to 70 you will get the range needed for most shots but only a tiny bit in the telephoto range. You will not need a wider angle than the 18 unless you do things like landscape photos. You may find you want more telephoto but you can always get those later

Answer 3

Well, in terms of zooming in, they are pretty much equal (72mm v 70mm)

However, with the 18mm lens, you will find you wont be able to zoom 'out' as far, such as for taking large landscape photos.

that said, it all varies depending on the size of the sensor, so the difference may not be that noticeable, and you will still be able to take decent landscape photos with the 18-70mm

Answer 4

I find that my 18-200 and my 50mm from nikon are fine....