# Lens question

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#### sonix

##### New Member
Hi all,

Newbie here in terms of lenses, just have a few questions in mind.

I saw lens like
28-135mm
70-300mm

If let's say I divide 135/28 = 4.8
300/70 =4.2

Does it means that they can zoom at the same range? or the bigger the mm means it can zoom more? still a little bit confuse.

Thanks

#### Zerstorer

##### Senior Member
What zoom really means is how much difference there is between the tele and wide setting.

The actual angle of coverage/view of the lens depends on its focal length(mm).

V

#### vince123123

##### Guest
What you have done is to simply calculate teh zoom ratio, so a 28-135 lens has a ration of 4.8x, and your 70-300 has a ratio of 4.2x, not unlike those you see in videocams or digital cams which advertise a zoom ratio of 3.0x or 5.0x

to answer your question, the mm means the focal length of the lens. at the risk of simplifying, the lower the mm number, the wider the lens, ie at 28mm is a wide angle, 300 is a telephoto.

zooming more or less is an ambigious term. for a 28-135 lens, it means that it can zoom from 28mm (wide angle) to 135mm (short-mid telephoto)

likewise the 70-300 can zoom from a focal length of 70mm (short telephoto) to 300mm (telephoto).

hope that helps

Cheers

Originally posted by sonix
Hi all,

Newbie here in terms of lenses, just have a few questions in mind.

I saw lens like
28-135mm
70-300mm

If let's say I divide 135/28 = 4.8
300/70 =4.2

Does it means that they can zoom at the same range? or the bigger the mm means it can zoom more? still a little bit confuse.

Thanks

#### mervlam

##### Senior Member
the longer the focal length, the higher the magnification of the image. that's optical physics.

zoom ratio is also the magnification ratio.

#### sonix

##### New Member
Great thanks for the explanation, I understand now

now I'm still wondering to get 24-85mm or 28-135mm for my new 10D.

I tried 24 - 85mm but not 28-135 yet... 24 mm * 1.6 is around 38.4mm which is just nice, close to 35 mm.

Any suggestion which one to get, price difference is quite high tho but at the same time i love the 24mm too.

Regards,
Sonix

#### Prismatic

##### Senior Member
IMO, the 24-85mm isn't such a good lens; the edge definition isn't good and there's quite a fair amount of distortion at the 24mm end. Think you will be better off with the 28-135mm.

Also, you might also want to wait for the new 17-40mm lens if you are into wide angles.

#### sonix

##### New Member
Ok thanks a lot, I think I will go for the 28-135mm, eventhough it's quite pricey.. it think around \$900+...