I'm Confused - mm?

[Fireblade2K4]

Ok, I've only recently gotten into photography, I've moved from a Canon A95 to a Canon S3 IS and thus far I have to say I am loving it, just the sheer satisfaction I feel after getting some nice shots, its a real joy! Plus posting them on here and getting positive and constructive feedback makes it all the more enjoyable.

So far i've pretty much managed to figure out what most aspects of photography and taking pictures are about and how they effect the overall shot, all except one, well one so far anyway unless I come across some others...it is "mm" or "focal length"

Now I will be moving to D-SLR soon, most of the people on here using a D-SLR when talking about lenses always talk in "mm" which I know is millimeters, but how do you work out what a lens is going to offer you from the "mm" of it. For instance using one off the top of my head, the Canon 18-55mm or Nikon 18-70mm what are they going to offer, how much zoom will they give me?

This might sound stupid but its just something I can't get my head round so would someone be kind enough to explain it to me please, I know it has something to do with the focal length but how do you know what these "mm" are going to give you?

Hope this makes sence as I found it a bit difficult to put into words.

Cheers
Stu

 

[Fireblade2K4]

Thanks for that link....very infomative indeed

Stu

 

[Fireblade2K4]

The best way to get your head round it is the field of view. This is how much you can see. At the wide end, you can see lots, zoomed in you can see little, but in more detail.

Your A95 had 38-114 mm equivalent
Your S3 has 36-432 mm equivalent

What this means is that your S3 can zoom in far further.

On SLR lenses, the mm focal length is for a film camera, or a d-SLR with a sensor the same size as a piece of film. However, most d-SLRs have a sensor that is smaller than a 35mm piece of film, so in effect this crops the image, and 'zooms' you in more on the image. Therefore, on a D-slr, you have to take the mm of the lens and multiply by 1.5 for Nikon and 1.6 for Canon to get the 'equivalent' focal lengths. So,

Canon's 18-55 becomes 28.8-88
Nikon's 18-70 becomes 27-105

However the greatness of D-SLRs is the flexibility, in that you can change lenses, and so focal lenths

Hope that helps matters!

Kimmett

edit: Too slow!

Ok so would I be right in saying that a 70-300mm lens on a Canon would actually give a focal length from 112mm - 480mm?

Stu

 

[Fireblade2K4]

Well I have to say that I do now understand what it is all about, I tried to work it out myself but just a tad too complicated so I thought I would ask the people who would know, thank you all very muchly

Stu

 

[Fireblade2K4]

Indeed it would, just a touch longer reach than your S3.

Hope that between us all we have managed to clear everything up

Kimmett

You sure have thanks a lot...will make looking for a d-SLR and lenses now so much easier...thanks again all.

Stu