Help Crop Sensor Magnification

[Guitarman0]

Hello there,

I am new to DSLRs and I have recently picked up a Canon 550D with the standard 18-55mm f3.5-5.6 kit lens. I have however been reading around on the internet and now understand the difference between a crop sensor and a full frame sensor but am wondering, with my current kit lens, am I getting 18-55mm or 1.6x that? Also, if I were to buy the Canon EF-S 18-135 mm f/3.5-5.6 IS Lens, I assume I would get the 18-135mm rather than 1.6x that as (correct me if I am wrong) the "EF-S" means it is designed for crop sensor bodies?

Sorry if that is a really stupid question, I just want to be clear when any mistakes could be very costly

Cheers

 

[James J]

The focal length is the same for the full frame and crop cameras, just the crop versions have an "equivalent" focal length due to a narrower field of view. An example being the field of view on my nikon 35mm lens is 47 degree if used on a full frame camera, but 38 degrees (give or take) on a crop sensor one. The same field of view on a full frame camera is around 50mm instead of 35 to achieve the same rating.

Its not the best explanation of it. But your right that you multiply your current focal length by the crop factor to achieve the "full frame focal length" equivalent. In real world performance though, you won't miss the extra field of view unless you start photographing weddings or other similar events where you might want more subjects in the photo.

 

[neil_g]

It's not really magnification it's just a different field of view of the same frame Personally I wouldn't worry too much about working it all out, just decide if a particular sensor and focal length combo is right for you.

Otherwise here's a little comparison I did a while ago for the different canon sensors..

1.6x

1-20D by neilgates, on Flickr

1.3x

2-1Dmk3 by neilgates, on Flickr


3-5Dmk2 by neilgates, on Flickr

 

[Andy90]

Wikipedia article on Crop Factor

http://en.wikipedia.org/wiki/Crop_factor

 

[Guitarman0]

Really useful stuff guys, thanks

 

[olv]

Ef-s or not 18mm will be the same regardless of the lens. Ef-s just means it has a smaller image circle and the rear of the lens protrudes further into the body so they can't be used on FF cameras.