BetterPhoto Q&A
Category: New Questions

Photography Question 
Robyn Gwilt
BetterPhoto Member Since: 7/15/2005
 

Four Thirds & Aspherical


""Sigma launched today a new Four-Thirds system compatible, large aperture zoom lens; Sigma 18-50mm F2.8 EX DC Macro"" This is from the Photokina w/site. Can someone please explain what the four-thirds system is, how does it differ from anything else? And what does it mean when it says 'Aspherical' on the lens, and how does this differ from other lenses. Apologies for being dense!


To love this question, log in above
10/18/2006 8:01:18 AM

 
Kerry L. Walker   Aspherical lenses are lenses in which at least one element is not spherical in shape. This allows one lens element to take the place of more than one element, making for a lighter lens. Also supposed to help with chromatic abberation.

Four-thirds is simply Olympus's name for their digital sensor which has a 4/3 aspect ratio. Four Thirds System is a copyright of Olympus.

You don't need to apologize for being dense. You have that right! LOL j/k

Sorry, but I couldn't help myself on that one.


To love this comment, log in above
10/18/2006 8:29:13 AM

 
Robyn Gwilt
BetterPhoto Member Since: 7/15/2005
  Thanks Kerry, so aspherical should be somewhat superior then? I'm still not sure about four-thirds i.e. how does it relate to the Canon sensor? Does it still mean a 1.6x crop factor, or is it closer to a full frame? Is it important to have it or not? If the lens is a 'four-thirds' compatible lens, what is it NOT compatible. Thanks,
Yours in eternal-fog-of-the-spotless-sensor!


To love this comment, log in above
10/18/2006 10:25:27 AM

 
Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
  Aspherical lens elements are a good thing in lenses that benefit from them. They help minimize spherical abberation, where straight lines look curved.

I don't want to say that a lens is a good lens or bad lens because it has an aspherical element or it doesn't have one. Some lens designs benefit from aspherical elements while others don't. The Canon 70-200mm f/2.8L is widely considered to be one of the best lenses you can get, but it doesn't have any aspherical elements. The Canon 85mm f/1.2L is another excellent (pronounced "expensive") lens and it has an aspherical element. Go figure.

Like Kerry said, the 4/3 sensor just has a different aspect ratio than other SLR sensors (and film). The sensor in the Olympus E500 is smaller than the sensor in the 30D. It has an area of 224.9 sq mm, while the 30D's sensor has an area of 328.6 sq mm. The FOV crop factor of the E500 is 2x, so it's not closer to a full frame.

It is closer to the aspect ratio of an 8x10 and an 11x14, though. With most cameras, a 4x6 will need no cropping, but an 8x10 will need cropping from the long dimension to make it closer to a square. With the Olympus, an 8x10 will need very little cropping, but a 4x6 would need cropping from the short dimension to make it more rectangular. With that camera, you would be better off with a 4x5 print.

Unless you're planning on buying an Olympus, you don't need to be concerned with four-thirds lenses.

Chris A. Vedros
www.cavphotos.com


To love this comment, log in above
10/18/2006 11:58:32 AM

 
Robyn Gwilt
BetterPhoto Member Since: 7/15/2005
  Thanks Chris. I'll stick with my Canon's :) :) - the fog is lifting :)


To love this comment, log in above
10/18/2006 12:01:43 PM

 
Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
  P.S. - the Sigma lens that you mentioned is also available in other mounts (like Canon). ;-)

Chris A. Vedros
www.cavphotos.com


To love this comment, log in above
10/18/2006 12:02:18 PM

 
Michael H. Cothran   If I can add my 2 here -
The 4/3rds system was developed by Olympus, with the hope that other manufacturers would get on board. So far, not too many to my knowledge have. If you want to see what a 4/3rds image ratio looks like, just pick up a piece of letter paper (8.5 x 11), which happens to be a 4/3rds size. If you like the proportion, you will probably love shooting 4/3rds, as I do. Other samples of 4/3rds proportion ratios (4:3 or 3:4, whichever way you want to look at it) would be 6x8, 12x16, and 18x24. A 35mm ratio (2:3 or 3:2), would yield a 6x9, 8x12, 12x18, or 18x27.
I personally like the "looks" of 3:4 much better than the longer 2:3 proportion. I think this comes from years of shooting medium format (6x4.5cm and 6x7cm cameras tend to print well at a 3:4 ratio). It is a beautifully balanced ratio, and again, in my opinion, simply superb for vertical shots and studio portraits. Of course, with a little cropping, any DSLR can provide a 3:4 ratio.
Michael H. Cothran


To love this comment, log in above
10/18/2006 2:59:12 PM

 
Robyn Gwilt
BetterPhoto Member Since: 7/15/2005
  Thanks all - the fog has lifted :)


To love this comment, log in above
10/18/2006 11:44:09 PM

 
Christopher A. Vedros
BetterPhoto Member Since: 3/14/2005
  I think Panasonic is the only other camera manufacturer to use the 4/3rds system on a digital SLR so far.

Chris A. Vedros
www.cavphotos.com


To love this comment, log in above
10/19/2006 10:26:52 AM

 
Jon Close
BetterPhoto Member Since: 5/18/2000
  Leica's newly introduced Digi-LUX 3 is also 4/3 compatible. Looks like their own D-system lens(es), but the body appears virtually identical to Panasonic's DMC-L1 and has a lot of commonality with the Olympus E-330.


To love this comment, log in above
10/19/2006 10:59:52 AM

 
Log in to respond or ask your own question.