Lens structure

[sorvju-f]

I was looking one light pancake lens from Olympus...if this one can be so small, why otherones have to be so big?

http://www.photoreview.com.au/Olympus/reviews/cameraaccessories/olympus-zuiko-digital-25mm-f28-lens.aspx

It gave me a question from the subject I don,t know much...lens structures:

Specification is saying feg. 18 elements, 12 groups, ED glass, aspherical, super ED etc

http://www.olympusamerica.com/cpg_section/lens/dea/products/lens/7-14_40/com.html

I have to ask if someone can translate these terms and what is important to know from these details?

Jukka

[Jonathan Bird]

1. Short focal length (i.e. wide angle) but not an extremely short focal length.
2. Not very fast (only f/2.8)
3. Not a zoom
4. Designed for a small format sensor

[sorvju-f]

1. Short focal length (i.e. wide angle) but not an extremely short focal length.
2. Not very fast (only f/2.8)
3. Not a zoom
4. Designed for a small format sensor

Jonathan can you tell something about why its needed lenses in structure of 18 elements and 12 groups?

Jukka

[Jonathan Bird]

Zoom lenses have a very tough job of maintaining sharpness and perspective across a wide range of focal lengths. For wide angle lenses, this is especially difficult and involves a lot of lens elements. I don't profess to know much about how it is done, but CAD has helped a lot as well as the use of ELD glass, aspherical lens grinds and of course anti-reflective coatings.

It used to be (20 years ago) that zooms could never touch fixed focal length lenses in sharpness. Now they are very very close, to the point where most pros shoot zooms now.

Jonathan

[sorvju-f]

Zoom lenses have a very tough job of maintaining sharpness and perspective across a wide range of focal lengths. For wide angle lenses, this is especially difficult and involves a lot of lens elements. I don't profess to know much about how it is done, but CAD has helped a lot as well as the use of ELD glass, aspherical lens grinds and of course anti-reflective coatings.

It used to be (20 years ago) that zooms could never touch fixed focal length lenses in sharpness. Now they are very very close, to the point where most pros shoot zooms now.

Jonathan

So its sounds like that these structures of lenses are big secrets and actually the best referenses are the comments of users:cool:

Jukka

[Jonathan Bird]

Jukka,
Advanced lens design is a science and an art known to few! I'll get there are only a handful of people in the world that can design lenses like this. I say just read the reviews from someone you trust (camera magazines or websites like DP Review (http://www.dpreview.com/) or my favorite Ken Rockwell (http://www.kenrockwell.com/) (although he is only Nikon I think). If they say it's good, buy it!

The Tokina 10-17 fisheye zoom seemed like a great concept but I was unsure if it was as good as my fixed focal length lenses (10.5 and 16 fisheye). When Stephen Frink said it was as sharp or sharper, I bought it. Love it! Who would have thought a few years ago that a zoom like this could be as sharp as a fixed focal length lens and a zoom to boot??

Jonathan