Camera Hacker

: :

Add Comment | Related Links | TrackBack
Related Content

Sigma 20mm f/1.8 D EX DG Aspherical Lens

"abundance of peripheral illumination" means low light fall-off or low vignetting?

Hash
Wed, 7 Dec 2005 13:41:37 -0800

RTFFAQ: The Digital Lens FAQ
2.1) Sigma "DG" lenses

Sigma says that the DG lenses are "designed specifically for digital SLR cameras" and that the lenses "feature superior light distribution, so that there is minimal light fall-off or vignetting, even when used at maximum aperture". Aside from this, they are not saying what constitutes "designed specifically for digital". From Sigma�s lens data sheets, and from measurements on several Sigma lenses, we see that the most noticeable design feature is that the DG lenses have large back focus distances. This means the light from the lens is nearly perpendicular to the sensor, even in the far corners of the sensor. This prevents vignetting (dark corners) and reduces chromatic aberrations (color fringes). This is especially important on cameras with large sensors and cameras that use "micro lenses" on their sensor to increase sensitivity.

The Sigma 20, 24, and 28mm DG lenses have exit pupils from in the 80mm range. Equivalent Nikon and Canon lenses have exit pupils in the 50-55mm range. The lenses do not feature reduced coverage circles, or noticeably less chromatic aberration than wide angle lenses from other manufacturers.

JoBo
Thu, 16 Feb 2006 05:06:00 -0800

Sigmas DG lenses are optimized for bolth digital and 35mm SLRs. If you want a lens that is for digital only you would have to use the DC lenses. these lenses can not be used with 35mm.

BillBO
Thu, 01 Jun 2006 13:28:40 -0700

Chromatic aberration is a digital problem. Light hitting a sensor at an angle causes fringing. With a large rear element projecting onto the sensor, the light angles at all points across the sensor are more perpendicular to the sensor--minimal fringing.

Bergster
Thu, 08 Mar 2007 10:07:49 -0800

Digital lenses also have coatings optimized for the light requirements of ccd/cmos sensors. Wouldn't it be nice to have lenses optimized for b/w vs. color reversal vs. color neg. film, too! We would all have wheels on our kit bags. And weights on our wallets to keep them from floating off...

BergOne
Wed, 13 Feb 2008 06:47:39 +0000

<< Back to Article

Add Comment | Related Links | TrackBack
Related Content

Did your message disappear? Read the Forums FAQ.

Add Comment

Spam Control | * indicates required field
Your Name: *
E-mail:
Remember Me!
Comment: *
File attachment is optional. Please do not attach a file to your submission unless it is relevent.
Attach File:
(20 MB Max)
Spam Protection: * Answer of 9 + 7?
Click button only once, please!

TrackBack

TrackBack only accepted from WebSite-X Suite web sites. Do not submit TrackBacks from other sites.

Send Ping | TrackBack URL | Spam Control

No TrackBacks yet. TrackBack can be used to link this thread to your weblog, or link your weblog to this thread. In addition, TrackBack can be used as a form of remote commenting. Rather than posting the comment directly on this thread, you can posts it on your own weblog. Then have your weblog sends a TrackBack ping to the TrackBack URL, so that your post would show up here.

Messages, files, and images copyright by respective owners.