sigma 10-20mm lense

[clive francis]

anyone tried this lens yet?

anyone seen any underwater shots with this?

its wider than the nikon 12-24 and only half the price, as wide as the 10.5 without the fisheye.

 

[cdiver2]

anyone tried this lens yet?

anyone seen any underwater shots with this?

its wider than the nikon 12-24 and only half the price, as wide as the 10.5 without the fisheye.

Is this a digital lens or film

 

[Rocha]

The Sigma 10-20 is a digital lens (for cropped sensor cameras). It is shipping in slow quantities and there are not many out there. I've seen a few underwater samples at wetpixel, nothing excellent yet, just people trying to figure out what ports and extension rings to use with it.

 

[Rocha]

as wide as the 10.5 without the fisheye.

It is not as wide as the 10.5. The 10.5 is a fisheye lens with a field of view of 180 degrees. The 10-20 is a rectilinear wide angle lens and has a field of view of 102 degrees at 10mm.

 

[cornfed]

The Sigma 10-20 is a digital lens (for cropped sensor cameras).

The term "digital lens" is somewhat of a misnomer. The lens will work just as well on a film body as it does on a digital body. The only difference being the focal length "changes".

 

[Rocha]

The term "digital lens" is somewhat of a misnomer. The lens will work just as well on a film body as it does on a digital body. The only difference being the focal length "changes".

That's wrong, lenses designed for cropped sensor digital cameras will not work on film or full frame digital cameras. Nikon's DX, Canon EFS, Sigmas DC, etc. lenses (developed for cropped sensor digital SLRs) won't work properly on a full frame body because the image circle that they project won't cover full frame, you will have black borders around the image. So, unless you plan to crop and use only the center portion of the image, these lenses cannot be used in full frame film or digital cameras.

Here is the explanation coppied and pasted from Nikon's site:

"When Nikkor lenses originally designed for the 35mm [135] format are used on the Nikon DX Format, photographers believe that the lens' focal length is increased by a factor of 1.5. For example, a 10.5mm full-frame fisheye lens would become a 16mm fisheye lens. Technically, that is not correct. In fact, there is no change of focal length as you switch the lens from one format to the other. The actual change is that the picture angle of the lens is narrowed on the digital format because the digital format is smaller in relation to the lens' image circle projected on the sensor. Focal length and reproduction ratio remain constant for the comparable viewed portions of the image. It is the picture angle that changes."

 

[Rocha]

And here is the explanation copied from the Sigma site:

"Vignetting will occur if DC type lenses are used with digital cameras with image sensors larger than APS-C size or 35mm SLR cameras."

 

[cdiver2]

If you use a digital lens on a 35mm camera (example) 10-20 on the film camera it becomes a 15-30mm?

 

[ssra30]

If you use a digital lens on a 35mm camera (example) 10-20 on the film camera it becomes a 15-30mm?

Well, you will get the image with lots of black border since the image would not be projected over the entire 35mm sensor. However, on certain lens, the black border will disappear once you zoom in a bit more. I think I read somewhere, for example, Nikkor 12-24mm is usable on 35mm film camera from about 17mm to 24mm with no black border. So may be 10-20mm lens may act more like 14-20mm lens!

If you use a full frame 10-20mm lens on a 1.5 cropped sensor, it will become 15-30mm lens but it does not work in the opposite direction when you use lens designed for cropped sensor on full frame sensor.

 

[Rocha]

No, it remains 10-20, but it will only project an image equivalent to a 15-30, and only on the center of film. Let me give you an example, take a look at this Canon 5D preview at dpreview:

http://www.dpreview.com/articles/canoneos5d/

Scroll down, close to the bottom you will see an example of a photo taken with a 17mm lens, and the image that you will get with a full frame (5d, real 17mm) and with a cropped sensor (20d, coverage of ~27mm). If you do that comparison with a 17mm lens designed for cropped sensor, most (if not all) of the additional area covered by the full frame will be black, and you will have only the central protion (~27mm). You can still use the image if you crop it, but you will lose pixels.