Comments on: Sigma SD1 flagship DSLR breaks cover

By: Anonymous

Anonymous — Wed, 06 Jul 2011 18:24:00 +0000

Bottom line is the foveon photos are uniqued and more vivid with more colors than any other camera.

By: Charles

Charles — Tue, 16 Nov 2010 23:42:42 +0000

A fair comparison between Foveon and Bayer sensors is to count the green pixels. The new Sigma camera has 15.36 MP of green, a Bayer sensor with 15.36 MP of green would be called a 30.72 MP camera.

The Bayer sensor cannot use all of its pixels for resolution. If they did the moire patterns would kill the quality of the image. Most algorithms smooth the data a bit (sometime there is a slight blurring filter on the sensor) and then try to reconstruct the image by doing a slight edge enhancement after conversion to RGB. If you compare a gray scale sensor and the same sensor with a Bayer CFA you will find that the resolution of the Bayer sensor is about half of the gray scale sensor, or the same as the green part of the image.

I did a small study once having experts access the quality of fundus images that had been developed using different Bayer demosaic algorithms. I fond that MTF and perceived image quality did not always go together. If you have access to a three chip camera you can do your own comparison with little effort.

By: bodhisattvah

bodhisattvah — Wed, 22 Sep 2010 02:37:06 +0000

Well, a camera with a bayer pattern like a D3x at 24 megapixels has 6 million red, 6million blue, and 12 million green pixels. But since they are not stacked, they all contribute to resolution and image detail, since they are all at different locations. The algorithms for assembling a finished image out of a bayer pattern are well established, tried, and tested. The foveon design is new and quirky.

It’s not really a redefinition at all. They are counting sensors sites just like other manufacturers. Those site just happen to be stacked, which lowers the effective output resolution.

High ISO noise seems to be a big issue for the previous foveon sensors. I’m not sure if that’s an inherent design problem to do with less light getting to the bottom of the stacked CFA, or if it’s just a problem of R&D dollars. Either way, I think the big boys are willing to ride out the wave of existing technology and buy up the wreckage of the foveon patents when they expire/go out of business.

By: salsaman

salsaman — Tue, 21 Sep 2010 22:34:40 +0000

Agreed, their spec is correct according to their redefinition of the measurement, but then other manufacturers should multiply their MP by 4 since there are actually four times more pixels when using a Bayer sampling grid!

Agreed, the Foveon sensor model is amazing! The results are just brilliant. Too bad other folks (ahem, LEICA?!) aren’t using them to take images to higher level of quality.

By: bodhisattvah

bodhisattvah — Tue, 21 Sep 2010 21:30:42 +0000

Well, their spec is correct in the way it counts sensor site, but is not useful for purposes of comparing actual resolution. The older 4mp sensor seemed comparable to a 6-8mp sensor. If this compares to a 20-30mp sensor well, that’s quite a feat! However, the foveon sensors have tended to have rather weak high ISO performance.

That said, kudos to Sigma for forging ahead and making this. The only question mark for me is ease of use/ergonomics/menu speed. And the Achilles heel of this camera is the mount. Sigma has some unusual and wonderful lenses, but can’t really compare with a lineup like a Canon or Nikon, especially when it comes to image quality and resolution.

By: salsaman

salsaman — Tue, 21 Sep 2010 17:40:57 +0000

1) That is not a “giant” sensor, it’s the standard size for most consumer grade DSLR’s, APS-C.
2) Sigma should stop multiplying the resolution by the number of channels. The *images* it outputs are 4800 x 3200, which is ~15.4 MP. That’s a healthy resolution for a DSLR sensor, but it’s *not* 46 MP, which would be ~8300 x ~5500 pixels. It’s clear that they want to highlight their layered sensor, and its lack of a Bayer filter grid, but that doesn’t mean that they get to redefine the megapixels spec.