What chance has Sigma's SD1?

[BFoto]

If it's noisy in low light, they're gone.

[KevinA]

Now three choices of 35mm style camera Leica, Sigma and all the others.

Kevin.

[EsbenHR]

I have to admit I don't follow this segment of the market very much (my expertise being medium format capture and software). But I love new cameras and new ideas and am a tech-nerd in general so I went ahead and read through several pages of various sourced info/opinions I am left in utter confusion.

Given that we sell camera kits anywhere from $5k-$60k and to a broad range of kinds of customers I'm the first to tell you that price is not always a stumbling block. But I'm finding it very hard to find the unique selling points that would compel any of our customers to spring for this compared to the other options out there.

I make this post honestly in hopes that someone will chime in with some compelling reasons.

Doug Peterson (e-mail Me)

The Foveon sensor have several advantages, but most of them are unfortunately theoretical. The following assumes that the new sensor is similar to the previous Foveon sensors, which is not a given.

Advantage 1) increased sensitivity.
The color-filters used in a typical Bayer-design will allow approximately 40% of the light to pass. A Foveon sensor should be able to get a about 1,3 stop advantage.

But...

1a) you only get this advantage if you can match the noise-level in the rest of the system.
1b) the color response can not be chosen as flexibly as a Bayer design.

Tech speak: to convert a RAW-image into a typical color-space (e.g. sRGB or Adobe1998), you usually start by applying a "camera matrix". This will increase the noise by a factor called a "condition number" (gory details here: http://en.wikipedia.org/wiki/Condition_number). If the color filters have a large overlap, the condition number is large. Typical Bayer-designs have a condition number in the range 1-2. Previous Foveon designs had condition numbers exceeding 10 (rough estimate). Thus, the color-noise is increased by at least 3,5 stops in practice.


Advantage 2: improved lens correction.

It is significantly easier to fix problems such as lateral chromatic aberration perfectly in software.

But...

2a) the wide color-filters means that the color channels will loose sharpness due to CA. This is similar to a panchromatic BW-image using a lens with a lot of CA.
2b) you need software that will do it.

Sigma could fix 2b... May I suggest cutting a deal with someone who makes an advanced RAW converter ;-)

* * *

The SD1 should be great as a pure BW-camera. All the disadvantages of the Foveon sensor mostly vanish in this case. This does, of course, assume that the software does the right thing and does not add a lot of noise before converting to BW.

[Erick Boileau]

Now three choices of 35mm style camera Leica, Sigma and all the others.

Kevin.

Sigma is not a 35mm , it can compete certainly with a Sony Nex 5

[marcmccalmont]

I have no experience with foveon sensors but aren't we as photographers trying to capture what the eye sees?
I understand this sensor mimics color film's layers but the eye has individual cones (RGB) and rods (B&W). It seems to me a sensor with individually colored photosites would mimic the eye better?
I always thought if the RGB sites were arranged in a pseudo random pattern (latin square) vs Bayer pattern we might have something. Other than mimicking film I don't see the advantage of a foveon sensor
Marc

[Christoph C. Feldhaim]

I have no experience with foveon sensors but aren't we as photographers trying to capture what the eye sees?
I understand this sensor mimics color film's layers but the eye has individual cones (RGB) and rods (B&W). It seems to me a sensor with individually colored photosites would mimic the eye better?
I always thought if the RGB sites were arranged in a pseudo random pattern (latin square) vs Bayer pattern we might have something. Other than mimicking film I don't see the advantage of a foveon sensor
Marc

If you'd want a sensor mimicking the eye you'd also get halos - they eye does a lateral inhibition which causes these - sometimes one can see them.

[Bart_van_der_Wolf]

The price is a bad joke.

Apparently the camera body is cheaper when bought together with a Sigma lens, or is the price of a body already dropping as well?

Cheers,
Bart

[CharlesRamsey]

Actual tests of the SD15 have found the resolution equivalent to an 8 or 9 megapixel Bayer pattern sensor so the SD1 will have the equivalent of a 24 to 27 megapixel Bayer sensor. 8 to 9 megapixels also happens to be the equivalent of 35 mm film so the SD1 can claim to be a medium format camera based on megapixels. Theoretical calculations have found the Foveon sensor to be equivalent to 2 times the resolution of a Bayer pattern in the red and blue and square root of 2 times a Bayer in the green so the SD1 will have the equivalent of a 22 to 31 megapixel Bayer sensor. The Foveon sensor gathers 3 times the light of a Bayer pattern so the SD1 has the area equivalent of 2.3 times a full frame Bayer sensor so SD1 can claim to be a medium format based on light gathering ability. 

[Alex MacPherson]

A crop sensor 35mm body is NOT medium format no matter how you work the slide rule.

[Bart_van_der_Wolf]

Actual tests of the SD15 have found the resolution equivalent to an 8 or 9 megapixel Bayer pattern sensor so the SD1 will have the equivalent of a 24 to 27 megapixel Bayer sensor.

Charles,

I'm sorry that I have to step in. Damage control.

I don't know who performed these tests, but they are comparing the performance of a sensor without an AA-filter with a sensor with an AA-filter. Apples and oranges, especially since most MF Digital Backs don't use AA-filters.

8 to 9 megapixels also happens to be the equivalent of 35 mm film ...

Says who? I stopped scanning film when the 35mm sensors surpassed 16MP. Maybe my scans were superior?

Theoretical calculations have found the Foveon sensor to be equivalent to 2 times the resolution of a Bayer pattern in the red and blue ...

In a theoretical worst case scenario of Blue against Red and only when they have similar Luminance, a situation (2 opposite sides of the visual spectrum next to eachother) very uncommon in real life.

... and square root of 2 times a Bayer in the green ...

Sorry, nonsense. A Bayer CFA sensor collects luminosity at each sampling/sensel position. It's the AA-filter that deliberately reduces artifacts that causes a loss, which BTW is to a large extent recoverable with deconvolution sharpening. The Bayer demosaicing is only losing some 6.4% of Luminance resolution, as demonstrated on this page.

The Foveon sensor gathers 3 times the light of a Bayer pattern ...

Irrelevant, because a Bayer CFA sensor captures Luminance at each sensel position (the spectral bands that are filtered out are calculated and added back in at demosaicing time), only attenuated by the peak transmission of the filter. The Foveon sensor also only uses 1/3rd of the spectrum per color, although it only loses light to the increased amounts of circuitry that produces a smaller fill factor, and the other unutilized photon energy.

Cheers,
Bart

[nightfire]

Apparently the camera body is cheaper when bought together with a Sigma lens, or is the price of a body already dropping as well?

Convincing people to buy Sigma lenses is much harder than getting them to buy the body, hence the discount 

[Dave Millier]

I have a SD9, Sd14 and DP1.  My own testing of the SD9 against my 350D showed convincingly that was essentially no visible resolution difference between them (there were visible differences in the type of aliasing artifacts however, which was fun to evaluate). 

Likewise, in my Sd14 vs Kodak 14nx article that is quite well known, I showed that in prints up to 24x16 inches there is for all practical purposes, no resolution difference. 

Overall, I'm happy with a rule of thumb that says the Sigma cameras have a resolution that roughly, approximately on a par with Bayer sensors of around twice the spatial pixel count. It's what Sigma themselves think when they are not busy marketing it at 3x the count.

Of course, there'll always be something to quibble over and someone to produce a piece of academic research that says differently, but for practical everyday shooting purposes, testing shows the 2x ratio is a reasonable rule of thumb for rough equivalence.

[Bart_van_der_Wolf]

Likewise, in my Sd14 vs Kodak 14nx article that is quite well known, I showed that in prints up to 24x16 inches there is for all practical purposes, no resolution difference.

Hi Dave,

I noticed that in that article the Kodak 14n (I don't recall an nx, but suppose its resolution is the same), was shot a f/11. That will produce a diffraction blur pattern with a diameter of 14.9 microns for Green (555nm) light. That's 1.9 sensels diffraction blur in diameter, not really optimal for resolution, shooting it at f/8 would have been significantly better. Raw converters also make a difference.

That the differences were further mitigated by using a good upsampling application is good for that application, but it doesn't allow to compare the camera's themselves well enough to make a quantitative judgement, other than that both can produce output that comes close, if the right software is used to blow the images up.

Cheers,
Bart

[KevinA]

Sigma is not a 35mm , it can compete certainly with a Sony Nex 5

I never said it was, I said 35mm style.
Now if the thing shoots MF detail without moire and great colour, the size of the sensor hardly matters.

Kevin.

[KevinA]

I will wait for real World production images before I decide wether the price is a bad joke or the bargain of the century. Mathematics never convince me one way or the other about a cameras capabilities or usefulness on a days work.
I hope it's bloody brilliant and I hope you can get an adapter to use  Canon lenses. Why would anyone not wish it to be the best thing ever to capture light, I long for something new and exciting to hit the market, instead of the same 'ol same 'ol slightly better than the one it replaced offerings of everyone else.

Kevin.

[Dave Millier]

14nx was a 14n that had a factory fitted sensor upgrade to SLR/n spec.

[Cineski]

This.  The most laughable thing is Sigma saying they're going to be grabbing medium format users....which means they're going after photographers that don't really know better.  With that in mind, maybe this will be a huge hit with Ashton Kutcher and all the wealthy hobbyists?

A crop sensor 35mm body is NOT medium format no matter how you work the slide rule.

[uaiomex]

Excellent explanation, thanks. But in that case all future Nikon, Sony and Canon FF could be called digital medium format too.
Eduardo

 

Actual tests of the SD15 have found the resolution equivalent to an 8 or 9 megapixel Bayer pattern sensor so the SD1 will have the equivalent of a 24 to 27 megapixel Bayer sensor. 8 to 9 megapixels also happens to be the equivalent of 35 mm film so the SD1 can claim to be a medium format camera based on megapixels. Theoretical calculations have found the Foveon sensor to be equivalent to 2 times the resolution of a Bayer pattern in the red and blue and square root of 2 times a Bayer in the green so the SD1 will have the equivalent of a 22 to 31 megapixel Bayer sensor. The Foveon sensor gathers 3 times the light of a Bayer pattern so the SD1 has the area equivalent of 2.3 times a full frame Bayer sensor so SD1 can claim to be a medium format based on light gathering ability.  

[michael]

There's more going on with the SD1's launch price than meets the eye.

I'll have an article about it online later today.

Michael

[Christoph C. Feldhaim]

There's more going on with the SD1's launch price than meets the eye.
I'll have an article about it online later today.
Michael

Very clear analysis, I think. I hope they will listen - it would be a pity to see this interesting technology go down the gully because of someones stubborness ...