Foveon sensor, how good is it?

[caspert79]

Sigma users usually bought their camera because of its Foveon sensor, which distinguishes them from other dSLRs. Often is claimed that the Foveon sensor gives superior detail, clarity as well as a more realistic output than other sensors (when shooting in RAW). Also in this review, the writer is very positive about the Foveon sensor:

http://www.photoradar.com/reviews/product/sigma-sd15-review

Quote:"If you haven’t seen what the Foveon sensor can do, you’ll be amazed at the clarity of the fine detail the SD15 produces. Each pixel is razor sharp."

What do you think? Does the Foveon sensor really stand out?

[kds315*]

Yes it does, by the amount of dust that body collects compared to
the Olympus, Panasonic, Nikon and Canon DSLRs I have (in that order)

[ludoo]

You probably have read about my love at first sight with the DP2 in my other threads.

The Foveon sensor is indeed different: it won't be as reliable in producing ok pictures in different light conditions, but when light is decent it has a rendering which you won't often get with other cameras. And surprisingly, it's a great sensor for b&w work even at high iso.

It has its shortcomings of course, like loss of saturation and noise at high(ish) ISO (but it works great in b&w), lowish resolution (but with stunning clarity and detail), difficult wb or color hues (mostly solved with the SD15, DP1x, etc.), so it might be better to use it alongside a "regular" camera. Either in the form of one of the small DPx compacts, which can be found used for cheap (my DP2 cost 230€ with hood etc.), have stellar lenses and are almost pocketable, or if you have the money an SD15.

Edit: many will not agree with me, and technically it does not make much sense, but the DP2 to me is a bit like a 5D sensor on steroids: I found the 5D sensor to have a liveliness and luminosity which my other cameras have not, and the DP2 has the same qualities in greater quantity. In comparison, images from my Pentax Kx look 2D and kind of flat.

[Scheimpflug]

[a20010494]

[kds315*]

Maybe I give it another try this holiday season....

[LucisPictor]

The Foveon is special. It is different but it is no piece of magic!

My SD10 produced sharper images than my 300D, but the 40D and surely the 5D produces "better" images.
Of course, the SD15 and the SD1 (will) produce way better images than the SD10. But I haven't used those cams.

I like the colours that the Foveon renders, even if it needs some serious post-processing in order to get perfect results. And I have the impression that highlights burn out more easily than with CMOS sensors.

The SD10 is a slow cam if we consider the whole process from pushing the trigger to having the final shot in JPG.

I like the feeling when shooting with the SD10, it resembles shooting with a film cam somehow. But I still prefer my Canon models.

I would love to try the brandnew SD1 (once it comes out) with the Sigma 1.4/50, though.

I was very close to get a DP2 as well. Ludo has very convincing arguments (=images).
But I decided against it. The next cam I will order is a NEX, I guess.

[rbelyell]

warning: this is a very contentious topic!

i had an sd14 and i now have a 5d. i hated the sigma and love my canon, but for many reasons other than IQ:
sigma has possibly the worst vf in history, especially a problem if you want to use mf lenses. its like looking through a tunnel. 5d vf is among the best and brightest. perhaps it was me, but the sigma simply could not produce reliable images from iso 400 upward. 5d is amazing in its high iso IQ. the sigma does not have the same range of lens adapters than the 5d, so you really cant use much on it besides m42--cant use contax or p6 or deckel. you can find an adapter for pretty much anything on the canon.

having said that, shooting at iso 100 in good light, imho, the sigma produced images that were more stunning than the 5d--more multidimensional, more saturated. at its best, again imho, it was capable of much more than the 5d at its best. the problem was it was only at its best in a very narrow band of circumstances.

[ludoo]

[Scheimpflug]

[cooltouch]

I had the opportunity to try out a Sigma DP1s and can honestly say that I don't see what all the excitement is about regarding the Foveon sensor. In the DP1s, the 14.6 mp sensor isn't as much as one might think, since all those megapixels are divided up into three layers, each dedicated to a single color: red, green and blue. My tests showed that, by doing this, color accuracy was good. But I was rather disappointed by the loss in total resolution. And while the lens was sharp and well-corrected, it didn't focus very close.

If you're interested I did a comparison between the DP1s and a cheap Canon A1000IS p&s digicam, and posted the results in my blog. Read it here (scroll about 1/3 of the way down):

http://mcbroomsez.blogspot.com/

[Scheimpflug]

[cooltouch]

Well, perhaps I didn't make it clear enough in the blog text, but I actually shrank the Canon's image so that it was equivalent to the Sigma's when doing a 100% examination of the Sigma's. But I do believe it was a fair comparison when I showed the difference between closest focus with each camera.

I'll grant all the arguments in favor of the Foveon. What I noticed most about it was its color accuracy. But to me, the biggest stumbling block to the Sigma was that its 14.6 megapixels aren't counted the way they are in other cameras. That A1000IS's 10.1 mp sensor provides an image that is much larger than the Sigma's. And size matters a great deal when it comes time for enlargements or crops. It's something that you can't get around with the Sigma, no matter how great the sensor is -- you're limited to a relatively small maximum image size.

[rbelyell]

regarding how sigma counts megapixels, i cannot offer a technical argument or rebuttal, but from my understanding, the way they count pixels is exactly the point of difference sigma folks are seeking in relation to other slr's. red green and blue are 'stacked' so they are each always present at each pixel point, unlike other slrs wjere each pixel point is only one of red blue or green. sigma thus counts 3 in each spot whilst othwrs count one. but the IQ point here is that stacking the pixels creates a depth and multi dimensionalism and saturation that cannot be otherwise achieved. my results, as stated above, bear this out in practice.

[cooltouch]

Yep, these are the benefits to the Foveon the way I understand it as well. But, as I'd mentioned before, because the pixels are stacked, a Sigma 14.6 mp image is not going to be as big as a "regular" 14.6 mp image. Size matters -- especially with digital images.

And in terms of size only, let's use the Nikon D3100's sensor to compare with the 14.6 mp Foveon. The D3100's is 14.2 mp, which is the closest I can find. It creates a file with the maximum size of 4608 x 3072 pixels. The Foveon generates a file with a maximum size of 2640 x 1760 pixels -- at least the one on the DP1s does. I could make an estimation that would probably be very close that, based on the D3100's sensor's resolution, a 14.6 mp sensor's resolution would be 4738 x 3158 pixels. But either way, they illustrate how much maximum resolution is being lost because the Foveon's pixels are stacked.

And even though there is supposedly one pixel for each color, it doesn't quite break down that way. If it did, using my estimate, we would expect to see 4738/3 x 3158/3 or about 1580 x 1050 pixels. So there's some creative math going on there somewhere. But still, if we're willing to count my estimation as close, the Foveon's image size is only about 46% of what it otherwise would be. And as I've already stated, this is my biggest complaint about it. When we start seeing Foveons up in the 25 or 30 mp range, then their image size will compare favorably with SLRs that have the mid-level pixel counts (a 25 mp Foveon should give an image size of about 4500 x 3000 pixels). And then we can see images printed or otherwise displayed at large sizes where this pixel depth can be enjoyed and appreciated beyond our video screens.

[caspert79]

Thanks guys for sharing your view!