Advantages of Foveon sensor Locked

Started Jun 23, 2013 | Discussions thread
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bobn2 Forum Pro • Posts: 59,060
Re: Advantages of Foveon sensor

Lin Evans wrote:

Bobn2 wrote:

Laurence Matson wrote:

Bob (if that is your name),

Hi Laurence (if you're not posting under a pseudonym)

Before we start up this old squeezebox, because you have decided to be all over this topic, and because you yourself once wrote:

"Better guide is what you yourself think about the cameras, try them see which you feel more comfortable with."

That is a something that I say often, and that I think is very important. I have no argument with anyone's personal choice of camera, or any reason that they choose it. These things are personal, and none of us has any right to question another's preferences. So, if someone prefers Sigma colours, or Sigma rendition, or anything else about their camera, that is their right and privilege, and you will not find me ever saying anything else. That, however is not what this thread is about. This thread is about what are the advantages of Foveon sensors. That is an objective, not subjective question, one of engineering fact, not personal preference.

What is you real experience with a Sigma (or Polaroid branded but really Foveon) camera?

Do you have any samples of what you got?

All of course irrelevant, since we aren't talking about cameras, just sensors.

Of course it's "very" relevant since, in the relevant sense, only Sigma cameras and one Polaroid model use Foveon sensors.

No, it is irrelevant. What we are talking about here are the advantages of Foveon sensors, not why people like Sigma cameras. People have every right to like Sigma cameras for whatever reason they want. It has no bearing at all on what are the engineering advantages of Foveon sensors.

My list below with your annotations reveals a considerable lack of familiarity with terms commonly used in this forum for over ten years. Whether they are correct or incorrect is immaterial unless you understand the jargon.

The question would more be whether you understand the jargon.

I think Laurence understands the "jargon" very well Bob. But obviously you are having issues.

In that case he can provide some illumination as to the meaning of 'edge roll-off' and how it is different from acuity. Or you could, since from the links he posted, it seems to be your jargon.

We can redefine everything for you again, and then we can get into arguments about the definitions, and ultimately recycle some very old discussions. Or, you could use the search function and do some digging yourself. Or you could just continue to poke with your skepticism and ultimately leave everyone frustrated.

In short, do some homework please. The dpreview function now works quite well.

For instance:

Uses the term 'roll-off at edges' but is quite unrevealing about what it means, and has not much precise or meaningful.

It' is "very" precise Bob, but because you don't know and understand the term, your knowledge of how to relate to it is faulty.

The post, I meant - it says nothing about what 'edge roll-off' is, it just uses the term.

Normally, I wouldn't bother to repeat what is quite commonly known here on the Sigma forum, but for your elucidation:

That's not a good attitude - if something needs teaching you should be willing to teach it. The 'superior to thou' attitude to people that you think know less than you just makes you appear arrogant - not very pleasant.

Edge roll-off is a very simply concept. How many pixels are there which separate adjacent detail objects?

There is a theoretical answer to that - one. that is a basic part of information theory - it is the reciprocal of the Nyquist frequency.

If you photograph a very plain and featureless pure black object with sharp edges on a pure white and featureless backdrop, at the edge boundaries there is not a single pixel of black adjacent to a single pixel of white. There are a number of pixels, from the black perspective of varying shades of gray until finally a pixel of 255, 255, 255 white.

I think what you are talking about is the 'edge spread function'. This is a concept that I am fully familiar with - I just use the 'jargon' that is used by the optics community, rather than making up my own.

If you make the identical photograph with a CFA based camera using identical focal length, identical pixel file dimensions, identical ISO, identical lens and other relevant settings, there will be fewer pixels separating the white and black with the Foveon sensor. This is irrespective of the AA filter which adds to the number of these pixels. The CFA process itself creates additional pixels. The Foveon image is therefore sharper than the CFA image. It's been tested, measured and posted on this forum and discussed numerous times.

I don't think anyone has denied that a Foveon sensor has a higher effective sampling frequency than a Bayer sensor with the same pixel count, which is what you are saying in a long winded way. It is a result of sampling all three channels at each pixel location, which is its sole advantage, so far as I can see.


The search is similarly unrevealing about what is meant by 'edge roll-off'.

Then it's your search skills or the amount of effort you wish to put into finding it.


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