Discovering the SD15...

Roland Karlsson wrote:

papillon_65 wrote:

My experience of foveon sensors has been that the brighter the light, the better they are. They shine in two areas for me, bright light and limited exposure nightscapes, in those scenarios they have always delivered for me. Colour on all my foveon cameras can go a bit wayward once the light drops below a certain level.

That is because of the noise. It is very hard to tame the color behaviour when the noise dominates the RAW data.

This is true for high ISO pictures obviously, but I found that my Merrill takes good low light pictures using low ISO's and long exposures.

Jan

xpatUSA wrote:

Roland Karlsson wrote: I am only talking abot flower photography. So, show me some (brightly colored) flower photos (that not are manually corrected) that contains green, naturally looking healthy grass.

I will, this very day. Natural-looking healthy grass is hard to find around here but we've had some rain lately

I'm hoping we will not need spectrometer readings to complete this sub-discussion. I'll use a DP1s instead for comparison. Might provide Some Chroma numbers too. They would be a little more convincing that words like "greener", eh?

Well, I found some lantana camara in front of the shack, with leaves and a bit of grass:

There is very little difference between the DP1s and the SD14, so this comparison would have proved nothing much, if I had not included the card. Fortunately, the card comes with a leaflet which lists the L*a*b* color values for each patch.

Anyone not familiar with the CIELAB color space and the meaning of chroma as it relates to saturating can stop reading here.

Using Bruce's CIE calculator , the green patch's L*a*b* values give a CIELAB chroma of 50 and a hue of 141 degrees. The same calculator can be used to convert SPP's color-picker RGB values (sRGB working space) into chroma and hue. I estimated the lighting as D55 (diffusing clear plastic roof under part sunlight).

Comparing chroma and hue angle:

Card: 50 & 141°

SD14: 62 & 128°

As we can easily see, the chroma for green from an unadjusted SD14 is more than it should be, which proves to me that the SD14 does not shoot under-saturated greens, in spite of Roland's claim.

xpatUSA wrote:

In spite of the snide remark about users here, I have never seen on this forum any complaint about de-saturated greens with the SD14 (apart from yours). Unless you can produce a link or two to such complaints, I must assume that your memory is at fault.

Yes, you are quite right. It is only me. But, I am very sure of it. There have been lots of images posted in this very forum that absolutely do not look like other photos. Very desauturated greens for flower photos. It is more common than not IMHO. And I am very surprised that it seems like no one else cares. Maybe it is because I live in a very green country. So green is important to me.

I guess that you are referring to SD14's out-of-camera jpeg color accuracy and less than perfect WB, in which case I agree.

Might be. I have no idea whether the photos I have seen is OOC JPEG or not. That could explain a lot.

I will, this very day. Natural-looking healthy grass is hard to find around here but we've had some rain lately

I'm hoping we will not need spectrometer readings to complete this sub-discussion. I'll use a DP1s instead for comparison. Might provide Some Chroma numbers too. They would be a little more convincing that words like "greener", eh?

he he

Nte again, I do not doubt you can make images with healthy looking grass. I have seen that. It is still so that I have seen a surpringly high percentage of desaturated greens for flower photos.

And, it is totally possible that I have mixed up the images from pre Merrill crop 1.5 sensors. Cant remember it all. What I do remember is the green/magenta splotches for the SD14, but I assume the fix for that is doing noise reduction in conversion.

I will further state that the sensors are all quite close to to each other as far as sensor output is concerned

That I do doubt.

Then kindly publish response graphs for, say SD14 versus Merrill or Quattro that show they are not quite close.

Even though I can prove nothing, I do doubt it. The difference in behaviour is too large.

The response graphs found on the net are very sparse so you cannot compare sensor generations. And when one is found, it is not really sure what it shows.

jande9 wrote:

This is true for high ISO pictures obviously, but I found that my Merrill takes good low light pictures using low ISO's and long exposures.

There is a general confusion regarding - low light - long exposure - high ISO.

Some say that Foveon need lots of light and some says it needs to exposed at low ISO. I rememeber that someone proved that some Foveon camera gave perfectly fine high ISO images in bright sun light. And you shoe low ISO and very little light. Confusing!

mike earussi wrote:

The SD9 and SD10 are very different cameras regarding color. The SD9 has very punchy but highly distorted color whereas the SD10 has the best color any Sigma camera has ever produced.

That is strange as they have the same sensor.

What's wrong with pink? What specific colors were you looking for?

Do you mean the white, slightly pinkish flowers?

In that case, they are not so saturated I would say.

I assume my main point really is that in order to not get over saturated colored flowers you need to lower saturation and then the green parts also goes down in saturation. You cannot have both, without bending the color space unnaturally.

But - those flowers are nearly white - so no need to desaturate.

Roland Karlsson wrote:

mike earussi wrote:

The SD9 and SD10 are very different cameras regarding color. The SD9 has very punchy but highly distorted color whereas the SD10 has the best color any Sigma camera has ever produced.

That is strange as they have the same sensor.

They're different nonetheless: http://www.dpreview.com/reviews/sigmasd10

and if you ever get a chance to play with one you might find you like the color.

What's wrong with pink? What specific colors were you looking for?

Do you mean the white, slightly pinkish flowers?

They look very pink to me (and not white), but I guess that's a  matter of definition.

In that case, they are not so saturated I would say.

I assume my main point really is that in order to not get over saturated colored flowers you need to lower saturation and then the green parts also goes down in saturation. You cannot have both, without bending the color space unnaturally.

But - those flowers are nearly white - so no need to desaturate.

-- hide signature --

/Roland
X3F tools:
http://www.proxel.se/x3f.html
https://github.com/rolkar/x3f

Roland Karlsson wrote:

The response graphs found on the net are very sparse so you cannot compare sensor generations. And when one is found, it is not really sure what it shows.

I can. I have a great many graphs, published by Foveon, or obviously sourced from Foveon.

As a Kalpanika developer, it is a little surprising that you don't

Roland Karlsson wrote:

That is strange as they have the same sensor.

No, they do not.

mike earussi wrote:

They're different nonetheless: http://www.dpreview.com/reviews/sigmasd10

and if you ever get a chance to play with one you might find you like the color.

OK - the main problem here is that it is so many variables. Sigma have experimented with almost every generation of their cameras. So - it is almost impossible to test it all and remember exactly how it was.

I remember the old and funky colors. My memory tells me it was SD9 and SD10. It was blue and yellow and also sometimes cyan. But, maybe you are right, and it was mainly SD9. I also remember the discussions about 7 lines that become 5 in a test chart, and if smooth or textured lawns were best when grass leaves were to small to be resolved and the pine needles.

Then I remember SD14. That was the prime time for magenta and green splotches. I also remember it as a time for desaturation of shadows and high ISO. Was that not so? I am rather sure. OK - but maybe the desaturated green when photographing brightly colored flowers was later. Maybe. Although I saw one in this very thread. But - maybe it was mainly the TRUE engine.

Then came the series of DP1 and DP2 variants. Green hue anyone? And green corners? And red grid? Evolutionary steps made them better and better, except when it sometimes got worse

And now, lets see ... those red cars that became pink ... was that not SD14? Yes, I think so. Or was it DP cameras? No ... I think it was SD14. And also red flowers that become yellow and/or orange and/or white.

Then came SD15 and SD1. SD15 was said to have the best colors so far. But ... not many images were posted on the forum really. So, I am not sure how good or bad it is. And the SD1 did cost $10,000 or so and only a hand full enthusiasts in the forum got one.

Then, after some agony ... came the SD1M and the DPnM cameras. The best colors so far (except maybe for SD10), but a bit harsh regarding fine texture.

The same thing happened with SD1M as for SD15, Not many images were posted in the forum. Some of the images posted rendered red as orange. That was never investigated. Moreover, it was said that SD1M did not handle legacy glass all that well with colored corners. Nothing that was demonstrated with examplas as far as I remember.

The DPnM cameras got popular though, and we have lots of nice images taken with those. Their exaggeration of micro contrast is often nice but sometimes makes it look too harsh IMHO. The Merrill cameras are superior monochrome cameras! The best so far. The enhanced micro contrast is a great plus then.

Then came the Quattro as a surprise to us all. There Sigma did abandon the idea with three detectors per pixel. Still three layers per pixel. The color is as good as the Merrill and the rendering is not as harsh. Some do not like that. Personally I do, even though I can see the use of Merrill. The resolution is slightly better than Merrill, but some claim that there is slight fuzziness at pixel level. There is also a noise, that some call sand.

The green and magenta splotches still plague Merrill and Quattro sometimes. The reason for this is quite simple - the green channel (after conversion) is very noisy. Strong noise reduction (before converting) is needed. And noise reduction might add a bias. If it does, then it will be green if the bias is positive and magenta if it is negative. And if it varies you get magenta/green splotches.

So - why is the green channel noisy? That is also quite simple. The top layer is desaturated blue. The bottom layer is desaturated red. The middle layer is very stronly desaturated green, nearly grey. So - to extract green you take middle layer minus top layer and also minus bottom layer. Can you visualise that the green channel almost only is noise?

BTW - another interesting feature is the extra clipping pixels in Quattro. A sparse pattern of pixels with lower sensitivity can be found in the Quattro sensor. Those are (probably?) used for compensating for over exposed areas. At least Foveon has such a patent.

I think I have seen the effect of those detectors in an image. Among the trees the sky is shining through - and all is out of focus - and therefore soft. In certain areas the signal clips. All thre channels clips eventually. Still the clipped areas are of a reasonable color and luminosity. Then, it clips to white with a narrow grey edge around the white patches.

Is that good?

Maybe. But the grey edges looked weird. And I assume it would not have worked so well if the area was sharp.

papillon_65 wrote:

You also have to sharpen the X3F's from the SD15 by quite a bit, which isn't how I remember the files from the DP2X, which I think has the same sensor, the colour definitely seems the same as the 2X anyway, which is good as I liked it, the dynamic range also seems pretty much the same and a bit more forgiving than the Merrills.

I never could sharpen my SD15 shots much, maybe only 20% before the haloes came out.

Try SPP at least once, just to check.

xpatUSA wrote:

UsingBruce's CIE calculator , the green patch's L*a*b* values give a CIELAB chroma of 50 and a hue of 141 degrees. The same calculator can be used to convert SPP's color-picker RGB values (sRGB working space) into chroma and hue. I estimated the lighting as D55 (diffusing clear plastic roof under part sunlight).

Comparing chroma and hue angle:

Card: 50 & 141°

SD14: 62 & 128°

As we can easily see, the chroma for green from an unadjusted SD14 is more than it should be, which proves to me that the SD14 does not shoot under-saturated greens, in spite of Roland's claim.

Just to rub it, this unadjusted (except EC) shot of my street shows how over-saturated SD14 greens really are:

No way my street looks that green, even after all the rain we've had recently.

Note to self: must develop a camera profile for daylight to use in RawTherapee

xpatUSA wrote:

No way my street looks that green, even after all the rain we've had recently.

I have not the slightest idea what you want to prove. I have only talked about unnatural desaturated green parts when taking photos of brightly colored flowers. Nothing else.

And I have also admitted that I am starting to get unsure about SD14. Maybe I remember wrongly.

Note to self: must develop a camera profile for daylight to use in RawTherapee

I think the photo you just showed was rather good. At least at my monitor.

Roland Karlsson wrote:

xpatUSA wrote:

No way my street looks that green, even after all the rain we've had recently.

I have not the slightest idea what you want to prove. I have only talked about unnatural desaturated green parts when taking photos of brightly colored flowers. Nothing else.

And I have also admitted that I am starting to get unsure about SD14. Maybe I remember wrongly.

Note to self: must develop a camera profile for daylight to use in RawTherapee

I think the photo you just showed was rather good. At least at my monitor.

Thanks for the compliment, Roland.

I'm being much too pedantic and I promise to let it drop. I should have done so after my big 'proof of chroma' post - but, you know me, I just can't resist one last dig and I do take your point about brightly colored flowers.

Sorry if I ruffled any feathers.

xpatUSA wrote:
Sorry if I ruffled any feathers.

Nema problema.

I am rather seasoned by being in this forum for some time now!

Back in the older days when this kind of things were more discussed I should have asked the one showing the image for a RAW version that I could play around with in SPP.

One problem is that people often have no clue. They say that the image they show is not processed. But it is, manually or automatically. So, the desaturated image with a red rose migh have been taken with lower saturation or the auto function might have done something when seeing the rose or it is actually under exposed and at least for the older sensors, Sigma did desaturate under exposed images and high ISO images.

One reasonable thing that might have happened during processing is that the rose clipped the red channel and then, automatically or manuall, the "exposure" slider is decreased. And then, to avoid the rest of the image to be extremely dark, using "fill light" or "shadow compensation". And, voila, the greens have lower contrast.

Of course, low contrast is not the same as low saturation. But anyhow.

Roland Karlsson wrote:

xpatUSA wrote:
Sorry if I ruffled any feathers.

Nema problema.

I am rather seasoned by being in this forum for some time now!

Back in the older days when this kind of things were more discussed I should have asked the one showing the image for a RAW version that I could play around with in SPP.

One problem is that people often have no clue. They say that the image they show is not processed. But it is, manually or automatically. So, the desaturated image with a red rose migh have been taken with lower saturation or the auto function might have done something when seeing the rose or it is actually under exposed and at least for the older sensors, Sigma did desaturate under exposed images and high ISO images.

One reasonable thing that might have happened during processing is that the rose clipped the red channel and then, automatically or manuall, the "exposure" slider is decreased. And then, to avoid the rest of the image to be extremely dark, using "fill light" or "shadow compensation". And, voila, the greens have lower contrast.

Of course, low contrast is not the same as low saturation. But anyhow.

All makes sense to me

[/end]

Tom Schum wrote:

papillon_65 wrote:

You also have to sharpen the X3F's from the SD15 by quite a bit, which isn't how I remember the files from the DP2X, which I think has the same sensor, the colour definitely seems the same as the 2X anyway, which is good as I liked it, the dynamic range also seems pretty much the same and a bit more forgiving than the Merrills.

I never could sharpen my SD15 shots much, maybe only 20% before the haloes came out.

Try SPP at least once, just to check.

I do use SPP, just not for sharpening.

-- hide signature --

Tom Schum
Celebrate mediocrity (in moderation)

Tom Schum wrote:

I never could sharpen my SD15 shots much, maybe only 20% before the haloes came out.

I've never owned an SD15. In SPP, are the review images already "pre-sharpened" at the zero setting, similarly to all the other cameras? Meaning that, as a consequence, halos would show up on edges pretty quick when going above zero?