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FYI - good high iso b&w from foveon sensor
Old 06-04-2013   #1
GaryLH
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FYI - good high iso b&w from foveon sensor

http://www.getdpi.com/forum/other-ca...i-thought.html

An interesting discussion on how to get good high iso results from a foveon sensor using b&w plus color mixer.

Some iso 4000 ad 6400 examples.

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Old 06-05-2013   #2
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Sounds logical but if you're relying almost totally on the pixels from the blue layer it's going to be a fairly low resolution image I'd imagine.
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Old 06-05-2013   #3
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Quote:
Originally Posted by Keith View Post
Sounds logical but if you're relying almost totally on the pixels from the blue layer it's going to be a fairly low resolution image I'd imagine.
Isn't the point of Foveon that there are as many blue sensors as there are pixels? i.e. if the image is 1000x1000 pixels, there are a million blue, a million red, and a million green light sensors?

That's how I understood it, anyway.
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Old 06-05-2013   #4
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Quote:
Originally Posted by thegman View Post
Isn't the point of Foveon that there are as many blue sensors as there are pixels? i.e. if the image is 1000x1000 pixels, there are a million blue, a million red, and a million green light sensors?

That's how I understood it, anyway.

I was guessing so you may be right!
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Old 06-05-2013   #5
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Quote:
Originally Posted by GaryLH View Post
http://www.getdpi.com/forum/other-ca...i-thought.html

An interesting discussion on how to get good high iso results from a foveon sensor using b&w plus color mixer.

Some iso 4000 ad 6400 examples.

Gary
Thanks for bringing that to our attention over here.

BTW, I've never had satisfactory results from that debanding tool in Dfine2. I tried it on some of the shots where I had banding in daytime blue skies at low ISOs, and it always left artifacts around object (cloud, tree, mountain) borders.
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Old 06-05-2013   #6
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I have better luck w/ b&w using defin for banding issues then color myself..
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Old 06-05-2013   #7
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I'd say Sigma's high-ISO b&w SPP converts are indeed fairly decent stuff for a digital.

I post one of my Sigma DP2s ASA1600 shot, SPP exported raw, no noise reduction. For a digital camera I love that "straight-" looking grain from a color sensor. I reckon no interpolating Bayer-sensor can make the same grain unless with serious software simulating/emulating in PP, IMHO.




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Crop to see the grain features.


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Old 06-05-2013   #8
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Quote:
Originally Posted by thegman View Post
Isn't the point of Foveon that there are as many blue sensors as there are pixels? i.e. if the image is 1000x1000 pixels, there are a million blue, a million red, and a million green light sensors?

That's how I understood it, anyway.
Yep, each pixel location has all three colors, so no loss of resolution, but loss in grey scale (tonal quality) instead.

I would suspect that the best use of this is to basically use the color wheel to get the best compromise and then use your favorite denoise sw to clean up the rest or add grain to hide it...

Btw, if u need to be shooting at f2.8 iso 1600, the af hunts a lot... Once it starts hunting, your probability of getting a focus lock on anything is really small.. Better off going to mf mode once u the light is that low..

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Old 06-05-2013   #9
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Nice example Margus...

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Results from my own testing
Old 06-05-2013   #10
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Results from my own testing

High ISO testing using a recent pic taken this week.. This was hand held at 1/15th so not going to be sharp picture to begin with.

Comparing the results from using DFINE2 with Noise settings in SPP set to -2 versus using various color wheel settings with various reference pics.

All pictures are from same RAW file converted to TIFF16. The shot was a ISO 4000 @ f2.8 and 1/15 second. No sharpening was done to any of these pictures or any other enhancements outside of what is mentioned for each pic.

These were all taken around 9PM in Morro Bay. Overcast night, no moon, only light is from local business and whatever harbor lights were around.

These were converted from full size TIFF16 to max of 1024 JPG for use in web.

The crappy color shot. All the known color issues - default SPP values Luminous at 0 and Banding at 0 (L0-B0)



The same as above but Monochrom (L0-B0)



Noise setting changed in SPP to L -1 and B -1



Noise setting changed in SPP to L -2 and B -2



The L -2 and B -2 shot run thru DFINE2 - auto analyze setting



The L -2 and B -2 shot with color wheel set to Red 0 Green 0 Blue 100



The L -2 and B -2 shot with color wheel set to Red 19 Green 0 Blue 81



The L -2 and B -2 shot with color wheel set to Red 17 Green 20 Blue 63



The use of the color wheel does remove the noise caused by the effects of signal amplification of the Green and Red color receptors without the de-sharpening that occurs when u use a de-noise application such as DEFIN2. Using 100% Blue gives best results at expense of loosing some of the tonal range. So long as u can keep the other color receptors (Green and Red) to some lower number, the results to me, look pretty decent in terms of bringing back some tonal quality.

Anyway what do u think?

Gary

Ps. Looking at these shots from my iPad, hard to c the noise, but on my iMac it is pretty easy to c the difference.

Last edited by GaryLH : 06-05-2013 at 13:21. Reason: Ps
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Old 06-06-2013   #11
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i do see some differences but they're tough to see on my small and crappy work monitor. i can see a much bigger difference in the pics in the getdpi link, perhaps because it's an inherently brighter photo and more close up.

thanks for the link, i'll have to play around with the color mixer on some high iso b/w pics i've taken. if only spp were faster, i actually like it but it's sooo slow on my laptop.
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Old 06-06-2013   #12
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I tried this with an image in SPP and it definitely works ... we discover interesting things about the foveon sensor as we use these unique cameras more. It's a big part of their appeal IMO ... it's not 'just another digital camera!'
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Old 06-06-2013   #13
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Gary,
Thank you so much for bringing this to our attention. I was able to take some low light photos outdoors tonight during the tropical storm that is passing through North Florida tonight.
This is very interesting and a great deal of fun.
And learning more about SPP was fun as well!
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Old 06-06-2013   #14
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Quote:
Originally Posted by Eric T View Post
Gary,
Thank you so much for bringing this to our attention. I was able to take some low light photos outdoors tonight during the tropical storm that is passing through North Florida tonight.
This is very interesting and a great deal of fun.
And learning more about SPP was fun as well!

SPP isn't a bad piece of software IMO ... especially when I think back to how godawful 'silkypix' that comes with Fuji's cameras is.
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Old 06-07-2013   #15
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After playing around w/ this, I feel pretty comfortable w/ using higher iso for monochrom stuff.. My c1 and c2 setups are for mono my c3 color will remain the same.

I changed my c2 setting to use autoiso w/ max at 3200 and switched my c1 setting to mf, f16 and autoiso max at 6400.. Too bad it does not remember the distance.. At f16, I can set a hyper focal @12ft and be in focus around 7 to inf on the dp2m.

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Old 06-07-2013   #16
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I took some test shots and it's amazing what the reliance on blue channel can do in certain circumstances.
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Old 06-07-2013   #17
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Quote:
Originally Posted by noimmunity View Post
I took some test shots and it's amazing what the reliance on blue channel can do in certain circumstances.
Yep...

It really shows what is really happening at the pixel level. The blue layer being the top color pixel needs very little signal amplification compared to the green or red layer below it. To get the equivelent signal amplification of the top most layer, each additional layer needs more amplification, thus introducing more noise w/ each additional layer.

If this had been a pure monochrom sensor, I would suspect one would get clean iso up to 6400.

The color wheel was originally intended to be used to emulate different color filter effects on the mono image. Since the raw image has RGB info (0-255 for each color), using the color wheel to isolate to info for blue layer is pretty easy.

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Old 06-07-2013   #18
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Quote:
Originally Posted by GaryLH View Post
If this had been a pure monochrom sensor
Where's a latter-day Paul Simon when you need him?

"Mama don't take my foveon away-hey-hey-hey!"
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Old 06-07-2013   #19
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Quote:
Originally Posted by noimmunity View Post
Where's a latter-day Paul Simon when you need him?

"Mama don't take my foveon away-hey-hey-hey!"

I wonder what Sigma are doing regards foveon technology ... will they work to remove some of the quirks, imrove high ISO etc?
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Old 06-07-2013   #20
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Quote:
Originally Posted by Keith View Post
I wonder what Sigma are doing regards foveon technology ... will they work to remove some of the quirks, imrove high ISO etc?
I had to do a lot of driving today so that gave me time to think about improving the foveon sensor for better low noise performance at high ISO.
I think the basis of the outstanding high ISO performance of blue-channel only B&W photos gives us the answer.

It seems to that a combination of foveon and x-trans sensor technologies would solve all (or nearly all) problems. Recall that foveon pixels each have blue, green and red channels. Now randomize the order of the three color channels on each pixel. That is, blue channel would be on top in 1/3 of all pixels on average, red on top for 1/3, and green on top for 1/3. Next randomize the order of the top pixels on the upper surface of the sensor. This might require a large sensor than APS-C.

This strategy should give the high resolution of a foveon sensor and the low noise, high iso performance of the x-trans sensor with no moire.

However, this would probably require the collaboration of Fuji and Sigma because of their respective intellectual property. I have no idea if that is possible.
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Old 06-07-2013   #21
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Quote:
Originally Posted by Eric T View Post

Recall that foveon pixels each have blue, green and red channels. Now randomize the order of the three color channels on each pixel. That is, blue channel would be on top in 1/3 of all pixels on average, red on top for 1/3, and green on top for 1/3.
not sure this would work because according to one of the articles posted, http://www.foveon.com/article.php?a=67, the layers are ordered based on the finding that red, green, and blue penetrate silicone to different depths. so i don't think it's possible to randomize for all 3 layers. you could do it on the top layer but for example you can't put blue on the second or third levels because the blue light won't penetrate the silicone that far. but good try.
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Old 06-07-2013   #22
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Hi, its darn fantastic!!!

Gary Thank you so much for posting this!!!

Ill check immediatelly!!!
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Old 06-07-2013   #23
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Quote:
Originally Posted by PKR View Post
Why speculate, when you can read and understand ?

http://www.foveon.com/article.php?a=67

http://www.foveon.com/article.php?a=74

Away with web BS !
You mean Richard Lyon's speculations about cybernetic 'evolution' of the human eye?
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Old 06-08-2013   #24
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Quote:
Originally Posted by dfatty View Post
not sure this would work because according to one of the articles posted, http://www.foveon.com/article.php?a=67, the layers are ordered based on the finding that red, green, and blue penetrate silicone to different depths. so i don't think it's possible to randomize for all 3 layers. you could do it on the top layer but for example you can't put blue on the second or third levels because the blue light won't penetrate the silicone that far. but good try.
I couldn't find the article that states that light penetration varies with the color of the channel. Not sure that is the case. Even if it is true, it is a matter of degree. Amplification of the signal may vary for each channel in data processing (which already occurs with the X3 sensor).
The biggest problem I see with my proposed new generation of Foveon sensor is that the data processing required for each image would be HUGE. None of today's cameras could handle it.
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Old 06-12-2013   #25
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Took a selfie today at 6400 and underexposed by a stop so effectively 12800!

Did all the things recommended and I have to say I like the look in black and white ... very 'noir' and although there is a little banding I'm fairly impressed. Definitely gives the little Merrill another string for its bow!


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Old 06-13-2013   #26
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As matter of interest this how that same image looks when you open it in SPP as the original raw file.


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Old 06-13-2013   #27
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Keith, I'm impressed with that processing!
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Old 06-13-2013   #28
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Keith, I'm impressed with that processing!

It's mainly a matter of removing all the bad information and concentrating on the good stuff that's left. The in camera processing engine combined with SPP really mutilates the files at these high ISOs.
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Old 06-13-2013   #29
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Great stuff folks! Thanks Gary!
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Old 06-13-2013   #30
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impressive...

ive done myself some tests, but im sticking to the 800 iso limit...although using the blue and a little green chanels really makes a huge difference...

BTW i have the ef-140 dg flash and it works really well!
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Old 06-26-2013   #31
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Thanks for posting this. I'll have to try this out.
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Old 08-07-2013   #32
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I couldn't find the article that states that light penetration varies with the color of the channel. Not sure that is the case. Even if it is true, it is a matter of degree.
Yes, that is the case. Silicon (not silicone) is transparent to IR, red penetrates deeply, green not so much, blue not well at all. When I was in grad school, I had a professor (who earned his PhD in Carver Mead's lab) who encouraged me to investigate and design a similar imager as a course project, which I did. As I was using a commodity CMOS process, I was limited to a 2-layer stack instead of 3. Sadly, my lab partner was unwilling to commit to the testing of the IC which would have to continue on into the next semester, so we never fabbed the chip.

Using the penetration depth vs. wavelength characteristics of silicon means less control over the spectral width of the bandpasses (varying the layer thicknesses), and more importantly the steepness of the cutoffs. The penetration depth is a statistical distribution, not a "435 nm light penetrates exactly 0.35 micron, no more no less" exact value. I'm guessing that there's more to RAW conversion with the Foveon than just separating the colors; there's probably some post processing to better separate the primaries, but that's just a guess based on my planning for what I would have had to do for my 2-color version.

Sadly, these days I'm not involved in IC fab and this design project was getting on 10 years ago. Some of the specifics have faded, and of course the X3 is almost certainly more sophisticated than my design and with a process that can be tuned to their specific needs. However, I'm pretty sure ( insert winky smiley here) that there aren't color filters between the layers as in color film, and so randomizing which color is on top simply isn't an option using the Foveon process. For that matter, there really isn't going to be a silicon-based process that picks up blue photons at the bottom of a 3-pixel stack. Even without any color filter, those photons simply won't penetrate that deep.
And a thin silicon layer on top won't pick up many red photons, so the detection efficiency will be terrible.
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Old 10-26-2013   #33
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Just discovered this thread. Very exciting ! Will try this out. I just wondered- have ben using Iridient instead of SPP. Does this work as well re: the B&W Monochrome for high ISO ? I'm not sure I'm having much success doing this. Only, I prefer Iridient for color work with the Sigma DP2M as it is quick , and I don't see the "beach ball" slow processing at all, compared to the SPP.
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Old 10-27-2013   #34
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I don't have problems w/ spp giving me the beach ball...

In terms of iridient, so long as u have ability to control all three RGB channels separately it should work.

Gary
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Old 10-28-2013   #35
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Here's something to report-
Picture of my dog, at ISO2000, converted, and noise corrected in Iridient. It took some exploring to figure out the options, but very pleased...


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