Full Spectrum Street

[xpatUSA]

A older snap of our street - re-visited today in RawTherapee:



Altered the two tone curves to brighten up the lows and mids and backed off the sky a bit.

Used the 'HSV Equalizer' to add a purple cast to the sky.

Did some nifty RL de-convolution sharpening.

Shot with the Sigma SD1 Merrill, hot mirror removed, Sigma 18-50mm f/2.8 EX DC Macro, no lens filter, custom WB, low resolution raw mode 2236x1568px.

Posted full size - 2MB, 92% 4:4:4 JPEG, RT_sRGB profile.

All comments welcome

[Wavelength]

Is that not a bit over? my eyes tend to withdraw......

[xpatUSA]

Is that not a bit over? my eyes tend to withdraw......

Yes, full spectrum shots do tend to be a bit "in your face". For example, here's the un-processed embedded JPEG extracted from the raw file:



IR and full-spectrum shooters seem to go for extreme sharpness and high contrast - probably because sharp captures are pretty hard to get, especially in IR.

[Mike Buckley]

Displaying this image at the uploaded size reveals tons of really fascinating detail that can't be appreciated at the smaller sizes. There are several compositions that would work with this image depending on the story being told.

You mentioned that the second image is the "unprocessed embedded JPEG." Were any of your camera settings, especially those relating to the curve and saturation, different from the default standard settings? What was your custom white balance setting?

[xpatUSA]

Displaying this image at the uploaded size reveals tons of really fascinating detail that can't be appreciated at the smaller sizes. There are several compositions that would work with this image depending on the story being told.

Thanks Mike,

Yes, I have to put images up on my own site 'cuz TinyPic banned me forever - for some unstated reason.

You mentioned that the second image is the "unprocessed embedded JPEG." Were any of your camera settings, especially those relating to the curve and saturation, different from the default standard settings? What was your custom white balance setting?

All my camera settings for JPEGs are neutral or zero.

On Sigmas, Custom WB is done by taking a shot, unlike other cams where you can play with the color temp and tint.

Kodak white card facing the sky - take a shot in Custom White Balance mode - the firmware analyzes it and creates a 3x3 matrix setting, based on the captured image, and includes that in the raw X3F file's meta-data.

Here's the matrix for the street shot:

BEGIN: CAMF matrix meta data (CustomCCMatrix)
float [3][3]
3.07031 -3.42969 1.35938
-1.61719 3.82031 -1.20313
0.820313 -4.09375 4.27344
END: CAMF matrix meta data

[Shadowman]

Very vibrant capture.

[Mike Buckley]

The display of color in your image on my calibrated monitor is incredibly vibrant, especially considering that you have now explained that your camera settings and white balance are the settings that would not embellish anything beyond the design of the sensor.

[xpatUSA]

The display of color in your image on my calibrated monitor is incredibly vibrant, especially considering that you have now explained that your camera settings and white balance are the settings that would not embellish anything beyond the design of the sensor.

Mike, judging by the comment, it seems like you may be unfamiliar with "full-spectrum" photography using a Sigma DSLR.

Firstly, the "hot mirror" UV/IR blocker is easily removed from the camera, no surgery required. Now the Foveon sensor is sensitive to wavelengths from about 300nm up to about 1100nm. In the scene that I posted, any green vegetation becomes dominant due to it's high IR reflectivity - thus showing up as a bright brownish-red due to the sensor characteristics. That is to say that the "embellishment" is due to the high near-IR response of the uncovered sensor, not due to me waggling a 'Vibrance' slider.

That said, the Custom WB is nowhere near perfect, designed as it is for raw conversion of scenes captured with the hot mirror in place. In fact, my SD14 refused to capture a Custom WB when the hot mirror is removed and I use 'Incandescent' instead.

I have many versions of that shot. This one is a raw composite with no conversion at all:



The 3 raw Foveon channels raw values are sent straight to an image with no conversion or processing at all, apart from scaling and gamma. Although the red channel may not look particularly dominant or indeed "vibrant" above - when a normal conversion to RGB is done, the weaker red channel from the Foveon is multiplied by 4 or so and comes out pretty bright if there was a lot of IR in the scene.

[Mike Buckley]

Mike, judging by the comment, it seems like you may be unfamiliar with "full-spectrum" photography using a Sigma DSLR.

I'm not intimately familiar with it but I am aware of it. Perhaps it would have been clearer if I had explained how impressed I am with the effect of full-spectrum photography without using other embellishments that could have been used.

[xpatUSA]

I'm not intimately familiar with it but I am aware of it. Perhaps it would have been clearer if I had explained how impressed I am with the effect of full-spectrum photography without using other embellishments that could have been used.

OK, now I understand. Pardon my big lecture, please.

[ionian]

I was not aware of this technique so your explanation was very handy for me Ted - thanks. I therefore can't judge it within the style you describe, but I can appreciate the beautiful colours although the purple sky is a step too far for my taste!

[xpatUSA]

I was not aware of this technique so your explanation was very handy for me Ted - thanks. I therefore can't judge it within the style you describe, but I can appreciate the beautiful colours although the purple sky is a step too far for my taste!

Thanks, Simon,

As soon as we step into the world of full spectrum or, even more so, IR or UV, the word "color" (as defined by CIE i.e. something we can see with human vision) goes out the window so to speak. That is to say, an IR image, for example, should only be shown in gray-scale because IR is not a color and can not be seen.

And in full spectrum, although a leaf is green to the eye, it is also reflecting lots of IR in the sun - and green + red (albeit Infra-) does come to brown . . . . your color metamerism at work ;-)

As to the purple sky, I understand. I could claim it was because of all that IR pouring out of the sky but I would be lying

[Wavelength]

May i conclude things to the ground level keeping aside the technical jargon, like this?
: The device we use can be made to "see" colors beyond the human visible spectrum, by some technical adjustments; but once it is brought to visible level, it has to be converted to some visible color already known to human eyes instead of producing new colors man has not seen so far... so naturally some colors are intensely boosted up - as the red and orange in the enhanced spectrum image above. Am i appreciated?

[xpatUSA]

May I conclude things to the ground level keeping aside the technical jargon like this.

you may indeed.

The device we use can be made to "see" colors beyond the human visible spectrum, by some technical adjustments

No need for "technical adjustments" - just remove the hot mirror and your silicon-based "device" will see from ~300nm to ~1100nm.

but once it is brought to visible level

Sorry, I don't understand "brought to visible level"

it has to be converted to some visible color already known to human eyes

Or gray-scale?

instead of producing new colors man has not seen so far... so naturally some colors are intensely boosted up - as the red and orange in the enhanced spectrum image above.

enhanced?

Am I appreciated?

Indeed, I do appreciate the conversion of my technical jargon into layman's terms.

[Wavelength]

#As we all know human eyes are incapable of seeing the whole visible spectrum(actually i meant electromagnetic spectrum; corrected only after this mistake being pointed out by George in the following comment); right?

#Some other animals are known to see even beyond this spectrum to some extend...

# If by some means or device we are able to see beyond normal visible spectrum (390nm-700nm)won't some new colors are introduced to our spectrum, which are hither to unseen?

# As far as i know grey scale is a binary equivalent of colors where all colors are converted to two basic colors black and white and their various shades...

#By removing hot mirror, you make the sensor to see more, not our eyes....; what is additionally seen by the sensor is converted to or brought within (390-700)nm so that we perceive it... am i right?

# this adjustment enhance the colors as in your image...that is what i meant....

[george013]

#As we all know human eyes are incapable of seeing the whole visible spectrum; right?

This seems a contradiction in itself.
I think I know what you mean.

The main important thing is the A/D conversion. It's not a A/D conversion. The analogue wavelengths are not digitized.
The bandwidth in wavelengths of the light is limited by the different filters. What is digitized is the used amount of capacity of the individual sensel: 0 is minimal and 255 is maximal with a 8-bit depth.
When showing that info on a screen you see the same ratio on the screen but calculated from the bandwidth of that screen. You just see wrong colors in terms of our visible spectrum..

Just my thoughts.

George

[xpatUSA]

#As we all know human eyes are incapable of seeing the whole visible spectrum; right?

We are having a problem with communication. What I read is probably not what you meant to say. If you had said "capable", I would have agreed.

#Some other animals are known to see even beyond this spectrum to some [extent]

Yes, and some humans can see some UV wavelengths that others can not.

# If by some means or device, we are able to see beyond normal visible spectrum (390nm-700nm)won't some new colors [be] introduced to our spectrum, which are hitherto unseen?

No. More communication difficulty, sorry. We do not do the seeing, therefore new colors are not "introduced to our spectrum". If radiation is not visible, it can not even be called a "color". For example, infra-red is not a color; in fact, "infra" in this context means "beyond visible red".

I think you are saying that radiation captured by the sensor, that is not within the CIE 1931 gamut of vision, must be transformed to the inside of the gamut. Going further, if your monitor displays sRGB, more transformation is required for it to appear on your monitor.

# As far as i know grey scale is a binary equivalent of colors where all colors are converted to two basic colors black and white and their various shades...

Yes, that is one way of putting it. This is a more technical way of addressing gray-scale:

https://en.wikipedia.org/wiki/HSL_an...Hue_and_chroma

#By removing hot mirror, you make the sensor to see more, not our eyes....; what is additionally seen by the sensor is converted to or brought within [approximately] (390-700)nm so that we can perceive it... am I right?

Yes.

# this adjustment enhances the colors, as in your image...that is what I meant....

OK, I understand - if "enhances" means "makes visible".

[Wavelength]

Ouch; i meant electromagnetic spectrum not visible spectrum; regrets

[Wavelength]

Says Ted: OK, "I understand - if "enhances" means "makes visible"."

Sorry sir, i meant "enhanced' only:I will try to explain, why i felt so; by removing the hot mirror, the sensor registers more radiations; when these registered rays are reproduced as colors, probably a shift from infra red to near by red -that is from invisible to visible- that enhances the already existing red.......


I am not sure about this explanation, but see it as a possibility only

Thank you for your patient explanation sentence by sentence

Regards

[xpatUSA]

Said Ted: OK, "I understand - if "enhances" means "makes visible"."

Sorry sir, i meant "enhanced' only:I will try to explain, why i felt so; by removing the hot mirror, the sensor registers more radiations;

No, the sensor becomes sensitive to a wider spectrum of radiation, approx 300nm to 1100nm wavelength.

. . when these registered rays are reproduced as colors, probably a shift from infra red to near by red

there is no frequency shift involved, sorry. It is only due to removal of the hot mirror that IR is allowed to reach the sensor.

Here are some response curves for one of my cameras (Sigma SD9), plotted without and with such a filter:

-that is from invisible to visible- that enhances the already existing red.......

Taking any one channel from the curves above, say red, we see that the response without filter peaks at about 700nm. BUT if we only view that channel output and no other, it is impossible to say what "color" caused that output. It could have been a few photons at 700nm, or the same output could have been from more photons at 550nm or a very large number of photons at 450nm.

That is why we have to design a converter that recognizes a combination of the three channel outputs as being a particular color: if, in figure 7, it sees 100 red, 50 green and 25 blue, it will rightly say that the pixel is visibly reddish but it did take three channels to work that out.

Take out the hot mirror, i.e. figure 6, and the converter is fooled totally and will give false color everywhere but especially above say 625nm.

I'm hoping that we are getting on the same wavelength, Wavelength, ho ho