D800 Monochrome Sensor Conversion - Comparison

[bobfriedman]

An initial comparison.. processed identically in DarkTable, some level/contrast enhancement, demosiac turned off, matrix exposure, identical lighting D55

Nikon D800M ,Zeiss Apo Sonnar T* f/2 135mm
1s f/5.6 at 135.0mm iso100


Nikon D800 Stock ,Zeiss Apo Sonnar T* f/2 135mm
0.62s f/5.6 at 135.0mm iso160


100% crop center

Nikon D800M ,Zeiss Apo Sonnar T* f/2 135mm
1s f/5.6 at 135.0mm iso100


Nikon D800 Stock ,Zeiss Apo Sonnar T* f/2 135mm
0.62s f/5.6 at 135.0mm iso160


D800 Stock Color Image

[Kuri]

Thanks Bob. I want to see the bottle with label again, shot the same as before with stock and M, but just without the vibration which messed up that test.

[bobfriedman]

Thanks Bob. I want to see the bottle with label again, shot the same as before with stock and M, but just without the vibration which messed up that test.

it wasn't vibration.. the focal plane shifted..

[David H. Hartman]

it wasn't vibration.. the focal plane shifted..

The focal plane shifted? Can you mount the camera securely to a 1 cubic yard block of granite?

At some degree of magnification an image simply must exhibit vibration. If you hear a camera it's because the camera moved and caused the air to vibrate. At some point a flaw in an image will be so minute it will be impossible see in any practical sense. “now we know that we shall never know.” or something close to that. A nuclear physicist regarding the change in the behavior of particles when observing them.

Back to our reality...

Bob,

Can you re-shoot the bottle lables again and post them?

Dave Hartman

[bobfriedman]

the problem was that there are grooves in my tile floor where the grout lines are and one of the tropod legs was precariously perched on an edge.. it shifted when i shot the stock D800 image and hence moved the focal plane enough to show up in 100% crop of the neck but with the image still appearing reasonable sharp overall... so guess what guys.. the stock D800 will be sharp. as you can see from the colorchecker cards. maybe not quite as sharp as the monochrome converted sensor but sharp. 

the stock D800 bottle neck i posted was just not in focus.

[Kuri]

Bob, I am confused. It wasn't in focus, or the tripod 'shifted'?  Also, 'shifted' is what I meant by vibration, which we discussed.
Anyway, I want to see a bottle label comparison again now with a non 'shifty' shot.
Right?

[Akira]

Bob, I observe very fine grid patterns on the patches of color checker (100% crop?) shot with the stock D800.  Are they caused by the demosaic turned off?

[Kuri]

Personally, I can't see any grid pattern in the color shot, but I certainly do with the other shots.
I would like to see the same comparison again that was done before in the other topic, with the D800 and D800M, with the label,
with/without the demosaic turned off/on if you want, but I would like one to be like the comparison before.
I want to judge that first.

[Akira]

Personally, I can't see any grid pattern in the color shot, but I certainly do with the other shots.
I would like to see the same comparison again that was done before in the other topic, with the D800 and D800M, with the label,
with/without the demosaic turned off/on if you want, but I would like one to be like the comparison before.
I want to judge that first.

Kuri, I was referring to the second last B&W image where you should be able to see the grid pattern clearly.

[Kuri]

Akira, Oh yes, I agree, the black and white shots show the pattern.
But why even start a new topic.
Show me the label. :-)
Who wants to look at a color checker in black and white?
Show me the label again.

[Akira]

But the same crop by D800M doesn't show the grid.  That's why I suspected that the demosaic turned off.

[bobfriedman]

Bob, I observe very fine grid patterns on the patches of color checker (100% crop?) shot with the stock D800.  Are they caused by the demosaic turned off?

yes.. demosaic turned off..  the reason you see this is that those colors with greater grid pattern have a purer red or blue channel.. since there is 25% red, 25% blue and 50% green, the colors with more green components will have more contributing pixels..   consequently more resolution 36mpx = 9mpx red + 9mpx blue + 18mpx green

the monochrome conversion sensor has the full 36mpx resolution

[Les Olson]

yes.. demosaic turned off..  the reason you see this is that those colors with greater grid pattern have a purer red or blue channel.. since there is 25% red, 25% blue and 50% green, the colors with more green components will have more contributing pixels..   consequently more resolution 36mpx = 9mpx red + 9mpx blue + 18mpx green

the monochrome conversion sensor has the full 36mpx resolution

But resolution is determined by luminance, even in colour images, because "the human brain enables rather coarse color information to be added to fine spatial information and integrates the two almost seamlessly". (http://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html).  It can do that because the channels are not pure, however pure the colours on the card are, because there is a lot of spectral overlap in the filter transmission. The result is that most of the spatial data from any colour is in all the channels when you have a Bayer array (ie, the MaxMax site's [https://maxmax.com/b&w_conversion.htm] statement that "suppose the target is illuminated with a blue light?  You would only get 1/4 of the pixels possibly seeing the blue light" is badly wrong).  The blue filter has the least overlap, so spatial resolution is lower for monochrome blue areas - so in your images the texture in the Colorchecker squares should be least evident in squares 3, 13, and above all 8, and it isn't.

One thing that bothers me is that the lightness of the patches of the Colorchecker are as they should be in the native images but they are not in the Bayer-less images. For example, square 2 should be the same as square 21 and in the native images it is, but in the Bayer-less images it isn't; another example is 17 and 18, which should be the same. 

[TedBaker]

yes.. demosaic turned off..

What is purpose of turning of the demosaic? i.e. what are you trying to show?

[bobfriedman]

What is purpose of turning of the demosaic? i.e. what are you trying to show?

i would search for monochrome cameras on the web.. e.g. below

http://www.red.com/learn/red-101/color-monochrome-camera-sensors