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09-10-2019, 01:53 PM   #1
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Who does Pentax monochrome conversions?

I checked with maxmax and they offer monochrome conversions but don't work on Pentax cameras. Kolari Vision works on Pentax cameras but they do not offer a monochrome option. I wish these two would get together. Is anyone working on Pentax cameras and offering monochrome conversions?

09-10-2019, 02:51 PM   #2
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Just a quick thought- pixel shift raws converted to raw would have some really solid detail and DR!

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09-10-2019, 03:21 PM - 1 Like   #3
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QuoteOriginally posted by Adam Quote
Just a quick thought- pixel shift raws converted to raw would have some really solid detail and DR!
In theory, a monochrome conversion from a PS TIFF should have full tonal data and detail similar to a bayer-filter-removal monochrome conversion. Even better might be dedicated monochrome processing from a PS PEF/DNG where spectral composition might be taken into account in a manner similar to panchromatic film.


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09-10-2019, 03:30 PM   #4
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How do monochrome conversions even work? I'm familiar with IR conversions but can't really wrap my head around how they'd make a camera only output b&w.

09-10-2019, 03:43 PM   #5
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Cameras are colorblind and only produce shades of grey. They put a colored filter on each of the pixels to break them up into squares of R, G, and B and put those values back together at the expense of resolution. Removing the colored filters makes the camera colorblind again - but, you get a lot more resolution and an extra EV stop in the process.
09-10-2019, 03:53 PM - 1 Like   #6
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QuoteOriginally posted by ZombieArmy Quote
How do monochrome conversions even work? I'm familiar with IR conversions but can't really wrap my head around how they'd make a camera only output b&w.
They strip the Bayer filter array from the sensor with the option of also removing other layers of the stack too. How that translates to RAW processing, I have no idea. I would expect that a custom processor might be required, one that does not do Bayer interpolation.


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09-10-2019, 05:39 PM   #7
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QuoteOriginally posted by stevebrot Quote
How that translates to RAW processing, I have no idea. I would expect that a custom processor might be required, one that does not do Bayer interpolation.


Steve
Yah this is the part that confuses me. Sure you can strip the Bayer filter but how do you get the full resolution again? I assume if it were as easy as removing the Bayer filter it'd be offered a lot more like IR modifications are.
09-10-2019, 06:14 PM   #8
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This is an overview of algorithms etc, "mono" is the option for mono sensors Demosaicing - RawPedia
I am a bit curious how "mono" differs from "none", since I thought that when there's no color array the sensor values are used directly, but not curious enough to read the source code

09-10-2019, 06:20 PM   #9
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I thought through this a little bit, for the possibly inevitable day when my K50 A-block decides to quit.

You need a raw processor that can skip the demosaic step. Rawtherapee and darktable can both do this (mono mode in RT and passthrough mode in dt).

Aside from the expense, the major drawback I can think of is that you can no longer simulate colored filters in post-processing, since the file no longer has any color information to manipulate. Which means going back to using actual glass filters like in the film days. But even that is a loss of flexibility because you lose the ability to selectively apply color filters to only some parts of the image. Plus simulated filters come in any color/strength you want.
09-10-2019, 07:02 PM   #10
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The only thing that comes to mind that might work would be a full spectrum conversion like what is done for astrophotography when they will then shoot with various filters. One person over in the astro group recently had this done to their K-5iis and said they had it done at Spencer's Camera. I'm not really sure what this all entails and if it is what you are after but seems like it might be.
09-10-2019, 07:47 PM   #11
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QuoteOriginally posted by ZombieArmy Quote
Yah this is the part that confuses me. Sure you can strip the Bayer filter but how do you get the full resolution again? I assume if it were as easy as removing the Bayer filter it'd be offered a lot more like IR modifications are.
Let's say you start with a 24 MPix camera and strip the Bayer filters. Instead of 6 MPix of red-sensitive pixels, 12 MPix of green, and 6 MPix of blue, the stripped sensor will be a full 24 Mpix of full-spectrum pixels.

It's like doing pixel shift resolution (but in monochrome) with a single shot.
09-10-2019, 08:54 PM   #12
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QuoteOriginally posted by Sir Nameless Quote
Which means going back to using actual glass filters like in the film days.
Event that goes away because the unfiltered spectral sensitivity of the sensor is dissimilar to panchromatic film.


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09-10-2019, 08:58 PM   #13
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QuoteOriginally posted by photoptimist Quote
Let's say you start with a 24 MPix camera and strip the Bayer filters. Instead of 6 MPix of red-sensitive pixels, 12 MPix of green, and 6 MPix of blue, the stripped sensor will be a full 24 Mpix of full-spectrum pixels.

It's like doing pixel shift resolution (but in monochrome) with a single shot.
Yep, though the full-spectrum part comes at the cost of the sensor being colorblind in a sense similar to that of ortho emulsions of 100 years ago.


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09-10-2019, 09:06 PM - 1 Like   #14
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QuoteOriginally posted by aaacb Quote
I am a bit curious how "mono" differs from "none", since I thought that when there's no color array the sensor values are used directly, but not curious enough to read the source code
I suspect that "none" means no interpolation is done, leaving spectral holes; while mono means doing the interpolation with RGB values at each pixel normalized to gray.


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09-10-2019, 09:07 PM   #15
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QuoteOriginally posted by photoptimist Quote
Let's say you start with a 24 MPix camera and strip the Bayer filters. Instead of 6 MPix of red-sensitive pixels, 12 MPix of green, and 6 MPix of blue, the stripped sensor will be a full 24 Mpix of full-spectrum pixels.

It's like doing pixel shift resolution (but in monochrome) with a single shot.
Then I'm not sure why people would choose not to work on some brands of cameras, sony sensors are pretty standard across the range. Disassembling different cameras is a cakewalk compared to stripping the filters.

Personally what I'd do is try to get in contact with them to see if it'd be possible to work on that sony sensor in your pentax camera, even if it might cost a bit more for them to do.

Last edited by ZombieArmy; 09-10-2019 at 09:19 PM.
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