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Old 01-10-2013, 11:36 AM
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Demosaicing Mono Images?

G'day

I have been playing around with my mono 350d and am unsure weather to demosaic my RAW images, the RAWs are quite dark and low res and once demosaiced look pretty nice with a bit of colour on the left over CFA and hot pixels. I don't understand why the hot pixels have colour?

Anyway if anyone can give me any ideas or opinions it would be appreciated.

Cheers
Jo
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Old 01-10-2013, 12:49 PM
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Originally Posted by nebulosity. View Post
G'day

I have been playing around with my mono 350d and am unsure weather to demosaic my RAW images, the RAWs are quite dark and low res and once demosaiced look pretty nice with a bit of colour on the left over CFA and hot pixels. I don't understand why the hot pixels have colour?

Anyway if anyone can give me any ideas or opinions it would be appreciated.

Cheers
Jo
By demosaic I assume you mean debayer? You say your camera is a mono? If it's a DSLR it has to have a bayer matrix. The software you use to debayer will dictate which pixel go in which channel. Alternatively you could bin2x2 to get a mono output and get rid of the bayer pattern.
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Old 01-10-2013, 01:10 PM
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Yes I agree with Marc. The whole point of a mono DSLR should be to do away with the Bayer Matrix and the 4 colour pixels formed into one colour dot in the image process.

How are you outputting the image - in RAW? JPEGs would already be demosaiced I imagine.

Greg.
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Old 01-10-2013, 01:13 PM
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The only other way to get rid of the bayer matrix would be to strip the micro-lensing on the sensor but I don't even know if that can be done without damaging the chip in the first place. Then you would have a true mono and be able to use every pixel on the surface.
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Old 01-10-2013, 01:16 PM
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The only other way to get rid of the bayer matrix would be to strip the micro-lensing on the sensor but I don't even know if that can be done without damaging the chip in the first place. Then you would have a true mono and be able to use every pixel on the surface.
Depends Marc if the micro lenses have the Bayer colour filter array on them or separate.

I thought they scrubbed the lot off as its does not differentiate between micro lenses or Bayer in the sanding off the filter step of monoing.

Greg.
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Old 02-10-2013, 06:15 AM
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Originally Posted by multiweb View Post
The only other way to get rid of the bayer matrix would be to strip the micro-lensing on the sensor but I don't even know if that can be done without damaging the chip in the first place. Then you would have a true mono and be able to use every pixel on the surface.
This is what I have done, I've removed the micro lenses and colour bayer array and so have a true mono sensor, my question is, do I still need to demosaic the images?(convert to colour?)

I would be interested to know what people do with mono ccd's and such.

Cheers
Jo
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Old 02-10-2013, 07:15 AM
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Originally Posted by nebulosity. View Post
This is what I have done, I've removed the micro lenses and colour bayer array and so have a true mono sensor, my question is, do I still need to demosaic the images?(convert to colour?)

I would be interested to know what people do with mono ccd's and such.

Cheers
Jo
If that the case then you have a true mono sensor and you don't have to debayer. Every pixel counts.
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Old 02-10-2013, 07:27 AM
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Originally Posted by nebulosity. View Post
This is what I have done, I've removed the micro lenses and colour bayer array and so have a true mono sensor, my question is, do I still need to demosaic the images?(convert to colour?)

I would be interested to know what people do with mono ccd's and such.

Cheers
Jo
hi Jo
I've debayered a 350d as well (scraped off the microlens layer and the cfa layer underneath) and you do not need to debayer.
to get b&w, take a pic of a white screen on your laptop, use that as a custom white balance and then take images as raw+jpg. you'll see that the jpg's are in black and white with no colour.
I normally open the raw in maxim and save as fits and then stack in dss as you can set the fits in dss to be treated as mono.
the other option is to use a program called dcraw and save as tiff.
finally you could use the jpg's themselves if youre testing.

as you'd know, the af on lenses wont work if you dont have the cover glass so you'll have to focus manually or add an ir filter glass.

and yes, the microlenses do get removed as they are above the cfa layer.


cheers
Alistair
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Old 02-10-2013, 07:46 PM
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Thanks Greg, Marc and Alister, that's what I wanted to know

Cheers
Jo
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Old 12-10-2013, 05:27 AM
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Perfect, just the thread I was after, and I thought I was alone too, LOL.
I have a Sony NEX3, with the Bayer matrix removed, (done by a guy in the US) so essentially a mono camera.
I didn't buy it so much for astro, but am thinking to try it just the same.
Up until now I Have shot JPEG (portraits/family), but want to try the RAW format as well. I figured that the Sony software would automatically "debater" the image, and this obviously isn't needed.
Given a predominantly terrestrial use, I was wanting something other than Maxim etc for opening the files. I'm on a Mac as well, so I don't think DCRAW is very useful (is it??).
Open to suggestions here guys.
Gary
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Old 14-10-2013, 04:08 PM
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Perfect, just the thread I was after, and I thought I was alone too, LOL.
I have a Sony NEX3, with the Bayer matrix removed, (done by a guy in the US) so essentially a mono camera.
I didn't buy it so much for astro, but am thinking to try it just the same.
Up until now I Have shot JPEG (portraits/family), but want to try the RAW format as well. I figured that the Sony software would automatically "debater" the image, and this obviously isn't needed.
Given a predominantly terrestrial use, I was wanting something other than Maxim etc for opening the files. I'm on a Mac as well, so I don't think DCRAW is very useful (is it??).
Open to suggestions here guys.
Gary
G'day Gary,

Sorry I missed your post, great to hear of another guy with a mono camera

On my mac I use Aperture to import the images and it automatically debayers them as they load, if you haven't got Aperture I would recommend it, as it's an Apple program, runs beautifully, and is awesome to process images with.

Cheers
Jo
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Old 14-10-2013, 05:24 PM
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Thanks Jo.
Yes, good to have a few others to bounce ideas about with.
I use LightRoom 4 (might spring for LR5 yet). It works well for any of the "normal" cameras, this one is not normal though.
What I don't want is the actual debater process, why would I/we, there is no Bayer Matrix, or am I missing the point here?
Gary
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Old 15-10-2013, 10:01 AM
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A RAW image (unconverted CR2 file) will have to be "demosaiced" to turn it into a useable image, this is what I meant when I mentioned debayering.

Jo
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