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Old 29-10-2017, 07:51 AM
glend (Glen)
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Debayered sensor report from ChipMod

ChipMod seems to be doing some work for QHY, in an effort to deliver a mono CMOS APS-C camera to market (based on debayering an existing QHY camera sensor). They (ChipMod) are running a thread on CN that reports on this:

https://www.cloudynights.com/topic/5...era/?p=8183364

The obvious downside of debayering, like artifacts and loss of micro lenses ( hence QE reduction), is sort of glossed over in their report. As i posted in that thread i will not repeat it here, other than to say i believe it is a poor choice as a serious camera due to performance trade offs.
If your interested, have a look.
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Old 29-10-2017, 10:41 AM
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Camelopardalis (Dunk)
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Can’t say I’m that interested in an APS-C mono, it’s not all that larger than the 1600...a bit wider, which might help with some targets, but not a major revolution.

The real game changer will be a larger mono sensor, APS-H or full frame. Having said that, I bought a smaller mono sensor (ASI178), not a larger one
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Old 29-10-2017, 04:45 PM
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billdan (Bill)
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I think Chipmod would agree with you Glen
i.e this mod will never be as good as a mono chip with the microlens. They say its only a stop gap measure until newer CMOS mono chips become available.

They allude that this mod will be more efficient behind narrowband filters, compared to its OSC version looking thru narrowband filters. But the mod is less efficient in RGB broadband compared to the OSC.

It also seems that QHY has given the go-ahead for Chipmod to do the whole QHY CMOS range of APS-C and full frame cameras.

I have yet to see any images taken with these new cameras that have been modded, until that happens I will reserve judgement.
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Old 29-10-2017, 05:54 PM
glend (Glen)
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Quote:
Originally Posted by billdan View Post
I think Chipmod would agree with you Glen
i.e this mod will never be as good as a mono chip with the microlens. They say its only a stop gap measure until newer CMOS mono chips become available.

They allude that this mod will be more efficient behind narrowband filters, compared to its OSC version looking thru narrowband filters. But the mod is less efficient in RGB broadband compared to the OSC.

It also seems that QHY has given the go-ahead for Chipmod to do the whole QHY CMOS range of APS-C and full frame cameras.

I have yet to see any images taken with these new cameras that have been modded, until that happens I will reserve judgement.
Bill, of course there are coping strategies that could be used, like dithering to eliminate artifacts, and long sub lengths to make up for the lower QE. I have used these myself with my debayered Canon sensor. Yes it can be a stop gap measure but are people that desparate? Consider QHY has to make some money, and ChipMod has to as well, are people willing to pay for a hacked OSC to get an APS-C sensor size? The Panasonic mono sensor in the ASI1600MM is only slightly smaller. I can not understand the business case for this camera?
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Old 29-10-2017, 06:54 PM
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Two things come to mind:
1. They may have managed to perfect the debayering technique so that there are no artifacts.

2. If the first tests of the removal of microlenses and CFA can be believed, they actually show 32% increase in QE for red and 12% and 6% decrease for blue and green respectively (when compared to the colour version of the same sensor). If true this is actually quite good.

At this stage I would like to see more independent tests and real images before making any conclusions.
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Old 29-10-2017, 08:32 PM
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the broadband signal difference between mono and Bayer should be about 2.5x. The measured difference shown in that report is less that that, suggesting that the loss of the microlens structure has reduced the QE to ~0.6x what it would be if they had not been removed.
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Old 29-10-2017, 11:02 PM
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That is of course true. But unless I am mistaken the removal of CFA brings up the broadband signal about 1.6x compared to the colour sensor. So in terms of QE we have:
real mono sensor = 1
debayered sensor = 0.6x
colour sensor = 0.4x

If I am right the debayered sensor sits in between the other two in terms of QE. If they can do the debayering well this may be the market for the new camera, depending on the pricing
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Old 29-10-2017, 11:12 PM
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that's a good way to look at it. when you add in the time to take RGB data in addition to the lum, the deBayered camera has no advantage over the Bayer camera for broadband - it is of course much better than the Bayer camera for narrowband.
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