Serious thinking of the Pentax 645 or shall wait? Locked

Started 3 months ago | Discussions thread
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bobn2
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Re: Serious thinking of the Pentax 645 or shall wait?
In reply to qianp2k, 3 months ago

qianp2k wrote:

bobn2 wrote:

qianp2k wrote:

bobn2 wrote:

marcio_napoli wrote:

I agree, but considering there's only 1 CMOS DMF sensor available, and no one really knows its performance for sure, I think the CCD backs are still relevant.

Specially if you consider these will be the backs most will afford on the used market.

The new sensor, used in the 645Z, P1 IQ250 and 'blad H5-50c is a Sony Exmor - it's performance is pretty predictable. It has a 5.3 micron pixel, equivalent to about 30MP on FF - so it should be a pretty known quantity, if we know hoe the Sony A7R and Nikon D800E perform, it will perform much like those, but with a bigger sensor.

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Bob

CMOS sensor is better in high ISO that is sure. Not sure how it compares to CCD sensor in low ISO such as even bigger MF CCD sensor (so-called fullframe MF sensor) in 80mp CCD PhaseOne and Mamiya MF cameras.

The latest generation Exmor CMOS exceeds the quantum efficiency and full well capacity of the CCD technology used in those. The big advantage that CCD had was that it was essentially ISOless, with the same read noise across the ISO range. This gave it better DR than Canon style CMOS. The base ISO figures would be something like 30 e- for Canon, 10-20 for CCD. But the Exmor is typically around 4-6 at base ISO, so should better the CCD in every way. Remember, hardly any progress is being made in CCD imaging because the market is so small, there is nothing to pay for extensive R&D effort, while Sony ploughs in millions, based on their sales as the number one imager manufacturer.

I am just questioning if still some inherited difference between CCD and CMOS at base ISO as I heard CCD sensor has some unique characters at base ISO. I hope DXO or some lab will also test 80mp CCD sensor in PhaseOne IQ 280 and Mamiya 645DF, so-called fullframe MF at 0.64x crop that is bigger than 1.3x crop MF sensor found in 645Z at 0.78x crop.

I think that the unique mystique of CCD is one of these mythological things, and certainly nothing that would come out in DxOmark tests, where CCDs measure very badly. I suspect it mostly has to do with CFA response, where CMOS CFAs have been progressively desaturated in the interests of QE.

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Bob

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