just a random survey about pentax...

Started Aug 30, 2005 | Discussions thread
Sophie Wilson Senior Member • Posts: 1,759
Re: Yes - provided ...... (part 1)

richardday wrote:

Hi Sophie

Okay, I understand (I think) about the reduction in MP with NR.

Easy to see in the pictures. Just never mentionned. And it would be easy to test!

Does this mean that if we stick to APS-C isze sensors, we are not
going to be able to get better resolution AND better dynamic range
AND lower noise than we currently get, EVER - Correct?

Pretty much.

The electronics can improve (14 bit ADCs) and some of the problems are related to the noise floor.

But most of it is about the quantum efficiency of the sensor and there's little possibility for improvement (especially as James Doohan is dead - "ye cannee change the laws of physicks")

To get more MP's, better DR and lower noise we HAVE to have a
bigger sensor, yes?

Yes. And its not all gravy here, either. As the sensor gets bigger, the bit lines get longer and thus their contribution to the read noise gets bigger. But at least the bit lines only get longer by the square root.

What about Fuji's APS-C sensor in their S3, that is supposed to
have some of the features we all are after, doesn't it?

It doesn't seem to work that well. My guess is that the reduction in area of the larger sensor combined with the microlens decreases the quantum efficiency and increases the noise of the larger sensor. There may also be problems when it saturates - electrons tunnelling to the smaller sensor. Or they simply can't map the ranges of the two sensors sensibly. Either way, the demonstrations in compact digicams were appalling and in the DSLR less than convincing - Phil only gave it "Above Average"! (his worst rating for a DSLR?). Note that many other DSLRs can get this much dynamic range already!

From what I understand, a FF sensor with the same sensor site size
as we currently have, would equate to about 14MP, am I correct?

Yes, which is why the EOS 5D is expected to do well on noise tests - pixels are larger.

Otherwise cropping a FF image to get a similar FOV with an APS
sensor would result in an inferior image, MP wise, is this not so?

And the 5D will be inferior to the *ist D if you crop both to the same area - it will have fewer pixels even though they're nicer pixels.

Therefore the Canon 1DSmk2 with 16.6MP will produce a noisier image
than an equivalent 6MP APS-C camera if cropped to a 1.5x FOV?

Yes - a few more pixels, a noisier image. As noted above, the noise gets a little worse due to the size of the large sensor's bit lines.

Is that why the 1Dmk2 with 8.2MP sensor (equal to a 5.5MP APS
sensor) tends to produce the lowest noise, and better DR etc than
most other DSLR's?

Yes: the 1D mk II at 8MP has both more pixels and they're larger and its bit lines aren't as long as the full frame monsters.

Does this indicate to you that the new Canon 5D with 12.7MP on FF
will have similar noise to the 1Dmk2 and better than the current
crop of 6MP APS sensor'd cameras?

Pro: larger pixels. Con: longer bit lines.

I reckon it will turn out to be really close between the 5D and 1D mk II. Without being able to see the specs of Canon's sensors, I'd guess the 1D mk II will win. But I'd guess the 5D will have better noise performance than the 6MP cameras though it depends a lot on the in camera processing. (What in camera processing? CMOS sensors have a lot of regular noise - "pattern noise" - which is removed in camera even if you are making RAW files. The *ist D as far as I know has no in camera noise processing at all...)

What are your views of the Dalsa 11MP FF chip, the forunner of
which was utilised in the aborted MZ-D? This is half of the chip
used in the Mamiya 645 digitals. Is this an interesting path for
Pentax, in your opinion?

All the Dalsa/Fill Factory/Kodak designs have a lot of noise. Mostly I guess due to the long bit lines. They have decent dynamic range in terms of headroom for highlights, but look more like film than I might like in terms of there being little shadow detail. The Hasselblad/Imacon design is similar but seems a little less noisy and at least they allow you to shoot at ISO800 (at half resolution).

Continued in part 2...

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