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Old Mar 2, 2006, 6:28 AM   #1
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http://www.kodak.com/global/plugins/...00LongSpec.pdf

The one above will probably be used in the coming Pentax 645D with cropped sensor size less than 6 x 4.5cm. DR listed in this "layman" (IMO) or simply marketing datasheet is 75dB.

http://www.kodak.com/global/plugins/...00LongSpec.pdf

For this one, I don't know what DSLR will use it! as it has a 1.24 crop factor, really strange to me afterall. Will the coming PEntax 10M DSLR used this? WHo knows.. DR listed is 67dB.

So, the question is how we intrepret this into the usual EV units we are familiar with??

dB is a *comparative* logged unit in log-base *10* multipied by 10 for signal level difference and 20 if given the signal levels but we wish to calculate the power or energy difference.

f-stops is a *comparative* logged unit in log-base *2*.

I don't know if the Kodak datasheet is about voltage level or energy level on the dB (as it doesn't define it clearly). I bet it is probably about energy level difference base on voltage level difference, though, for a typical datasheet for this type of device. Thus, a 67dB means the logged-10 ratio is 3.35 (derviated by divding 20). To convert back to the f-stops, one need
to multiply the log-10/log-2 ratio which is 3.32 when rounded up. Then, the DR should be 11.13 f-stops (3.35 x 3.32) instead! which I think is pretty good!

For the 645D sensor, its theoretical DR can reach 12.45 EVs! Amazing!(?) :-))

Congrats Pentax! But hope she don't spoil the excellent sensor in the 645D!

Finally, noted that the CCD is a *linear* device and actually each pixel is a light sensitive capactor. The voltage in each pixel stored in *proportional* to the light energy received in a *linear* way.. Thus, I have just derived to the voltage difference in "how many doubles" last time about the voltage and this is essential equal to the light energy ratio.

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Old Mar 3, 2006, 11:39 AM   #2
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RiceHigh wrote:
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For this one, I don't know what DSLR will use it! as it has a 1.24 crop factor, really strange to me afterall. Will the coming PEntax 10M DSLR used this? WHo knows.. DR listed is 67dB. To convert back to the f-stops, one need
to multiply the log-10/log-2 ratio which is 3.32 when rounded up. Then, the DR should be 11.13 f-stops (3.35 x 3.32) instead! which I think is pretty good!
You may be able to get close to that with your Pentax if you make sure to expose to the right on the histogram and shoot in raw.

Dave Etchells got pretty interesting results with the Konica Minolta Maxxum 5D (which also uses a Sony CCD, like the Pentax models), shooting in raw, overexposing, and converting with Adobe Camera Raw. It even bested the full frame Canon EOS-1Ds Mark II by a small margin (but the Fuji S3 Pro tops it).

Of course, the cameras probably have differences in AA filter design, Analog/Digital Converters, etc. that make them different. But, I'd be curious as to how much DR you could pull out of one. Dave hasn't used Imatest to measure DR with raw files from any Pentax models yet (AFAIK).

See Dynamic Range Tests here for the KM Maxxum 5D shooting in raw (the jpeg images are not as good, probably because they're a bit contrasty using the default settings, but you can dial back the contrast setting via camera menus).

http://www.imaging-resource.com/PROD...M5DIMATEST.HTM

Quote:
For this one, I don't know what DSLR will use it! as it has a 1.24 crop factor, really strange to me afterall. Will the coming PEntax 10M DSLR used this? WHo knows.. DR listed is 67dB
My best guess (and it's only a guess) is that it will use a Sony sensor (probably similar to the one in the Nikon D200). They didn't say in their press release (only that the new 645 Digital would have a Kodak sensor).

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