2 New Nikon DSLR Rumours

[Craig Ruaux 0]

FYI: Julia Borg is a knowledgeable photographer and contributor at the dpreview forums.

 

 

As a lurker over there, I found it hard to believe that you let yourself get dragged into this morass.

 

I mean, come on, you were talking with a guy who uses the handle TestEng, and we all know there are 10 types of people who understand binary.

[craig 0]

I know and I'd successfully lurked there for years! The comments on Clark not knowing what he was talking about really set me off :-(

 

Here Julia says what I expect is true regarding the 40D: http://forums.dpreview.com/forums/read.asp...essage=24476549

 

Of course, just because the 14th bit isn't useful doesn't mean the 13th isn't a win!

[herbko 0]

I have seen specs as high as 78dB for 12 bit converters as well. That would exceed their resolution though.

 

Assuming 12 bit converters can do 74dB or better and 14 bit converters do 78dB, a 14 bit converter only offers 2/3 stop over 12 bit. Julia Borg, the source of this information, claims that an engineer gave her these numbers and it corresponds to her observation that the 1D3 only offers a 2/3 stop improvement over the 5D.

 

Perhaps the reason we haven't seen 14 bit converters before now is that they have been impractical as well as unjustified in these systems. I would think this would improve with time, but for now expecting a 2 stop improvement with 14 bit is, perhaps, too optimistic.

 

FYI: Julia Borg is a knowledgeable photographer and contributor at the dpreview forums. Her father, Iliah Borg, is the author of Raw Magick, a well respected raw converter for Windows.

 

The maximum dynamic range of a 12-bit A/D is 20*log(2^12) = 72db. State of the art for high speed ones seems to be around 70db.

 

http://www.analog.com/IST/SelectionTable/?...on_table_id=197

 

The 14 bit converters are probably ~1.5 bit better than the 12-bit ones.

 

The 5D cell area is about 30% bigger. The new generation sensor design from Canon may not have improve things that much.

[craig 0]

Note the following:

 

http://www.maxim-ic.com/appnotes.cfm/appnote_number/641/

 

http://www.seis.com.au/TechNotes/TN200410A_SNR.html

 

Each of these sources say that 12 bits is equivalent to 74 dB. Where the 2dB difference is I don't know and don't really consider important. It's a constant in the equation though. Each bit is 6dB. The important thing is that 78dB means 12 2/3 stops, not 13.

 

Now, here is the 78dB link: http://forums.dpreview.com/forums/read.asp...essage=24467785

 

Note that Julia says that it was an ADC design engineer who told her and her father that. What exactly 78dB means in the context of a 12 bit converter I don't know. It would seem to me, like you, that 12 bit converters will all be below 74dB.

 

I really don't think we can assume anything about the effective difference between current 12 and 14 bit converters. Julia reports 2/3 stop improvement for the 1D3 over the 5D and Clark reports that the 5D achieves nearly 12 stops. If Julia is to be believed, the 1D3 is only achieving about 12.5 stops. If there is really a 1.5 bit advantage like you say, then the 1D3 should do better. Perhaps it does.

 

Interestingly, Sony's new CMOS DX sensor has many parallel ADCs. I wonder if that implementation results in a lower noise conversion since the ADCs are clocked much slower.

[herbko 0]

Each of these sources say that 12 bits is equivalent to 74 dB. Where the 2dB difference is I don't know and don't really consider important. It's a constant in the equation though. Each bit is 6dB. The important thing is that 78dB means 12 2/3 stops, not 13.

 

The 6 db/bit is the range. The difference is that to get to the maximum signal-to-noise, SNR, that most specs quote, you have to divide by the quantization noise which is a fraction of a bit, so that number is about 2db higher.

 

I really don't think we can assume anything about the effective difference between current 12 and 14 bit converters. Julia reports 2/3 stop improvement for the 1D3 over the 5D and Clark reports that the 5D achieves nearly 12 stops. If Julia is to be believed, the 1D3 is only achieving about 12.5 stops. If there is really a 1.5 bit advantage like you say, then the 1D3 should do better. Perhaps it does.

 

It could be limited by the sensor or the A/D. If a careful test gives 12.5 bits we still won't know which it is.

[herbko 0]

Interestingly, Sony's new CMOS DX sensor has many parallel ADCs. I wonder if that implementation results in a lower noise conversion since the ADCs are clocked much slower.

 

First, they are 12-bit converters, and the state-of-the-art in that is probably good enough to be not much of a factor. Also, multiple A/D's have threshold matching problems which can show up as noise or patterns. Since, Sony is sending this out they're likely to have a good handle on it, but it's not clear that is not a noise contributer.

[kramer92911 2]

http://www.photographybay.com/2007/08/22/p...-and-d300-leak/

 

 

Popular Science leaked this info this afternoon.