Thom on Nikon's unanswered questions...

Started 9 months ago | Discussions thread
David314
Veteran MemberPosts: 4,697
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analog to digital conversion
In reply to brettchris, 9 months ago

why is that odd?

expeed 3 can obviously proces DX crop in the D800 at 9 fps,

again, i think the limitation is getting the data converted in 14 bits AND keeping the read/thermal noise low

I wonder why Nikon didn't let the D800 go to at least 8 fps in DX mode, let me repeat DX mode, at 12 bits

i do NOT expect any firmware upgrade from Nikon,

With the current strategy from Nikon, one might was well wish for a flying pony because that is more likely to happen than a real performance firmware upgrade.

if it is a data transfer from the chip issue,  it would depend on the databus width: it might be 8 bits and take 2 reads. If that were the case it might be able to read twice as fast by just taking the first 8 and dropping the 2nd:  like a low res version.

But, seeing as the D300 slows down considerably from 12 bit to 14 bit, i suspect D300 is a 12 bit bus and you would expect the D800 would be the same or maybe 14 bit.

If that is the case it would be very difficult to get performance gains on the transfer short of overclocking it. probably not a good idea on a dedicated piece of hardware!

more likely, an analog to digital conversion issue, not digital bandwidth from the sensor

the sensels analog voltage is converted on sensor to digital data and on the sony exmoor sensors the Digital to Analog (D2A) converters operate on columns of data.

this is my theory on why fps speed doesn't scale direclty as a function of the megapixels used, it scales as function of the vertical column size, and this is what we see on the D800

so if shooting in DX crop (1.5) you have 2.25 less pixels, less so, if 4 fps is max in FX, then if it were bandwidth or processing power you would expect 9 fps in DX mode,

however if it were column D2A time, and shoot in DX crop the speed up is only 1.5 times, 4 fps x 1.5 is 6 fps, at 1.2 crop you would expect 4 x 1.2 or 4.8, roughly 5,

The faster the D2A runs, the more heat and the more read noise - and that affects dynamic range at base iso

of course as the ISO increases, read noise becomes less important, and while 14 bit is useful at ISO 100, it really doesn't do much at the higher ISO

so i would be perfectly happy with a 12 bit 9 fps DX mode on the D800, it is probably technically possible with the existing hardware.

is Nikon going to do that on the D800? No. Hell will freeze over first. So I guess we will never know. Perhaps the D800's replacement will do this.

but if Nikon stays true to their past, they will introduce a low megapixel D800 replacement that will leave all the high megapixel D800 users scratching their heads and thinking Canon grass is really green

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