D800 Autofocus issues II

Started 11 months ago | Discussions thread
Robin Casady
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Re: The absence of evidence is not evidence of absence
In reply to fPrime, 11 months ago

fPrime wrote:

caspianm wrote:

fPrime wrote:

caspianm wrote:

fPrime wrote:

Not sure about this one, so take with a grain of salt, the liveview mode apparently accentuate the soft focus issue.

What?

Agreed, the grammar here leaves something to be desired. Just for clarity, this was the Amazon user's commentary (not mine).

I believe the only reasonable interpretation of what he's saying is that the Left AF mis-focus was detectable simply viewing the images produced with PDAF and that when compared to images produced with CDAF in Live View the mis-focus was accentuated.

fPrime

I realized it wasn't yours. If he was testing PDAF, it could not be accentuated by CDAF. CDAF is the reference. Something is amiss.

Regarding amazon reviews looking at D800E reviews show excellent numbers. But the catch is both unit have the same focusing system. Go figure.

I hear you. How about this conspiracy theory... the source of the Left AF focus problem is caused by simple production variability in the 51 point PDAF system. The most accurately aligned modules are hand picked for the D4 first with the D800e next. The D800 is inevitably built with the least planar PDAF modules that are left over in a calculated risk that the users for these low end models will be less sensitive to any resultant focus accuracy variation. The D7100 picks up the absolute worst 51 PDAF FX modules and repurposes them into DX modules since the smaller DX image circle puts less optical stress on focus performance of the edge sensors.

Then extend the conspiracy... the reason the D600/610 and Df use the 39 point PDAF system wasn't just to cripple the feature sets of the D800 and D4 respectively. They had to use it because sufficiently "accurate" 51 point PDAF modules couldn't be produced to simultaneously support six different Nikon DSLRs including the D7100.

Before dismissing this out of hand consider that Intel sells the exact same CPU as a lower or higher performing model purely based on how tolerant it is to performing accurately under load during internal QC testing.

fPrime

There is software that compensates for planar irregularities in the AF module. So, I doubt your CT. Here is mine: The earthquake damaged one of the machines Nikon uses to calibrate the AF system. They thought they had it recalibrated for the D800 run, but they didn't. So, a percentage of the D800s were improperly calibrated. That is "My theory, which belongs to me, is mine."

Anne Elk

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Robin Casady
http://www.robincasady.com/Photo/index.html
"Get your facts first, then you can distort them as you please."
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