hands-on review of the D7100

Started Mar 15, 2013 | Discussions thread
photoreddi
Senior MemberPosts: 3,708
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Re: Resolution and AF Re: Very good hands-on review of the D7100
In reply to rhlpetrus, Mar 16, 2013

rhlpetrus wrote:

photoreddi wrote:

rhlpetrus wrote:

...

AF: that may be the most relevant aspect of this new camera. Have you tested the various points. Since its sensor is denser than the D800's and I have seen some problems with PDAF for extreme lateral points (mostly the leftmost AF point), I wonder if you have checked that.

If there are problems with PDAF at the extreme lateral AF point, that shouldn't have anything to do with the sensor density since the AF sensors are located off-sensor, below the mirror box IIRC. No?

Thanks for the good job, rather fast!

Yes, excellent job. If Thom Hogan needs to hire another assistant ...

YOu forget that people check AF accuracy at full res. The D7100's full res is 50% higher (pixels per unit area) than the D800's. What was ok at 12MP (D700) seems not to be ok at 36MP, the D7100's sensor density at FF would provide 54MP worth of pixels.

No, I've long been aware of the D7100's higher pixel density and have cautioned others to be aware of this when they're pixel peeping. But the AF sensors won't perform any better or any worse no matter what the sensor is that's in the camera or what its pixel pitch is because by design PD AF is not intended to produce perfect focus. This may have been acceptable with older, lower resolution sensors but with cameras like the D800 and D7100, for the best AF accuracy Live View's CD AF should be used.

The problem that you're referring to ("mostly the leftmost AF point") is due to Nikon's imperfect alignment/calibration procedures which has supposedly been corrected at this point. It would be good to check for this, but most D800 owners wouldn't have an AF problem, at least those that mainly use the center AF sensors. If the D800s with the left AF sensor issues could magically have the sensors replaced with the D700's 12mp sensors, the AF issue would remain the same as before, but it would be much harder to detect due to the lower resolution of the sensor. But you're already aware of this and I've posted several times (last year) the amount of megapixels that an FF sensor with the same pixel pitch of some of the other 20mp and 24mp cameras (such as the NEX7) would have.

Speaking of forgetting, you recently replied to one of my posts, trying to correct me, saying that when I wrote that the 18.5mm 1-Series lens had an f/1.8 aperture, that I was mistaken, that it had a maximum aperture of only f/2.8. I owned that f/1.8 lens and my reply to you included a photo of it and IIRC, a link to it on B&H's website. Did you not see that reply, or did you just forget to acknowledge your error?

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