Why no focus issues with D5100 or D3100 compared with D7000

Started Oct 28, 2012 | Discussions thread
Mako2011
MOD Mako2011 Forum Pro • Posts: 25,468
Not shutter/Mirror Vibration

dirtdiver82 wrote:

Mako2011 wrote:

dirtdiver82 wrote:

Mako2011 wrote:

dirtdiver82 wrote:


I'm also aware that my Panasonic FT2 has a crappy 1/2,3" 14MP sensor that has a much greater density than the D7K and has much worse colors, DR, etc, BUT you can take a picture with one hand on a sunny day and despite the noise, the poor colors, etc it's tack sharp.

The Panasonic FT2 is a CDAF only camera. To compare realistically you need to shoot the D7K in Live view only (comparing focus).

BTW, to confirm a focus issue with the D7K, a proper CDAF vs PDAF comparison will show it or rule it out.

I wasn't comparing focus accuracy, that's another story... This isn't about D7K AF, it's about how the system handles the vibrations caused by the mirror and the shutter itself.
I wanted to point out that while some people justify the D7K small amount of motion blur in handheld shoots at certain shutter speeds due to wrong shooting techinque acquired with lower pixel density Nikon DSLRs, my FT2 has in fact a much higher pixel density and never experienced this problems.

Of course compacts are different species, but you can't justify this behaviour just because of a bit higher pixel density. Vibrations affect to every DSLR, only that in the D7K to a higher extent.

Seems there're more people concerned with this problem:

"To my eyes the D7000 exhibits mirror slap blur in those photos starting at 1/4, reaches its worst at 1/30, then has tapered off to barely noticeable at 1/125. I don't know if I'd classified it as "bad" because I don't know what the standard should be relative to other DSLRs but compared to the D5100 the D7000's blur seems rather pronounced (I don't see blur on the D5100 photos at any of the tested shutter speeds)."
http://forums.dpreview.com/forums/thread/3031067

All true and easily mitigated, but you were speaking of shots faster than 1/250s. That's not mirror slap.

I"s this really mirror vibration or is it shutter induced vibration? I found that shooting at high frame rates with my D7000 actually reduced apparent vibration induced softness compared to slow shutter speeds, which is counter-intuitive to the mirror slap theory as the cause. After experimenting with my D7000 at various shutter speeds and using mirror lock up on a tripod, I came to the conclusion that the shutterslap vibration was more of the softness culprit at slow shutter speeds than mirror slap. I also found that anything that added mass (like the vertical grip with battery), to the camera reduced vibration induced softness at slower shutter speeds. A high quality tripod and head really makes a difference as well."
http://forums.dpreview.com/forums/post/41245214

You can use live view to see, it's not a shutter vibration issue

Yes, in my experience I suffered some motion blur shooting at 1/500s while shooting my D7K as steady as I could and holding my breath with the 70-300VR at higher focal lengths.

I understand but that's not caused by shutter or mirror vibration.

The inconsistent low-light AF performance must be user fault too. And it's tendency to overexpose in certain situations...
Don't get me wrong, I liked my D7K, but got stolen so I want to invest my money on a system that has most of the "limitations" of the D7K fixed. Name it D400 (thats what I hope).

The low-light focus issue is a AF sub-mirror calibration issue as I pointed out above. It occurred in a few models and is now easily fixed and very rare in regards latest samples.

Overexposure in certain issues is not a fault of the camera. Live View does it on purpose in certain conditions to match the rear LCD and Focus Point bias needs to be accounted for in PDAF/Matrix

D7000-overexpose see part 2

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