DX/FX sharpness: is there a real difference? (and other DX-FX questions)

Started Feb 14, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 53,589
Re: DX/FX sharpness: is there a real difference? (and other DX-FX questions)

ishtar74 wrote:

Hi all!

I've been itching to go to FX after reading many enthusiastic reviews of the D610, but I'm having a hard time justifying it...! I might just have GAS again, even though I just bought a SB-910 but HEY - it's my birthday! I read about the differences FX can make on IQ - better bokeh, low noise, better DR... I also came accross the DXO site and comparing the 24-120 (which I have my eye on, should I make the move), I see it scores so much better on a FX than a DX! I must admit, I'm a bit of a pixel-peeper and I like my pictures very sharp. Is sharpness that much better on FX? How are these tests done, really?

I'm currently using a D7000. I'm not especially into wildlife or sports, I shoot just about everything, mostly family/friends meetings, kids, travel photography, and some macro. My D7000 does the job, I don't feel limited in anything but I would like a more precise and fast AF (been struggling with AF fine tune on many of my lenses, but the body might not be the one to blame here). What should I expect by moving to FX, really? Would AF improve? I know the AF zone on the D610 is a bit limited and that scares me, to be honest. But if the AF is more precise than the D7000, that would still be a plus!

And finally, with the low prices on the D600 - is it crazy to consider it? Is the dust/oil issue so annoying, considering I rarely shoot low apertures? Could more recent units be better?

Thanks in advance!


A lot of the differences are quite subtle and down to how you use the cameras. As a working example, let's compare a D7100 and D610, both 24MP cameras with a similar spec. You asked about sharpness. Both cameras have 24MP so both can in principle produce equally 'sharp' images (though the D7100 doesn't have an AA filter, which maybe makes it a bit sharper). However, since the D7100's sensor is only 2/3 the linear size, any lens must project an image with 1.5 times the linear resolution to make the same sharpness. In practice, very few do (though the smaller pixels of the d7100 extract a bit more sharpness from the lens) , so the D610 will end up fractionally sharper. However, the D7100 can produce image quite sharp enough for most purposes.

The next question you ask about is noise and DR - well, the D610 does offer better noise and DR, but only if you are willing to sacrifice depth of field (or use longer exposure times) to get it. If you work in deep DOF, and set the two cameras up to produce the same DOF, with the same shutter speed, the noise and DR will be pretty much the same.

So, whether in IQ terms FX offers you anything depends on your photography. Since you say you 'rarely shoot low apertures' by which I assume you mean small apertures, on might assume that you are doing shallow DOF work, in which case FX might be a benefit.

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