Sony NEX goes full frame

Started Aug 17, 2012 | Discussions thread
AdrianGray
Regular MemberPosts: 119
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Re: Sony NEX goes full frame
In reply to blue_skies, Aug 17, 2012

blue_skies wrote:

Because the noise floor is lower (larger pixel sites), you can up the ISO much more on a larger sensor camera than you would on a smaller sensor camera:
e.g.

  • P&S ISO400

  • APSC ISO3200

  • FF ISO13200

DxOmark rates the ISO difference between D800 and 5N almost 3x.
3x in ISO means 3 stops in aperture.

Wait a sec, if the ISO performance of the D800 is 3x the 5N (2853 vs 1079), then the difference should be (almost) 2 stops, not three. Right?

Or, f/1.8 on APS-C then becomes f/5.6.

DOFmaster suggests DOF for

  • APS-C, 35mm, f/1.8, 10 feet to subject -- DOF = 1.8 feet

  • FF: 50mm, f/5.6, 10 feet to subject -- DOF = 4.25 feet

The D800 would be shooting at F4, which gives 2.94 feet. Still greater than the 5N, but not by so much.

Of course, this is just comparing the D800 to the 5N, which may or may not be equivalent. If we compared, say, the Canon 5D III (2293) with the Pentax K-5 (1162), the difference is only one stop, so the 5D would be shooting at F2.8. Here's your comparison (using F2 instead of F1.8):

  • APS-C, 35mm, f/2, 10 feet to subject -- DOF = 1.99 feet

  • FF, 50mm, f/2.8, 10 feet to subject -- DOF = 2.06 feet

And the different in low-light DOF performance is a wash.

Now let's throw in a a mFT camera. The Olympus E P3 (536 ISO score on DxO) is about a stop behind the K5, so it would have to open up to F1.4. At 25mm, the DOF would be 2.07 feet.

If the OMD EM5 has ISO performance in between the E P3 and the 5N, then it would easily beat all these cameras except perhaps the Nikon D800 in low-light DOF performance. The Sony RX100 could also be a candidate for good low-light + wide DOF performance.

If your only consideration is low noise (as measured by DXO ISO performance) and wide DOF, then which sensor size is better? If the above analysis is correct, the answer is: "depends on which cameras you are looking at." Sometimes, smaller sensor cameras can beat larger sensor cameras at low-light performance for a given DOF.

If we add in other considerations to camera low-light performance beyond ISO, such as dynamic range in your darks, and auto-focus performance, then the equation is completely different. We would have to consider how well different systems AF at a given DOF, and the DR performance of FF sensors at higher ISO vs. the DR of smaller sensors at lower ISO.

For 5 feet distance this becomes 0.2ft versus 1ft, and so on

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/ (appareil1) 792|0 (brand) Nikon (appareil2) 737|0 (brand2) Sony

filmrescue wrote:

I'm having a hard time getting my head around FF allowing a "much larger DOF" than a smaller sensor.

blue_skies wrote:

Ever shoot under low light?

FF allows much larger DOF if you need it, or shallow DOF if you prefer it.

APS-C does not have as much flexibility - you deal with noise/ISO rather quickly.

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Cheers,
Henry

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