New Nikon 24mp sensor (D5200) is made by.... Toshiba! New kid on the block?

Not likely. The D3200 24MP sensor is a Nikon sensor, according to Chipworks who know this kind of thing.

https://chipworks.secure.force.com/catalog/ProductDetails?sku=NIK-NC81369R&viewState=DetailView&cartID=&g=&parentCategory=&navigationStr=CatalogSearchInc&searchText=image%20sensor

And DxOMark rates the two sensors the same at 81..

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/801|0/(brand)/Nikon/(appareil2)/736|0/(brand2)/Sony

So it is logical to assume that Nikon chose the Toshiba sensor over their own sensor and the  Sony sensor because it is capable of  better image quality. Otherwise Nikon could have just used their own sensor in the D5200.

Sourcing their sensors from different manufactures (Apical, Toshiba and Sony),  as well as their own home grown designs, gives Nikon an advantage over other camera makers in being able to pick and chose the best sensors available for their cameras, regardless of who makes them.

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"Pay no attention to that man behind the curtain! The Great Oz has spoken!"
- Jon