Full Frame sensor does not necessary giving you better IQ than smaller sensor

Started 8 months ago | Discussions thread
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yfan
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Full Frame sensor does not necessary giving you better IQ than smaller sensor
8 months ago

I noticed that there is a trend to upgrade to Full Frame (FF) among photography enthusiastic. The intention is to get better IQ at high ISO. If you look at image quality comparison pictures in this site, it’s not difficult to draw conclusion that FF is about one full stop better than APS-C. For example, the IQ of D5300/D3300/D5200 24 MP sensor at ISO 3200 is about the same as D610 (also 24 MP) at ISO 6400. So by upgrading to FF you will automatically gain 1-stop in IQ, as simple as that, right?

In my view this is quite misleading. In theory it seems right, practically it is not necessary true. Here is why: for a lens in similar size, the lens for the smaller sensor is always faster than bigger ones. In the FF vs APS-C case, the latter is about 1 full stop faster! You see my point now. You can open your ASP-C lens one stop wider to achieve the same IQ as FF. In fact, you will even get the same (similar) DOF. Have you noticed that there are so many “Speed Booster” lately? It basically refocuses the image to use the half of light that was wasted on smaller sensor and their size is “the same” (minus SB adapter of course) as FF. It is practical to make ASP-C lens one full stop faster than that of FF lens. In other words, the bottle neck is not in the rear of your camera system - the sensor (it used to be in the early Digital Camera), rather it’s in the front. You lens’ physical diameter (translates to maximum aperture) will determine your image’s IQ at low light. For an analogy, you will not get more water by using a bigger bucket if your tap only drops.

Here comes my conclusion: choose a smaller sensor camera and put your savings on faster lenses is the best practically strategy. After all, you don’t have to carry a big and heavy bucket all the time when there is not much water anyway.

 yfan's gear list:yfan's gear list
Nikon D3200 Nikon AF-S DX Nikkor 35mm f/1.8G Sigma 10-20mm F4-5.6 EX DC HSM Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 18-250mm F3.5-6.3 DC Macro OS HSM +5 more
Nikon D5300 Nikon D610
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