Will you jump to FX for 'affordable' D600?

Started Jul 20, 2012 | Discussions thread
Kim Letkeman
Forum ProPosts: 32,313Gear list
right ... and wrong ...
In reply to Photographer124, Jul 23, 2012

Photographer124 wrote:

... I've been shooting full frame Canon and crop factor for many years, and now have a D7000... DX sensor does not "magnify" your image by the 1.5 times... It is purely a crop of the image in the center. 300mm lens is still a 300mm lens on both cameras.

Optically, you are quite correct. The smaller sensor can only see a part of the circle. Advantage: sweet spot effect where lens corners are not in play. Disadvantage: smaller sensor means less light gathered means more noise overall.

On FX you just get the full view of the 300mm, where as on the DX you only see the middle - cropped- portion of the image, as captured by the smaller sensor. It is not "magnified" by any means.

Put the same number of pixels on the smaller sensor and you cannot tell much difference between the FX camera with 50% more focal length and the DX camera with the starting focal length.

So you are effectively wrong. The "sensor" sees this crop, which of course results in narrower FOV, which is effectively magnification.

And here is where the downside comes into play. This works great at low ISO, where noise is not a factor. As ISO rises, the squeezing of the same number of pixels into a smaller space results in poorer performance (more noise.)

However, that bar is raised every few years, so we really don't need to worry too much about that issue ... the one issue we do need to worry about is subject isolation, which works better on FX with the 50% longer FL (i.e. equivalent images.)

The fact that the pixel density is higher SOMETIMES compared to the FX means you can in theory crop further crop that image and get a bigger subject so to speak, but say comparing to a 36mp D800, there is no longer an advantage.

No ... you cannot introduce digital magnification into an optical magnification discussion. You can always increase effective magnification at the pixel level by using more pixels. But that has nothing to do with the optical crop issue of DX. That is a 1.5 or 1.6 (Nikon, Canon) increase in effective focal length.

By the way ... we talk about EFL all the time with compacts ... marketing people even advertise the "effective" range of a lens and not the actual range. So why should there be special rules for DX and FX just because you can mount the same lens on two bodies?

The DX are inferior, cheaper sensors, with less light gathering capability and less DOF, etc. It is what it is...

This is a ridiculous summary ... sounds very beginner-ish ...

DX are not inferior at all. Each has its strengths.

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