DX crop with D800 vs crop in post (vs teleconverter)

Started Oct 20, 2012 | Discussions thread
bobn2 Forum Pro • Posts: 57,416
Re: DX crop with D800 vs crop in post (vs teleconverter)

Kerry Pierce wrote:

The disadvantages are that you lose a stop of light, which usually requires boosting ISO and it can adversely affect AF in lower light levels. In low to very low light levels, the TC loses most of its advantages, IMO.

You lose exactly the same amount as light as you would taking a 1.4x crop (assuming a 1.4x TC) - because you are using the same crop from the original lens, just magnified to fit the whole sensor rather than cropped from it - the amount of light going into the image is the same. Boosting ISO doesn't of itself create noise, the reason boosted ISO looks noisier is that the image is made with less light. So, a 1.4x crop and a 1.4x TC with the ISO boosted 2x will look pretty much identical.

The AF problem is to do with when the actual f-number gets small enough to shade the AF-sensors. With Nikons now AFing to f/8, it's less of a problem than it was.

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