A reminder for some memebers as to what the F stop is all about.

Started Jan 26, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 43,010
Re: Both sides are sort of right

jkrumm wrote:

As far as I can tell, the amount light is relative. Light does not increase in density or anything like that with a full frame, and 2.8=2.8 as far as shutter speed and iso goes.

This is correct. However, since a given scene luminance and shutter speed results in the same density of light (same amount of light per area on the sensor), the larger sensor collects more total light in proportion to the ratio of sensor areas, and it is the total amount of light collected by the sensor, along with the sensor efficiency, that matters, not the density of light falling on the sensor (exposure).

The main difference with sensor size is that the larger the sensor, the less you have to enlarge the image when developing it. That's why full frame (and medium and large format) tend to have more resolution even with the same megapixels. It was the same in film days. Increased megapixels is sort of like using a finer film grain, but it's only going to get you so far.

Of course, 4/3 lenses are sharper than FF lenses, which offsets that advantage for FF somewhat. That is, if a 4/3 lens is twice as sharp as a FF lens, it will resolve as well as a FF lens for sensors with the same pixel count and AA filter.

Depth of field differences we all know and can all agree on.

Indeed. However, as seen above, many do not understand the connection between DOF and noise.

DR and noise differences depend as much on current tech as anything else, so we see a D7100 outscoring Canon full frame sensors on DXO. Clearly though, we can see the there is both a correlation between sensor size and these things, and sensor tech and these things, at least at this point in digital camera development.

DR is, in my opinion, even more misunderstood and Equivalence. If you have any interest, here's a rather detailed write-up I did on it which discusses, in detail, what DR is, how it is affected by pixel count, sensor size, and sensor efficiency:


including examples with some modern systems.

All that said, the differences between these cameras is not worth arguing about (though I admit it can be fun sometimes).

If you flip through the challenge winners here on DPR, I'm sure you would not be surprised to find that IQ rarely, if ever, plays a role in how people vote, and that the IQ differential between systems  is usually unimportant in terms of the "success" of the photo.

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