Michael Reichmann's take on smaller full frame Sony FE mount lenses

Started Dec 18, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Michael Reichmann's take on smaller full frame Sony FE mount lenses

harold1968 wrote:

Anders W wrote:

harold1968 wrote:

Anders W wrote:

harold1968 wrote:

However this is still not an equivalent, as f1.4 vs f2.8 is a pretty large difference for light gathering (given that the DOF will in fact be the same and therefore equivalent).

F/1.4 on MFT is equivalent to f/2.8 not only with regard to DoF but also total light accumulation. The amount of light collected per square mm of the sensor will be only one quarter for FF at f/2.8 versus MFT at f/1.4. But since the FF sensor has an area that is about four times larger, the total amount of light collected for the image as a whole will nevertheless be approximately the same.

I agree for DOF but not on light gathering. Remember that, given the same technology for the sensor and pixel pitch, pixel level detail should be the same given the same light available.

The fact that more pixels get illuminated in FF is very useful but f1.8 for the smaller area is still the same as f1.8 for the same size area in the larger sensor.

The proof is that I find meter readings and the equivalent shutter speed (using aperture priority) pretty much the same between M4/3s, APS-C and FF given the same aperture and equivalent ISO setting.

This is a great advantage for M4/3s in terms of light gathering ability vs relative size.

In order to understand what I am trying to say, you must make a distinction between light accumulation for the entire sensor (and thus for the entire image) on the one hand and light accumulation per sensor area unit (e.g., light accumulation per square mm) on the other.

Exposure refers to light accumulation per sensor area unit, which explains why your meter readings are the same regardless of sensor size. And with regard to exposure, an f-stop (say f/1.8) is an f-stop no matter what the sensor size.

However, if you consider how much light the sensor as a whole accumulates, then there is a two-stop difference between FF and MFT. In other words, for the sensor as a whole, f/2.8 on FF gathers the same amount of light at the same shutter speed as f/1.4 on MFT. This in turn means that an image shot at for example f/2.8 and 1/100 s at ISO 400 on FF will be equally good with regard to signal-noise performance as an image shot at f/1.4 and 1/100 s at ISO 100 on MFT, everything else equal (including display size/display resolution and the efficiency of the sensor).

yes I completely agree, which is why, given the same sensor technology, things like DR, ISO performance, etc. would tend to be better on the bigger sensor

However given that I can achieve the same aperture and speed settings with the Oly 12-40mm f2.8 zoom as I can achieve with the Canon 24-70mm f2.8 that's pretty remarkable given the difference in weight and size. The Canon lens weighs more then the E-M1 and the 12-40mm together. A Canon FF body would then effectively double that weight.

In terms of the quality difference, I think technology has developed to the point that the sensor on the E-M1 is excellent, and on the A7 is awesome.

I can live with this difference given the difference in size, weight, speed, shutter noise, and other things that are important to me.

I too certainly appreciate what MFT has to offer or I wouldn't have chosen it as my system and invested as heavily in it as I have. Even if FF lenses can be built about as small and light as MFT lenses, if they are made two stops slower and if we exclude longer teles, the selection of such lenses isn't all that great. So if you are ready to sacrifice a bit of "DoF control" for more "FL control" (more lenses in my bag rather than in a drawer back home), then you are better off with MFT, now and in the foreseeable future. What happens in the longer run is as always difficult to foresee.

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