Crop Factor, Low Light and Aperture with m4/3 lenses?

Started Jun 15, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Nice summary but the supplement needs improvement
5

Sergey_Green wrote:

Great Bustard wrote:

50mm f/2.8 on FF is equivalent to ~30mm f/1.8 on APS-C which is equivalent to 25mm f/1.4 on mFT. By "equivalent to" I mean:

  • The same diagonal angle of view.
  • The same DOF for a given perspective (subject-camera distance) and same diffraction.
  • The same total amount of light falling on the sensor for a given shutter speed.

Any differences in noise will be due to differences in sensor efficiency (as opposed to differences in the ISO setting that is used to get the same brightness for a given shutter speed).

Keep in mind that the lower noise of larger formats (since, for a given exposure, as opposed to same DOF and shutter speed, more light falls on the larger sensor) necessarily results in a more shallow DOF, for better or worse. So, unless low noise matters more to you than a deeper DOF, mFT will be a better choice than larger formats for handheld photography in low light.

Very nicely summed up, I would only add few words about the low noise, if I may. Most of the scenes in the world are middle-gray (or reflect about 18% of light),

On the contrary, most scenes are not middle gray. Rather, most scenes include tones that range all the way from very dark to very bright.

and that is where the larger formats are often ahead regardless of what sensors they have.

On the contrary, smaller sensors are more efficent than larger and therefore tend to do better for equivalent photos like those described by Great Bustard above. This is true for middle gray but even more so for darker tones, which have the poorest signal-noise ratio and where noise is therefore most visible.

The dark shadows, on the other hand, is usually not where the least most important information in the images is,

On the contrary, both the bright and dark tones of an image tend to be important. And the dark tones do not need to be in the shadows. A black cat remains black even if lit.

and can be cleaned without ill-effects to the rest of the captured scene. That is, if anyone is bothered by it.

On the contrary, the dark tones cannot as a rule be "cleaned" without ill effects. Consider for example the hair of the girl in the example to which I link below.

http://www.dpreview.com/reviews/image-comparison?attr18=lowlight&attr13_0=oly_em1&attr13_1=sony_a7&attr13_2=sony_a7r&attr13_3=nikon_d800&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=3200&attr16_1=12800&attr16_2=12800&attr16_3=12800&normalization=print&widget=1&x=0.8342357734262059&y=0.2753099540100277

Here is a good example (this is from LTZ470),
http://acwilli.smugmug.com/Other/Jakes-B-Ball-Jan-2014-EM1-35/

As you can see there is a lot of noise in the images in general, but none of it effects the most important areas (middle-gray), where the most relevant information is.

On the contrary, for reasons already spelled out, such is not the case.

And the difference between larger and smaller formats in these areas is not that far off anyway, even if it mattered, which it does not.

On the contrary, the efficiency advantage of smaller sensors can be quite substantial at times, as illustrated for equivalent photos in the link below:

http://www.dpreview.com/reviews/image-comparison?attr18=lowlight&attr13_0=oly_ep5&attr13_1=sony_a7&attr13_2=sony_a7r&attr13_3=nikon_d800&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=3200&attr16_1=12800&attr16_2=12800&attr16_3=12800&normalization=print&widget=1&x=-0.12336706531738732&y=-0.9872719691061603

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