How can Oly EM-1 compete when FF DSLR with L zoom goes for $2300?

Started Sep 1, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 42,724
I'll have a try.

StephanSchmidt wrote:

But I understand that you will never get it, and never engage in a civilised and proper discussion. You, like many others in this forum, actively resist learning and actively spread FUD, as well as group mutual hypnosis.

But I understand that you will never get it, and keep believing in your equivalence religion even when everyday cropping in photoshop shows you that noise and exposure doesn't change.

The difference between you and me is that I don't go into FF forums to stir up trouble for the sake of it.

Have fun.

Let's see if either of these explanations don't help you understand:

Equivalence in 10 Bullets:

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor). However, the effect of both the focal length and the f-ratio very much depend on the sensor, and scale in direct proportion to the size of the sensor:

25mm f/1.4 on mFT (4/3) is equivalent to 31mm f/1.8 on 1.6x (Canon APS-C), 33mm f/1.9 on 1.5x (APS-C for everyone else), and 50mm f/2.8 on FF (FX), where equivalent to means:

  • The photos all have the same diagonal angle of view (25mm x 2 = 31mm x 1.6 = 33mm x 1.5 = 50mm) and aperture diameter (25mm / 1.4 = 31mm / 1.8 = 33mm / 1.9 = 50mm / 2.8 = 18mm).
  • The photos all have the same
  • The photos all have the same DOF (as well as diffraction softening) when they have the same focal point and display size.
  • The photos all have the same motion blur for the same shutter speed (regardless of pixel count).
  • The same total amount of light falls on the sensor for the same DOF and shutter speed.
  • The same total amount of light falling on a larger sensor will result in a lower exposure for the larger sensor, since the same total light over a larger area results in a lower density of light on the sensor.
  • The larger sensor system will use a concomitantly higher ISO setting for a given brightness for the LCD playback and/or OOC (out-of-the-camera) jpg due to the lower exposure.
  • Other elements of IQ, such as bokeh, color, distortion, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

Equivalence as a Teleconverter:

Given a 25 / 1.4 lens, a perfect (aberration free) 1.25x TC (teleconverter), 1.33x TC, and 2x TC, an mFT (4/3) sensor, 1.6x sensor, 1.5x sensor, and FF sensor, all equally efficient with the same number of pixels and same strength AA filter, and a photo of a scene from the same position with the same focal point:

  • with the bare lens on mFT (4/3) at f/1.4 1/200 ISO 100
  • with the lens + perfect 1.25x TC on 1.6x (Canon APS-C) at f/1.8, 1/200, ISO 150
  • with the lens + perfect 1.33x TC on 1.5x (Nikon, Sony, Pentax, et. al., APS-C) at f/1.9, 1/200, ISO 180
  • with the lens + perfect 2x TC on FF at f/2.8, 1/200, ISO 400

then the resulting photos will not merely be Equivalent, but identical.

Another situation where the photos would not be merely Equivalent, but identical, is if the same lens were used on the same settings on each camera, all sensors had the same size pixels (as opposed to the same number of pixels), same AA filter, and were equally efficient, a photo was taken of the same scene from the same position with the same focal point, and all photos were cropped to the same framing and displayed at the same size.

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