Comparing Olympus 4/3lenses to FX "Full Frame" offerings

Started Jan 25, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 42,270
Re: As a photographer ..

Tiger1 wrote:

Sergey_Green wrote:

Tiger1 wrote:

Now why do you think that anyone would care about the aperture diameter? The aperture diameter is only relevant when it is coupled to the focal length because as a photographer I actually measure light intensity (or luminosity) when I use a light meter. It actually gives me an F stop and a shutter speed. It does not give me an aperture diameter and then asks me for a focal length or vice versa. So f/2 IS f/2 when it comes to taking photos! Isn't that what this whole website is about? It is not about people like you getting so pedantic as to confuse everybody about what really is important.

The aperture diameter only explains why, but of course no-one should care what the exact size is. However, as a photographer, were you to shoot with different formats, would you care what your pics would look like at the end. After all, f/2 from FT and f/2 from FF are hardly the same. Would that matter?

F/2 is F/2 no matter what the format when it comes to exposure - that is what I'm talking about.

No one denies that.

As a photographer I am interested in getting the correct exposure.

Please define "correct exposure". For example, if the "correct exposure" for a scene is f/4 1/200 ISO 400 on an E5, what is the "correct exposure" for the same scene with a FF DSLR?

ISO, shutter speed and F stop determine exposure.

Actually, the exposure is determined by the:

  • the scene luminance
  • the f-ratio (more properly the t-stop)
  • the shutter speed

The ISO setting does not change the exposure except inasmuch as it indirectly changes the f-ratio, shutter speed, and/or flash power, depending on the AE (auto exposure) mode you're in.

When it comes to DOF that is another matter. The effect of F stop on DOF will depend on the focal length of the lens. Because different formats have different angles of view, one has to change focal lengths to get the same perspective for each format.

The same goes with the total amount of light projected on the sensor for a given shutter speed, and thus the noise.

Changing the focal length at a given aperture will then affect DOF. To get equal DOF one has to increase ones aperture as the format gets smaller to retain the same perspective.

The F stop will still determine the exposure with the shutter speed for a given ISO.

So when it comes to EXPOSURE f/2=f/2=f/2 no matter what the format.

No one denies that f/2 = f/2 = f/2 when it comes to exposure. The point you're missing is that it's not the exposure that matters, but the total amount of light falling on the sensor. The competent photographer will seek to maximize the exposure (and thus also maximize the total light falling on the sensor) for the format they are using within the constraints of DOF / sharpness, motion blur / camera shake, and noise / blown highlights.

P.S.:  When you have a moment, Bob had a question for you downthread.  Be sure to click on the photos to see fullsize -- it may help in answering the question.

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