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: Glad that you had such big aperture
1

philosomatographer wrote:

Anybody still participating in the "equivalence" debate have a serious dead-horse-beating fetish - they should get out and take some photos, possibly with a "full-frame" system. Just remember to stop down those lenses to f/8 for a nice and even performance across the frame!

I've taken a few.  Would you like to see some?

I use four thirds, 35mm "full-frame" (Leica), 6x7cm Medium Format (Mamiya), and 4x5in (Linhof) all on a regular basis. There are no optically better lenses than the Olympus SHGs when looking across all optical parameters.

Are you talking about lp/mm (line pairs per millimeter on the sensor) or the photographically more meaningful measure of lw/ph (line widths per picture height)?  Or are you talking about some other measures or combinations of measures (e.g. flare, bokeh, AF, etc.)?

Zeiss is the only manufacturer to have "caught on" with having to produce retrofocus, oversized lenses for ultimate performance on digital (the Otus 55/1.4). Manual focus, no weather sealing, single focal length, $3.5K

It'll be a while before somebody applies those ideas to an ultimate-performance f/4.0 (for "equivalence"), fast-focusing, fully weather-sealed zoom lens for 35mm sensors. Then we'll talk about cost and size, compared to the ZD 14-35mm f/2.0!

You mean like the Canon 70-200 / 4L IS?

As it stands, we have junk like the Nikon 16-35mm f/4.0 that is not only huge like a telephoto lens, but distorts like a fisheye. See - only if they severely compromise on one parameter (distortion) do they manage a good showing with the others.

Truly uncompromising lenses are very rare in the 35mm world, yet we have them in the form of four zooms covering 7mm to 250mm in the four-thirds system. Of course, due to abandoned development, we are stuck with a "compromised" sensor, but such is life.

Compromises always exist.

So - what were we debating in this thread again?

I think it was about the relationship between relative aperture (f-ratio) and virtual aperture (entrance pupil), the difference between the amount of light per area that falls on the sensor (exposure) and the total amount of light recorded by the sensor, and how these relate to the visual properties of the captured photo.

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jnd
tko
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