4/3 has no focal length advantage-correct him if he is wrong

Started Nov 15, 2008 | Discussions thread
Jon Stock Senior Member • Posts: 1,608
Re: 4/3 has no focal length advantage-correct him if he is wrong

clevechan wrote:

However, this understand seems to differ from that of Jon.

Could someone correct my understanding?

My understanding could have been better said.

I was talking about an object in the field of view and how the object is the same size when projected by any lens of the same focal length.

You were talking about the diameter of the total amount of light being projected by the lens.

I think we are both correct.

The magnification of an object in the middle of the sensor is the same - all 50mm are equal - the diameter of the light projected by the complete lens is different - Olympus is smaller. Project the same sized object over a smaller area it will fill more of that area = focal length magnification.

Using the 50mm lens as an example.

If the object being imaged with the 50mm lens projects a 1cm by 1cm image on the imaging surface = 1 cm² then the image of that object would look different based on the imaging surface size:

Olympus E3 = 10mp x 2.43 cm²: 1 cm² object covers 44% of image area = 4.4mp of detail.

Canon 40D = 10mp x 3.28 cm²: 1 cm² object covers 30% of image area = 3mp of detail.

Canon 50D = 15mp x 3.32 cm²: 1 cm² object covers 30% of image area = 4.5mp of detail.

Canon 1D III = 10mp x 8.64 cm²: 1 cm² object covers 11.6% of image area = 1.16mp of detail.

Canon 5D = 12mp x 8.64 cm²: 1 cm² object covers 11.6% of image area = 1.39mp of detail.

Canon 1Ds III = 21mp x 8.64 cm²: 1 cm² object covers 11.6% of image area = 2.43mp of detail.

The Canon 1D III would have 1.16mp reading info from the 1 cm² object image the E-3 would have 4.4mp doing the same.

The Olympus camera would image the object twice as large (covering 4 times the number of pixels) - on a computer screen and printout. The output - not the image - is doubled by the extra pixel density(with equal pixel count).

Everything is a compromise:

The Canon would have 2 stops extra light gathering ability (4 x the surface area)
This is an advantage when you need it - at iso 1600+ at 800 they are very close.

FF can image 2 stops shallower depth of field - if you want shallow - and are willing to use primes. Olympus f2 SHG zooms are 1 stop faster than the fastest lenses from anyone else. They are often 2 stops faster than other zooms. (The 70-200mm f4 is more common than the f2.8 version.)

You need to stop down 2 stops to recover depth of field when you want it (this cancels the high ISO advantage)

My personal reason for getting Olympus:

I want depth of field. I need it for landscapes, macro, and telephoto wildlife. For me the high iso advantage would be canceled out by stopping down to get DOF.

The IS on all lenses is a huge boost.

No dust on any image ever.

I like zooms more than primes - wildlife does not usually wait around while you "zoom with your feet"

Live view and tilting screen help with low to the ground and weird shots. I stay clean (er) and dry (er) and still get the shot.

I am outdoors when I take pictures - rugged build and water resistant is very useful - even in winter - fine blowing snow melts into warm camera gear.

Good quality lenses: I don't have to keep thinking that wider than f8 is not so good, and smaller than f16 is also bad. Olympus SHG lenses have a wide band between compromises.

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Jon
Stony Plain Alberta

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