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

Started Jan 25, 2014 | Discussions thread
Tiger1 Contributing Member • Posts: 519
Re: Oh?

Great Bustard wrote:

Tiger1 wrote:

Ian Stuart Forsyth wrote:

Nikon 300 F4 to Zuiko ed 150 F2 to canon 300 F4

No this is where we disagree. Olympus 150mm F2 is the same as a 300mm F2 FF lens.

It is not. It has neither the same focal length nor aperture diameter.

Of course it's not literally!  Are you that daft?  I'm talking of field of view and magnification and amount of light hitting the sensor per unit area.  In those respects it is!!!!!!!

F2 = F2!!!

It's not "F2", it's "f/2", where the "f" in "f/2" stands for focal length. For example, 150mm / 2 = 75mm and 300mm / 2 = 150mm. The quotient gives us the diameter of the virtual aperture (entrance pupil), and it is the diameter of the aperture that determines the DOF for a given perspective, framing, and display size, as well as how much light falls on the sensor for a given scene luminance and shutter speed.

I'm sorry but now you're getting pedantic.  Look through this entire site and what manufacturers write next to their lenses.  By convention it is written F2 even though in reality it is f/2.  You are stating something obvious that has nothing to do with the argument.

If you like f/2 = f/2.  There!

The only reasonable argument is that a FF photographer could buy a 300mm F4 lens and shoot at a higher ISO to compensate for the loss of lens speed because as a general rule the latest FF sensors are less noisy than their FT counterparts.

FF sensors are not "less noisy". Instead, what happens is that the larger aperture diameter of FF lenses projects more light onto the sensor for a given shutter speed, and it is this greater amount of light falling on the sensor, not the sensor itself, that makes FF less noisy.

Gee whiz.  Give up!  FF sensors using a certain design/technology are less noisy than smaller format sensors with equivalent photosite count and design/technology BECAUSE their photosites are larger and therefore collect more photons and so need less amplification of signal (which introduces noise).  Basic physics!  The light hitting the sensor per unit are is THE SAME. Because the area of the sensor is larger the amount of light IN TOTAL is larger as it's unit area is larger.  The larger aperture allows more light spread not more intense light!!!!

Imagine you are peering through a hole at the sun.  It's bright.  Now that hole becomes really small. It would seem the light intensity has fallen, right?  No.  it is the same.  Just spread across a smaller area. If you don't think so, imagine now that you shrink yourself into an ant.  That hole is now relatively large again and the sun seems just as bright.  That is what is happening with the format changes.  Understand now?

Then you can argue that the quality of both shots would be roughly equal.

There is more to a photo than the quantity of light that falls on the sensor, but the amount of light falling on the sensor, coupled with the sensor efficiency, does determine the noise in the photo.

I know buddy.  I'm talking about quality of image creation via the sensor. Thanks.

It is important to note that the DOF will be not be equivalent and I have always agreed on that.

What you, and 99% of the people on this forum, fail to understand is the relationship between the relative aperture (f-ratio), the virtual aperture (entrance pupil), the amount of light per area falling on the sensor (exposure), and the total amount of light collected by the sensor, and how these quantities relate to both noise and DOF.

I understand.  You don't.

You, and those like you, would do well to make an effort to understand these things, rather than simply chanting "F2=F2!!!" with religious fervor, having no real understanding about how and why things are the way they are.

Mate.  Go back to school.

Here, let me make it plain to you. Let's say we have an absolutely perfect 2x TC (that is, a 2X TC that is completely free of aberrations) and mounted it behind the 150 / 2. The 150 / 2 is now a 300 / 4, right?

Yes obviously.

Now, if we put that 300 / 4 in front of a FF sensor, the image it will record will be all but identical to the image recorded by the bare lens in front of a 4/3 sensor. Of course, I'm assuming you know how a TC works, so...

No it won't mate.  The TC optically magnifies the image leading to a four fold loss of light.  The 4/3 sensor "magnifies" the image because its like putting the 150mm F2 lens in front of a FF sensor then taking the middle part of the image and "digitally" magnifying it.  The amount of light hitting the sensor is the same for both per unit area.  How could it be any different?


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