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

Started 8 months ago | Discussions thread
Great Bustard
Forum ProPosts: 23,471
Oh dear.
In reply to Tiger1, 8 months ago

Tiger1 wrote:

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?

You're asking if I'm daft because I said that a 150 / 2 is not the same as a 300 / 2 when you said, "Olympus 150mm F2 is the same as a 300mm F2 FF lens"?  Huh.

I'm talking of field of view and magnification and amount of light hitting the sensor per unit area. In those respects it is!!!!!!!

Then you would say that a 150 / 2 on 4/3 has the same diagonal angle of view and projects the same amount of light per area on the sensor as a 300 / 2 on FF, not that they are the "same".

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!

Now, what does the "f" stand for?  It stands for "focal length".  And 150mm / 2 is not the same as 300mm / 2, so f/2 does not equal f/2 unless the focal lengths are the same.

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).

You are, of course, completely and totally wrong.  Take a pic of a scene with the same camera and lens at 50mm f/2.8 1/200 ISO 3200 and 100mm f/2.8 1/200 ISO 3200.  Crop the 50mm photo to the same framing as the 100mm photo and display them both at the same size.

So, we're using the same f-ratio, the same shutter speed, the same ISO, the same pixel size, and the same sensor tech.  Which photo is more noisy and why?

Basic physics!

It is, but you insist on ignoring it.

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!!!!

Exactly.  And more light on the sensor means less noise.

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.

That's what Creationists say to people explaining Evolution to them.

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.

To teach people like you?  How much will I be paid?

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 light is lost?  Where did it go?  Remember, we are mounting the 150 / 2 + 2x TC (which is the same as a 300 / 4 -- rather different than your use of the word "same" from the top) in front of a FF sensor.

So, where did the light go when the 2x TC was mounted on the back of the lens?

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.

Yes.  But what about the total amount of light falling on the sensor, as opposed to the amount of light per area?  I ask, because in terms of the visual properties of the recorded photo, it's the total amount of light that matters.

How could it be any different?


Here's another question for you.  Let's say we have a FF DSLR with a 2x crop mode.  We take a photo at 50mm f/2 1/200 ISO 3200 in the crop mode and another photo at 100mm f/2 1/200 ISO 3200 not in the crop mode.  We display both photos at the same size.  Which photo is more noisy and why?

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