Equivalence thread (including posts moved here from other threads)

dalto

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Looking at the expected specs of this lens (about the same size as the 12-40 2.8) when attached to an E-M1, and you'll see that Olympus has built a camera/lens combo that is similar in dimension to the Canon's 1.2L + Full Frame combo (and is actually quite a bit smaller than Canon's 80D when paired with the 35 1.4L).
But a f/1.2 lens for m43 and an f/1.2 lens for FF aren't equivalent so comparing those lenses isn't really apples to apples. Not just in DOF but in virtually every way that matters.

Sorry, but if u43 isn't about small size with good-enough IQ then what *is* it about? If I want shallow DOF, fast shutter in low light or high ISO with low noise then I'd be in FF land (probably A7) since u43 isn't the ideal platform to do these things. I know that u43 with this sort of fast glass *can* get me there, but frankly it still won't be as good. It's definitely about horses for courses - but the best horse for narrow DOF is to buy an FF camera and not try to adapt a small-sensor to that task.
+1, there are more effective systems if size isn't a consideration.

Although, if you only use this lens in limited circumstances and don't want to have to buy/carry a second body I can see where it could make sense for a niche market.
 

tkbslc

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And the FF equivalents of that trio are roughly the same price.
  1. Nikon AF-S NIKKOR 24mm f/1.4G ED $1996
  2. Nikon NIKKOR 50mm f/1.2 $699
  3. Nikon AF-S NIKKOR 85mm f/1.4G $1596
That's pretty much my point, though. You'll be spending FF prices and you'll still have a two stop (or close to it) disadvantage everywhere that a fast prime counts.
 

Phocal

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But a f/1.2 lens for m43 and an f/1.2 lens for FF aren't equivalent so comparing those lenses isn't really apples to apples. Not just in DOF but in virtually every way that matters.


+1, there are more effective systems if size isn't a consideration.

Although, if you only use this lens in limited circumstances and don't want to have to buy/carry a second body I can see where it could make sense for a niche market.
Actually an ƒ1.2 lens from each and every system are exactly the same. Aperture is the nothing more then the relationship between focal length and the size of the opening of the lens. DoF is not a product of just the lens.....lots goes into determining what it will be in every given situation......like distance to subject, focal length of lens, aperture used, and yes.......format (we know the differences between the formats so no use going into that).

So, in what ways are they different?
 

dalto

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Actually an ƒ1.2 lens from each and every system are exactly the same. Aperture is the nothing more then the relationship between focal length and the size of the opening of the lens. DoF is not a product of just the lens.....lots goes into determining what it will be in every given situation......like distance to subject, focal length of lens, aperture used, and yes.......format (we know the differences between the formats so no use going into that).

So, in what ways are they different?
The actual size of the opening, the total amount of light allowed to hit the sensor and the resultant image you will get for starters. When comparing lens and body combinations it seems reasonable to also factor the effect that sensor size has on the equation.
 

DanS

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That's pretty much my point, though. You'll be spending FF prices and you'll still have a two stop (or close to it) disadvantage everywhere that a fast prime counts.
Again, as I mentioned in another thread, light gathering is a very valid reason to have a fast prime. It blows my mind that you continually ignore or downplay this point.

Why don't you switch to FF instead of constantly bemoaning mft?
 

dalto

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You'll have the light gathering of 1.2 , dof of 2.4 and people will shoot weddings and portraits with it without wafer-thin focus planes.
This is different from my understanding. You are not gathering the same same amount of light as with a bigger sensor. In reality, you have the light gathering of 2.4 and the DOF of 2.4 assuming 2.4 is the right number for whatever system you are comparing.

Please note, I am not complaining or trying to say one system is better or worse. I love my m4/3 gear. That being said, I do believe the original premise was valid. Which is as the lenses get bigger the value of m4/3 decreases.
 

DanS

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This is different from my understanding. You are not gathering the same same amount of light as with a bigger sensor. In reality, you have the light gathering of 2.4 and the DOF of 2.4 assuming 2.4 is the right number for whatever system you are comparing.
The size of the sensor is only a small part of the equation. The size of the photosites on the sensor, and their sensitivity are more important. This is why you will sometimes hear photographers disparage a new body, because all it offers is more megapixels.
 

dalto

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The size of the sensor is only a small part of the equation. The size of the photosites on the sensor, and their sensitivity are more important. This is why you will sometimes hear photographers disparage a new body, because all it offers is more megapixels.
While I don't disagree with what you are saying it doesn't change the fact that the amount of light that reaches the sensor from an f1.2 25mm lens is significantly less than the amount which hits the sensor from an f1.2 50mm lens assuming that that the sensor is appropriately sized to take advantage.

Sensor technology technology changes over time and across platforms so you never have perfect apples to apples but assuming technology of roughly the same vintage it is often close enough for comparison. Especially if you ignore the ultra high resolution options and focus on the mainstream.
 

DanS

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While I don't disagree with what you are saying it doesn't change the fact that the amount of light that reaches the sensor from an f1.2 25mm lens is significantly less than the amount which hits the sensor from an f1.2 50mm lens assuming that that the sensor is appropriately sized to take advantage.
take a look at this comparison.
MFT: f/1.2 25mm
FF: f/1.2 50mm

The area of a perfect aperture circle.
MFT: Pi * ((25/1.2)/2)^2 = 340.9 mm^2
FF: Pi * ((50/1.2)/2)^2 ~= 1363.5 mm^2

so a FF "equivalent" lens gathers 4 times more light. However now we need to take a look at how the sensor fits into the projected image circle.

the sensor sizes are:
MFT: 17.3 mm x 13mm (4:3 Ratio)
FF: 36mm x 24mm (3:2 Ratio)

The minimum diameter of the circles that will fully inscribe the sensors is as follows.
MFT: 21.64mm
FF: 43.26mm

the area of these circles is:
MFT: 368.8 mm^2
FF: 1470.2 mm^2

So even though the FF "equivalent" lens gathers 4 times more light, it has to project it onto an image circle 4 times larger as well. So, the amount of light hitting a given unit area on the sensor is the same. FF sensors are "better", because the photosites are bigger and collect more photons, thus yielding a better signal to noise ratio.
 

fredlong

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I'm pretty sure he is talking about light gathering.
There's no such thing as light gathering. Light isn't gathered by a sensor. The intensity of the light hitting a photo site is measured. Larger photo sites generally have a better signal to noise ratio.

Depth of field a function f-stop and image size. Period.

For the same field of view and f-stop a "full frame" sensor has twice the image size as m43 and so has less depth of field.

Fred
 

ijm5012

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So even though the FF "equivalent" lens gathers 4 times more light, it has to project it onto an image circle 4 times larger as well. So, the amount of light hitting a given unit area on the sensor is the same. FF sensors are "better", because the photosites are bigger and collect more photons, thus yielding a better signal to noise ratio.
Yes, this is the argument that I try to make with the ludites over on DPR when they want to start an equivalence war (which this post/thread was never intended to be about). You've shown that although a m43 lens lets in 1/4 the amount of light, it's hitting a sensor that has 1/4 the surface area as well, so the "total light" (I honestly never understand what the hell "total light" is when these imbeciles start talking about it. Last time I checked, there is no "total light" corner of the exposure triangle) is really these same when accounting for sensor size. The real difference comes from the size of each one of those pixels, which is why I struggle to see the benefit of releasing a 20MP sensor simply for the fact of "keeping up" with the competition, rather than working on improving a 16MP sensor in areas like DR or base/high ISO (assuming that there is something left to discover in these sensors, which are 4 years old at this point).

Anyway, my original post was never mean to lead to a whole discussion about equivalence. It was meant more to showcase the size and weight difference between a m43 camera and a FF camera with lenses covering the same FoV, with roughly the same aperture (give or take).
 

DanS

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There's no such thing as light gathering. Light isn't gathered by a sensor. The intensity of the light hitting a photo site is measured. Larger photo sites generally have a better signal to noise ratio.
Scroll up and read what I posted. I'm not talking about the "light gathering" sudo science most people referr to.
 

DanS

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Anyway, my original post was never mean to lead to a whole discussion about equivalence. It was meant more to showcase the size and weight difference between a m43 camera and a FF camera with lenses covering the same FoV, with roughly the same aperture (give or take).
I think it's inevitable. Every time a discussion starts about an expensive MFT lens, comparisons to FF are drawn.
 

tkbslc

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Again, as I mentioned in another thread, light gathering is a very valid reason to have a fast prime. It blows my mind that you continually ignore or downplay this point.

Why don't you switch to FF instead of constantly bemoaning mft?
Light gathering capability is greater on larger sensors due to the noise ceiling, so that's the "close to two stops" I was mentioning.

Can you point to where I am "bemoaning MFT"? I may have said I feel that some lenses are too expensive and impractical for the sensor size, but when did I say anything about the system as a whole?
 

pellicle

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not wishing to get recursively pedantic here ...
.... Light isn't gathered by a sensor. The intensity of the light hitting a photo site is measured. Larger photo sites generally have a better signal to noise ratio.
its not gathered by the "sensor" but is by the photosite ... so (as I'm sure you are meaning) as the pixel pitch gets smaller the number of photons that will fall into that well reduce for a given intensity.

Depth of field a function f-stop and image size. Period.
agreed
This very old page (apologies for the web developers out there) demonstrates this with some roll overs.

Depth of Field - the effect of the size of the hole

You can see that (hovering over the 20D image to swap it out to f8) that its DoF is about the same as that of the compact cam is at f3 (the presented image on the right). The second row shows the same images at 100% pixels for clarity. Its a bit painful on a phone, as it needs a mouse
 

Phocal

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they are different in that for a given aperture diameter (which is what that ratio is of) Depth of Field is influenced.

So when shooting at medium distances the OOF backgrounds will be more pronounced on the larger diameter.

So as a 50mm f1.8 has a diameter of 27mm
and a 25mm f1.8 has a diameter of 13mm the DoF will be greater with the smaller diameter.
Even at f1.2 it will still be only 20mm diameter.

For instance:
View attachment 484523

This is well established stuff ... I'm surprised that you didn't know this (meaning I'm wondering if you were getting at something else)
I'm pretty sure he is talking about light gathering.
Yes the size of the hole is larger on a 50mm ƒ1.2 lens then a 25mm ƒ1.2 lens, but it also has to gather and focus that light twice the distance (remember, long ago a 50mm lens was actually 50mm long). For this to work for exposure systems they developed the ƒ stop idea which is based on the ratio between the focal length and the size of the hole. This is why if I put a 100mm lens on a FF, a 75mm on an APSC and a 50mm on a µ4/3 and point them all at a white wall with the cameras set at ISO 200 and all of them set to ƒ1.2.........in theory they should all provide me with the exact same shutter speed for a perfect exposure (this assumes they have identical metering systems and the lenses have the same light transmission characteristics aka Tstops).

While DoF is influenced by the aperture size, it is also influenced by the sensor size as well as the distance to subject. My comment was in regards to the person who said something (to lazy to go back that far in the conversation) about you can't compare a 25mm ƒ1.2 for µ4/3 and a 50mm ƒ1.2 for FF because of their being to many things different more important then the aperture size (which they were really talking about DoF). My point being that in terms of exposure the to lenses will yield the same exposure under the same conditions and the DoF difference is between the two is because of sensor size and not the lens.
 

pellicle

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Yes, this is the argument that I try to make with the ludites over on DPR when they want to start an equivalence war (which this post/thread was never intended to be about). You've shown that although a m43 lens lets in 1/4 the amount of light, it's hitting a sensor that has 1/4 the surface area as well, so the "total light".
well it was perhaps more obvious in film days, but ISO being the same you get the same exposure ... so if you were using a bit of film you could show that an APS camera, a pocket 110 , a 35mm, a 6x9 and a 4x5 all give the film the same level of density (exposure) irrespective of anything as long as the lens is at (say) f5.6 and the shutter speed is the same.

Its just that the 35mm lens needs to project its light over a larger area. We can see that with C-Mount lenses which don't cover the full area but do expose the central portion of the sensor the same.

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:)
 
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