1. Reminder: Please use our affiliate links for holiday shopping!

Equivalence thread (including posts moved here from other threads)

Discussion in 'Back Room' started by dalto, Sep 6, 2016.

  1. dalto

    dalto Mu-43 Regular

    186
    Jul 6, 2016
    Texas
    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.
     
    • Like Like x 1
  2. tkbslc

    tkbslc Mu-43 Hall of Famer

    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.
     
  3. Phocal

    Phocal Mu-43 Hall of Famer

    Jan 3, 2014
    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?
     
    • Agree Agree x 1
    • Winner Winner x 1
  4. dalto

    dalto Mu-43 Regular

    186
    Jul 6, 2016
    Texas
    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.
     
    • Sad Sad x 1
  5. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    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?
     
    • Winner Winner x 1
  6. dalto

    dalto Mu-43 Regular

    186
    Jul 6, 2016
    Texas
    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.
     
  7. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    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.
     
  8. dalto

    dalto Mu-43 Regular

    186
    Jul 6, 2016
    Texas
    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.
     
  9. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    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.
     
    • Agree Agree x 1
    • Funny Funny x 1
    • Winner Winner x 1
  10. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    I'm pretty sure he is talking about light gathering.
     
    • Agree Agree x 1
  11. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    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
     
  12. ijm5012

    ijm5012 Mu-43 Hall of Famer

    Oct 2, 2013
    Pittsburgh, PA
    Ian
    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).
     
  13. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    Scroll up and read what I posted. I'm not talking about the "light gathering" sudo science most people referr to.
     
  14. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    I think it's inevitable. Every time a discussion starts about an expensive MFT lens, comparisons to FF are drawn.
     
  15. tkbslc

    tkbslc Mu-43 Hall of Famer

    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?
     
  16. DanS

    DanS Mu-43 Veteran

    393
    Mar 8, 2016
    Central IL
    Check you im.
     
  17. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    not wishing to get recursively pedantic here ...
    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.

    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
     
  18. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    I'm waiting for "micro contrast" to emerge ;-)
     
    • Funny Funny x 1
  19. Phocal

    Phocal Mu-43 Hall of Famer

    Jan 3, 2014
    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.
     
  20. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    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.

    4348718725_af74fdcc5a_o.

    :)