G9 vs. Z6 @ 2.8 in low light

Started 1 month ago | Questions thread
MOD Tom Caldwell Forum Pro • Posts: 43,200
Re: The theory isn't all that difficult
  1. Anders W wrote:
  2. olrett wrote:

    Sundre wrote:

    I'm bad at theory and tried googling this first but couldn't make heads or tails of most threads/articles. To be honest, I can't make heads or tails of the more technical posts in this thread either

    Yes, indeed, too many technicalities make these posts kinda blurry... and you start to skip big chunks of them. Just as you would stop listening to conversations at a party that take off on a tangent.

    I experienced something similar when I was still diving. Divers would seldom talk about the sea and the life in it, but go on forever about brands and specs, ending up arguing as if their life depended on it. In the case of diving gear, however, one's life may indeed depend on it, so they at least had a valid excuse.

  3. Actually, the theory you need in order to compare formats isn't terribly complicated and it would be very helpful in discussions like these if more people were aware of it. For example, when you compare FF with MFT you need to know the following:
  4. To get the same angle of view, you need twice the focal length on FF (e.g., 25 mm on MFT is equivalent to 50 mm on FF).
  5. To get the same total amount of light collected, the same depth of field, and the same diffraction, you need to stop down two stops more on FF (e.g., f/2.8 on MFT is equivalent to f/5.6 on FF).
  6. That's all as far as the theory is concerned.
  7. But when the theory meets reality, a few more complications arise. For example, the same amount of light collected implies that the noise level will be the same if the sensors in question perform equally well for any given amount of light. But that's not always the case in practice. As I pointed out in a prior post, for example, the data at our disposal suggest that the OP's camera (the G9) has about one stop more dynamic range (and thus correspondingly less shadow noise) than the one he is considering (the Z6) when the two are used to shoot equivalent photos at higher ISOs.

Well said Anders and although equivalence enables comparing between formats that does not make it right as the best gear for an individual.

As I have tried to show - my investment in exceptional EF mount lenses years ago for use with both aps-c and FF dslr bodies I regarded as more than good enough for my purpose.

These days I find that improvements in M4/3 gear have allowed me to be equally happy with what I can do now with this gear.  I also have FF gear including the excellent FF 5Ds which I can now use with my retained EF mount lenses.

That equivalence can help me understand format relationships is useful but neither I nor many others need to be constantly corrected as to the equivalence relationship.

My eyes can tell me that my M4/3 kit can make me images that are now more than good enough for my purpose.

I simply do not need the implications that any equivalent lens on any FF camera body will make equal quality images to that a current state of art M4/3 camera body can do with a top-rung equivalent lens purpose built for use on m4/3 bodies.

This is the essence of the argument: equivalence explains the nexus between sensor size formats but it does not necessarily mean equivalent quality images because there are other factors involved.  Not only the essence but maybe a clue to the understanding that we are talking about different things - the image that comes out of your camera box versus the technical understanding of the effect of any given lens between different sensor size formats.

If we took it to its absurd conclusion we might try and relate 4/3 sensor equivalence to mobile phone cameras and imply that the 4/3 sensor must make much better images than the super-slow equivalent lens in the mobile phone.  Try telling that to any mobile phone user.

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Tom Caldwell

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