“Full Frame Equivalence” and Why It Doesn’t Matter

Started Feb 4, 2013 | Discussions thread
sarlo100 Senior Member • Posts: 1,323
Re: He was more-or-less okay, until he went off the rails

ljfinger wrote:

Here's where the "article" went off the rails:

"What IS true is that the 75mm f/1.8 is not capable of the same ultra shallow depth of field as, say, something like the Sony Zeiss 135mm f/1.8 on full frame. However, this is essentially the ONLY way that it is inferior. It passes the same amount of light, and it exposes as an f/1.8 lens because it IS an f/1.8 lens. If I’ve chosen a smaller format system, I’m already OK with the fact that it doesn’t equal a full frame camera in the noise department, so there is no ‘aperture advantage’ after the fact. Those who harp on aperture equivalence as it relates to shallow depth of field also IGNORE all the BENEFITS to having more depth of field for the same aperture:

Those highlighted areas are all wrong, and he partially says so!

  • It passes the same amount of light. No, it passes the same light intensity, which is 1/4 the amount of light, which is what he said earlier in the article.
  • "there is no ‘aperture advantage’ after the fact". This is a funny one since he contradicts is just before saying it, "it doesn’t equal a full frame camera in the noise department".
  • "BENEFITS to having more depth of field for the same aperture". There are no such benefits. You can recover all those "benefits" by stopping down the larger sensor by two stops and elevating ISO by 2 stops. Together, those will give you the same picture as the smaller sensor, thus there's no advantage either way.

This is all true.  And it extends all the way into compact territory.  Can you close down a full frame lens to f/16, crank ISO to 3200, and still get a better (or at least as high of a quality) picture with the same DOF as something like an LX7 with similar shutter speeds?  Yep.

Can a FF camera do things that a more humble m4/3 or compact camera do in regards to DOF and total light hitting the sensor which gives "better" technical photographs at the top end?  Absolutely.

However...full frame will never, ever be as portable or inexpensive as m4/3 or compact cameras.  And that's where the "equivalence crowd" steps on their own cranks.  They think, because *THEY* demand the absolute technical maximum out of their photographic equipment, that anything that doesn't deliver the technical maximum is garbage.

That isn't the case for the vast majority of photographers out there, and it's why I ultimately laugh at the equivalence religion.  "Good enough" is good enough for most people.

And explaining aperture/sensor size/focal length differences using standard 35mm notations, while perhaps not technically accurate, gives a good enough set of reference points to the vast majority of people who care about such things.

You (the equivalence crowd - not you, Lee Jay) may be right.  In fact, you are right.  But very, very few people give a damn.

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