I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
Great Bustard Forum Pro • Posts: 39,704
Re: It's the loonies who are the problem.

Guy Parsons wrote:

Great Bustard wrote:

The main aim of equivalence always appears to be trying to put down M4/3 as a usable platform for photography.

Have I ever put down mFT? Link and quote even one disparaging comment I've made about mFT.

No, Joe, you personally have not put down M4/3...

I appreciate that you recognize that fact.

...but there's a strange band of loonies who pop up with "equivalence" all too often in their efforts to tell us that M4/3 is a waste of space.

They give equivalence a bad name.

The trouble is that people only half read your page and come away with confused ideas. Way too often people land here looking into M4/3 for the first time and appear to understand that the effective focal length is different to full frame, but also muddle in with that the aperture changes too and think that M4/3 f/2.8 is really effectively f/5.6

Here's the deal: 50mm f/3 is 50mm f/2 no matter what sensor you put behind it. But the effect of 50mm f/2 changes as a function of format, and both the effect of the focal length and f-ratio change in the same proportion: 50mm f/2 on mFT is equivalent to 100mm f/4 on FF.

It takes a while to convince people that f/2.8 is always f/2.8 at any sensor size, just the depth of field shrinks with smaller sensors/lenses so an f/2.8 lens covering the same field of view as full frame behaves more like f/5.6 only as far as depth of field in concerned.

Not merely DOF, but in terms of the total amount of light projected on the sensor for a given shutter speed. And the reason that is key, is because, for equally efficient sensors, the noise is determined by the total amount of light that falls on the sensor.

The "total amount of light" on the sensor also confuses many.

Well, it really shouldn't. Put two buckets out in the rain for the same amount of time, one twice the width of the other. Both will fill to the same height, but the larger bucket will have four times as much water in it.

Sure that's important to understand but is not the be-all and end-all of understanding how to get an image. It just helps to explain why smaller sensors behave the way they do.

It has everything to do with the noise in a photo, and the two most discussed elements of IQ are noise and detail.

The M4/3 line lives with more noise at low ISO than any full frame camera, but in the final print or view on the screen it just does not matter.

Whether the difference matters or not depends on many factors -- the scene, the display size, the viewing distance, and the QT (quality threshold) of the viewer. See, the thing is, mFT is just a wee bit closer to FF than the XZ-1 is to mFT. So, if the difference between mFT and FF doesn't matter, then the difference between an XZ-1 and mFT doesn't matter.

So for those that are satisfied with the 14-56mm range in mFT, why mFT rather than the significantly smaller, lighter, and less expensive XZ-1?

As I keep saying, if stretching the print size to ridiculous or cropping like crazy, some noise is needed in the image to help soften the effect of decreasing detail as the pixels per inch falls below critical limits. Otherwise the result looks plastic and sterile and badly digital.

Now there's a twist -- someone arguing that more noise is better! I've never seen a photo that was hurt because it wasn't "noisy enough". So, how's that XZ-1 with it's f/1.8 - 2.5 zoom work for you? It's photos look even more detailed at the higher ISOs because of the "special feature" noise that it offers!

In short, anyone who would spend $1300 for a 12-35 / 2.8 over a $135 14-42 / 3.5-5.6 will have some idea as to why some value FF over smaller formats.

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tko
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