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

Started Feb 4, 2013 | Discussions thread
sean000
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Re: “Full Frame Equivalence” and Why It Doesn’t Matter
In reply to Macx, Feb 4, 2013

Macx wrote:

The reason you should care about total light is because it helps you understand why it's easier to make relatively noise-free cameras with large sensors than with small sensors.

But I already knew that, and I think most people here do as well. I've known that for at least ten years: Technology being equal, a larger sensor will always have an advantage, but so what? There are disadvantages as well (mostly cost and system size/weight), otherwise we would all be shooting digital Medium Format. I also know that it's not just about sensor size. My E-M5 is capable of producing high ISO images with far less noise, and more dynamic range, than my seven-year-old APS-C Nikon D200. Of course a Nikon D7000 is going to be a different story, but it just goes to show that there is more to the story than total light and sensor size. The sensor size mattered a lot more a few years ago than it does today. Yes it still makes a difference, but if a smaller sensor provides the image quality you need then why care?

In fact, it seems to me, that equivalency helps us understand that there is no physical disadvantage in using a 4:3 camera as long as you use it inside its "comfort zone". It's when you go outside this zone that the advantages of the 135 format appears: If you want a SNR like the ISO 100 and 200 on the 135 cameras, there is as of yet no equivalent in the 4:3 world. If you want lenses with the same field of view and speed as e.g. 35/1.4, 50/1.4 or 85/1.4 there are no equivalent lenses for 4:3, yet. In other words, 135 cameras allow you a wider "gamut" of exposure than 4:3.

Of course a 25mm f/1.4 is a 25mm f/1.4 no matter what format it is on. On m4/3 it will have a field of view equal to 50mm on 135, and it will allow you to shoot at the exact same shutter speed as f/1.4 on 136 (assuming the same ISO and the same scene). The 25mm lens will get you more depth of field (assuming the same focal distance), which might be a good thing or a bad thing depending on the photo. And yes there will be more total light captured by the 50mm f/1.4 on 135, but that won't matter for the vast majority of photos. One also needs to be aware of the diffraction issues, but that's just a matter of knowing your format. All formats have a point where diffraction starts to become an issue.

If this isn't needed, there is no disadvantage in using a 4:3 sensor, instead you get the advantage of the smaller size and bulk.

Exactly, and thank you for what was one of the more clearly stated explanations of the physics behind the lens.

And remember, there are no laws prohibiting you from using the right tools for the job: A 135 camera for the shots that are outside the 4:3 camera's comfort zone, and a 4:3 camera for all the shots that is, where you don't want to deal with the extra weight, size and conspicuousness of the larger system.

I agree. I currently still own both Nikon and m4/3 gear. I'm debating whether or not to sell my Nikon gear, but I own some very nice Nikon lenses (most of them full frame lenses), and one of these days I could see buying a newer Nikon body. But it would be my specialized system, while m4/3 would be my all-rounder system (although there are some special applications where the smaller sensor helps).

I think my point was that there seems to be more obsession over the equivalency stuff today than there was two years ago. I guess that's a sign that m4/3 is gaining in popularity (and performance) and attracting more people who are struggling to understand what the differences are. I think many of the earliest adopters of m4/3 knew this stuff and didn't think the obvious needed to be stated in every thread. We already made the decision to use m4/3 as our primary (or only) format, and prefer to discuss the gear on its own terms... instead of using 135 as a point of reference. Actually I don't mind comparing formats since I shoot two formats, but the thing that chaps my hide is when someone says, "That 45mm f/1.8 is really a 45mm f/3.5." No, it isn't. It's a 45mm f/1.8. Those are the physical properties of the lens. When you talk about equivalency you are really talking about effects of a lens combined with a sensor, and if you have to talk about your m4/3 gear in terms of 135 equivalency the threads tend to get confusing... so it's best to save those conversions for threads where they really matter.

Sean

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