All this talk about "equivalence" is silly

Started Jun 10, 2011 | Discussions thread
Le Kilt Senior Member • Posts: 2,420
Re: All this talk about "equivalence" is silly

Marc de Vries wrote:

Howard wrote:

Someone wrote a web page about "equivalence" some time ago. Let me first say that I perfectly understand the concept (it is really about perspective, DOF, framing, etc.), but I think all this talk about "equivalence" is silly, confusing and mostly bogus.

For example, the "equivalence" adherent will say that a 300 f/4 lens is "equivalent" to a 480 f/5.6 lens on a crop camera, or some such. But this has severely limited applicability -- that is, only if you are narrowly concerned about perspective, DOF and want to duplicate exactly the same image as on a FF camera. But this is not the only, or most important concern for most people. Actually, I want to argue that for most people, this is not a concern at all.

Most people make snapshots, and don't think about most aspects of their photos.
So yes, for most people this is not a concern at all.

The web page about equivalence was meant for people who put thought in their shots.

People who have envisioned a certain shot and have specifcally choosen a certain perspective for their shot, have choosen a certain DoF for their shot, have choosen a certain shutter speed for their shot.

If those factors matters for your shot, than equivalance is extremely important and will explain the implications if you want to make that shot with a different camera.

Some cases in point:

Case 1: if you want to stop action, in the same lighting condition, with the same ISO, a f/2.8 lens gives you the same shutter speed on a crop sensor or a FF sensor, so to same something like a 300 f/4 lens is "equivalent" to a 420 f/5.6 lens is completely misleading.

The mistake you make here is that ISO values on different cameras are NOT the same, even though they are called the same. ISO 1600 on a crop camera doesn't give the same noise level as ISO 1600 on a FF camera or ISO 1600 on a compact camera.
When you say "the same iso" you really mean: "different noise levels".

And yes, in the same lighting conditions with different noise levels a f/2.8 lens gives you the same shutter speed on a FF sensor as on a compact sensor.
But it's a completely useless comparison.

Case 2: if your primary concern is reach, then a 300 f/4 lens is decidedly similar to a 480 f/4 lens on a 1.6 crop camera, not 480 f/5.6.

No it's not the similar, because the 480/f4 lens gives a different DoF compared to the 480 f5.6

If your only concern is resolution and everything else in the shot is not important to you, then indeed equivalence is not a concept that you will use.

And if you really understand equivalence you will also understand the advantages of each camera format and will then be able to make a decision which is best for your situation.

You can then decide that a crop camera gives you more advantages than disadvantages when you are limited in reach.
It is equivalence that lets you understand why!

Anyway, I can go on. But I think this "equivalence" talk is very confusing to beginners and causes more harm (confusion) than good (clarification).

For beginners, the best thing is not to tell them about crop factors and other sensors at all. Just let them learn how to get the best results with their cameras.

The problem is that people always tell them about crop factor, but not about the rest. And then people get confused and want to know how it really works. Either tell them the whole story (equivalence) or not at all. But don't tell them only about crop factor. Because that is far more confusing them equivalence.

Lol, I think crop factor is far easier to explain than equivalence ! Maybe we don't know the same sort of 'beginners'.

Try telling someone why they don't get the same picture with a 200mm on their crop sensor that you get with your 200mm on your FF without mentioning crop factor !!!

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