I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
Dorus
Senior MemberPosts: 1,063
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Re: makes you wonder why there is an aperture control ?
In reply to iano, May 23, 2012

iano wrote:

Ok, so we have established that four times more light produces a better picture.

The more light, the better the picture. So why do we ever stop down a lens?

Good question, but somewhat unrelated. There are many reasons to stop down a lens, including, but not limited to:

  • depth of field control

  • preventing overexposure

  • hitting the 'sweet spot' of a lens which is often not at wide open

Why did medium format ever win out over larger format, and now 35mm appear close to matching medium format, despite the difference between medium format and 35mm being far greater than the difference between 35mm and 4/3?

Practicality I think. Few people have the stamina to be the next Ansel Adams and lug those large contraptions around.

Or is the answer in the words from Dorus about recent improvements in sensor quality at the heart of the issue.

I think that improvements in the media (plates, film, sensors) continually allow one to keep downsizing the system with minimal loss in IQ. Many current compacts produce better pictures than first-generation DSLRs. So the basic tenet of equivalence really only applies to same generation sensors.

There are times where every bit of light counts. This is low light/high iso shooting. But the truth is we most often simply do not need more light to produce an optimum image. Very often we have more light than we need, which is why an aperture control makes sense. As technology improves, the best size compromise gets smaller.

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