The Economist article on mirrorless cameras

Started Jun 7, 2014 | Discussions thread
Jerry Fusselman
Jerry Fusselman Contributing Member • Posts: 849

Erik Magnuson wrote:

Jerry Fusselman wrote:

In particular, the extra dynamic range from the a6000 at ISO 100 is wonderful.

Yes, the base ISO DR advantage is large and readily exploitable in real world photography. This is a great example of mapping a DxO number to a real world use case.

but I believe it does not pay to take either of these two cameras beyond ISO 1600.

Is there a different camera you would take past ISO 1600 or do you just not shoot past that?

I'm not going to go into great detail on this, as I said before. As to the theory underlying all of this, I'll offer just a hint without jargon: Every camera seems to have a maximum ISO, call it M, which it cannot truly go beyond except through software. I think M for the A7r is around 1600, and M seems near 1600 for the Canon 5D M3 too.

But who cares about the theory? Your results are what counts. So here is the experiment so that you can verify my thinking:

Find a static subject, put your camera on a tripod, and choose the aperture and shutter speed you want to use. Also dial in any exposure compensation you deem appropriate to the sceen. Set ISO to Auto. Now, what ISO does the camera choose for you? The test I am about to describe for you is no good unless the camera here chooses an ISO significantly higher than M. Suppose it chooses ISO 6400.

Now, for the test, keep your aperture and shutter speed as they are and shoot two exposures: One at ISO 6400, and one at ISO 1600 (that is, M), even though the second exposure is quite dark. Let's use raw files for both exposures.

From the these two raw files, build three images:

  1. Develop your ISO 6400 image normally.
  2. Develop your ISO 1600 image in Lightroom using some thought and good exposure correction.
  3. Develop your ISO 1600 image using PPW techniques as described by Dan Margulis.

I expect that you will like image 2 a bit better than image 1, and image 3 will be clearly the best of the three. No doubt this would be a surprise to you.

If my prediction is correct, that is the reason not to go beyond ISO 1600 when you want the best possible image with your equipment under the circumstances.

Each camera has its own value of M, which can be determined through experimentation. With some point-and-shoot cameras, M equals the base ISO, in my opinion.

To answer your question, yes, there is a different camera I would take past ISO 1600---it is the Sony A7s. How far past? I can only guess. Based on what I've seen and read, it must be somewhere between 3200 and 102,400. (There is a huge increase in noise from 102,400 to 204,800.) If I was forced to guess one value, I would think it is about 12,800---wouldn't that be great?

Or maybe I'm too optimistic. We'll see.

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Jerry Fusselman

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