a57 v d5100 for first DSLR

Started Apr 6, 2013 | Questions thread
Fat Dragon
Regular MemberPosts: 192
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Re: Neither
In reply to Leonard Migliore, Apr 10, 2013

Leonard Migliore wrote:

It's not a free lunch. Shots taken with exposures consistent with high ISO's will be noiser than ones with more exposure. It's just that the ISO dial doesn't do much besides change the exposure.

Let's say you're shooting indoors and need 1/2 second at f/2.8 at ISO 100. You know that's no good for motion blur. You want to shoot at 1/125. The standard way to do this is to bump the ISO to 6400. And this is going to be noisy. But with the Sony, you would get the same noise and better highlights if you kept the ISO at 100 and set your exposure manually to 1/125. Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does.

You'll get more noise with low exposure regardless of the ISO setting. So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400.

So it's just a software function within the camera. Gotcha. Is that true for all digital cameras or just some?

ISO is a standards organization. They developed a photographic exposure standard for film. It's used for digital sensors but it wasn't created for them and it's probably too late to create a new paradigm.

I'm familiar with the ISO, but I always thought camera ISO was something different. I've heard it called "Initial Shutter Opening" before, which, to a layman like myself, simply sounds like a camera jargon term. Since a Bing search (Google's unreliable here in China) shows 8 results for "Initial Shutter Opening", I'm not really certain where I heard this term. Always good to learn something new like this, especially when it cancels out something I had wrong before.

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