Olympus OM-D (EM-5) comparison samples are now.. (continued)

Started Mar 17, 2012 | Discussions thread
john175bramley Regular Member • Posts: 295
Re: DPR v DxO ...

RicksAstro wrote:

Big Ga wrote:
... or not as the case may be...

Andy Westlake wrote:

cameras can compensate for differing light levels by using different shutter speeds.

Ah. But therein lies the issue. Cameras might be able to, but often, photographers cannot!

Here is a hypothetical (albeit very common) scenario which I'm sure you're aware of, but I need to write it down to illustrate the point. You are photographing some lowish light sport event. Your 300/2.8 lens is at its widest because you want as much light as possible and you also want as much isolation as you can get. You've decided you want to freeze some fast action and so 500th of a second is the figure your experience tells you will just about let you get away with your 'freeze'. So your aperture AND shutter speed are fixed. There is nowhere to go except change the ISO so this is how you shoot.

Now, after reviewing the shots, you decide you might want to buy a new camera because you want better noise performance. You now need to review some identical side by side comparisons from different cameras, so really these need to be taken under the same conditions, which means the same source light intensity, the same aperture and the same shutter speed. Only then does side by side camera ISO comparison make real sense if you're trying to decide on which camera to buy based on its noise v ISO performance.

Let's expand on this...the next time you go, you find they decided to change their lighting system and it's now metered to be twice as bright, so you choose to up your shutter by a stop to compensate and still use the same ISO. This should yield exactly the same noise, shouldn't it?

I think that was Andy's point. Even though their lighting may change slightly, that shouldn't affect the results at all.

But in real life (as opposed to testing) you wouldn't choose to up your shutter by a stop, you'd drop your ISO and achieve better IQ.

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