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

Started Mar 17, 2012 | Discussions thread
Big Ga Forum Pro • Posts: 18,623
Re: No, no, no

Andy Westlake wrote:

Big Ga wrote:

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.

No, this is the whole point. You want examples that use the same exposure, as a function of light level, shutter speed and aperture. It doesn't matter what combination you use as long as the sensor gets the same amount of light.

I agree. So to clarify this for me - if we look at the G3 and EM5 RAW samples, I see that at ISO6400 (which I assume is the value that the camera reported to you yes?) both cameras are shot at f6.3 (I assume the 50mm oly macro), yet the EM5 has a shutter speed of 1/1600th of a sec, but the G3 has a much shorter 1/2500th.

So are you saying that you varied the power of your lighting to compensate for this shutter speed difference?

(and also - can you confirm that you did NO exposure adjustment within ACR to obtain the uniform JPG output??)

No, no, no. This is completely the wrong thing to do. You cannnot mix and match DxO's ISO numbers and our JPEG samples, you'll get entirely the wrong answer. DxOMark's ISO rating tells you nothing about the relative exposure we've used. We determine the correct exposure based on JPEG brightness, re-ratng cameras using DxOMark's ISO would result in JPEGs of different brightness.

What I was suggesting was not that one did a 'mix and match' as such, only that you can use the DPR samples to see how a specific camera changes its image characteristics over the range of testing parameters you change (things like ISO, and NR settings), however, it seems to me (although there is so much confusion here now that I might be wrong!), that you would need to check the DxO graphs if you were comparing different cameras, to try and glean what ISO values would actually result in specific shutter speeds if you were shooting RAW and using an external lightmeter for example.

What many people are asking for is a truly fixed set of parameters. Fixed lighting. Fixed aperture. Fixed shutter speed. The same for all models.

Then in these studio samples you'll get significantly different depth of field between sensor formats, so that would be a really poorly-designed test. People get sufficiently upset over tiny differences in focus as it is.

I understand that. And I did start writing about how I realised you had to do this in terms of the sharpness test, but its a pity you don't ALSO have a truly 2D target for the high ISO comparisons. Then I thought of your mental health having to do all of that as well, so I deleted the request

At the moment, it seems you can't look at an ISO6400 file from one camera, compare it with an ISO6400 image from a different model, and simply by looking at the test results, work out how the cameras are actually going to perform in real life when you have to take shutter speed into account.

No, this is the whole point I've been making. This is exactly what our samples allow you to do (but you do need to note our ISO test results for the cameras you're comparing).

Sorry ... I'm obviously being a bit dim here - can you clarify this bit. What exactly am I needing to note? are you talking about the ISO accuracy tests? or the test images at different ISOs, or what ??

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