E-5 Raw noise performance = E-30/ ballpark E-3's

Started Dec 18, 2010 | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 61,146
Re: Actually...

luisflorit wrote:

Quite likely the reason could be that the ISO on the E5 is fake by more than 1 stop. So ISO800 gives underexposed RAWs, that you have to push heavily to match the exposure of the other cameras.

You're going on DxO data? The ISO is not 'fake', and the DxO measurement is not ISO.

The RAW ISO is fake.

There is no such thing as a raw ISO. ISO only exists in the sRGB colour space, so is completely dependent on processing. A raw file can be processed to any ISO you like (with varying degrees of success, obviously)

If you compare the JPG and RAW files, you'll see that the RAW is 1 to 4/3 stops underexposed.

What do you mean that they are 'underexposed'? There is no 'underexposed' in raw files - there is only the exposure used to make the file.

If you look at DxO, this is exactly what they say, and they are absolutely correct.

There may be a correlation between their reported figure and what you are seeing, but it has nothing to do with 'fake' ISO's. In any case, as I pointed out, under the REI method, there is no 'fake' - just what Olympus says the ISO is.
I think you need to separate this out into separate issues.

  • is the metering giving you the exposure you'd expect for the ISO you've set? That is really all that ISO refers to, and even then, under REI there is a lot of leeway.

  • does the processing of the resulting file give you the range of densities that you'd expect? If not, then if you're using Olympus' tools, all it means is that their opinion of the best range of tonality is different from yours. If you're using an independent tool then it could also be that the manufacturer of that tool has a different view of the best tonality for that file. You can adjust it, of course, when you process.

This is a really common misunderstanding of ISO - it is solely to do with processing. It has been confused by the fact that many cameras require the capture hardware to be configured differently for different exposure ranges, but that really has little to do with ISO.

It is one reason why a sensible comparison between cameras is to test a given exposure not as metered with the metering set to some ISO. Camera review sites confusion on this results in the inconsistent exposure we get for many test shots, rendering them virtually useless for comparisons.
--
Bob

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