Olympus E-PM2 Actual ISO vs IS0 set in camera?

Leo wrote:

Hi Anders,

I finale got it :-). Thank you for the help and patience.

Sounds good. What you should find, if you test right, is that the GX1 and the E-PM2 will behave in pretty much the same way as far as metering and the overall brightness of OOC jpegs (or default LR converstion) is concerned. However, if you start checking what goes on under the hood, in the RAW file (and the easiest and most precise way to do so is by means of RawDigger), you will find that the GX1 will start clipping the highlights nearly one stop before the E-PM2 does. This is the real implication of the difference in DxO "measured ISO".

The E-PM2 sensor is significantly better than that of the GX1, particularly for demanding (high DR) scenes at base ISO. But you will underexploit its capacity unless you give it as much exposure as it can take (which will be nearly one stop more than the GX1 can manage with both cameras at their base ISO). To get the exposure right, see the practical advice I already provided in that regard earlier on. When properly exposed from a RAW-shooters point of view, the E-PM2 images will sometimes look too bright when you review them in camera. But as long as the highlights are not clipped in the RAW file, you can just pull the exposure back in the RAW converter and enjoy an even more noise-free image than the one you'd otherwise get.

Anders,

Later today I will run a simple and practical test to find how much room each camera has from the camera defined exposure to the point of the start clipping and post results on this thread. I will add to the test D7000, which I do not use much. I will post my results here. This test should give some intuitive feel for the use of overexposure. Even it would be different based on the scene my guess won't be that wild

Yesterday, I have pointed each of three cameras (all set the same)  on the same litem object and their selected shutter speed was the same. Stopped as it was too late. Today I will step through the exposure compensation (+1/3EV step) until the clipping.

Again, thank you for the help!

Leo

i had time to try overexpose on PM2 only at ISO 3200 and 6400. In most cases the overexposure of+2EV did not cause highlight clipping and was correctly adjusted by -2EV (Exposure slider). The result is much cleaner image. The same can be used for any ISO based on light and handheld or tripod.

Olympus offered again reconditiond PM2 with two lens  for $319.

Leo

What DXO insists on referring to as "ISO" is what the actual ISO standard 12232 describes as the lower limit of the exposure latitude of the camera at a given "ISO speed" setting: basically a measure of how much exposure you can give the camera at that setting without saturating the sensor and blowing the highlights: "SSAT" in the jargon of that ISO standard.

ISO standard 12232 actually recommends a different measure of sense speed or sensitivity, "SSNR40", which is basically about getting a SNR of at least 40:1 in the mid-tones; this measured shadow handling, and is much closer to what the ISO film speed refers to.

BJL wrote:

What DXO insists on referring to as "ISO" is what the actual ISO standard 12232 describes as the lower limit of the exposure latitude of the camera at a given "ISO speed" setting: basically a measure of how much exposure you can give the camera at that setting without saturating the sensor and blowing the highlights: "SSAT" in the jargon of that ISO standard.

ISO standard 12232 actually recommends a different measure of sense speed or sensitivity, "SSNR40", which is basically about getting a SNR of at least 40:1 in the mid-tones; this measured shadow handling, and is much closer to what the ISO film speed refers to.

BJL,

Thank you for the clear and easy to understand comment!

Now I low were the number 40 came from

Leo

BJL wrote:

What DXO insists on referring to as "ISO" is what the actual ISO standard 12232 describes as the lower limit of the exposure latitude of the camera at a given "ISO speed" setting: basically a measure of how much exposure you can give the camera at that setting without saturating the sensor and blowing the highlights: "SSAT" in the jargon of that ISO standard.

ISO standard 12232 actually recommends a different measure of sense speed or sensitivity, "SSNR40", which is basically about getting a SNR of at least 40:1 in the mid-tones; this measured shadow handling, and is much closer to what the ISO film speed refers to.

BLG,

I just checked DXO. The mucked noise level is 32 db vs 26 db recommend by standard 12232. I mane wrong as there db calculated differently of levels and power. Which is related to the image noise? … probably levels.

Leo