Hi all, This is a long post, please accept my apologies... If you find it boring, move on Having recently picked up an E-P5 and upgraded my E-M5 to the latest firmware, I'm now the proud owner of two cameras with an ISO 100 ("LOW") capability. I was curious to see what is going on so did a bit of experimentation. Here's a shot I took of my E-P5 with the E-M5: General view - ISO 200, 1/10s f4, EV+0.5. LR5 processed from raw. Corrected for WB, but no additional sharpening or EV correction. It's at EV +0.5 to counteract the large amount of white in the image. The camera's over/under "blinkies" showed only a little overexposure on the edges of the EP-5 top plate. In fact, when I opened the file in Lightroom and turned on its clipping viewer, the area of overexposure almost exactly matched what was on the screen. I then took two more shots: - ISO 100 EV+0.5 - 1/4s f4 - ISO 200 EV+1.5 - also 1/4s f4 (i.e. overexposed by an additional 1 stop). I then pulled the ISO 200 EV+1.5 back by 1-stop in LR. The images all look pretty much similar: Left to right - ISO 100 EV+0.5, ISO 200 EV+0.5, ISO 200 EV+1.5 & pulled back -1EV in LR And here are the LR clipping regions for all three: Screengrab from LR showing clipping on the top-plate. ISO 200, 1/10s f4, EV+0.5 ISO 100 EV+0.5 ISO 200 EV+1.5 & pulled back -1EV in LR The fact that the clipping is nearly identical on both the ISO 100 and overexposed ISO 200 shots is pretty incriminating evidence as to how the ISO 100 is being implemented. I then decided to let Rawdigger take a look. For those who don't know Rawdigger, it's a program that gives a statistical view of the pixel values in raw images. The results were a little surprising (to me at least!): Stats from image. ISO 200, EV+0.5 Stats from image. ISO 100, EV+0.5 Stats from image. ISO 200, EV+1.5 You can see that the ISO 100 and ISO 200 +0.5EV have over 50% of the pixels apparently past the max value (i.e. completely blown). However, neither the camera's on-screen blinkies, nor the LR clipping view reported this at all. The max value was auto-determined by Rawdigger as 3792 and mousing over the image reveals that large areas are indeed all showing levels of 3792 - i.e. blown. This didn't make sense... So, I then went back to LR and tried to recover some detail in the "blown" areas. The camera was resting on some mounting board and looking at the ISO 200 non-overexposed image, I found that by cranking down the highlights and pulling the exposure back by -1.5 stops, I could find some detail: Recovering highlights - ISO 200, EV+0.5. Highlights -100, Exp -1.5 I then did the same thing on the ISO 100 and over-exposed ISO 200 shots (the ones that Rawdigger says are completely blown!): Recovering highlights - ISO 100, EV+0.5. Highlights -100, Exp -1.5 Recovering highlights - ISO 200, EV+1.5. Highlights -100, Exp -2.5 So, I've successfully recovered details in these two shots too - which doesn't tally at all with what Rawdigger is saying, but does with what LR says. Pixel peeking on all three didn't reveal any significant difference in the level of detail either. And just to underline what Rawdigger is saying, here's its clipping display: RRawdigger clipping display Now, I know this is only a single test and since it's under artificial light maybe the DR isn't wide enough to uncover problems, but here are my conclusions anyhow: 1 - Rawdigger is getting it wrong! 2 - Shots at ISO 100 and ISO 200 overexposed by 1 stop then pulled back in LR give the same results 3 - Highlights can be recovered from both ISO 100 and overexposed ISO 200 shots to a level pretty much the same as a normally-exposed ISO 200 shot 4 - I'll have no hesitation using ISO 100 in the future You still there (and awake!). Hope it makes sense and at least one other person finds it useful!!