Canon EOS RP RAW editing flexibility?

dpfan32 wrote:

Yeah this was an interesting point.

ISO 50 setting make a +1EV overexposure right?

Well in Canon cameras the extended ISO 50 introduces a metering bias, which effectively makes the camera overexpose compared to the same metering mode at ISO 100 (note that 'overexposure' is relative to the current metering mode, no more no less).

In connection to ETTR. When you hint the right side of the Histogram this doesn't mean that it's the end.

This only means that this is the last point where the JPEG wouldn't blow out!

Yes, that's why you might want to use something like UniWB (so called universal white balance) if you really want to maximise the DR of your camera.

The RAW file can handle up to 2 EV overexposure, I read somewhere.

The question is, this overexposure - it's 'over' against what exactly? If you're on standard evaluative metering, you may already be blowing out some highlights because metering makes mistakes, so overexposing +2 ev against evaluative metering can easily make things much worse.

If you don't want to go for all the hassle with UniWB, there's another simple technique to ETTR: use spot metering on the brightest part of the scene (e.g. white clouds), then use exposure compensation of +3 stops (the exact amount has to be tested with your particular camera). This may bring you pretty close to ETTR. Unfortunately, with Canon cameras, spot metering is bound to the dead centre of the frame, which means you'll have to recompose every time you change the exposure, which makes this method impractical if you're shooting from a tripod.

Another method - use RGB histogram and ignore red and blue channels, ETTR by the green channel only (suggested by Iliah Borg IIRC). Again, unlike UniWB, it's not 100% reliable, but it may work in many daytime situations.

The reason I actually shot at some point wit ISO 50 on my EOS 6D Mark II was actually a EOS RP review I watched on YouTube, where the reviewer showed, that the ISO 50 setting had much less noise in the shadows that ISO 100!

Of course he didn't shoot a high dynamic range scene.

The result had been the same if he overexposed the ISO 100 RAW 1 stop while shooting and made the image darker afterwards.

Am I right?

Yes.

But this is IMHO a good practice for ETTR:

In my opinion, no, shooting at extended ISO 50 is not ETTR. There was a similar very interesting debate on DPR recently, I don't remember who it was with exactly.

So the issue is, as above, that with ISO 50 you effectively use a constant metering bias against your current metering mode, and it doesn't guarantee you're getting a constant 2.5-stop headroom. And even when you are, you're still 1.5 stops away from the 'ideal' ETTR.

But yeas I still use the RP an my main camera and please tell me if my thoughts are correct about the ISO 50 with the ETTR I did at some point or did I misunderstood this ISO 50 thing

I'm not sure about the RP, but in the R5 the histogram may be showing no clipping at ISO 50 but you actually get clipped highlights in raw.

Yes in many cases ISO 50 brings you 1 stop closer to 'ideal' ETTR, but it's not very reliable so occasionally you will be getting blown out shots.