ISO 50 & Dynamic Range (EOS 6D)

So what's the deal with ISO 50? I realize it can get you longer shutter speeds in bright sunlight situations, but do you lose dynamic range doing so? If that's the case, what ISO gives you the best tradeoff between noise and DR?

Well the lowest non expanded ISO should get you the best DR/Noise. If you also choose to exploit all of that DR by shooting RAW and exposing to the right, you are most likely to end up with an exposure that would be more consistent with having actually shot at ISO 50 or 64. Shooting at the ISO values that are derived from analogue amplification only and shooting RAW and ETTR will always give the best DR/noise situation for any situation.

If you must shoot in camera JPEGs then ISO 50 would theoretically give the biggest move to shooting to the right for an in camera JPEG. ISO 50 digitally drops you a whole stop, 100 down to 50, against ISO 160, which only drops you 1/3rd of a stop.Not looked at DR/noise for a camera with ISO50 included, but for in camera ISO160 would seem to offer the optimum results.

Alan

ISO 50 is the only way I can shoot my primes wide open. I'd rather have 1/8000.

GeoKras1989 wrote in post #17179816
ISO 50 is the only way I can shoot my primes wide open. I'd rather have 1/8000.

Yup. I tried to go back to a 6D and this was one reason I couldn't. I don't want to fuss with ND filters since I go from outside to inside a bunch and shooting at 1.4 in day sun you need 1/8000 and ISO 100. I never have to move down to 50 but at least it's there.

ISO 50 is just ISO 100 with different processing pre-applied. If you're shooting RAW, there's really no point in using it. The DR is the same in both cases, but with respect to the preview you see on-screen, the DR is essentially "shifted" a stop from the highlights to shadows.

brettjrob wrote in post #17179915
ISO 50 is just ISO 100 with different processing pre-applied. If you're shooting RAW, there's really no point in using it. The DR is the same in both cases, but with respect to the preview you see on-screen, the DR is essentially "shifted" a stop from the highlights to shadows.

If I am at f/1.4, 1/4000 and ISO 100 and still have a 1.3-stop overexposure, ISO 50 is pretty darn handy. As mentioned 1/8000 would be a better solution.

GeoKras1989 wrote in post #17179940
If I am at f/1.4, 1/4000 and ISO 100 and still have a 1.3-stop overexposure, ISO 50 is pretty darn handy. As mentioned 1/8000 would be a better solution.

Typically sunny daylight at 1.4 will require 1/8000 shutter at iso 100. Only a few times will you need ISO 50 but ya. 8000 helps a bunch.

So the consensus is that it's a hack

hiketheplanet wrote in post #17180219
So the consensus is that it's a hack

Concur. It is hack. Just like ISO H1, and H2, there if you really need them, but mostly useless.

One of the best discussionsI have read on ISO is at http://www.clarkvision​.com/articles/iso/.

hiketheplanet wrote in post #17180219
So the consensus is that it's a hack

You can try it and see. Fortunately for me I had some software that 'forgot' to recognize ISO50. So when I shot raw ISO50 at 1/200s f1.8 was exactly the same as ISO100 1/200s f1.8. (I believe LR does do something different with ISO50 than ISO100, but I don't have LR.)

I then processed the same ISO50 raw in DPP to see the differences. Highlights were the same but midtones were down 1/2 stop and shadows down 1 stop. So it's not going to save you if you need to keep highlights - they will be the same as using ISO100.

So it's just a tone curve applied to the raw file shot at ISO100. Semi-useful if you shoot SOOC jpeg and like the ISO50 'look'. Pointless if you shoot raw. I have no idea if the 6D is different than the 5DII, but I think it's pretty safe to assume it is.

hiketheplanet wrote in post #17179479
If that's the case, what ISO gives you the best tradeoff between noise and DR?

You might think that is an easy question to answer, but it's not really. I'm going to answer it this way:

1. if you are taking pictures with your lens cap on to see read noise only, then ISO160 (at least for most Canon cameras)
2. If you are actually taking a photo of something and ETTR, then ISO100.

And I'm not saying any more or getting into an argument with anyone on this topic. I don't really care what anyone else does.

John from PA wrote in post #17180251
One of the best discussionsI have read on ISO is at http://www.clarkvision​.com/articles/iso/.

That was a good read, and a good rule of thumb for ETTR unless you're pushing higher ISO values.

I took a few shots today before the sun went down using ETTR, I'll put them through Lightroom as soon I get the chance and see what the difference is (I've never used the ETTR practice)