ISO 160 lower noise than ISO 100?????

[Steve Axford]

As I'm starting to get into video I'm learning what video people think about cameras. I came across this odd thing where it is thought that ISO 160 (and multiples thereof) is actually better than ISO 100 on Canon cameras. This didn't make sense to me so I questioned it and was referred to the following articles http://photocascadia.wordpress.com/2011/05/13/canon-eos-5d-mark-ii-iso-noise-test/ and http://kriskoster.com/2010/08/optimising-your-5d-mark-ii-for-filmmaking/
It still didn't make sense though if you can be bothered reading the first article all the way through it starts to. The second article is just plain wrong (in respect to ISO at least).

It turns out that (with Canon cameras) ISO 100, 200 etc is the only hardware settings for ISO and that the other settings ISO 125, 160 etc are got by setting to ISO 100, in the case of 125, and applying an amplifier gain or 25%. ISO 160 is got by setting to ISO 200 and damping the gain by 20%. Thus the apparent noise increase or reduction.

See what you think of these articles and the mistakes you can make if you are not careful.

[arthurking83]

I would believe it.

Way back when the D300/D3 were new, claims were made that the D300 was best at ISO160(ISO Lo 0.7) which produced the best dynamic range and noise quality.

Probably for the same reasons.

I found that ultimate shadow recovery, and hence minimal noise, was best at ISO100(ISO Lo1) and basically stuck to using this ever since. But of course you lose out in the highlights at Lo1, so all I had to do was not over expose highlights by more than 1 full stop(1.7stops at ISO200 .. or base ISO gave me back more detail).

The differences were quite small, but in a few cases noticeable. One you have this info, it simply allows you to shoot with a few baseline camera settings in mind.

So while it may also work best at ISO160 for your purposes, watch for highlights if they blow out, as they may be less recoverable than at the hardware ISO settings.

[Steve Axford]

I just use 100, 200, 400 etc and expose them correctly. I did gain a better understanding of what goes on by investigating all this, but it is similar to Highlight Tone Priority. You can gain a bit on the dark tone noise by sacrificing dynamic range or visa versa with Highlight tone priority.

[arthurking83]

Makes sense.

IIRC, the 5DIII has an ISO50 setting too.

This is the equivalent to my D300's ISO100, which is one 'processed' step below base ISO.

For almost all landscape shooting, I prefer this Lo1 setting over base ISO, as it gives better shadow noise(and a bit better colouring) recovery, as long as I expose properly for the highlights and then later on process to regain only the shadows.

Alternatively if the scene doesn't allow for good use of filters, where I can't properly expose for both shadow AND highlight recovery as much as I'd like too, I'll then switch back to base ISO, and shoot to blow out the highlights more than I would at ISO Lo1, knowing that at base ISO I can recover more detail.

I'm not sure I fully understand this highlight tone priority thingy, as Nikon don't really have an equivalent setting.

They have ADL, which may be similar, but not the same .. it doesn't specifically target highlight protection .. only to capture and process the scene with as much dynamic range as possible.
I now prefer not to use it, as I don't have a need to process images speedily for any deadline .. I found that the same dynamic range effect(called D-Lighting) in Nikon's software works better, and the camera is more predictable in it's exposures.

The problem with the term exposing correctly is also something I have trouble understanding too.
What I mean to say tho, is that I understand the fundamentals of exposing correctly, even tho we all probably have differing opinions of how this actually pans out for our own needs, the problem with exposing correctly lies when you can't.
(and I have an intrinsic phobia towards HDR! :D)
If the scene requires 15stops of dynamic range and the camera can only capture 12, how do you expose correctly .. even taking into account that I'm the sort that has a need to use as many filters as possible to get exposure correct.
I think that this is about when you can't expose correctly, due to an oversupply of dynamic range in the scene, that all this talk becomes important.

[Steve Axford]

Correctly exposing is an interesting one. Correctly exposing for one thing may not be correctly exposing for another. For macro or portraits (except high key) I often underexpose so that the subject, face or mushroom, is at about 70%. I find that that works best in those situations, but it doesn't stick to the rules.