Best base settings to use? Thank you :) Locked

Started 2 months ago | Questions thread
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knickerhawk Veteran Member • Posts: 6,957
Re: Best base settings to use? Thank you :)

bobn2 wrote:

knickerhawk wrote:

bobn2 wrote:

David1961 wrote:

Yes the two approaches should end up with the same f-number and shutter speed in theory.

The other member wouldn't accept that my raising ISO did no harm to the final image quality when highlights are not clipped.

He was probably under the misapprehension that ISO causes noise.

No, because that "other member" was I.

Oh, right ho. You wouldn't be under that misapprehension, unless you'd suffered a brainstorm.

I wouldn't mind suffering a brainstorm. It's those damn brain f@rts that I wish I'd stop having.

The real problem here is that David1961 has either mischaracterized (or misunderstood) what I was arguing in that thread. The green text above that I've bolded is at the crux of the mischaracterization. David recommended using ISO to increase shutter speed when in aperture priority mode. He argued that, even when trying to optimize the raw exposure, his ISO-only approach always works better that EC (followed by ISO if appropriate) because it guarantees a preservation of output lightness (per the originally metered level). He seemed to believe that there was never any downside to this approach. It was only after I raised the potential for exacerbating highlight clipping in high DR conditions by using his ISO-only approach that he added the bolded conditional. We never really got beyond that point to explore the consequences of using the ISO-only approach when the scenic conditions and metering choices present this bind. I believe the reason for that was because he just couldn't accept that increasing ISO would have any adverse effect on what highlights would be captured or clipped.

Well, clearly if you raise the ISO too much, at some stage you're likely to clip the highlights. And, as we know, when you reach the point where your camera is more-or-less ISOless, there isn't much to be gained.

I believe it's the case with many reasonably current cameras that the read noise improvement from bumping up ISO tends to be negligible and is surprisingly often offset by the highlight clipping price you pay. It's a tradeoff, of course, but I personally prefer to deal with a tiny bit of extra noise than deal with blown highlights. Even with the DPR studio scene, which is certainly not set up for emphasizing highlight issues, you run into the tradeoff (or at least having to decide whether to worry about which highlights and how badly blown they are). Below I've used the ISO invariance test shots for the EM5ii (my current camera). The raw histograms shown are for the paint pan in the lower right corner where there's the scene's strongest highlights. The ISO 1600 shot is clearly clipped in all three channels in the pan and metallic fitting around the brush. The ISO 400 is not clipped in the red channel and just barely clipped in the green and blue channels. As an aggressive ETTR shooter I frequently end up working with shots that are just barely blown like the ISO 400 one. They can usually be managed with a few postprocessing tricks. Shots like the ISO 1600 version are usually beyond hope if those particular highlights are important.

from the EM5ii ISO 1600 DPR ISO invariance studio scene

from the EM5ii ISO 400 DPR ISO invariance studio scene

What about the noise side of the tradeoff? The ACR-converted renderings from the two shots are shown below (identical default settings applied). Yes, there's a very small difference in noise, but that difference is the type that can be offset with a tiny bit of targeted noise reduction in the areas of the image where it could actually be seen. YMMV, but I'll take the bit of extra noise fixing every time over the challenge of fixing clipped highlights of meaningful parts of the image when it's one of these read noise improvement vs. highlight protection choices.

from the EM5ii ISO 1600 DPR ISO invariance studio scene

from the EM5ii ISO 400 DPR ISO invariance studio scene

I think it's a bit of a futile discussion, though, because the auto and semi-auto modes are engineered around the whole film emulation thing, and using other controls to subvert them just makes life more complicated, IMO.

That's a matter of personal preference. But if you're going to commit to an optimized raw exposure strategy, I think its best to commit all the way rather than try to straddle (which is what so many JPEG+raw shooters think they're successfully doing).

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