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Forum: General Photography
12-15-2019, 09:36 PM
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You have nailed it!!
I had expected a bit of loss of iso invariance. The KP is supposed to rock for high iso performance and I presumed this was from the accelerator unit. And I thought it was supposed to have an effect on iso invariance. But if the results from your tests are near enough visibly then that is all you need.
I have always noticed a certain amount of variation in results when experimenting but never one procedure noticeably worse than the other.
For me - once I had confidence in IsoIn -- my workflow now revolves around base iso in manual mode. I tend to guess exposures and set my preferences for aperture and shutter and then to chimp to see how much gap is on the right hand side of the histo. I look at that gap and think of noise rather than think about iso. It is an extremely simple workflow but is dependant on an iso invariant camera.
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Forum: General Photography
12-14-2019, 09:39 PM
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I think that means they are not iso invariant but does the relationship become linear above iso 400?
This set up is exactly the wrong way to do it. Think of the aperture and shutter as putting a quantity of light on the sensor and the Iso applying amplification to the resulting signal.
So you under exposed by cutting back that quantity of light and thereby starving the sensor - hence more noise in the signal/noise ratio.
This is supposed to be a test of comparing increased EV in PPing against the noise from Higher Iso
Try replicating your test but make the correct exposure at iso 3200 and decreasing iso to under-expose.
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Forum: General Photography
12-13-2019, 07:03 PM
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No one is attempting to be smarter than others. Iso-invariance is a feature of the recent Sony sensors. It is simply good practise to utilise it to gain more control over your highlights if that is what you wish.
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Forum: General Photography
12-13-2019, 06:56 PM
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Could you clarify your test. Which was the "correct" exposure? It needs to be the "+4" one. So in manual mode take a "correct" exposure at your higher iso at take progressively underexposed shots by decreasing the iso and correcting these in post. This may be what you did but your wording is confusing. I would hate to think that later generations of cameras are moving away from being iso invariant but I gather it might be to do with the accelerator units in like the K1ii. From memory it is something like iso-invariant above iso 400.
maybe for a jpg shooter.
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Forum: General Photography
09-04-2018, 07:16 PM
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I think it is all in the way you think - I think of it as two variables and an awareness of the perils of unnecessary underexposure ( low signal to noise ratio).
But however you think the outcome is essentially the same. (And the correct setting highly subjective!!).
EDIT How about a compromise? -- it is best visualised as a triangle but there are only two variables.
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Forum: General Photography
09-04-2018, 02:32 PM
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I always have struggled with understanding dynamic range.
So in editing can I recover the lost dynamic range of an image taken with a higher Iso ?
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Forum: General Photography
09-04-2018, 01:51 PM
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That is right and in an Iso invariant camera that is via aperture and shutter speed alone - the exposure triangle no longer exists.
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Forum: General Photography
09-04-2018, 01:48 PM
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I am querying about the editing of the image - not the taking of it Norm.
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Forum: General Photography
09-04-2018, 01:27 PM
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Just to clarify for me - In the case of the horse on the beach - by just lightening the shadows and keeping the highlights back and the anchors on the histogram in the same place - does the edited image still have the overall dynamic range of the original Iso 100 image?. (obviously with tonal curves in different areas).
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Forum: General Photography
09-03-2018, 01:11 PM
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Iso invariance is not a concept - it is a description of the performance of certain sensors.
Utilising Iso invariance is a concept - a subtle change in technique. Many Pentaxians are instinctly using it anyway.
It does not improve noise -it merely improves your control over the dynamic range.
The horse on the beach can serve as an example.
I presume it is at Iso 100. Lets say it would be good to have some more detail in the dark areas.
So we use the curves tool in pp to bring up the shadows two stops and hold the highlights back where they are now.
In a non Iso invariant camera the shadow area would be degraded.
In an Iso invariant camera the shadow area would effectively be at Iso 400 with the usual noise associated with 400 and the highlight area will have the tonal range and noise of the original 100 Iso
It is simple as that.
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Forum: General Photography
09-01-2018, 01:47 AM
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Well I OPed this thread which shows some examples --
Iso invariance - PentaxForums.com
And pasted this example elsewhere -
 and 
Is that what you mean?
As for being complicated once you get your head around it utilising Iso invariance simplifies your photography - there is only two variable inputs to your sensor - shutter and aperture . So set to Raw, choose the widest aperture and slowest shutter that are appropriate for your environment and check you are not clipping the highlights. You are now at best practice - how simple can that be!!
Oh and the Iso invariance principle and ETTR are totally compatible because ETTR is only valid at base Iso.
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