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Archive 2017 · ISO invariance?

  
 
maestrofilms
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p.1 #1 · p.1 #1 · ISO invariance?


I've seen a few articles and vids referencing Sony cameras and ISO invariance. The theory being you only shoot in ISO 100 or 640, whichever is closest to the exposure you want, and then raise exposure in post. I guess you maximize your dynamic range that way, because higher ISOs just apply gain anyway and is no different than bringing it up in Lightroom or other editors.

Is there anything to this? Doesn't seem practical in the long run, and you would have to guess at the appropriate aperture and shutter speed sometimes. Anyone ever try it?



Jun 20, 2017 at 06:23 PM
AdaptedLenses
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p.1 #2 · p.1 #2 · ISO invariance?


It's more so that if you shoot at 100 or 500 and adjust you aren't going to see a lot of difference. I thought I remembered it was slightly better to shoot at 500 than lift 100, but pretty minor anyway. 640 only applies to the A7RII that uses a different tech to help out higher ISO.

Did you check out Jim Kasson's blog?



Jun 20, 2017 at 06:28 PM
maestrofilms
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p.1 #3 · p.1 #3 · ISO invariance?


No, just curious really. I don't see myself changing my shooting style. I'll check it out, though. Thanks.
Yes, 640 was mentioned for the A7RII, you're right.



Jun 20, 2017 at 06:35 PM
arbitrage
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p.1 #4 · p.1 #4 · ISO invariance?


A9 and A7R2 are invariant at 640 and above. Before that it is slightly better to shoot at the proper ISO in camera and you should never shoot below 640 and lift in post past 640.


Jun 20, 2017 at 08:56 PM
maestrofilms
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p.1 #5 · p.1 #5 · ISO invariance?


So, is there any point to leave the ISO at 640 if dark enough? Will the final product be any different?


Jun 20, 2017 at 09:02 PM
arbitrage
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p.1 #6 · p.1 #6 · ISO invariance?


maestrofilms wrote:
So, is there any point to leave the ISO at 640 if dark enough? Will the final product be any different?


I'm no expert on this but my understanding is that you will come out even whether you up ISO in camera or up it in post to get your proper exposure with an ISO invariant sensor. I would just use the proper exposure in camera although you can err on the side of protecting highlights and just take the ISO hit in the shadows and midtones with lifting in post.

The only sensor that I've seen that is invariant over the entire ISO range is the Nikon D7200.



Jun 20, 2017 at 09:23 PM
snapsy
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p.1 #7 · p.1 #7 · ISO invariance?


It's just as you described - maximum dynamic range and the alleviation of worrying about whether you (or the camera) have metered the scene correctly. The downside is you can't review the results while shooting (too dark) and a bit more PP work to get to your baseline exposure.


Jun 20, 2017 at 10:34 PM
Holger
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p.1 #8 · p.1 #8 · ISO invariance?


Bespoked wrote:
I don't agree with this and I base this on crap loads of real testing, but what do I know.
I shoot +1.7EV, or, meter with highlights and over expose the highlights by 1.7EV, then pull back in post, sometimes up to 3EV, very clean shots with much more shadow detail.


If you overexpose you run in danger of clipping and loosing information. The data is lost irreversibly and your maximum DR possible is reduced. Maybe your jpg setting is such that exposing to the right by about 1.7 ev hardly clips data and maximizes the information gathered in your case.
Otherwise, as explained here and in other places if you know your camera is iso-invariant in a certain region it makes sense to push in post to protect highlights which would otherwise be blown out at no cost.

http://blog.kasson.com/the-last-word/is-the-d810-isoless/
https://www.dpreview.com/articles/7450523388/sony-alpha-7r-ii-real-world-iso-invariance-study



Jun 21, 2017 at 02:00 AM
scrappydog
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p.1 #9 · p.1 #9 · ISO invariance?


I also shoot 1.7EV above the zebra clipping point (at 100+ in the zebra menu option) with some shots on the A7R2. It does not clip and the SNR is clean. I generally do this with ISO 100 shots.


Jun 21, 2017 at 06:56 AM
genji
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p.1 #10 · p.1 #10 · ISO invariance?


snapsy wrote:
It's just as you described - maximum dynamic range and the alleviation of worrying about whether you (or the camera) have metered the scene correctly. The downside is you can't review the results while shooting (too dark) and a bit more PP work to get to your baseline exposure.


Another downside is that it complicates the process of reviewing and selecting images for post-processing (again, too dark) although Fast Raw Viewer has an option to apply exposure correction on opened RAW files.



Jun 21, 2017 at 07:38 AM
arbitrage
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p.1 #11 · p.1 #11 · ISO invariance?


scrappydog wrote:
I also shoot 1.7EV above the zebra clipping point (at 100+ in the zebra menu option) with some shots on the A7R2. It does not clip and the SNR is clean. I generally do this with ISO 100 shots.


A proper exposure is a proper exposure. But with an ISO invariant sensor if you are upping ISO in camera to get that +1.7 then you could do that in post instead and the result would be identical. It has nothing to do with whether +1.7 above zebra clipping is or is not the proper exposure. If that is proper and you don't clip highlights using that method then no reason to underexpose.



Jun 21, 2017 at 07:40 AM
snapsy
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p.1 #12 · p.1 #12 · ISO invariance?


genji wrote:
Another downside is that it complicates the process of reviewing and selecting images for post-processing (again, too dark) although Fast Raw Viewer has an option to apply exposure correction on opened RAW files.


LR users can solve this by turning on Auto Tone for the import.



Jun 21, 2017 at 08:05 AM
LBJ2
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p.1 #13 · p.1 #13 · ISO invariance?


maestrofilms wrote:
I've seen a few articles and vids referencing Sony cameras and ISO invariance. The theory being you only shoot in ISO 100 or 640, whichever is closest to the exposure you want, and then raise exposure in post. I guess you maximize your dynamic range that way, because higher ISOs just apply gain anyway and is no different than bringing it up in Lightroom or other editors.

Is there anything to this? Doesn't seem practical in the long run, and you would have to guess at the appropriate aperture and shutter speed sometimes. Anyone ever try it?


If you read the same threads/posts I did, I think this applies to the A9's dual conversion gain technology describing ISO 100 and 640 as "dual base/native ISO settings." So in theory change from ISO 100 directly to ISO 640. Which I did recently during an A9 birding shoot in low morning light and overcast skies. Unfortunately, I was so busy keeping up with the fast moving bird activity, I didn't get a chance to compare ISO640 to 200/400 but have been meaning to test this out again for myself.

As far as the A7rII goes, IMO ISO 100/200 take your pick and use as needed.



Jun 21, 2017 at 12:32 PM
maestrofilms
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p.1 #14 · p.1 #14 · ISO invariance?


What I saw was mostly about the A7RII and a Nikon model.


Jun 21, 2017 at 12:43 PM
scrappydog
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p.1 #15 · p.1 #15 · ISO invariance?


arbitrage wrote:
A proper exposure is a proper exposure. But with an ISO invariant sensor if you are upping ISO in camera to get that +1.7 then you could do that in post instead and the result would be identical. It has nothing to do with whether +1.7 above zebra clipping is or is not the proper exposure. If that is proper and you don't clip highlights using that method then no reason to underexpose.


I have made "proper" exposures in my Canon bodies with ugly results in the shadows. I will take my +1.7EV because, frankly, it is my proper exposure. Clearly YMMV.



Jun 22, 2017 at 07:09 AM
genji
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p.1 #16 · p.1 #16 · ISO invariance?


snapsy wrote:
LR users can solve this by turning on Auto Tone for the import.


That seems to imply that every frame one shoots gets imported into Lightroom, without review, rating, or culling. Or am I misunderstanding?



Jun 22, 2017 at 07:10 AM
chez
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p.1 #17 · p.1 #17 · ISO invariance?


genji wrote:
That seems to imply that every frame one shoots gets imported into Lightroom, without review, rating, or culling. Or am I misunderstanding?


That's exactly what I do, import into LR and then do my rating and culling within LR. Now I don't shoot thousands of images during an outing, but do bring back thousands from travel.



Jun 22, 2017 at 07:20 AM
genji
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p.1 #18 · p.1 #18 · ISO invariance?


Interesting. Thanks for the clarification.

chez wrote:
That's exactly what I do, import into LR and then do my rating and culling within LR. Now I don't shoot thousands of images during an outing, but do bring back thousands from travel.




Jun 22, 2017 at 02:35 PM





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