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ISO

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skm.sa100 View Drop Down
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Post Options Post Options   Quote skm.sa100 Quote  Post ReplyReply Direct Link To This Post Topic: ISO
    Posted: 14 March 2019 at 11:13
I don't seem to have paid enough attention to what ISO exactly means.
I recently read something that piqued my interest.
I've thought (apparently incorrectly) that bumping up the ISO is making the sensor more sensitive to light. In reality, that seems to mean that the image is still captured at a base ISO and then a multiplication factor is applied.
If that's the case, would that be the same if we were to deliberately under expose to the extent needed and then just increase exposure in post? If the processing algorithm has better ISO performance control, would that result in a cleaner image compared to the camera output?
Where do the hardware limits (sensor sensitivity) lie and the software processing kicks in?
Thanks
Sashi
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beautiophile View Drop Down
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Post Options Post Options   Quote beautiophile Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 11:52
Do you refer the Tony Northup's video?
If so, or not, there are two clips I think they may give you some ideas
https://youtu.be/hwRsWomRzVQ
https://youtu.be/Vbxz_Dn1ElY
The latter tells some interesting things about ISO on new Sony cameras, specifically the A7iii.


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QuietOC View Drop Down
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 12:21
Sony cameras don't multiply raw numbers when you raise the ISO setting. They do clip the highlights (which doesn't make any sense to me).

The Photonstophotos Shadow Improvement Charts intent is to show what if there is any advantage to raising the ISO in camera for raw. My A68 basically sticks to 0 Ev. The dual gain A7III gets a 0.75 Ev bump at ISO 640 and higher.

The dual gain is implemented by having two different size capacitors at every pixel. This switch happens on the analog side.

Edited by QuietOC - 14 March 2019 at 13:49
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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 16:23
Originally posted by skm.sa100 skm.sa100 wrote:

... would that be the same if we were to deliberately under expose to the extent needed and then just increase exposure in post? If the processing algorithm has better ISO performance control, would that result in a cleaner image compared to the camera output?

Sometimes, at some ISOs. It depends on the camera.

Where do the hardware limits (sensor sensitivity) lie and the software processing kicks in?

That also depends on the camera ... but with the examples I've seen the improvement is usually negligible; and the process is just too nerdy to interest me personally. But google ISO invariance if you want to pursue it.
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jkkyler View Drop Down
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Post Options Post Options   Quote jkkyler Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 16:27
This is worth a view regarding iso and adjusting in camera vs post.

https://youtu.be/hwRsWomRzVQ
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addy landzaat View Drop Down
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 16:32
Fstoppers did some quick and dirty tests and properly exposed pictures look better then pictures taken at 100iso and pushed in post. The difference is not big, but it is there.
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LAbernethy View Drop Down
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Post Options Post Options   Quote LAbernethy Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2019 at 17:51
Originally posted by jkkyler jkkyler wrote:

This is worth a view regarding iso and adjusting in camera vs post.

https://youtu.be/hwRsWomRzVQ


thanks.
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