Jump to content

ISO Woes


Laidley

Recommended Posts

Advertisement (gone after registration)

3 minutes ago, jaapv said:

And me in previous Auto ISO discussions. It all depends on the camera you are using.

Not on my cameras at least. All work exactly the same way. Auto iso in manual mode is an exposure technique for many years now. Claiming that an exposure technique does not change exposure sounds somewhat strange if you ask me.

Link to post
Share on other sites

Ha! Now you have gotten my point! :) That is why ISO is not an exposure parameter. You are confusing the amplified output of the camera's electronics with the amount of light hitting the sensor. The first controls the preview on you computer screen, the later the sensor response.

Link to post
Share on other sites

1 minute ago, jaapv said:

Ha! Now you have gotten my point! :) That is why ISO is not an exposure parameter.

We don't speak the same language then. In auto iso in manual mode the only thing that changes automatically is iso and this suffices to brighten or darken images as expected.

Link to post
Share on other sites

56 minutes ago, lct said:

We don't speak the same language then. In auto iso in manual mode the only thing that changes automatically is iso and this suffices to brighten or darken images as expected.

Precisely, or, -sometimes better- fix the ISO in the camera and do the brightening in the computer. The computing power in the camera is limited and may do the job less well. Auto-ISO does not brighten images. It amplifies the camera output.

Link to post
Share on other sites

30 minutes ago, jaapv said:

Precisely, or, -sometimes better- fix the ISO in the camera and do the brightening in the computer. The computing power in the camera is limited and may do the job less well. Auto-ISO does not brighten images. It amplifies the camera output.

Hi Jaapv, I think this is what you mean:

https://improvephotography.com/34818/iso-invariance/

 

John

Link to post
Share on other sites

Advertisement (gone after registration)

On 9/7/2019 at 7:36 PM, jaapv said:

Yes, and shift the exposure slider and you will get exactly the same image (sometimes with less noise and/or better DR) if your camera is ISO invariant (many are)

https://improvephotography.com/34818/iso-invariance/

In that case the ISO setting on the camera is irrelevant, thus proving that it ISO is not an exposure control.

A camera without LCD needs (if (sorry to use the word again ;) ) ISO-invariant) no ISO setting, nor Auto-ISO. The brightness can be set on raw conversion.

In fact, as explained in the linked article, there can be advantages in shooting at base ISO and underexposing dramatically, especially to protect highlights  - but certainly not with a Canon :lol:

Yes, time has been moving on over the last decades, changes are afoot and we must change with them ;)

Yes, I do. ;) Post #5.

Link to post
Share on other sites

51 minutes ago, jaapv said:

Precisely, or, -sometimes better- fix the ISO in the camera and do the brightening in the computer. The computing power in the camera is limited and may do the job less well. Auto-ISO does not brighten images. It amplifies the camera output.

Computers work after the shot then cannot prevent clipping by definition. Auto iso in M mode allows for that easily. Reminds me of discussions i (we?) had around a beta testing in 2014. I used my Fuji X-E2 to show how it works then as auto iso in M mode was not yet implemented in the M240. 3200 iso above, 1250 iso below. 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Link to post
Share on other sites

2 minutes ago, jaapv said:

You compare to an overexposed image...🙄 you should compare to an underexposed image at base ISO.

"overexposed", your own words :). Yet both images were shot at the same aperture (f/2) and the same shutter speed (1/125s) under the same light. 

Link to post
Share on other sites

2 hours ago, lct said:

Computers work after the shot then cannot prevent clipping by definition. Auto iso in M mode allows for that easily.

We can also see it the opposite way: If an image is mistakenly overexposed because of too high ISO (auto or not) it cannot be recovered in post. But if you shoot at base ISO and then lift the exposure in post, the highlights will be preserved.

Edited by evikne
Link to post
Share on other sites

1 minute ago, evikne said:

We can also see it the other way: If an image is mistakenly overexposed by ISO (auto or not) it cannot be recovered in post. But if you shoot at base ISO and then lift the exposure in post, the highlights will be preserved.

And you will introduce a lot of artifacts in the shadows. I think it best to agree we have different methods and neither is right or wrong. As this thread is in the M cameras forum, it is reasonable to assume we are discussing M camera sensors, not some hypothetical camera mirage.

Link to post
Share on other sites

6 minutes ago, pedaes said:

And you will introduce a lot of artifacts in the shadows. I think it best to agree we have different methods and neither is right or wrong. As this thread is in the M cameras forum, it is reasonable to assume we are discussing M camera sensors, not some hypothetical camera mirage.

I agree that in the most extreme situations raising the ISO can make better results with a camera that is not ISO invariant. But in most cases, with only a moderate increase of exposure in post, there will be no practical difference. 

  • Thanks 2
Link to post
Share on other sites

1 hour ago, lct said:

"overexposed", your own words :). Yet both images were shot at the same aperture (f/2) and the same shutter speed (1/125s) under the same light. 

Yes, but you are comparing the wrong things. Take a correctly exposed image at ISO 1250. Then keep the EV settings  the same, but crank down the ISO to base ISO, i.e. 200. Afterwards pull up the ISO 200 image to the equivalent of 1250.

Link to post
Share on other sites

4 minutes ago, jaapv said:

Yes, but you are comparing the wrong things. Take a correctly exposed image at ISO 1250. Then keep the EV settings  the same, but crank down the ISO to base ISO, i.e. 200. Afterwards pull up the ISO 200 image to the equivalent of 1250.

Genuine question - do you not discard a load of information the sensor could have captured doing this? 

Link to post
Share on other sites

2 hours ago, evikne said:

We can also see it the opposite way: If an image is mistakenly overexposed because of too high ISO (auto or not) it cannot be recovered in post. But if you shoot at base ISO and then lift the exposure in post, the highlights will be preserved.

OK but the question raised in this topic is to know if iso can be considered an exposure parameter when taking actual photographs, not when tweaking them in PP. A "third exposure parameter" so to speak according to my links above. It proves to be so in that it determines the actual exposure and allows for preventing clipping at this very moment. And this is true in auto iso mode as well as in full manual mode actually. Last boring test. Same camera (digital CL), same exposure mode (manual), same lens (35/2 asph v1), same aperture (f/2.8), same shutter speed (1/640s), different iso (800 above, 100 below), same light, 100% crops. Try to recover pics like the above one in PP. It's too late if exposure has not been set properly when shooting, including isos. 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Link to post
Share on other sites

1 hour ago, pedaes said:

Genuine question - do you not discard a load of information the sensor could have captured doing this? 

The point with an ISO invariant image sensor is that all data is captured at base ISO. Afterwards the information is only "stretched", either in the camera or on the computer. The result is practically the same.

But no Leica sensor is yet fully ISO invariant as I know, so increasing ISO is still reasonable in very dark surroundings.

Edited by evikne
  • Thanks 1
Link to post
Share on other sites

1 hour ago, pedaes said:

Genuine question - do you not discard a load of information the sensor could have captured doing this? 

No, because, as the amount of light falling on the sensor remains the same, the amount of data is the same. The only thing you are influencing is the in-camera signal amplification, AKA ISO. 

  • Thanks 1
Link to post
Share on other sites

21 minutes ago, lct said:

OK but the question raised in this topic is to know if iso can be considered an exposure parameter when taking actual photographs, not when tweaking them in PP. A "third exposure parameter" so to speak according to my links above. It proves to be so in that it determines the actual exposure and allows for preventing clipping at this very moment. And this is true in auto iso mode as well as in full manual mode actually. Last boring test. Same camera (digital CL), same exposure mode (manual), same lens (35/2 asph v1), same aperture (f/2.8), same shutter speed (1/640s), different iso (800 above, 100 below), same light, 100% crops. Try to recover pics like the above one in PP. It's too late if exposure has not been set properly when shooting, including isos. 

Again. It is not about recovering overexposed images...

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...