Does the camera ISO change exposure?

RichardC

Mu-43 Hall of Famer
Joined
Mar 25, 2018
Messages
2,192
Location
The Royal Town of Sutton Coldfield, UK.
Real Name
Richard
Now could anyone advise as to anything I have got wrong and if not this would seem to be a summary I can use
Assuming I have got this about right - anyone joining late could easily use this summary to save themselves reading through the thread ?
Please note I did not get as far as page 5 so if I’ve missed anything then please forgive my error 🤗🤗🤗
ISO = Gain = loud button
 

Erich_H

Mu-43 Top Veteran
Joined
Feb 8, 2020
Messages
915
Location
Eastern Denmark (annexed in 1658 by Sweden)
Real Name
Erik
Interesting Erich, you had the courage to post emojis all over the place, make weird statements throughout but not the self-confidence to debate? That's OK 😮 would probably not have been really interesting. Don't forget to take a lens with you...😂
You're quite right! I do not have the self-confidence to contribute in this debate.
Partly because it is way beyond my limited level of photographic abilities, and partly, as I mentioned, because my eyes tear up, which gives me great difficulty finding the right emojis on my virtual keyboard.

Presumably that is why they are not to your liking. I'm truly sorry about that!

And you are also totally correct in assuming that I sometimes forget to take a lens! This gives me results in this category, which, I must admit, I generally refrain from posting:

Subscribe to see EXIF info for this image (if available)


Thanks for taking the time for commenting upon my weird statements, though.

This is certainly giving my self-confidence a much needed boost!

Have a wonderful Saturday night!

Best regards/Erik

Note: No insults still implied or intentionally intended!
 

RS86

Mu-43 Top Veteran
Joined
Mar 26, 2019
Messages
569
Location
Finland
You and RS86 summed it up perfectly. Probably the most important statement in the complete discussion is:-

The moments are more important than some noise and you can always make it B&W.

I also think you understood the concept of "brightness" versus "exposure" tool. For that day you really want to push out every little detail & low noise from the sensor you will also know what to do...

This morning I was walking in our local forest with an old Panasonic LC1and the dynamic range was so wide that no matter how I moved the histogram, no joy. I ended up taking bracketed exposures to create HDR shots in PS.

Best - love to see some of your images... :)
Yeah, thanks. The Auto-ISO is a new thing to me & myself, found out about it with GX9 and more when I bought used PEN-F 6 months ago.

It's not of use with macro photography as I mostly stay at ISO 200 and without flash try to max. at 800 to be able to print good quality. And just to challenge myself.

But there are some of my photos on recent pages of the Olympus 60mm thread if interested.
 

mfturner

Mu-43 Regular
Joined
Aug 6, 2019
Messages
151
I will say that my acquisition of the PM1 and its lack of decent controls forced me to make peace with auto-ISO and shutter priority for walking about. Combined, they do a decent job of an ETTR-ish exposure, the ISO will stay on 200 until the aperture is wide open, and only then will ISO increase while holding aperture wide open. So effectively it tries to give an optimum base exposure of ISO 200, and when it's too dark for my shutter speed selection and lens aperture it then adds gain. When i then walk from shade into bright sunlight, i can still get a decently exposed photo, or easily spin its one rotary control to a faster shutter speed if appropriate.

In aperture priority, which i had used for years in the Canon ecosystem, the PM1 will only let the shutter speed go down to 1/(2×FL), where it will start increasing ISO. Even with the PM1's ancient IBIS i can do much better than that, which often meant 1/200th of a sec with the 35-100 f4 zoom at ISO 1600 for a still subject where i could otherwise use 1/20th of a sec. My m10.3 does this too, i don't know about other bodies.

Manual mode with auto ISO works well with the extra rotary controls on my m10.3, but it's irritating with the PM1 to change between controlling the aperture and controlling the shutter speed. But i can understand the value in this mode in most any other cameras with varying lighting.
 
Joined
Mar 31, 2015
Messages
477
Location
Switzerland
Real Name
Siegfried
  • Thread Starter Thread Starter
  • #111
I will say that my acquisition of the PM1 and its lack of decent controls forced me to make peace with auto-ISO and shutter priority for walking about. Combined, they do a decent job of an ETTR-ish exposure, the ISO will stay on 200 until the aperture is wide open, and only then will ISO increase while holding aperture wide open. So effectively it tries to give an optimum base exposure of ISO 200, and when it's too dark for my shutter speed selection and lens aperture it then adds gain. When i then walk from shade into bright sunlight, i can still get a decently exposed photo, or easily spin its one rotary control to a faster shutter speed if appropriate.

In aperture priority, which i had used for years in the Canon ecosystem, the PM1 will only let the shutter speed go down to 1/(2×FL), where it will start increasing ISO. Even with the PM1's ancient IBIS i can do much better than that, which often meant 1/200th of a sec with the 35-100 f4 zoom at ISO 1600 for a still subject where i could otherwise use 1/20th of a sec. My m10.3 does this too, i don't know about other bodies.

Manual mode with auto ISO works well with the extra rotary controls on my m10.3, but it's irritating with the PM1 to change between controlling the aperture and controlling the shutter speed. But i can understand the value in this mode in most any other cameras with varying lighting.
Awesome post...

I loved this post. Looking at the world around us and all that is happening and then you see a guy walking around with a manually handicapped camera (plus old 12MP sensor) not complaining, not looking for reasons not too, not arguing but being creative and doing what is possible to get the most out his EPM1... amazing!!!

You made the point everyone experience. At times we can use ISO200 and we all prefer lower ISO's but there are also times the ISO increase. My point throughout this discussion... make sure you expose the sensor properly, no matter which ISO. Use whatever exposure technique that works best for you to move the histogram safely to the right. One rule - do not confuse ISO thinking its exposure...

For those who haven't read my articles or posts - when I say exposure its everything that affects how much light will reach the sensor. This I call exposure. Only 2 variable in question looking at only the camera, aperture & shutter speed

In one of my posts, I drifted a little suggesting working with an isolation technique. If you lock the ISO and the shutter speed (isolate them), then the histogram displays exposure and specifically the aperture. This means you geared for:
- ISO needs (darker areas)
- You made a decision on shutter speed (either IBIS to keep ISO low or Capture movement)
- You will now use the right lens & aperture (DOP) to control exposure & the histogram

In other situations, you could lock the aperture (isolate) and play with shutter speed...

Another poster posted something interesting saying with his Pen F he is happy to ignore the best possible exposure, basically, lock the aperture & shutter speed and vary ISO when taking B&W images - this is his creative choice...

If you after the best performance out the 12MP sensor then a proper exposure helps those older sensors a lot. I have tested the EP1/2/3, the EP1 and they all benefitted from selecting a proper exposure...

Me rambling... have fun and I loved your post... Agree the EM10.3 is completely different...
 
Last edited:

RS86

Mu-43 Top Veteran
Joined
Mar 26, 2019
Messages
569
Location
Finland
Another poster posted something interesting saying with his Pen F he is happy to ignore the best possible exposure, basically, lock the aperture & shutter speed and vary ISO when taking B&W images - this is his creative choice...
I'll note that Manual Mode + Auto-ISO will give me best possible exposure to freeze the motion in low-light.

As far as I know the method doesn't ignore the best possible exposure at all.

It depends on what is the goal. If I want to freeze motion then I have to make certain choices. If you photograph friends for example you don't want their faces blurred.

And I don't always do B & W with this. It just can hide noise in a pleasant way or help with burned highlights etc.
 

bassman

Mu-43 All-Pro
Joined
Apr 22, 2013
Messages
1,195
Location
New Jersey
Real Name
The Bassman
Are you saying that increasing ISO has no effect on the brightness of a RAW file ?
Raw files don’t have a “brightness”, or for that matter, an ISO. ISO is - by definition - a standard which describes how bright a jpeg should be. Raw files are just digital data representing the amount of light which hit each pixel. When you look at an image on the lcd or EVF of your camera, or on your computer, you’re looking at a jpeg generated from the raw data.

The camera takes the ISO specified and generates a jpeg which is displayed during replay, and which is encoded in the raw file along with the ISO. If you use a raw converter to interpret the raw file, it will use the ISO as part of its processing to generate a jpeg. It’s only jpegs that have “brightness“, as it’s only jpegs that you can view.
 
Last edited:

John King

Mu-43 Top Veteran
Joined
Apr 20, 2020
Messages
621
Location
Beaumaris, Melbourne, Australia
To add to that, @bassman .

If one shoots RAW + LSF JPEGs (as I do), your camera will display that LSF JPEG instead of the crappy preview JPEG that's embedded in the RAW file.

This practice makes for superior image quality judgements when reviewing in camera.

With my E-M1 MkI, 7x is about A2 print size. With my E-M1 MkII, this is achieved at 5x. Useful to know.
 

bassman

Mu-43 All-Pro
Joined
Apr 22, 2013
Messages
1,195
Location
New Jersey
Real Name
The Bassman
I’d also add that there’s nothing wrong with Auto ISO (or auto anything). Much of the time, it will make the same setting you would manually, only quicker. The key is to understand the difference between exposure - the amount of light hitting your sensor, controlled by SS and aperture - and ISO - the brightness adjustment you want the camera and/or raw processor on your computer to make. Every shot is a balance of these three, informed by the demands of the subject and the intent of the photographer. One needs to understand how your particular camera behaves.
 

PakkyT

Mu-43 Hall of Famer
Joined
Jun 20, 2015
Messages
3,369
Location
New England
The camera takes the ISO specified and generates a jpeg which is displayed during replay, and which is encoded in the raw file along with the ISO. If you use a raw converter to interpret the raw file, it will use the ISO as part of its processing to generate a jpeg. It’s only jpegs that have “brightness“, as it’s only jpegs that you can view.
I don't think this is correct. What you are implying is that the ISO is simply a setting stored in the RAW file much the same was as white balance, monochrome mode, or digital crop is applied where you can then choose later to simply not use it or use a different setting (deselect or change the option).

Instead, the ISO sets the amplification of the analog data from the sensor before it is digitized and saved as the raw data. In other words, the ISO amplification is baked into the data as I understand it.
 

swifty

Mu-43 Regular
Joined
Jan 30, 2013
Messages
158
Location
Singapore
Real Name
Dave
I don't think this is correct. What you are implying is that the ISO is simply a setting stored in the RAW file much the same was as white balance, monochrome mode, or digital crop is applied where you can then choose later to simply not use it or use a different setting (deselect or change the option).

Instead, the ISO sets the amplification of the analog data from the sensor before it is digitized and saved as the raw data. In other words, the ISO amplification is baked into the data as I understand it.
I believe you're correct, PakkyT. But I think the gist of what Bassman was saying is that the RAW files have no brightness, just digital numbers.
The interpretation of those DNs forms an image with brightness.
The analog multiplication happens either before or during the ADC digitisation (I'm not clear exactly when the analog ISO implementation happens) to produce the RAW files so it's baked in and cannot be undone once the RAW files are written.
 

John King

Mu-43 Top Veteran
Joined
Apr 20, 2020
Messages
621
Location
Beaumaris, Melbourne, Australia
Swifty, my (limited) understanding of modern sensors is that the ADC is/are part of the sensor assembly. i.e. a baked in attribute of the raw file.

This would also explain why lifting a file 5 stops in PP gives a very different result from getting the analog exposure correct in-camera.
 

swifty

Mu-43 Regular
Joined
Jan 30, 2013
Messages
158
Location
Singapore
Real Name
Dave
But I believe there are a set of instructions written on the RAW files to tell the RAW converters how to interpret the DNs and what brightness the image to display. Eg. Many cameras have 'Lo' and 'Hi' ISO settings as well as intermediate ISO settings between full 'stops' of ISO increments where the analog ISO implementation doesn't change. So despite no change in analog ISO multiplication, the RAW converters know how to display the JPEGs with different brightness so there must be accompanying instructions baked into the RAW files too.
 

Aristophanes

Mu-43 Top Veteran
Joined
Aug 9, 2017
Messages
985
Location
Rankin Inlet, Nunavut
Swifty, my (limited) understanding of modern sensors is that the ADC is/are part of the sensor assembly. i.e. a baked in attribute of the raw file.

This would also explain why lifting a file 5 stops in PP gives a very different result from getting the analog exposure correct in-camera.
And why it is superior to get ISO correct in-camera rather than rely on post-processing.
 

Latest posts

Links on this page may be to our affiliates. Sales through affiliate links may benefit this site.
Mu-43 is a fan site and not associated with Olympus, Panasonic, or other manufacturers mentioned on this site.
Forum post reactions by Twemoji: https://github.com/twitter/twemoji
Copyright © 2009-2019 Amin Forums, LLC
Top Bottom