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Understanding Exposure - a good book?

Understanding Exposure - a good book?

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riveredger said:
Iliah Borg said:
riveredger said:
I merely want you to tell me the definition of ISO sensitivity.
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I'm not an alchemist.
riveredger said:
Apparently, that is too hard for you to do.
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Yes. Let's take something more obvious, like how the lens focal length changes when a LF lens is mounted on a 1" system :)
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"Help, my smoke and mirrors are not working anymore!" - I. Borg, 11-27-13 :-)
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I was sure you do not understand that one too.

Let me explain. One can't change physical properties of an object by casting spells.
 
riveredger said:
The concept is very easy:

Aperture: the smaller the aperture (which means the larger the number on your aperture display since you are seeing the denominator of the actual aperture f/xx) the less light that hits the sensor, but the greater the depth of field. Using a smaller aperture (to achieve greater DOF, for example) will require you to use a slower shutter speed and/or greater ISO value to achieve the same image brightness in your photo that you would have using a larger aperture.

Shutter Speed - the length of time the shutter stays open when you press the shutter release. The longer the shutter is kept open, the more light is allowed to hit the sensor. SS also impacts image blur (longer shutter speeds will soften water, for example, and a faster shutter speed can freeze a player swinging a bat). When thinking about how long you want to keep your shutter open, you need to consider how wide or narrow you want to set your aperture. If you keep you aperture at say f/2.8 you will start to overexpose the image as you keep the shutter open longer.
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Good so far.
riveredger said:
But what if your lens does not have a bright max aperture and you want to use a fast shutter speed? If your aperture only opens to say f/5.6 and you need a shutter speed of say 1/500 in an inside gym, you will need to increase the ISO.
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You don't actually need to increase the ISO. You can shoot with a lower ISO and then increase the brightness in post. In fact, if shooting RAW, then, depending on the sensor and the ISO setting, using the lower ISO setting and increasing the brightness in post may result in a better photo.
riveredger said:
ISO is the sensor's sensitivity to light.
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It is not, except inasmuch as for some sensors, higher ISOs result in less read noise (the additional noise added by the sensor and supporting hardware) than lower ISOs. For example, with my camera, the Canon 6D, a photo of a given scene at f/2.8 1/100 ISO 6400 will be less noisy than a photo of the same scene at f/2.8 1/100 ISO 400 pushed four stops in the RAW conversion. On the other hand, there will be no difference between the two if you did that with a D800.
riveredger said:
The higher the ISO, the brighter the resulting image will be if the SS and aperture are left unchanged. Increasing the ISO introduces noise to the photo, however.
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Increasing the ISO does not "introduce noise to the photo" directly. What happens is that a higher ISO setting on the camera results in a more narrow aperture, faster shutter speed, and/or less flash power, any and all of which will result in less light falling on the sensor, and it is the lesser amount of light falling on the sensor that causes the increase in noise.
riveredger said:
Next post will be about metering modes and how they use your camera's built in light meter to determine the "proper" expose values when shooting in auto, A or S modes.
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The "proper exposure" is simply the exposure that best balances DOF/sharpness, motion blur / camera shake, and noise / blown highlights in the context of the artistic intent of the photo.
 
Iliah Borg said:
riveredger said:
Iliah Borg said:
Iliah Borg said:
I merely want you to tell me the definition of ISO sensitivity.
Click to expand...
I'm not an alchemist.
Iliah Borg said:
Apparently, that is too hard for you to do.
Click to expand...
Yes. Let's take something more obvious, like how the lens focal length changes when a LF lens is mounted on a 1" system :)
Click to expand...
"Help, my smoke and mirrors are not working anymore!" - I. Borg, 11-27-13 :-)
Click to expand...
I was sure you do not understand that one too.

Let me explain. One can't change physical properties of an object by casting spells.
Click to expand...
 
riveredger said:
physical properties are not changed
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Good.
riveredger said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
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What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
 
GeorgianBay1939 said:
I did say that Exposure is a function of three variables: f/( or more precisely T/), shutter interval, and Scene Luminance. It is NOT a function of ISO speed.

To suggest that Exposure a function of ISO using the above argument is mathematically incorrect, physically incorrect and specious at best.

Are you saying that by twiddling the analogue / digital gain knob you are changing the Exposure? I hope not.

Yes, EXPOSURE is affected by twiddling the ISO dial when the camera is set to an AE mode (P, A, S). That is because the AE system is linked to S through the above relationship between (EV, L, S and K)
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I think it's confusing when people conflate "exposure" as measured at the sensor with "exposure" as suggested by the camera's metering system with "exposure" which is the "correct" one by some standard. Then you just end up with a lot of arguments where people call each other ignorant or stupid just because they mean different things (even when people probably realize, from context, what was meant).
 
Iliah Borg said:
Iliah Borg said:
physical properties are not changed
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Good.
Iliah Borg said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
 
riveredger said:
Iliah Borg said:
riveredger said:
physical properties are not changed
Click to expand...
Good.
riveredger said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
Click to expand...
 
bobn2 said:
riveredger said:
Iliah Borg said:
bobn2 said:
physical properties are not changed
Click to expand...
Good.
bobn2 said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
Click to expand...
Click to expand...
 
riveredger said:
bobn2 said:
riveredger said:
Iliah Borg said:
riveredger said:
physical properties are not changed
Click to expand...
Good.
riveredger said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
Click to expand...
Click to expand...
Click to expand...
 
bobn2 said:
riveredger said:
bobn2 said:
riveredger said:
Iliah Borg said:
bobn2 said:
physical properties are not changed
Click to expand...
Good.
bobn2 said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
Click to expand...
Click to expand...
Click to expand...
Click to expand...
 
riveredger said:
PS - physical properties are not changed, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed. Research digital signal processing if you still can't grasp this whole concept.
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Digital signal processing still can't change the physical properties of what the sensor captures.
 
riveredger said:
bobn2 said:
riveredger said:
bobn2 said:
riveredger said:
Iliah Borg said:
riveredger said:
physical properties are not changed
Click to expand...
Good.
riveredger said:
, but the camera's reaction (and what it eventually writes to your memory card) to the digital signal is changed.
Click to expand...
What is digital signal here? Something after the ADC? So, camera reacts to the signal coming from ADC? How? Or you mean photon flux is in a certain way digital?

Or, maybe you want to start with reading a definition of sensitivity, before suggesting others to discuss digital processing?
Click to expand...
Click to expand...
Click to expand...
Click to expand...
Click to expand...
Click to expand...
 
riveredger said:
I don't understand the resistance. I guess you guys enjoy stirring the pot. Have a Happy Thanksgiving.
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The resistance is to misunderstanding which breads further misunderstanding. You have already illustrated the cognitive tangle that comes from this:

Increasing the ISO introduces noise to the photo, however.

Loading…

www.dpreview.com

Please do explain the process by which 'increasing the ISO introduces noise into the photo'.
 
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