July 23, 2014, 09:08:41 PM

Author Topic: ISO 50  (Read 34608 times)

sanj

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Re: ISO 50
« Reply #150 on: January 23, 2013, 02:05:46 AM »

In your test Canon does not look as good as Nikon counterpart. I hope Canon fixes this asap.
That is because he is not exposing for each sensors optimum performance, he is exposing them to the same absolute values, as I keep saying, if your goal is maximum dr then you must overexpose the Canon more, there is a lot more headroom in a Canon file than a Nikon file.

Confused about this. When I shoot I want to expose for what the scene demands rather than what my sensor is comfortable with. Don't u agree?

I don't, unless I'm shooting JPG. For RAW, I go for optimum sensor performance because the image will be post processed anyway and I need as much headroom / DR possible.

JR what does it mean to expose for 'optimum sensor performance'?

I expose for what the scene needs, as to what will make the scene look best. Eg if I am shooting a sunset I would expose for say the clouds and not the sun. Thx JR...

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Re: ISO 50
« Reply #150 on: January 23, 2013, 02:05:46 AM »

sanj

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Re: ISO 50
« Reply #151 on: January 23, 2013, 03:32:34 AM »

[/quote]
To be blunt, you can safely ignore the drivel that Mikael is spouting about changing ISO somehow affecting the amount of light or number of photons hitting the sensor.
[/quote]

Even a child will agree that the amount of light hitting the sensor depends only on f stop/shutter combination. No dispute.
But what I am questioning is that if changing the ISO did not matter, why do we bother setting the ISO? Why does the picture over/under expose if the ISO is not correctly chosen?

ISO kicks in only after the shot is taken, ok. But but it DOES kick in. So should it be factored in while considering the camera calculating total light for that 'click'?

Head starting to spin...

neuroanatomist

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Re: ISO 50
« Reply #152 on: January 23, 2013, 05:22:51 AM »
Take now  your camera, set the camera on P and  100iso, start to metering  against a white wall, grey card what ever and se what values you get in  time / f-stop   ,  for example 1/60sec F-5,6
Start HTP  The camera now changes to 200iso  and at the same  you get 1 stop shorter time or F-stop.

You have now halving the in falling light /photons to the sensor compared to 100 iso by a shorter exposure time or one more f-stop or both

And Neuro and others, it is you who do not understand how things works
please stop to make your funny- try to understand instead

So, it is your belief that because enabling HTP when in P-mode with ISO 100 set forces a 1-stop change in aperture or shutter speed causing a halving of infalling light, that the mechanism of HTP is a 1-stop change in aperture or shutter speed causing a halving of infalling light?  You have repeatedly stated that HTP works by halving the amount of light/number of photons hitting the sensor.

We are all eagerly awaiting your explanation of how HTP works in P-mode with ISO 200, 400, 125, or any value other than 100, and how it works in M-mode even with ISO 100 set.  If you can demonstrate that enabling HTP always results in a 1-stop change in aperture or shutter speed, you are correct that HTP works by reducing the amount of light hitting the sensor. If you cannot, you are wrong and should admit it.
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neuroanatomist

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Re: ISO 50
« Reply #153 on: January 23, 2013, 05:36:06 AM »
Even a child will agree that the amount of light hitting the sensor depends only on f stop/shutter combination. No dispute.
But what I am questioning is that if changing the ISO did not matter, why do we bother setting the ISO? Why does the picture over/under expose if the ISO is not correctly chosen?

ISO kicks in only after the shot is taken, ok. But but it DOES kick in. So should it be factored in while considering the camera calculating total light for that 'click'?

Head starting to spin...

Not all children, seemingly.

Of course ISO should be considered. The analog gain is applied before the signal off the sensor is digitized, so it's 'baked' into the RAW file.  J.R.'s confusion was caused by statements in this thread suggesting that changing ISO directly alters the amount of light hitting the sensor (which it does not, although it can do so indirectly, in an auto-exposure mode, P/Av/Tv), or that changing ISO alters the number of photons able to be captured, e.g. reducing the full well capacity, which is also not true.
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J.R.

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Re: ISO 50
« Reply #154 on: January 23, 2013, 05:38:04 AM »

Are you  gays serious

Take now  your camera, set the camera on P and  100iso, start to metering  against a white wall, grey card what ever and se what values you get in  time / f-stop   ,  for example 1/60sec F-5,6
Start HTP  The camera now changes to 200iso  and at the same  you now get 1 stop shorter time or F-stop.

You have now halving the in falling light /photons to the sensor compared to 100 iso by a shorter exposure time or one more f-stop or both

And Neuro and others, it is you who do not understand how basic  things works and Im sorry that thou do not know  basic knowledge
And please  Neuro stop to make your funny on my behalf,  that Im writing drivel etc - try to understand instead .



First things first ... Please don't call us "gays". I guess it just might be a typo but nevertheless this is something I have to refute as it is typed out in bold.

If you read my above post, I specifically mentioned that as per my understanding the photons could be halved only by changing the shutter speed and / or the aperture - which is what you are also implying.

Also, I can agree that in the P mode, the photons hitting the sensors would be halved - but this will happen only if you started at ISO 100 in the first place - it is also of note that the halving of the photons happens only because of the in-camera override.

I also tried this just now ... Start out at ISO 400, meter a scene ... Now enable HTP ... Nothing changes whatsoever.

Thus concluded ... HTP does not change the number of photons hitting the sensor. If you we're to start out at ISO 100 though,the camera will automatically change the ISO, aperture and/or shutter speed when you are on ISO 100.
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J.R.

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Re: ISO 50
« Reply #155 on: January 23, 2013, 05:48:23 AM »

JR what does it mean to expose for 'optimum sensor performance'?

I expose for what the scene needs, as to what will make the scene look best. Eg if I am shooting a sunset I would expose for say the clouds and not the sun. Thx JR...

Sorry for the confusion, What I meant was that for some situations where I feel the scene warrants shadow recovery, it would be better to overexpose the shot slightly and adjust the highlights in post processing rather than lift the shadows.

The Sun is a bad example ... I guess you put it there trying to make it impossible for me to answer ;) an attempt at the answer would be that it all depends on what you shoot and your choice ... I feel that ETTR works for me. YMMV
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marinien

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Re: ISO 50
« Reply #156 on: January 23, 2013, 05:49:17 AM »
To whom is HTP for? To people who are using the camera in JPG mode and automatic mode to get better reproduction of contrasty motives , raw people with little knowledge understand under exposing and post processing

I will call you men  not gays , is that more proper?

Oh, Mikael, you forgot ISO100, didn't you?  ;D
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Re: ISO 50
« Reply #156 on: January 23, 2013, 05:49:17 AM »

sanj

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Re: ISO 50
« Reply #157 on: January 23, 2013, 05:51:02 AM »
@ Neuro. Ok I now learned that no matter what ISO is selected, the sensor collects equal amount of light but processes it differently depending upon the ISO setting.
Cool.
Thx.
I have not yet pieced it together in my mind how this causes blown highlights at 50 ISO, but since I do not intend to use 50 iso anymore, I will let this pass... Why bother taxing my not so technical mind... :)

J.R.

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Re: ISO 50
« Reply #158 on: January 23, 2013, 05:51:47 AM »
To whom is HTP for? To people who are using the camera in JPG mode and automatic mode to get better reproduction of contrasty motives , raw people with little knowledge understand under exposing and post processing

I will call you men  not gays , is that more proper?

Agree on the first part.

"Gays" means homosexuals in my part of the world ... I thought you meant "guys" which would have been correct - I mentioned as much in my above post where I said it could have been a typo.
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neuroanatomist

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Re: ISO 50
« Reply #159 on: January 23, 2013, 05:52:57 AM »
I have just done that.

and read the suedes answer at page 12 , he handles english much better than me


The suede:
Yes, compared to using the camera at ISO100, turning HTP on makes the camera expose for at least ISO200, which is a full stop difference in photometric exposure. A halving of the number of photons captured in a normal case camera-choice automatic exposure. True. But that's the intention and planned execution of the function, so that particular point needs no further discussion in my view.

Do you understand that the case of enabling HTP when at ISO 100 in a an auto-exposure mode causing a halving of the number of photons is a unique case applicable only when at ISO 100 in a an auto-exposure mode?

Several times, you made statements like:

mechanism behind HTP...
In HTP  the sensor  has now been hit by  less light/photons

and:

HTP. it is a halving of infaling light

If the 'mechanism of HTP' is to reduce the amount of light hitting the sensor, then that mechanism must apply generally, not only in the unique case of being at ISO 100 in an auto-exposure mode when HTP is enabled.

Since your explanation of the 'mechanism of HTP' is not applicable at most ISO settings in all exposure modes, your explanation is wrong.  It really is just that simple.
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J.R.

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Re: ISO 50
« Reply #160 on: January 23, 2013, 05:57:40 AM »

I have not yet pieced it together in my mind how this causes blown highlights at 50 ISO, but since I do not intend to use 50 iso anymore, I will let this pass... Why bother taxing my not so technical mind... :)

Same here - ISO 50 shall be used by me only in case I don't have a NDX at hand.
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neuroanatomist

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Re: ISO 50
« Reply #161 on: January 23, 2013, 06:03:48 AM »
I have not yet pieced it together in my mind how this causes blown highlights at 50 ISO, but since I do not intend to use 50 iso anymore, I will let this pass... Why bother taxing my not so technical mind... :)

Setting ISO 50 'causes' blown highlights only because you change aperture or shutter speed to maintain a metered exposure (relative to ISO 100).  The ISO change doesn't directly blow the highlights (if you change from ISO 100 to 50 in M-mode and then press the shutter, your meter will show a stop of underexposure).  But when you change aperture/shutter to let in more light, that can blow highlights that would not blow at ISO 100.

Point being, if you're at ISO 100 with almost-blown highlights and need a slower shutter or wider aperture, ISO 50 won't save your highlights - you need an ND filter in that case.
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sanj

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Re: ISO 50
« Reply #162 on: January 23, 2013, 06:04:29 AM »
@ Neuro. Ok I now learned that no matter what ISO is selected, the sensor collects equal amount of light but processes it differently depending upon the ISO setting.
Cool.
Thx.
I have not yet pieced it together in my mind how this causes blown highlights at 50 ISO, but since I do not intend to use 50 iso anymore, I will let this pass... Why bother taxing my not so technical mind... :)

what do we then have shutter speeds and different F-stops for?
I think the coin is falling down

Please explain more Mikael. Did not understand your comment. Thx.

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Re: ISO 50
« Reply #162 on: January 23, 2013, 06:04:29 AM »

sanj

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Re: ISO 50
« Reply #163 on: January 23, 2013, 06:06:09 AM »

JR what does it mean to expose for 'optimum sensor performance'?

I expose for what the scene needs, as to what will make the scene look best. Eg if I am shooting a sunset I would expose for say the clouds and not the sun. Thx JR...

Sorry for the confusion, What I meant was that for some situations where I feel the scene warrants shadow recovery, it would be better to overexpose the shot slightly and adjust the highlights in post processing rather than lift the shadows.

The Sun is a bad example ... I guess you put it there trying to make it impossible for me to answer ;) an attempt at the answer would be that it all depends on what you shoot and your choice ... I feel that ETTR works for me. YMMV

Ok we work the same way it seems. Even though I do not know what ETTR or YMMV mean. :)

neuroanatomist

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Re: ISO 50
« Reply #164 on: January 23, 2013, 06:09:27 AM »
neuro wrote

Do you understand that the case of enabling HTP when at ISO 100 in a an auto-exposure mode causing a halving of the number of photons is a unique case applicable only when at ISO 100 in a an auto-exposure mode?

yes I do, to create a head room which is described earlier

So, IF you understand that enabling HTP when at ISO 100 in an auto-exposure mode is a unique case only applicable at ISO 100 in an auto-exposure mode, THEN it follows that your explanation of the general mechanism of HTP as a halving of infalling light is WRONG.

Will you admit that?
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Re: ISO 50
« Reply #164 on: January 23, 2013, 06:09:27 AM »