ISO 50

[Loswr]

My G.... You two Neuroanatomist and Rpt don't know the basic how a sensor works, collecting photons and if you are halving the time= go from 100 iso to 200 iso you are halving the amount of hitting light/photons on the sensor and the amount of read out electrons by half.
God night

Seriously? Mikael, explain to us, step by step, how enabling HTP causes a change in the exposure time or the light/number of photons hitting the sensor.

Try this little experiment:

1. Set camera to M mode with HTP off
2. Set ISO 100, and set aperture and shutter speed to achieve a metered exposure.
3. Enable HTP.

Now, tell us - did the shutter speed change? Did the aperture change? If they did not change, how is the amount of light falling on the sensor any different?

I'm sure you'll point out that ISO changed to 200, and the meter shows a 1-stop overexposure. So, if you now change aperture or shutter speed by a stop to again achieve a metered exposure, that secondary change halves the light. But you did that, not HTP.

Now...that was in the very specific case of ISO 100. Repeat the above three steps, but in step two, set ISO 200 or higher. Did the shutter speed change? Did the aperture change? Try it again in P mode at ISO 200. Did the exposure change? Explain how in those cases, enabling HTP reduced the amount of light hitting the sensor. After you've explained that, please explain how a situation that arises in only a very limited set of circumstances, i.e. ISO 100 with an auto-exposure mode (Av, Tv, P) selected represents a general description of the 'mechanism of HTP'. After that, feel free to prove the general accuracy of that broken clock.

Or just ignore these questions, as you ignored dlleno's similar questions. Answering them would mean acknowledging your mistake, something you're evidently incapable of doing.

 

[Loswr]

My apologies as this comes very late in the thread and may seem like a noob question but I am just curious to understand ...

What decides the number of photons that actually hit the sensor? Is it the Aperture and Shutter Speed Or does the ISO play some role in that?

From what I understood previously was that the photons hitting the sensor are the same for the same Aperture and Shutter Speed setting and an increase in the ISO only boosts the signal from the sensor. in other words, it was only when at a particular Aperture Value and Shutter Speed the available light entering the camera (photons) were less that the ISO would require a cranking up to boost signal from the sensor.

After all this discussion abovein the thread, I am quite confused as I don't have a science / engineering background.

Your previous understanding is absolutely correct. Only aperture and shutter speed determine the amount of light (number of photons) reaching the sensor. Any ISO setting other than base ISO (which differs by camera model, is usually in the 60-200 range, and is often not even a user-selectable value, e.g. ISO 80) is gain (analog or digital) applied after the collected photons are converted to electrons and read out from the photosite.

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.

 

[J.R.]

My apologies as this comes very late in the thread and may seem like a noob question but I am just curious to understand ...

What decides the number of photons that actually hit the sensor? Is it the Aperture and Shutter Speed Or does the ISO play some role in that?

From what I understood previously was that the photons hitting the sensor are the same for the same Aperture and Shutter Speed setting and an increase in the ISO only boosts the signal from the sensor. in other words, it was only when at a particular Aperture Value and Shutter Speed the available light entering the camera (photons) were less that the ISO would require a cranking up to boost signal from the sensor.

After all this discussion abovein the thread, I am quite confused as I don't have a science / engineering background.

Your previous understanding is absolutely correct. Only aperture and shutter speed determine the amount of light (number of photons) reaching the sensor. Any ISO setting other than base ISO (which differs by camera model, is usually in the 60-200 range, and is often not even a user-selectable value, e.g. ISO 80) is gain (analog or digital) applied after the collected photons are converted to electrons and read out from the photosite.

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.

Thanks for confirming ... It's silly for Mikael to not accept this and defend an incorrect opinion, which in turn misleads others because he does seem to know what he is doing

 

[sanj]

Here you have a old link , there is a comparison between the D7000 and one of my 5dmk2 three years ago
It is up to you or me how to handle large dynamic , but one thing is clear, it is always better to have large DR , you have more freedom, exposure latitude etc etc, I will close the link after a day


https://picasaweb.google.com/106266083120070292876/DR5dmk2VsD7000

In your test Canon does not look as good as Nikon counterpart. I hope Canon fixes this asap. Talking JUST about sensor.

 

[sanj]

Yeah but if I overexpose a little I quickly loose details in highlights. I do not like that. For my tastes I prefer preserved highlights and richer blacks.

But sometimes the blacks are too dark and I want Canon to give me a little room to open up the blacks when I want to without noise increase. I know it already does give me room, but to my eyes Nikon seems to give bit more.

No stress, life goes on, photos get created. But it is nice to know what the other companies are doing.

 

[sanj]

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?

 

[J.R.]

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.

 

[Aglet]

So for all your talk you can't post one image that demonstrates the totally unusable files you regularly got from real world shooting the 5D MkII? Amazing...........

I've got more important things to do this week than appease your impatience.
In the meantime, start formulating how you will describe that the banding i've experienced with my 5D2 is my fault. Especially the upper midtone range. I really want an explanation for that one. [/cheeky]

And then outline how I can fix it with advanced PP skills. i know you are good at this so hopefully you will share some of this knowledge with us. I'd like to improve some of the shots that I otherwise like but have these little flaws that annoy me.

When I have time to prep the samples I'll be starting a new thread in this section.

Now I have to go retest a Nikon camera that they've serviced 3 times over 4 months and have made only more problems without addressing the initial one.
I'll give them that, Canon service in my area has been FAR superior to Nikon's.

 

[sanj]

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...

 

[sanj]

[/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...

 

[Loswr]

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.

 

[Loswr]

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.

 

[J.R.]

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.

 

[J.R.]

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

 

[marinien]

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

 

[sanj]

@ 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.]

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.

 

[Loswr]

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.

 

[J.R.]

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.

 

[Loswr]

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.