ISO 50

[TheSuede]

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?

I take it the answer was "yes".

I would think this concludes this argument series.
As far as I can understand from the [considerably more than!] somewhat confused string of comments in this thread, no party is/was actually strictly incorrect, since both parties are constantly avoiding the "Yes, but I'm talking about...." pretext of the responding posts.

Though I cannot help but feel that at least one side of the argumentation has gone out of it's way to not read the intended meaning of the "opposite side's" statements and argumentation. And the undertone of constant provocation isn't very unflattering.

This isn't meant to be condescending towards Mikael - since he is well aware of both his light dyslexia and his short temper - but this thread feels like a kindergarten playground where a pack of children are trying to provoke a dyslectic kid with very short temper into doing something stupid and aggressive while the teachers are watching - so they can say that "he started the violence!" and point the blame to him - and get him expelled. As I said: Not a very flattering impression.

In the end, from a factual PoV:

• HTP does not in any case UNLESS the one-off case where the starting point is ISO100 lower absolute photometric exposure. At set ISOs 200-800 it does however increase the electronic noise pollution in the finished image somewhat in Canon cameras.
• Exposure is exposure is exposure, and exposure sets the photon noise level in the image. It's set by the scene light emittance modulated by shutter speed and lens T-stop (aperture + losses), and actually also for all practical considerations: QE of the sensor. Not by ISO - though the ISO setting can change aperture and/or shutter speed when the camera is in auto- mode (anything but "M" mode), it's a secondary effect. ISO changes setting, setting changes exposure.
• ISO in digital cameras is a translating factor between exposure (exposure x QE = cell charge) and raw file ADU value.
• The amount of headroom available in a camera can NEVER be higher than when the camera is used on base ISO (ISO100 in the case discussed here) - Since the highest DR is always at base ISO, unless the construction is seriously flawed (actually totally botched!). This means that ISO200 + HTP has the same 'potential' headroom, since the actual physical amplification is set at ISO100, not 200
• ISO50 (or more generally "lower than actual base ISO") settings are useless for raw shooters, but may be of some use for jpg shooters.

Feel free to add constructive criticism, or point out any error(s). But be very ashamed if this post is considered OT and erased.

[J.R.]

This isn't meant to be condescending towards Mikael - since he is well aware of both his light dyslexia and his short temper - but this thread feels like a kindergarten playground where a pack of children are trying to provoke a dyslectic kid with very short temper into doing something stupid and aggressive while the teachers are watching - so they can say that "he started the violence!" and point the blame to him - and get him expelled. As I said: Not a very flattering impression.

Not really, IMHO it was just a matter of a very simple,yes or no. Not everyone is very good at the technical aspects and it becomes confusing when contradictory information is provided.

I believe that Mikeal is astute technically and knows what he is doing when it comes to cameras and their components ... But he categorically maintained that HTP will reduce the photons to half regardless of the base ISO setting and hence the confusion. Maybe you understand what he has been writing all along but then there are lesser mortals (such as me) who ponder whether or not what they have learnt (over the limited time they have been shooting) was correct.

[J.R.]

finally a breakthrough.  I really tried guys I really did.  I tried to get mikael to answer a very specific question and he avoided it with the great skill of an inkfish.

If you do not understand  the answers I have presented  it is nothing I can do about your problem= to understand, but do not make you funny on my behalf, it is time for you, Neuro and others to study the subject. In plain english, you gentleman seems not to have  a clue about what I have answer you many times,  head room  , the relation of time/f-stop and signal photons collecting / charge , and signal amplifying. I hope you others members who are not a member of a particular  persons fan club have learn something
Thank you the_ suede that you are supporting me.

Thanks Mikael. If you see my earlier post, that is what I was doing ... Studying the subject. Now, I always understood that the photons will be halved if the Aperture/Shutter speed is changed by 1 stop. But going by the thread I somehow got the impression that changing the ISO (what happens in HTP) automatically changes the amount of light hitting the sensor - something that Neuro, as well as yourself confirmed, Doesn't happen!

[J.R.]

Then you have  learn something new today?

Of course YES! That the ISO 50 is and HTP are basically useless if you shoot raw and post process. also, a basic understanding of how the sensor works.

Unless you know what's wrong you never know what is right

[neuroanatomist]

In the end, from a factual PoV:

• HTP does not in any case UNLESS the one-off case where the starting point is ISO100 lower absolute photometric exposure. At set ISOs 200-800 it does however increase the electronic noise pollution in the finished image somewhat in Canon cameras.
• Exposure is exposure is exposure, and exposure sets the photon noise level in the image. It's set by the scene light emittance modulated by shutter speed and lens T-stop (aperture + losses), and actually also for all practical considerations: QE of the sensor. Not by ISO - though the ISO setting can change aperture and/or shutter speed when the camera is in auto- mode (anything but "M" mode), it's a secondary effect. ISO changes setting, setting changes exposure.
• ISO in digital cameras is a translating factor between exposure (exposure x QE = cell charge) and raw file ADU value.
• The amount of headroom available in a camera can NEVER be higher than when the camera is used on base ISO (ISO100 in the case discussed here) - Since the highest DR is always at base ISO, unless the construction is seriously flawed (actually totally botched!). This means that ISO200 + HTP has the same 'potential' headroom, since the actual physical amplification is set at ISO100, not 200
• ISO50 (or more generally "lower than actual base ISO") settings are useless for raw shooters, but may be of some use for jpg shooters.

The only point I'd add to your astute summary is to correct the following:

• HTP does not in any case UNLESS the one-off case where the starting point is ISO100 lower absolute photometric exposure.

Assuming you're in an auto-exposure mode where the camera can change the aperture/shutter speed, enabling HTP lowers actual exposure any time the selected ISO is lower than 200, i.e. by 1/3-stop if ISO 160 is set, by 2/3-stop if ISO 125 is set, and by 2-stops if ISO 50 is set.  But only at ISO 100 is the amount of lowering equal to one stop, i.e. 'half the photons'.

[MarkII]

This isn't meant to be condescending towards Mikael - since he is well aware of both his light dyslexia and his short temper - but this thread feels like a kindergarten playground where a pack of children are trying to provoke a dyslectic kid with very short temper into doing something stupid and aggressive while the teachers are watching - so they can say that "he started the violence!" and point the blame to him - and get him expelled. As I said: Not a very flattering impression.

Not really, IMHO it was just a matter of a very simple,yes or no. Not everyone is very good at the technical aspects and it becomes confusing when contradictory information is provided.

I believe that Mikeal is astute technically and knows what he is doing when it comes to cameras and their components ... But he categorically maintained that HTP will reduce the photons to half regardless of the base ISO setting and hence the confusion. Maybe you understand what he has been writing all along but then there are lesser mortals (such as me) who ponder whether or not what they have learnt (over the limited time they have been shooting) was correct.

The quality of the discussion is terrible.

What makes this worse is that I think you can argue that both Neuro and Mikeal are correct. You view ISO200+HTP as ISO200 (the metering sensitivity) with a modified sensor sensitivity, or you can view it as ISO100 (the sensor sensitivity) with a modified exposure. You also need to keep in mind that not everyone is an expert in English.

A lot of hot air about nothing.

[J.R.]

This isn't meant to be condescending towards Mikael - since he is well aware of both his light dyslexia and his short temper - but this thread feels like a kindergarten playground where a pack of children are trying to provoke a dyslectic kid with very short temper into doing something stupid and aggressive while the teachers are watching - so they can say that "he started the violence!" and point the blame to him - and get him expelled. As I said: Not a very flattering impression.

Not really, IMHO it was just a matter of a very simple,yes or no. Not everyone is very good at the technical aspects and it becomes confusing when contradictory information is provided.

I believe that Mikeal is astute technically and knows what he is doing when it comes to cameras and their components ... But he categorically maintained that HTP will reduce the photons to half regardless of the base ISO setting and hence the confusion. Maybe you understand what he has been writing all along but then there are lesser mortals (such as me) who ponder whether or not what they have learnt (over the limited time they have been shooting) was correct.

The quality of the discussion is terrible.

What makes this worse is that I think you can argue that both Neuro and Mikeal are correct. You view ISO200+HTP as ISO200 (the metering sensitivity) with a modified sensor sensitivity, or you can view it as ISO100 (the sensor sensitivity) with a modified exposure. You also need to keep in mind that not everyone is an expert in English.

A lot of hot air about nothing.

Apologies ... English is not my first language either

[dlleno]

language problems, aside, when all parties are interested in finding truth, success can still happen.  The problem here is that truth wasn't discovered during the process.  it was hammererd out with great pain.  this what disapointed me about the discussion was that it did not converge.  instead it went  something like this:

HTP halves the number of photons hitting the sensor
no thats not true all the time
yes it is true, see my ISO100 example
ok for the special case of ISO 100 that is true, what about the other cases?
the number of photons is halved, see my ISO100 example
no that can't be true:  when ISO is 200 or 400 or 160, the number of photons is not halved
yes it is true, half the photons strike the sensor, see my ISO100 example
be specific:  how does HTP work with the ISO dial is set to 400.  is the number of photons halved?
HTP benefits jpg shooters
you need to say that the number of photons is not halved when the ISO dial is set too 400
no I won't please see my ISO 100 example.
Don't you see that when ISO is set to 400, HTP does not halve the number of photons
I've been saying that all along.

   
clear, precise technical explantions are more difficult when language is a issue, but they can still happen, and I hope they do, in the future.  I for one was frustrated becasue we could not get the conversation to converge on the true technical mechanism underlying HTP that would happen in the  majority of the cases and for the majority of togs, i.e. those who have not glued their ISO dial to "100".  suede I'm glad you finally summarized it.  whew

[J.R.]

Time for me to get some sleep with some hope that I won't be entertaining M/s ISO 50 or M/s HTP tonight. Won't be tempted to revisit this thread either ... It's taken it's toll on me 

[dlleno]

finally a breakthrough.  I really tried guys I really did.  I tried to get mikael to answer a very specific question and he avoided it with the great skill of an inkfish.

If you do not understand  the answers I have presented  it is nothing I can do about your problem, but do not make you funny on my behalf, it is time for you, Neuro and others to study the subject. In plain english, you gentleman seems not to have  a clue about what I have answer you many times,  head room  , the relation of time/f-stop and signal photons collecting / charge , and signal amplifying. I hope you other members who are not a member of a certain  persons fan club have learn something
Thank you the_ suede that you are supporting me.

most of us get all of that Mikael, we understand these concepts and your explanations were accepted.  I just couldn't correlate the "please see my ISO 100 example" approach to the case where the ISO dial is set to 400. 

My nature is the relentless persuit of technical precision and accuracy, which has nothing to do with membership into any presumed club, a comment which I find rude and uncalled for.  my suggestion is that if you relentlessly persue technical and linguistic precision in a conversation,  the personal nonesense disapears and you will be free to point out what is fact because it is fact, not because you or anyone else said it.   With the depth of understanding you have demonstrated,  I would say in the future  just please listen more carefully to the question being asked.

I will admit that my comment about the inkfish was condecending so you have my apologies for that.   Just please in the future be open to the technically-motivated goals of others and try to answer very specific questions with technical precision.  I realize English is not your primary language, and in fact your English is very good I would say, considering all of that.  I just found that for some reason you were unable to respond to a very specific question with a very specific answer, causing the whole  conversation to go crazy.

[seekthedragon]

Hi everyone!

This thread seems to be quite interesting, as I would really like to know more about HTP. However, would you kindly do me a favor and summarize the conclusion of this argument?  I tried to read it, but sometimes, it becomes quite pointless, and my English is just too poor to understand all the pages.

Your Sincerely

David

[dlleno]

Below is the best single summary to date

In the end, from a factual PoV:

• HTP does not in any case UNLESS the one-off case where the starting point is ISO100 lower absolute photometric exposure. At set ISOs 200-800 it does however increase the electronic noise pollution in the finished image somewhat in Canon cameras.
• Exposure is exposure is exposure, and exposure sets the photon noise level in the image. It's set by the scene light emittance modulated by shutter speed and lens T-stop (aperture + losses), and actually also for all practical considerations: QE of the sensor. Not by ISO - though the ISO setting can change aperture and/or shutter speed when the camera is in auto- mode (anything but "M" mode), it's a secondary effect. ISO changes setting, setting changes exposure.
• ISO in digital cameras is a translating factor between exposure (exposure x QE = cell charge) and raw file ADU value.
• The amount of headroom available in a camera can NEVER be higher than when the camera is used on base ISO (ISO100 in the case discussed here) - Since the highest DR is always at base ISO, unless the construction is seriously flawed (actually totally botched!). This means that ISO200 + HTP has the same 'potential' headroom, since the actual physical amplification is set at ISO100, not 200
• ISO50 (or more generally "lower than actual base ISO") settings are useless for raw shooters, but may be of some use for jpg shooters.

Feel free to add constructive criticism, or point out any error(s). But be very ashamed if this post is considered OT and erased.