ISO 50

[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...

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.

 

[sanj]

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.

 

[Loswr]

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?

 

[sanj]

@Micheal: Do you mean "the penny dropped"? ;D

So I am right? But is that not what Neuro has been saying and you disagreeing? Where lies MY confusion...?

Thx guy

 

[J.R.]

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

ETTR ... Expose To The Right
YMMV ... Your Mileage May Vary

 

[Loswr]

ETTR ... Expose To The Right
YMMV ... Your Mileage May Vary

TMBSITT ... Too Much BS In This Thread

I trust I don't need to spell out what BS means...

 

[sanj]

[/quote]
Setting ISO 50 'causes' blown highlights only because you change aperture or shutter speed to maintain a metered exposure (relative to ISO 100). Not clear as I am still exposing correctly for both ISO.

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). Agree, basic even for me.

But when you change aperture/shutter to let in more light, that can blow highlights that would not blow at ISO 100. Dont understand why. As I am still exposing correctly.

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. Agree. But I would attempt ISO 50 not to save the hightlights but to get even lesser noise.

[/quote]

 

[MarkII]

So, to summarise, what is happening is:

Camera Setting	Image EXIF Reports	Actual sensor gain	Actual metering gain	net effect
ISO 50	ISO 50	ISO 100	ISO 50	Brighter shadows; blown highlights
ISO 100	ISO 100	ISO 100	ISO 100	Normality
ISO 200 HTP	ISO 200	ISO 100	ISO 200	Highlights preserved; shadows burned

ie - ignoring any small shifts due the possibility that the 'native sensor base ISO is not exactly ISO100 - the only differences between the three modes are the metering and the subsequent processing to correct for the metering error.

If you shoot JPEG, the camera automatically compensates for the difference between the sensor and metering gain. If you shoot RAW, the file contains a flag that allows your RAW processor to do this. You can achieve a similar effect by simply using the exposure compensation setting and correction later - though the in-camera options will give better quality if you shoot JPEG.

The only real difference is in the exposure, metering and post processing. The metering gain changes really do mean that the number of photons hitting the sensor are affected by the mode setting - relative to the actual sensor ISO gain setting [edited for clarity].

Can anyone point out where this is incorrect?

 

[Loswr]

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?

even here you are missing the point, or do not understand, all started with that I explained it must be created a head room by under expose 100iso. Halving the read out electrons , halving the amount of light who are hitting the sensor. Some of you " cough cough " start to argue against that. This is way the camera are changing from 100 iso to 200iso and make the exposure time shorter or 1 more F-stop from example F-4 to 5,6.= cutting infallng light by one stop to hit the sensor
From 200iso and up the head room is created, and for evey iso stop or step i the head room will be one stop larger= the photons who are hitting the sensor is halving each iso step because of shorter exposure time/ or one more f-stop aperture and the gain is increased in every step / stop but only to the limit that there are still a head room left , then in the camera the software compensate with another curve and roling softer in the high lights .

So, your actual answer to my question is, "No, I will not admit that I am wrong."

 

[Loswr]

Yes, please go back to step one and explain how, at ISO 400 (or, in fact, any ISO other than 100), enabling HTP results in Half The Photons hitting the sensor.

We're waiting.

 

[marinien]

Yes, please go back to step one and explain how, at ISO 400 (or, in fact, any ISO other than 100), enabling HTP results in Half The Photons hitting the sensor.

We're waiting.

it doesn't, there already a head room created by halving the signal / e at 200iso from 100iso , and agin a halving from 200 to 400iso and from 400 to 800 etc etc , se earlier answer

Now I have a Sigma 35/1,4 to pick up and test/ compare to my canon 35/1.4

 

[J.R.]

TMBSITT :'(

 

[Loswr]

Yes, please go back to step one and explain how, at ISO 400 (or, in fact, any ISO other than 100), enabling HTP results in Half The Photons hitting the sensor.

it doesn't

Finally. So, before you stated that the mechanism of HTP was a reduction by half in the amount of light /number of photons hitting the sensor. Now, you are finally admitting that's not true.

Perhaps not quite the mea culpa we could have expected, but it'll have to do.

Enjoy the Sigma 35/1.4 - by all accounts, it's an excellent lens and I expect you'll find it trumps the Canon 35L in many ways.

 

[Meh]

So, your actual answer to my question is, "No, I will not admit that I am wrong."

Why would he, he now has his "special case" to yammer on about to avoid dealing with his mistakes. The most entertaining part is that the special case was suggested by someone else as a possible explanation for what he meant and now he adopts it like it's what he was talking about all along.

ETTR ... Expose To The Right
YMMV ... Your Mileage May Vary

TMBSITT ... Too Much BS In This Thread

I trust I don't need to spell out what BS means...

You should have mentioned.... Too much NPD in this thread

 

[rpt]

_______
/ \
/ \
/ \
| R I P |
| |
| |
^^^~~~~^^^~~~^^^

 

[sanj]

tre men waiting for a new canon 7d MK2 ?
se you

Hahahaha. Must say this is funny..... really. Good one!

 

[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.

 

[Loswr]

So who am I, Oprah?!?

 

[TheSuede]

[quote author=neuroanatomist]

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?
[/quote]
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.