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Messages - neuroanatomist

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6511
EOS Bodies - For Stills / Re: ISO 50
« 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.

6512
EOS Bodies - For Stills / Re: ISO 50
« 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.

6513
EOS Bodies - For Stills / Re: ISO 50
« 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.

6514
EOS Bodies - For Stills / Re: ISO 50
« 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.

6515
Lighting / Re: Fastest Sync Speed
« on: January 22, 2013, 11:58:02 PM »
Willing to use a smaller sensor?  The PowerShot G15 syncs at 1/2000 s (electronic shutter).  Willing to switch brands and shoot only at 35mm? The Sony RX-1 has a FF sensor and 1/2000 s X-sync.

But if you stick with a Canon dSLR, your best bet is to knock down the ambient sunlight with an ND filter (maybe a CPL, too), and light the subject with a few Einsteins.

6516
Lenses / Re: 70-200 IS2 + Canon 1.4x teleconverter question
« on: January 22, 2013, 11:01:34 PM »
A 70-200mm f/2.8 lens with a 1.4x TC becomes a 98-280mm f/4 lens.  With a 2x TC, it becomes a 140-400mm f/5.6 lens.  A TC doesn't change the minimum focus distance, so it increases the maximum magnification of the lens by the TC factor (1.4x or 2x).

6517
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 10:38:19 PM »
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.

6518
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 10:31:19 PM »
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.

6519
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 09:32:50 PM »
The time 0324 here in Sweden,
if you Neuro tell another person they are wrong
please point at the errors.

I have. Many times  I'd suggest the late hour is affecting your reading comprehension, but since I've told you several times now, at various times, that's not it.

In previous posts, you accused others of not being able to admit when they are wrong, and questioned our ability to read.  Ironic, isn't it...

6520
EOS Bodies - For Stills / Re: I love big gear
« on: January 22, 2013, 09:27:26 PM »
So you can keep your puny girly man Leica; it's a DSLR for me anyway.

LOL.

I agree.  This is why I don't see the point in a G-series type camera, for me.  The PowerShot S100 fits in the pocket of a tight pair of jeans.  That's my definition of 'small' and 'easy to carry'.  Any bigger than that, it might as well be a 1-series body and a bag of lenses....so usually, it is.

6521
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 09:20:05 PM »
That they gain a head room and a better reproduction of the high lights if they shoot JPG  and don't know raw, under or over  exposure, post processing etc .

no -- that is not the mechanism that is the  benefit.  how will you explain the HTP mechanism, the effect of exposure, and the number of photons striking the sensor.
I have just done that  both by text  and by and illustration. Now its up to you and understand  :)

I don't think you have, Mikael.  Here is the question again:  when the camera's ISO dial is set to something besides 100 (I mean it it is set to 160, 200, 400, or 800 or 1600, etc. etc.) how will you explain the HTT mechanism, the effect upon exposure and the number of photons striking the sensor?

My point from earlier, the explanation is 'right' in the same way a broken analog clock is 'right' twice a day. 

6522
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 09:13:02 PM »
My dear Neuro, do not tell me I am wrong with out  pointing out what is wrong.
short please
point by point

As you seem so fond of saying: Re-read my earlier posts.

There is no point by point, there is one point.

The 'mechanism of HTP' has nothing to do with altering the amount of light or number of photons hitting the sensor. Yet, no less than 5 times, you stated that it does.

6523
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 08:52:29 PM »
That they gain a head room and a better reproduction of the high lights if they shoot JPG  and don't know raw, under or over  exposure, post processing etc .

no -- that is not the mechanism that is the  benefit.  how will you explain the HTP mechanism, the effect of exposure, and the number of photons striking the sensor.

It would be so much easier if Mikael would simply admit that he was wrong in stating that the mechanism of HTP has anything to do with altering the amount of light or number of photons hitting the sensor.  But he won't. He will hand-wave, ignore his error, deny that he made statements which are recorded in the thread, respond indirectly, seemingly anything to avoid admitting error.  Some people are like that, there's a neuropsychological term for it, but it's not really relevant. 

Bottom line, Mikael is right about many things, but wrong about this.  Most of us know it.  Fortunately, for those reading this thread who lack a proper understanding of HTP, his mistake concerns the 'how' and not the 'what', and in this case the 'what' is much more important, so the impact of Mikeal's error is low.

6524
EOS Bodies / Re: EOS-1D X Firmware Specifcations
« on: January 22, 2013, 04:29:18 PM »
I tried the camera out at B&H photo the red light did not light in one shot mode but it worked it AI Servo mode.  I'm not knocking the camera... That monster ripped out some frames in that mode

Sorry, but that's what we call a wetware problem, i.e. The source of the problem is holding the camera.  ;)

AF points can light up in One Shot.  There is a setting that controls that behavior, it can either be off, auto (in which case the camera determines whether it should light up the AF point, depending on the available light level), or always on.  So, presumably, it was either set to off or auto in a bright enough environment, when you tested the camera out.

One-shot mode was never the problem, the problem was in Servo mode where the AF points would not light up during tracking. That problem was addressed with a previous firmware update.

So, the problem you identified...isn't - no need for a fix.  :)

6525
EOS Bodies / Re: EOS-1D X Firmware Specifcations
« on: January 22, 2013, 03:55:45 PM »
I hope they fix the focus point (red) for the one shot mode soon.

What's the problem with the focus points lighting up red in One Shot?

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