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Messages - neuroanatomist

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6286
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 05:56:51 PM »
What is it  you Neuro  and TrumpetPower not understand ?

Well, I'd like to say I don't understand your rudeness and steadfast refusal to admit when you're wrong, but I'm afraid I understand them all too well.

You say read your earlier comments?  Ok.

I read that you stated HTP halves the amount of light.  Do you believe that? 

The data recorded by the sensor (and, presumably, written to the raw file) is identical for ISO 50 and ISO 100; all that's changed is the meter is told to overexpose by a stop and the raw processing engine is told to underexpose by a stop.

no they are not
At 100iso  with the same metering the   sensor charge  is under 100 %  and at the read out =before overload and  clipping
with 50iso your double the time  or open up the lens 1 stop and therefore blow one stop of highlight.

I read that you stated that ISO 50 changes shutter speed or aperture by one stop. Do you believe that?

Neuro
put your camera in front of a white wall, see what you get for values ​​at 100 iso then compare with 50iso
you will find that the exemplel 1/60sec f-5.6 will be with 50iso 1/60 sec f-4, 0 = 1 stop richer exposed compared to 100iso and you lose 1 stop of high light

I'm talking about the RAW file, not the metering.  Unless I change the aperture or shutter, or let the camera do that (in an auto exposure mode like Av or Tv), there will be no difference in the sensor-derived image data between ISO 50 and ISO 100. Both are ISO 100 exposures, tthe ISO 50 data will merely be pulled down a stop by the RAW engine.

As for HTP, it's possible we're saying the same thing in different ways about the what (HTP ISO 200 is actually being underexposed at ISO 100 then brought back up).  But where you seem to be wrong is the when - your contention is apparently that the data are altered on the sensor.  Perhaps I misunderstand you, and you are referring to the actual ISO 100 exposure when ISO 200 is set in camera as that alteration. But what I'm saying, and TrumpetPower is saying, is that the HTP ISO 200 exposure RAW file is the same as an ISO 100 (non HTP) RAW file, and your statement that, "you halve the number of electrons" indicates you believe the RAW file is different. If you mean relative to an actual ISO 200 (non HTP) exposure, fine - but that's not what we've been talking about. 

If you mean ISO 100 RAW is different than HTP ISO 200 RAW, that's wrong, and if you think that's what the page you linked and keep on re-quoting is saying, you're misinterpreting it. It states: "In post-processing, the image data can be brought back up while preserving the highlights with a modified tone curve...."  Post-processing, not the RAW data file, as your statement about halving the number of electrons indicates. There is no change in the number of electrons between ISO 100 and HTP ISO 200, both are ISO 100 exposures, same number of electrons, just handled differently in post.  If you don't understand that, perhaps you should re-read those links of yours.

6287
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 03:19:45 PM »
HTP. it is a halving of infaling light

I think you must study the subject and understand how iso gain works together with full charge and then what it means by 200 iso= halving the number of electrons.

Which are we halving? Light or electrons? Are you going to admit being wrong about the light being halved, or just accuse others of not being able to admit when they're wrong?

Interestingly, I notice that you're consistently ignoring my question about ISO 50 changing aperture/shutter values...

last time I was answering you when you also where totally wrong I was turned off because of my language.it will not happen this time.

Questioning our ability to read, as I stated, is highly insulting, especially the fact that you took the time to edit your post to bold that remark.  It seems you have a history of insulting behavior here, which resulted in past consequences and yet continues. 

6288
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 02:41:56 PM »
No problem admitting when I am wrong.  But I'm not.

You stated:
HTP. it is a halving of infaling light

That's flat out wrong. The light is not being halved, rather, as we and the page you linked correctly state, the gain is being halved, relative to the selected ISO value.

Further, you suggested that setting ISO 50 changes time value and/or aperture...and that's wrong, as well.

6289
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 02:02:14 PM »
can you boys read?
http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html

it is hard  to discuss HTP etc if you do not know what it means


Can you not be insulting, boy?

6290
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 12:36:30 PM »
Well Neuro, read again what Im answering earlier, Im going to the gym for a hour , we can discuss it later

I don't need to read the same incorrect statements again, thanks.  Enjoy your workout!

6291
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 12:31:25 PM »
well then take a look what happening with HTP , 100 iso exposed as a 200iso exposure= under exposed and later adjusted .
not the same signal from the sensor ( and do nor mix apples with bananas this time)

The point is that ISO 50, ISO 100, and HTP ISO 200 are the same analog gain at the sensor, and if the aperture and shutter speed are held constant, the RAW data coming out of the ADC are the same for all three ISO settings.

regarding 50iso and 100 iso= not the same parameters regarding time

You're saying if I set my aperture and shutter in M mode, and then change from ISO 100 to ISO 50, my exposure time or aperture will change?  I'd like to see some evidence for that...

6292
EOS Bodies - For Stills / Re: ISO 50
« on: January 20, 2013, 12:19:40 PM »
the only purpose the sensor has is to collecting photons
agree?

Disagree - it does more.  The photon wells collect photons, there is a lot of additional circuitry on a sensor besides just the photon wells.

TrumpetPower is absolutely correct in his statement that, "ISO 50 and highlight tone priority are two special cases. The exact same analog signal amplification (i.e., none) is applied with all three exposures: ISO 50, ISO 100, and ISO 200 w/ HTP. If you use the same shutter speed and aperture, you'll get the exact same raw file in all three cases." (well, almost correct - the base ISO isn't exactly 100 for all sensors, so even at ISO 100, some gain may be applied - but it is the same gain in all three cases).  He's also correct about ISO 50 being a linear 50% reduction, but incorrect about HTP being a linear doubling (HTP processing is application of a tone curve to boost the shadows and midtones but not the highlights).
 
HTP. it is a halving of infaling light= halving of the amount of charged  electrons= go from 100 to 200 iso and make a head room, the analog signal is different = 100iso and 200 iso
Agree?

Disagree.  When you set ISO 200 with HTP, the camera is actually exposing at ISO 100, which is why ISO 100 cannot be set with HTP on, but (incorrectly) reporting ISO 200 in the metadata and setting the HTP flag.  If you open an HTP RAW file in something like Rawnalyze, you'll see it's a stop underexposed - it's not halving the incoming light, it's reducing the analog gain applied to the same amount of light, by one stop.

6293
Indeed, if you keep lens and distance constant, APS-C will give you lots more detail....

Yes, at low ISO.  But once you raise the ISO a bit, the FF delivers more detail in focal length-limited situations.

6294
EOS Bodies / Re: Patent: Noise & Aliasing Reduction for Small Pixels
« on: January 20, 2013, 11:55:10 AM »
Don't expect much from the 7D II somehow - except delays - perhaps even the same old sensor. Well you can't have everything!

Not that Canon hasn't done some unfathomably stupid things, but I can't see the 7D's sensor in a 7DII.  The 7D is all that and a bag of chips...except for the high ISO noise.

6295
EOS Bodies / Re: Patent: Noise & Aliasing Reduction for Small Pixels
« on: January 20, 2013, 11:25:14 AM »
as you can read the patent was filed 2011 and granted in 2013.
I read the CR post which only told me Canon had filed for a patent. Not a news post, I guess...

The public doesn't find out about patents when they're filed, we find out when they are published - 18 months after they are filed.

6296
EOS Bodies - For Stills / Re: My next upgrade...
« on: January 20, 2013, 11:19:26 AM »
Have to disagree about the Traveler. The 1542T is 3.5" taller extended than the 1541T. I like that 3.5" on the extended end more than I don't like it on the collapsed end. I have an Acratech GPS on top and the setup folds to 23".  The TQC-14 is half a pound heavier, and, more importantly, costs $370 more...

It really comes down to personal need, I think. 23" collapsed is too long for me - my travel tripod+head needs to fit inside a carryon hard case like my Storm im2500, and the RRS set does that (even when in its custom-fit bag).  I usually ignore the center column when looking at extended height - even the best center column adds too much vibration for me (try some testing with the center column down vs. up), so I consider center columns as 'raise in case of emergency only' and for that, the extra couple inches of the TQC-14 (center column down) helps. 

6297
Reviews / Re: Review - Canon EF 70-200 f/2.8L IS II
« on: January 20, 2013, 10:51:04 AM »
@ Viggo - Unfortunately, it seems you may have gotten a dud. You say you bought this copy used, I wonder if the seller fully disclosed the motive behind sale?

6298
EOS Bodies - For Stills / Re: 7D vs 5D mk2 trade off?
« on: January 20, 2013, 10:14:04 AM »
well, too bloody late now to reply. sold it. gonna get me a 5Dii

Well, ok then.  :)

From an IQ standpoint, the 5DII is far better than the 7D, and quite similar to the 5DIII. From an AF standpoint, you may be in for a rude shock, depending on your needs/habits. The 5DII's center AF point is good, outer points are not good at all (even your 60D had better overall AF performance). 

Having used both the 7D and 5DII for a couple of years, I don't think the poor performance of the 5DII's AF is overstated.  The in-focus shots are great, but the frequency of shots lost to missed AF is high.

6299
EOS Bodies - For Stills / Re: My next upgrade...
« on: January 20, 2013, 08:59:03 AM »
Hm... Yes... Gitzo. I will try that model out tomorrow. I haven't seen Really Right Stuff carried locally unfortunately.

You won't find RRS locally, unless you live in San Luis Obispo, CA - they don't use distributors.  But IMO, the RRS legs are a step up from Gitzo in terms of quality.  The Gitzo 1542T was mentioned, I think Gitzo dropped the ball on that one - they made the center column too long, so the legs don't fold over the ballhead (unlike the 1541T, and I guess they realized their error and released the 1544T, which is a clone of the 1541T).

FWIW, I just picked up RRS' "travel" tripod set, the TQC-14 and BH-30 LR.  The set is 3 lbs, the leg diameters are equivalent to the Gitzo 2-series legs, and while the weight rating of the TQC-14 is a conservative 25 lbs, I can swing my own weight from it...I wouldn't try that with a 1542T!

6300
EOS Bodies - For Stills / Re: Potential upgrade from 7D
« on: January 20, 2013, 08:03:21 AM »
... recently I've found myself cringing at the images taken using the 7D+15-85 combo in low light when it is necessary to bump the ISO up to 3200/4000.

You're using a really low quality lens.

 :o

I don't know that I've ever heard anyone describe the 15-85mm as a 'really low quality' lens.  In fact, it's an excellent lens.  A fast prime lets in more light, allowing lower ISO - but the tradeoff is shallow DoF, maybe too shallow for the image required.

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