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Messages - neuroanatomist

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6271
EOS Bodies / Re: Yet Another 5D vs 7D Question
« on: January 22, 2013, 10:10:49 AM »
Quite a while back, I formally tested the 5DII vs. 7D, and came to the conclusion that there was no significant IQ difference between an image taken with the 7D and an image taken from the same distance with the same lens (100L) on the 5DII, then cropped to the FoV of the 7D.  The only difference was that the 7D image was 18 MP, and the 5DII image was just over 8 MP - so, if 8 MP is sufficient for the intended output, there's no advantage to the APS-C.

Note that I'm comparing in a 'focal length limited' scenario - if you fill the frame with the subject on both cameras, the FF is the clear winner (compare the 7D to 5DIII or 7D to 1D X with the frame filled, i.e. closer with the FF)

More recently, I tested my 1D X vs. 7D with the same motive as yours - use with a 600 II, considering teleconverters as well (and the ability to AF at f/8 vs. f/5.6 on the 7D).  Comparing at the same focal length (bare lens or 1.4xIII), at low ISOs the 7D has a very slight advantage in terms of IQ.  But that advantage is offset by the better AF of the 1D X (shared by the 5DIII).  As you raise the ISO, the 7D is the clear loser - to me, that's a key factor, because at f/4 or f/5.6 with fast subjects, you often need pretty high ISO.  I can shoot the 1D X at ISO 6400, and it looks better than ISO 1600 on the 7D. Again, the caveat is that you have fewer MP in the final image from the FF camera if you're cropping.  But 7-8 MP is enough for decently-sized prints (16x24"), so I'm fine with fewer MP.

When you factor in the 2x vs. 1.4x TC to maintain AF, you need to crop the FF only slightly to achieve the same FoV as the 7D.  In that case, the IQ advantage of the FF is even greater and evident at lower ISOs, and that's despite the bigger optical hit with the 2x vs. the 1.4x TC (note: this is on a MkII supertele - I expect the results would be different on a lesser lens, but the MkII superteles take the 2xIII very well).

Like you, I had the 7D and 5DII combo, the former used for birds/wildlife/sports, the latter for pretty much everything else.  After getting the 1D X, I have come to the conclusion that my 7D is superfluous.  Perhaps worth keeping as a backup camera, but else mainly a paperweight.

Hope that helps...

6272
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 09:35:29 AM »
And where  is  my earlier  post?

The one where you made a derogatory remark directed at me?  No doubt it was deleted by a mod.

No it is about words, and what we mean.

HTP is nothing else than while the camera metering for 200iso  the gain is smaller (around 100iso gain) and thereby we get a head room.   ( I describe this as  an under exposure) because the camera  is metering after 200iso)
You get the same effect by under exposing 100iso 1 stop  and later correct the raw file  in the raw converter
In Jpg the camera lay a smoother contrast curve which make a smoother high light reproduction and also lift little bit in lower levels which make the noise little bit more visible.
I hope I have make this message readable so every one can understand

Yes, that's essentially (or maybe exactly) what you've posted previously, and it's clear that you understand the consequences of enabling HTP. 

But it is about words, and many times you used words describing a 'halving of light', 'shorter exposure', and 'the sensor collects less photons' as part of the HTP process, all of which are false.  When that was brought to your attention, you simply restated the same incorrect information.  So while you certainly understand the results of HTP, it's not at all clear that you understand the underlying mechanism, which has nothing to do with altering the amount of light hitting the sensor.  Looking at the responses above, it's evident that I'm not the only one who is aware that you made incorrect statements about the underlying mechanism by which HTP works (i.e., it does not change exposure per se, but only the gain applied).

Regardless, it's clear that you have not acknowledged that you provided wrong information about that mechanism, and I suspect you're unlikely to do so.  That's rather ironic, given that you earlier accused others of being unable to admit their mistakes.  But as I previously stated, I'm not at all surprised by that...

6273
EOS Bodies - For Stills / Re: EOS-1D X Firmware 1.2.1 in the Wild
« on: January 22, 2013, 09:09:58 AM »
EG-S support? :)
Why can't people use Live View? 1Dx has the best AF system in the game, do people really want to compromise that over not wanting to use LV?

If the camera is on a tripod, Live View is definitely preferred.  But usually, when I'm manually focusing it's with a fast prime like the 85mm f/1.2L II.  That combo is pretty heavy - not easy to hold it away from one's body to manually focus in Live View then take a shot, not to mention that such a posture results in increased susceptibility to camera shake.  Manually focusing through the VF allows a 3rd point of contact for better camera support, but it's not optimal for MF since the stock screen doesn't show the true DoF.  Thus, the desire for Eg-S support with proper metering.

6274
EOS Bodies - For Stills / Re: EOS-1D X Firmware 1.2.1 in the Wild
« on: January 22, 2013, 08:21:37 AM »

6275
Site Information / Re: Images not showing - Broken image icon
« on: January 22, 2013, 08:20:37 AM »
Haven't seen this issue.  Perhaps also try clearing your cache. If an image fails to load once, your browser may log that and just display the broken image every subsequent time, even though the image may be able to load at that point. Do note that Vimeo videos do not display within the threads.

6276
EOS Bodies - For Stills / Re: ISO 50
« on: January 22, 2013, 08:05:50 AM »
And not if ISO is reduced by a stop? Does the sensor not reject half the photons when it is 'asked' to be less sensitive?

Dont pounce on me, am learning here...

I can easily see that the amount of light reaching the sensor is a function of shutter/aperture combination. But am confused after that. I thought sensor reacts to the available light based on what ISO is set.
Thx...

No one should be pounced on for trying to learn!

The sensor has no control over the number of photons it collects.  The maximum capacity is determined by the design of the sensor.  Only aperture and shutter open time determine the amount of photons collected during the exposure (up to the max capacity of a photosite, which is when highlight clipping becomes unavoidable).  After an exposure, each photosite is 'read out' and at that point, analog gain (amplification) is applied to the signal according to the ISO set.  In other words, every exposure has the photons being collected at "base ISO" (which is different for different for different sensor designs, but is usually somewhere in the 60 to 200 range).  Following that capture of photons, and conversion to do electrons by the photo site, the signal has been applied (positive or negative, (within the "native" range of ISOs), then the analog signal is converted to a digital signal, and if necessary based on the selected ISO, additional digital gain is applied (for the "expanded" ISOs).

6277
Lenses / Re: CPL + Wide Angle = Sadness
« on: January 22, 2013, 01:46:29 AM »
...you induce that ever-so-nasty local darkening/brightening in the sky -- I've been calling it 'CPL-pseudo vignetting.'  (It didn't really need a term, to be fair.)

Need one or not, the phenomenon is usually referred to as 'uneven polarization'.  :)

6278
Lenses / Re: Canon EF-S 18-200mm F3.5-5.6 IS E-TTL-II compatible?
« on: January 21, 2013, 10:06:47 PM »
DPReview mentions it, and it's listed as E-TTL II distance-transmitting in one of my books (NK Guy's Mastering Canon EOS Flash Photography).

6279
Lenses / Re: Canon EF-S 18-200mm F3.5-5.6 IS E-TTL-II compatible?
« on: January 21, 2013, 08:39:50 PM »
Correct.

6280
Lenses / Re: Canon EF-S 18-200mm F3.5-5.6 IS E-TTL-II compatible?
« on: January 21, 2013, 08:31:17 PM »
Yes, it does.

6281
Lenses / Re: 70-200 f/2.8L IS II Problem
« on: January 21, 2013, 06:35:21 PM »
It will almost certainly have no effect on images. Might affect resale value.  If you can return it to the seller, I'd exchange it...

6282
EOS Bodies - For Stills / Re: ISO 50
« on: January 21, 2013, 05:34:09 PM »
Did I help clear anything up for anybody?

Nice try, but no.  If you choose to believe that Mikael understands clearly and is simply communicating that in a way we aren't comprehending, you're certainly welcome to your belief.  I see no evidence of that, quite the opposite...I see intransigent repetition of the same incorrect statements, but the statements themselves are articulated clearly.  Even if your assumption is correct, I'd say that someone who chooses a specific case that is an exception to the norm to describe a process (and hammers that same point over and over) has at best a limited grasp of the concepts behind that process. 

6283
EOS Bodies - For Stills / Re: ISO 50
« on: January 21, 2013, 04:10:42 PM »
well you can put  the d800, d600  at -6 stops then  you are even safer regarding blowing highlights in all photographic situations, nothing you can do with your cameras-or?

Sure. We've covered the fact that the D800's sensor has better DR than any current Canon sensor, ad infinitum.  Nothing new here.

Still no admission that you are wrong with your repeated statements about HTP working by reducing the amount of light falling on the sensor, 'eh?  Not even after accusing me and others of an inability to admit being wrong, 'eh?  I can't say I'm surprised.  I can't even say I'm disappointed, because I expected no better...

6284
EOS Bodies - For Stills / Re: ISO 50
« on: January 21, 2013, 02:26:03 PM »
LOL. Earlier, it was suggested that it means 'Half The Photons' - that seems to be Mikael's definition, anyway.

 'Half The Photons' is correct IF you concede that enabling HTP raised the effective ISO amplification +1EV from whatever ISO you were at before activating HTP.
so the resultant metering of course causes a -1 EV exposure - and HALF THE PHOTONS! :)

Sorry, but you seem to be falling into the same trap and suffering from the same misconceptions as Mikael.

It's only half the photons if the aperture is set a stop narrower or the shutter speed is set a stop faster. Are you suggesting that enabling HTP directly affects aperture or shutter speed? 

In fact, enabling HTP does nothing to the resultant metering - the camera meters for the ISO you select, it doesn't indicate that it's actually exposing at a 1-stop lower ISO, but it is (and that's why ISO 100 is unavailable with HTP enabled).  Try it - set ISO 200 or higher (but not a H expansion, since those are unavailable with HTP), meter a scene, then toggle HTP and see if the metering changes - does it?  Even in P Mode with Auto ISO where the camera is selecting all the parameters, enabling HTP does not change the aperture, shutter speed, or ISO selected. 

HTP doesn't raise the ISO, unless you have it set lower than ISO 200 before enabling HTP (and if you're at an H expansion ISO, enabling HTP lowers it).  I concede that in the specific case of the camera being set to ISO 100 before enabling HTP, the metered exposure will change by one stop, and IF you are in an auto exposure mode or you manually adjust exposure to compensate by one stop, then the number of photons will be halved.  Also 'halved' applies only if ISO 100 was set - if it was set to 50, 125, or 160, the change will be more or less than one stop (but not 'halved').  But that's a byproduct of how HTP works, applicable in a limited range of circumstances.  To conclude that reducing the photons by half is the mechanism by which HTP works is like concluding that a stopped analog clock is keeping correct time because you just happened to look at it at whatever time at which it was stuck.

As for misunderstanding Mikael, as I indicated earlier and Meh just wrote, that's clearly not the case.  He specifically stated, at least five times in at least four different posts, that HTP halves the number of photons and/or the amount of light hitting the sensor, and used that phrasing in describing the mechanism of HTP.  That manifestly demonstrates that his understanding of how HTP really works is seriously flawed, and if you are supporting that explanation, you are also failing to understand how HTP works.

6285
EOS Bodies - For Stills / Re: ISO 50
« on: January 21, 2013, 11:48:09 AM »
Maybe it's an especially contrasty scene, and a single stop of ETTL isn't enough to keep those highlights you're so interested in, so you'll want to underexpose not by one stop but by two stops, for example.

I eagerly await Mikael's comment that in such a situation, one should instead use a D800 where the motive can be to underexpose by four stops and allow bringing up of shadows without motive of banding and noise.  I understand the technique works very well for sunrises, sunsets, cluttered sheds, and barbecues with QPcards on them.

EDIT: too late, Mikael beat me to the punch.  ???

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