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Messages - dlleno

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346
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 31, 2012, 07:20:27 PM »
Dude Mt. Spokane thats no good.  I've got industrial noise and age related losses that frustrate my wife,  but nothing like you or rush limbaugh.  these outside-the-box methods are awesome and still emerging, to be sure ,and I certainly hope you are able to find some relief or improvement! 

@ Tron/AdamJ  lol forgive my reversion back to the technical -- I'd say that if you can't hear it, and you're hearing is ok/normal for your age, , then that is good!  Best case is that a teen-aged girl can't hear the sensor cleaning routine :D  then you know that no parasitic resonances are happening in the camera!   


347
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 31, 2012, 02:32:57 PM »
definately lots we don't know about the abiity of humans to perceive or detect external stimulii of various sorts (especially at high energy levels) in ways that are perceived to be 'hearing'.   thats for sure --  total agreement there.  For example, the ability to detect the application of mechanical energy directly to parts of the body (like vibrating the skull at ultrasonic frequencies) is amusing, too.  Imagine the variance among individuals, i.e. size of the head, bone density, etc, etc.  and maybe those with 5D3s can try pressing their cameras bodies against their heads!

The physiology and mechanics of detecing low levels of true acoustic energy transmitted via air ("hearing") is relatively well understood though, and more closely applies to the phenomena of hearing the sensor being cleaned. 


this has been a cool thread, actually, an amusing departure from Dxo scores arguments :D 

348
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 31, 2012, 01:17:02 PM »
People can generally not hear ultrasonic tones, but they can dectect pulse trains at much higher than ultrasonic frequencies.  They sound like a chirp.
 
http://grouper.ieee.org/groups/scc28/sc4/Human%20Perception%20FINAL.pdf


This is a fascinating study, but it is not about detecting ultrasonic tones and doesn't really apply to the subject of ultrasonic hearing.  The study is about human sensitivity to and detection of pulsed radio frequency energy, an energy which consists of oscillating electric and magnetic fields that travel in free (empty) space without air.  This is the energy that, for example  lives in the Amateur radio bands, well above the FM broadcast band for example,  and well into the microwave region.  This is the type of energy that eminates from Television brodcast antennas, cell phone towers, cordless phones, your laptop's WiFi system, and microwave repeaters.  The study is not about ultrasonic "tones" and it is not about acoustic energy.

Acoustic energy (sound) consists of mechanical pressure waves and cannot be transmitted without a medium (such as air or water).  This type of mechanical energy requires an energy source of mechanical origin -- something, like a speaker cone, clapping hands, or Placido Domingo's vocal chords, has to move the air.   The energy used to clean the sensor is acoustic in nature -- this energy is vibrating the bejeebers out of somethign (the sensor) to shake dust loose.  In this sense, we can think of the sensor as a really high frequency tweeter that no one can hear.  In any case,  if the acoustic energy emitted by the camera  is within the set of frequencies to which your ears are sensitive, you will hear something but it won't be the 100Khz cleaning frequency itself.    The question is -- how can a sensor cleaning device operating at six times the upper threshhold of human hearing result in an audible sound? 

by far the best insight into what actually happens in sensor cleaning has been provided by TAF .  Very nice info sir!  TAF showed that the fundamental acoustic energy of the cleaning routine sweeps from 100KHz to 125HKz and back.  there is no way that any human being of natural orgins and abilities can hear this. The acoustic pressure waves reaching the ear just do not produce any response from the eardrum. no way.

of course, if you blast your head with a tremendous high-energy assult of air pressure waves at 100KHz, something is bound to happen internally (to your body)  that can be detected.  but this is not what is happening with the tiny little speaker we know as the sensor cleaning routine.  its a tiny little tweeter producing a very small amount of acoustic energy at frequencies that no one can hear.   

what is far more likely, as TAF has rightly pointed out, is that there is some sympathetic or natural mechanical resonance that occurs within the camera structure itself -- much like the vibrations you hear from your dashboard when driving on certain roads...  The structures themselves are responding at some subharmonic (a sub multiple of the 100KHz fundamental) that is within the range of human hearing.  Note that if this sub-harmonic were present naturally in the sensor cleaning function itself you would hear a high-pitched tone that would sweep up and then back down, perhaps at the 7th or even 8th subharmonic (something between 12Khz and 18 KHz) The fact that no one has reported hearing a smooth frequency sweep is clear evidence to me that TAF is right --  there are fixed frequency mechanical resonances in the camera that will respond, some more than others, when the cleaning "sweep" reaches the right point in its sweep.  Note that if there are two or more natural structural resonances within the camera, then you will hear two or more distinct tones or perhaps they will sound like chirps.  in any case, you are not hearing the sensor cleaning function, you are hearing an artifact or side-effect of it.

what is clear to me , based on the above, is that  (1) there is  a very wide variation from camera to camera structural resonances, and owner to owner hearing abilities,  with respect to what is actually heard during the cleaning routine, and (2) human hearing cannot possibly be used to measure the presence of or effectiveness of the cleaning routine because the cleaning routine itself cannot be heard!. If you hear something, then your ears are sensitive to whatever frequencies your camera's internal structures are vibrating at.  Thats about it :D .  Moreover, when you compare your audible results with someone else, then you are not comparing your respective cleaning systems, you are comparing your own hearing sensitivies and the natural structural resonances present in your respective camera bodies :D

349
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 30, 2012, 08:42:32 PM »
I just took some measurements, and my 5D3 sensor cleaning 'sound' is a series of two smooth frequency sweeps from 100 kHz up to about 125 kHz and back down.

So I would conclude you are hearing some structure in the camera vibrating, and not the actual signal.

indeed, given this data,  it is probably sympathetic resonance.  so the sweeps themselves -- is this a single tone sweep or what is the bandwidth of the signal that sweeps through 100KHz to 125KHz?  I take it you were measuring with a wide band audio spectrum analyzer, measuring actual acoustic energy? 

the "vibrating structure" theory aligns well with the 'shifting chirp' experience as well -- the structure exhibits a natural harmonic resonance at two distinct frequencies as the source sweeps through its range.

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As an aside, although very few people can hear much beyond 20 kHz in free space, almost everyone can hear to ~40 kHz if the sound is directly coupled to their head ie: via bone conduction.  Dukane makes acoustic devices used to find the 'black boxes' from crashed aircraft underwater that ping at 37 kHz, and if one is held behind the ear, I've never met anyone who couldn't hear it loud and painfully clearly.  And it isn't just the pop of the pulse, you 'hear' the tone.

fascinating.  If he sound energy demonstrably above 20KHz is experienced and detected by a  human subject of natural abilities and origins, then it is either a sub harmonic, or it is not detected by the auditory nerve via exitation of the eardrum,  which is of course the basis of the "20Hz - 20 KHz" range of human hearing.  Conduction via bone structures is an entirely different mode of detection, which could include sub-harmonic exitation of those bone structures or even the eardrum itself,  which in this case would easily fall within the auditory range anyway.  Also -- sub or supersonic energy can easily be detected, or "felt" even when it is not heard tonally, especially if one's skull is subjected to such a direct mechanical assult :D

Incidently -- on the other end of the sonic spectrum, the lowest fundamental frequency of the largest pipe organ is 8 Hz, which is present on only a few organs in the world.  Such a pipe is there not because anyone can hear it,  but because they can feel it. 

now then, everyone go out and hold your 5D3 up to your skull during the cleaning routine and tell us what you hear!

350
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 26, 2012, 02:39:42 AM »
just to get anal about this...I'm not aware of any convincing evidence that any human can hear into the ultrasonic region, which of course is why they call it ultrasonic.  Not many of us, save perhaps young girls, can hear above 18K, and the world above 20K is just not audible to anyone of normal orgins :D .  Males above 20-ish and above rarely hear above 18K.

Frequencies in near ultra-sonic region are not usually identified as having a pitch either -- energy in this range contributes to tonal character and timre via harmonics but typically not pitch.  Thus the report of an audible chirp that changes pitch is clear evidence to me that this not at all ultrasonic energy detected by extraordinarily gifted hearing ability --it is sonic energy in the ordinary audible range. 

Baring some spurious mechanical resonance within the camera itself  there are only two possibilities:

1.  intermodulation distortion -- the combination of two or more frequencies above 20K, producing sum and difference frequencies, can result in sonic artifacts that can be heard (Otherwise, audiophiles and would not care about filtering energy above 20K).   For example, if the mechanical nuances of the sensor and the  ultrasonic mechanism that drives it were to produce  two tones at 40K and 25K (both inaudible), then the combination would produce an artifact at 15K which would be audible.  I suspect the spectral components of the actual sensor cleaning energy is quite broad (not just one frequency), not to mention dynamic, so this is entirely possible.

2.  The Canon system produces energy directly in the audible region.  I find this unlikely

351
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 25, 2012, 09:33:05 PM »
I doubt that the fundamental or primary ultrasonics are audible to any human, -- unless the distribution of cleaning frequencies is really that broad and some statistically small number of bodies do produce audibles (doubtful).   what seems more likely is some subharmonic resonance or other secondary artifact.  wouldn't hurt to ask Canon about it but I suspect its no issue. If you're really feeling anal you could experiment to see if what you are hearing is a mechanical artifact  -- for example you could take out the memory card(s) just to see if that has any effect and you could  plug stuff into the various electrical connectors while running the cleaning routine to see if this has any noise damping effect. 

352
EOS Bodies / Re: Are there 39mp & 50mp+ Test Bodies in the Wild? [CR1]
« on: October 23, 2012, 10:53:30 AM »
I can't even believe you just said that.  So, adding a TC reduces optical spacial resolution?  Better throw them all out then.

A TC doesn't change optical resolution.

Lee Jay -- are you really saying that the TC will not introduce diffraction artifacts due to the change in aperture, and that the additional glass elements will present or expose no further optical abberations in the image presented to the  sensor?  Please do explain the conditions under which modifying the optical system by adding a piece of glass cannot change it's optical resolution properties. 

353
EOS Bodies / Re: Are there 39mp & 50mp+ Test Bodies in the Wild? [CR1]
« on: October 23, 2012, 05:12:59 AM »
As for the question posed by PerfectSage, there does appear to be a real and practical answer, or at least rule of thumb, which would guide one towards the goal of advantaging all of that 116 lp/mm resolving power of the 7D sensor, and that is to choose optics that will present an image to the sensor with enough inherent detail.   if the source image truly does not contain the detail, the sensor will not find any that isn't there.  Whether or not that goal is a good one or not can be debated of course

Technically speaking, there is an asymptotic relationship in terms of spatial resolution. You can never actually achieve the same spatial resolution as the highest resolving component in an optical system. As you approach it, you begin to experience diminishing returns. Lets say you have a lens capable of resolving 86lp/mm. Nothing you ever do can ever allow you to resolve 86.1lp/mm...your upper bound is the resolution of the lens itself. At best, you could reach 85.99999999999... lp/mm, assuming you had a sensor with literally infinite resolution. You would need something like an f/0.3 lens to resolve around 115lp/mm of resolution, and approach the 116lp/mm of the 7D. Total "system spatial resolution" is derived from the RMS of the "blur circle" of each component in an optical system. The size of the airy disc at a given aperture in the lens, blur introduced by any and all TC's, the size of a pixel in the sensor, and if you want to get really accurate, the size of the blur introduced by low-pass and IR cut filters. Taking the RMS of each of those will give the the size of the blurry disc of a single point light source resolved by the entire system. Taking the reciprocal of that divided by two will give you the spatial resolution of the system as a whole in lp/mm.

very nice explanation Jrista, and the first coherant technical epistle I've seen here regarding the effects of lens choice as regards the resolving power of the sensor, both the contribution of individual components and the asymptotic behavior of the function.   Essentially, the 1/(2  * RMS) method suggests that when one component in the system is replaced by one that is significantly worse than the previous aggregate, that the effects will probabaly be noticed.  Moreover, the effect of such a substitution will be more noticeable with there are fewer components in the system.  Accordingly, using the approximation of only two components (the sensor/lpf and the lens), one can easily see that the choice of lens will influence the overall resolving power of the system.  Captain obvious, to be sure, but one could model the equation and see the effects (on end-2-end resolving power) of choosing one lens over another, an excersize left "to the reader", lol. .  I suspect most would rather look at photos though :D

354
EOS Bodies / Re: do crop sensors really add reach?
« on: October 22, 2012, 05:31:26 PM »
While we got sidetracked from the OP's origional question, to me the answer is that the OP would benifit more from the superior AF system of the 7D than a full frame 5D II, provided wildlife is the driving factor.

Totally agree, with the added benefit that the 7D will produce more detailed photos on top of the better AF.

provided distance limited wildlife is the driving factor, and where the OP as met the optimum conditions including glass, light,  and support to take advantage of the 7D resolution. 

355
EOS Bodies / Re: Are there 39mp & 50mp+ Test Bodies in the Wild? [CR1]
« on: October 22, 2012, 05:17:24 PM »

nicely articulated Jrista.   a clarification pls on a related topic:

... A teleconverter does not change ... the resolution of the lens. 

but it can change the optical resolution of the optical system
Quote

...If you use a TC or multiple TC's that reduce your aperture to f/8, then according to the laws of physics spatial resolution becomes limited (specifically to around 86lp/mm)

You're refering to diffraction artifacts here, but for example a bad 1.4TC on an f/2.8 lens introduces new optical elements and hence the potential for a reduction in resolution of the optical system, still avoiding any diffraction related side effects caused by a narrow aperture. 

As for the question posed by PerfectSage, there does appear to be a real and practical answer, or at least rule of thumb, which would guide one towards the goal of advantaging all of that 116 lp/mm resolving power of the 7D sensor, and that is to choose optics that will present an image to the sensor with enough inherent detail.   if the source image truly does not contain the detail, the sensor will not find any that isn't there.  Whether or not that goal is a good one or not can be debated of course

356
EOS Bodies / Re: Are there 39mp & 50mp+ Test Bodies in the Wild? [CR1]
« on: October 22, 2012, 02:47:14 PM »
for additional techical discussion on the topic of line pairs per mm and sensor resolving power, see this thread

http://www.canonrumors.com/forum/index.php?topic=3393.0

in which Jrista reports that for the 116 lp/mm resolving power of the 18mp sensor itself,  "The extremely high resolution of the 7D also means that outside of the best of the most recent Canon L-series lenses, namely Mark II's and new designs like the 8-15mm L Fisheye, the 7D is very likely outresolving most lenses except for their very centers"  Sorry Jrista I yanked that out of the above thread without quoting properly. 

so -- to me this means if you show Jrista a lens with less than 116 lp/mm resolving power in the center, at apertures that are abberation limited**, then he will show you a lens that is not capable of taking advantage of the 18mp sensor resolving power. 

** means a limitation of the glass itself, i.e. not due to small apertures which introduce diffraction and futher loss of resolving power.

357
EOS Bodies / Re: Canon 5DIII for $3200 @ BnH
« on: October 22, 2012, 02:39:58 PM »
the kit price has also come down nicely by about $500 as well

358
EOS Bodies / Re: Are there 39mp & 50mp+ Test Bodies in the Wild? [CR1]
« on: October 22, 2012, 02:38:50 PM »
My question, as I'm not an optics expert, is once you get into that realm of 30+ (if not before), how many current EF lenses are going to be able to leverage that sensor fully?

keep in mind that the latest Rebel is like 48MP FF equivalent

I don't have the answer either, but the pixel density of the all the latest 18mp crop bodies will probably eclipse some EF lenses, not to mention field techniques and less-than-optimum support.  Jrista has pointed out that with optically the best (arguably) lens known to man (the 300mm f/2.8) and a tripod he can extract all of that resolving power.  Someone with a deep knowledge of optical resolving power will have to chime in on this topic, but  PerfectSavage you are raising a good point which needs a more precise answer. 

359
EOS Bodies / Re: do crop sensors really add reach?
« on: October 19, 2012, 06:23:26 PM »
As for the 1.4x TC on 5D2 vs a bare lens on the 7D, I'm not sure. I think the 7D is more like a 1.9x crop factor or so so 1.4x TC would still be a ways off, granted the 7Ds heavy split greens make it a trace softer at 100% for a rtypical 18MP APS-C but I tend to doubt that would make up for that much, but I'd have to check and my numbers may be off, just going by vague recollection.


if the 7D's crop factor deviates substantially from Canons 1.6x, that would be good to know :D .    That aside, the various different results discussed here are interesting to note.  Some are reporting equivalent IQ when the 5D2 image is cropped to match the 7D FOV.  Accepting that, the 1.x4x TC on the the 5D2 would easily outrun a 7D with the bare lens, assuming good optics of course, becasue this approach advantages the FF. 

I think there is some confusion over terms as well.  when I refer to FOV being important in distance limited situations, I refer to the goal of the final output.  regardless of the tool employed, if the desire is an 11x14 print of the moose portrait, then you will crop the image in post to whatever level it takes to acheive the right framing and FOV that meets the objective of the photo, and then you will size the final output to 11x14.  In this situation the FF image will be cropped to about 39% of the original number of pixels, compared to the 7D.  It is astonishing that an 8mp image from the cropped 5D2 can be convincing against the 18mp impage from the 7D. 

When you look at numbers, the 7D wins substantially over the cropped 5D2,.  when you look at photos, the result is apparently much different. 

360
EOS Bodies / Re: do crop sensors really add reach?
« on: October 19, 2012, 03:56:35 PM »
And the thing is, if you say the 7D has no reach advantage over a 5D2 then you must also agree that usage of TCs is always a waste....

First of all, the money shots :D  there can't be compared meaningfully because they are not the same FOV, and therefore do not target the same output result.   For the purpose of advising the OP we are talking about the final output IQ of a 5D2 image that has been cropped to match the FOV of the 7D or t2i.  One has to ignore the pixel count and pixel densities, because these numbers by themselves do not meaningfully predict the outcome of such as test. 

No, the OP is asking about reach, what he can do when distance limited, nobody cares about your FOV when you are distance limited, FOV is meaningless when you are distance limited.

well, the OP was asking about effective reach with existing lenses on a FF body, in the context of cropping the FF image to yield equivalent final output of the crop body.  For this objective, equivalent FOV and IQ of the final equivalent-size output is the measure of success. 
Quote

He wasn't asking about what lens to use to get a certain landscape shot to give him the same FOV shot from the same spot.

correct;   In the paragraph that follows, I point out how different this is from the OP's objecitve.
Quote
Quote
secondly, I have to admit I'm struggling a bit to see the equivalence of using optical multpliers versus cropping the final image.  The comparison is interesting, to be sure, and valuable in its own right, but is not nearly as simplistic as stated. To be sure, optical multiplication introduces side-effects of its own but these are heavily dependant on the TC itself and the native lens to which it is attached.  Taking those into account, the advantage is that with careful choices one can present a larger image magnification to the sensor,  decreasing the FOV opticallly while taking full advantage of the sensor's native resolution and IQ.  This technique will advantage the FF body, and represents a very different test case than the OP has presented.   For example, take a photo, properly exposed and framed of course,  with the t2i and a 300 f/2.8 lens.  Then add the 1.4 III to the lens and mount the combination on the 5D2 body and crop the resultant image to match the 1.6 crop factor of the t2i.  is there any doubt as to which will produce a superior result in more situations?  To take the experiment further -- mount a 2x III to the 300 f/2.8 and take a photo with the 5d2, then take the TC off and take the same photo with the t2i, croping the result to match the FOV.  5D2 wins.

a single 1.4x TC won't even quite make up for teh 7D reach advantage and here is the point if you can manage to get close enough to the subject with whatever lens and TC you have then you are not reach limited

extending the results that have been posted here, the 1.4x TC on high quality native glass will produce a better image than the 7D using the same lens without the TC, even accounting for the necessary crop of the FF image to obtain the same FOV 
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when you are limited then he just pops the 1.4x or 2x TC on his 300 2.8 and shoots with his t2i and then does better than his 5D2 with that same combo being shot on his distant bird or moose or t rex or whatever

thats the point in question:  will the t2i really do better than the 5D2 with the same optical system attached?  The point of results posted earlier is that cropping the 5D2 image to produce the same final output size produces IQ that is remarkably similar to the 7D, with perhaps only a small (if any) advantage to the 7D.  That result may be debateable, but is the basis of my point.

if he has a 1.4x and not using it, then he is not distance limited. You are only distance limited when the same optical system is used on both cameras.   The point of results posted earlier is that when truly distance limited, the FF image can be cropped to the same FOV of the 7D and produce results that are better than the numbers imply.

Therefore, if you are not distance limited for the 7D, and you have a 1.4x in your pocket, then adding the 1.4x to the 5D2  should produce even better results than the 7D because the 5D image requires only a small amount of crop in post to acheive the same FOV.

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