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Messages - TAF

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106
Software & Accessories / Re: Canon Protective Filter Question
« on: November 03, 2012, 10:23:44 PM »
It would be interesting to hear reasons for their use on other lenses, beyond an abundance of caution.

I've taken my 70-300L down the beach a few times, to shoot surfers and things, the wind is always blowing a gale down there. Am I going to point my $1500 lens straight into the wind and have the front element sandblasted? Hell no, I point my B&W MRC filter into the wind, it only cost $60 or so, it has no measurable difference on IQ (as i tested on my 7D), and it's Multicoated so no extra flare in *normal* situations (i don't feel like testing it by pointing at the sun).
As to whether it's *needed* for weathersealing? Don't know, don't care. It can't make the sealing *worse*, and since it doesn't make the images worse either, then to me it's a no-brainer.
As for impact damage? Some people will claim that Hoods are better. They may be, it all depends on too many variables of height, floortype, angle, etc. Why not just use both? (And why not just don't drop it?) Hoods help a bit with less flare too. And if i dropped it i'd be more concerned about the IS elements rattling around and the mount breaking off the camera body than the outer elements smashing...

And when I am photographing jet engine tests, in high winds, or any other situation where I expect flying debris will hit the lens I use a protective filter as well.

But the question had become whether they were necessary to complete the weather sealing.  Now I know that some of Canon's lens do require the additional piece be added (very disappointing of Nikon not to go to court; clearly they're off their game).

As for the filter that broke, I never said I dropped it.  I didn't.  I was walking through a doorway in NYC with the camera over my shoulder and got bumped into the door frame.  The evilly  >:( designed Canon lens cap 'ear' got shoved into the filter and it shattered.  Had the filter not been there, the cap ear could not have made it to the front element.  Hence the protective filter cost me a lens.  Unless you live in the countryside, such is an unavoidable risk if you actually carry your camera.

Come to think of it, I have become a hood guy these days.  Never really thought about it until now...

You really should try shooting directly into the sun some time.  8)  The pictures that result can be quite beautiful.  Although as you note, you might have to remove the filter to really get the best IQ out of the situation.


107
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: November 03, 2012, 06:35:39 PM »
Follow-up:

1. The text book authors are Kinsler and Frey (and two other guys who I have forgotten)

2. My experimental results.  Putting the transducer to the bone behind my ear and exciting it with a sine wave, I could hear a tone up to around 50 kHz.  I did have to keep increasing the drive level.  I won't be repeating that experiment; above 50 kHz or so, all I got was a headache.  As for my four cats; the young ones (3 and 4) sat by the door staring curiously, the middle aged one (12) meowed, and the older one (15) slept (I think she's deaf).

3. All this got me to thinking, so I did a literature search.  A report from the Journal of the Acoustical Society of America (Corso J. Bone-conduction thresholds for sonic and ultrasonic frequencies. J Acoust Soc Am 35:1738-43, 1963) reports that the traditional human guinea pig (aka college students between 18 and 24 years of age) can hear out to 100 kHz under these conditions.

4. Interestingly enough, the other thing I found was reference to some research where they used an ultrasonic signal which was amplitude modulated, very much like an AM radio (eg: a 100 kHz carrier and a 2 khz voice band signal) and the test subjects heard not the 100 khz signal but the modulation.  Very interesting result.

My apologies for the digression.  I think you need not concern yourself with a small squeak.

When I learn how best to use the test gear, I'll report back if I find anything interesting about the cleaning sweep.


108
Software & Accessories / Re: What is wrong with my settings?
« on: November 02, 2012, 09:15:00 PM »
What's Ferrari's name for the color of the first car?  Perhaps "Mustard-fed stallion droppings"?  Probably not terribly poopular...

I suspect Ferrari has a nasty name for it, since that is a Lamborghini...


109
Software & Accessories / Re: Canon Protective Filter Question
« on: October 31, 2012, 10:52:08 PM »
I suspect an urban myth.

You suspect wrong.  Chuck Westfall has indicated that he recommends using a filter to complete the sealing of all sealed L-series that have front filter threads (i.e. not the supertele lenses).  Hearsay, yes - but he's Canon's technical guru, so the source is a good one.

Beyond hearsay, there are a few lenses which Canon explicitly states require a filter to complete the weather sealing.  Those are lenses with front element groups that move 'within the barrel' either for zoom extension or focusing.  Check the instructions for the 50mm f/1.2L, 17-40mm f/4L, or 16-35mm f/2.8L II and you'll see the following statement:


Excellent!  Thank you neuro!

The fact that they put that warning in the instructions for those lenses, and not in others (obviously I need to buy more lenses), strongly suggests to me that the need is primarily applicable to those lenses.  Your description of the why in those cases makes perfect sense.

It would be interesting to hear reasons for their use on other lenses, beyond an abundance of caution.

110
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 31, 2012, 10:35:52 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.


In the case of the Dukane pinger, you don't even need to hold it against the bone behind your ear to hear the once per second tick; it sound like a fairly loud clock.  Nothing special to that, the square wave pulse is obvious, and I suspect it is the end diaphragm of the device popping.

What I find interesting is that once you do put it against the bone behind your ear, and if you listen really carefully in a quiet room, you will start hearing the actual tone that comprises the pulse.  Imagine the highest pitch squeak you can, and then picture it getting higher in pitch still.  That's what it sound like.  It is a very odd experience.

This doesn't really surprise me, though.  The human ear is a very efficient acoustic filter, optimized for the frequencies we're supposed to hear.  It does a pretty decent job of reducing the 'out of band' signals that we're not really intending to listen for (the text book "Fundamentals of Acoustics" covers the math pretty well; my copy is at the office so I'll post the authors name tomorrow night).  But when you bypass the filter and put the input directly into the detector, finding that the little cilia in there vibrate at a much higher frequency than expected isn't shocking to me.

I have a few transducers that will operate out well past 50 kHz.  I'll have to try a few sine waves (no impulse to confuse things) and see what I can hear.  My cats may not like the experiment (the always sit outside the door to the workshop and meow when I play with ultrasonics), but I think I can confuse them for a few minutes for science.


111
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 31, 2012, 10:19:27 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? 



Yes, actual acoustic energy.

I am using a device specifically intended for detecting ultrasonic emissions, the Wildlife Acoustics EM-3:

http://www.wildlifeacoustics.com/products/ultrasonic-monitoring/em3

I'm still learning to use the instrument, so I cannot yet ascertain the purity of the sweeping tone.  It is fairly narrow on the spectrum display (which is very small), but until I can expand the range (or more correctly reduce the bandwidth so as to enlarge the displayed signal), I can't answer that.

I will post more when I get there.


112
Software & Accessories / Re: Canon Protective Filter Question
« on: October 31, 2012, 10:07:14 PM »
...a filter is necessary to complete the weather sealing on L lenses.

I have seen this statement many times at multiple websites, but I have never been able to find any reference to this in Canon's literature.

I would love for someone to point it out in Canon's official documentation.

I just checked the instructions that come with the 24-105L (says filters sold separately), the 70-300L (also says filters sold separately), and the 70-200L 2.8 (says filters are optional).  No where does it say they are needed for anything.  I then checked my copy of the book "EF Lens Work III", and it isn't in there either.

Given how competitive the camera industry is, if you really had to use a filter to make the L lenses properly weather sealed, Nikon would have long ago sued Canon for false advertising, since Canon doesn't provide the filter, yet advertises the lenses as being weather sealed.

I suspect an urban myth.

Personally, unless I am trying to take pictures in severe conditions, I don't use "protective" filters.  I had one shatter and destroy a lens once (where if the filter had not been there everything would have been fine), and won't make that mistake again.

Which is not to say I don't enjoy experimenting with polarizers, ND's, and graduated ND's...

113
EOS Bodies - For Stills / Re: 5D Mark III sensor cleaning noise (squeaks)
« on: October 28, 2012, 12:42:46 AM »
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.

The USM frequency is 30 kHz (and it is loud enough for the 2nd and 3rd harmonics to show up quite clearly), which is unfortunately right in the middle of house cats (and dogs) hearing range.  Which explains why it can be difficult to get good candid shots of our little furry friends sleeping; the lens focusing is very loud and distinct (to them).  This is why I am liking my short 40 so much, as it has no ultrasonic emissions.

I wonder if some of the better shots of lions we see in Canon's literature exist because the lion looked up at the sound of the camera lens focusing?

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.


114
This is going to sound a little creepy, but you should also bring a camera to family funerals (specifically the gathering that takes place afterward).

At least in my family, funerals are pretty much the only time we all see each other anymore (we're scattered all over the country), and our tradition is a large meal after the ceremony where we all get together and reminisce about the departed.  Some of the photos I've taken at the last couple of gatherings are the last photos ever taken of a few of my other relatives, and everyone was glad to receive them afterward.

Ask the immediate family if it is OK, and if they're OK with it, take as many photos as you can of everyone.  We're all going sooner or later, and you just never know when.

115
Canon General / Re: Would you rather . . .
« on: October 27, 2012, 10:27:39 AM »
I too will second Distant.Star's comments.

95% of my photography is for my own families enjoyment; so long as we like them, what else matters?  Don't get me wrong, I do truly enjoy reading the posts here, as I keep learning more and more from you folks to improve my skills.  But I'll probably never be selling my work or doing art shows, and that's OK with me.

We do have a hurricane approaching; maybe I can capture the feeling of the huge waves crashing on the beach...

My remaining photos I do for work as an adjunct to my real job (engineering) documenting what we do - and then it is only in those situations where the photo department guys can't come along (which usually means it's too dangerous for them to be there).

Those are the days I really love my 5D3 - outdoors in daylight with ISO set for 6400 so I can use 1/8000 shutter speed without anyone being able to tell my hand/what I am holding on to is shaking or the wind is howling.

116
EOS Bodies - For Stills / Re: Camera Modes
« on: October 18, 2012, 11:42:20 PM »
I concur with the notion that the designers seem stuck in the film era.  Your description makes sense.

I too wish they would provide greater flexibility...although the 'proper' UI, I'm not sure.

Perhaps providing a programming tool so you could set things up the way you want?

I'd gladly volunteer for a focus group (pun intended)... :o

117
EOS Bodies - For Stills / Re: I need some help my Canon friends!
« on: October 18, 2012, 11:39:21 PM »
If you want to add MF to the mix, my advice would be to add a Rollei TLR to your collection.

I would recommend the 2.8E model as they can be found for reasonable prices, and have spectacular optics.  And look special to your average person.  The F and G versions are still too expensive IMO.

I might also suggest upgrading the 5D2 to at least a 5D3 (or a 1DX if the wallet permits).

Film most definitely still has it's place, but I don't think I would dump all the digital stuff and go back.

I have a 5D3 (with a bunch of glass), a 2.8E, as well as a Super Ikonta 6x9.  Different tasks require different tools.

P.S. - try out a Hassy before buying one (actually, that probably goes for anything different you might go for).  Personally, I'd never own a Hassy, since for some reason I cannot see through the viewfinder properly.  Whether it is my glasses or something else, they're the only camera I've ever tried that I literally couldn't use.  I had no problem with the Rollei SL66 (essentially the same physical design), but something with the 500 CM just didn't work for me.  Your experience will no doubt vary.

118
Lenses / Re: Need quick advice Please and thanks! Choir photoshoot!
« on: October 10, 2012, 01:21:25 AM »
I'm with Picturesbyme; have fun with it.

What is their mascot?  Perhaps arrange the choir in that shape, with different folks wearing different colors (school colors, of course) to create a colorful image.


119
Lenses / Re: Need quick advice Please and thanks! Choir photoshoot!
« on: October 10, 2012, 12:01:16 AM »
50 kids and the director wants the something different than the typical riser shots

What sort of choir is it?  If a church choir, perhaps you could do the shoot outside, and arrange them in a cross arrangement, while photographing from above (perhaps the roof or from the announcers box at a nearby football field if available)?

Or maybe if they're into peace songs, in the shape of a peace symbol?

That sort of thing...

Outdoors makes lighting a bit easier (sometimes).

120
Another possibility is that the Japanese were sending a "message"; I suspect the real use is this (certainly for the large full wafer sensor from the same article):

http://www.spaceflightnow.com/h2a/f19/


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