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Messages - dr croubie

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1351
Anyone see a downside to this?

if the charger and battery circuitry are both designed properly, there should be absolutely no problem with leaving the battery constantly on the charger...

... but:
i wouldn't, a) because you can never fully protect against power surges. maybe the once every few year spike when it all goes wrong, it could easily arc over the internals of the charger and blow the battery (but then, you'd lose your pc, microwave, tv in that case too, if it happened).
b) charger constantly plugged in draws some power. constantly drawing some power produces some heat. some heat reduces lifetime of battery. maybe not by much, but it's nonzero. (and if any greenie comes past as says you should always remove everything from the wall socket to save carbon emissions, yes, that's true. or you could run your car for 2 seconds less each day, saves more carbon).
c) not relevant to you, but i've only got one battery. if it's not in the camera it's on the charger. if it's on the charger it's not on the camera. if it's not in the camera it's not taking photos. not taking photos makes me sad...

1352
EOS Bodies / Re: Will Canon Withdraw from the Megapixel War?
« on: June 21, 2011, 03:07:32 PM »
So diffraction is a problem now? Is it an indication that lens design might be falling behind sensor design? Well, lens engineer go solve it... Is this a limitation with laws of Physics? Did they not say that microprocessor will face an inevitable limit with laws of Physics at xx nm and there is no way to go beyond? ... well, we are well into 20nm territory now and going strong....

Well Diffraction is a slight problem now, and will only become more so with more (especially denser) megapixels, that's a law of physics. Moore's "law" was never a law, it was an observation made in the '70s and just happens to have held reasonably well since. Limitations at whatever-nm process were just based on the current knowledge, and the engineers managed to overcome the problems with new discoveries.
Diffraction is different, there's no way to change the relationship between DLA and pixel size, no matter what lens/sensor designers do.

But whether it's enough of a problem is the other thing.
Canon's 120 MP APS-H sensor has a DLA of f/4.  Ouch.
So there's still a good margin of MP to go before we really hit the limits, good to know. And as said, it's just going to reduce where the sweet-spot lies.
Put X lens on a 7D, you get so many lppmm at wide open, you get more at f/5.6. Put the same lens on 1Dsmk6 and you get more lppmm at wide open, but you get *less* than that at f/5.6. Changing the shape of the MTF charts is not such a bad thing, as long as you know how to use it.
In the end, the line "the lens sharpens up as you stop down" will disappear, at a few hundred MP every lens will be sharpest wide-open and will reduce with aperture size.

What it will be the worst problem for is bad lenses. Take the Sigma 20mm f/1.8. its resolution starts low, and does get better with higher f-number, peaking at f/8 (or higher, f/8 is the end of the graph). Put that lens on a sensor with a DLA of something closer to f/4 or so and the MTF will peak at f/4 or even lower, the lens will be worse at f/8 than at f/4 for the same higher mp sensor.
So in a way it means lens designers will have to become better, they won't get the benefit of a 'sweet-spot' as mentioned.


But some other ideas I like. Like the 'split sensor in 3' to do some in-camera combining for HDR, one other idea I had is an automatic 'focus on 3 different lengths for 3 shots and combine'. OK, so people do it manually now, and it only works for static/landscapes, auto-incamera would be nice though...

1353
EOS Bodies / Re: Will Canon Withdraw from the Megapixel War?
« on: June 21, 2011, 02:25:58 PM »
aside: this thread, and actually the whole issue in general, is reminding me waay too much of the MegaHertz race (later the GigaHertz race).
Short recap:
intel and AMD made computer chips, racing each other to have higher cpu MHz. Intel won the race, their pentium 4s got up to over 4GHz. But the AMDs were much more efficient, they got more number-crunching done for the same MHz, consumed less power, they brought in dual-core years before intel.
flash forward a few years, it turns out AMD's tech won the war, now it's reversed and almost a race to see how many cores you can put on a chip even at lower MHz, and lots of marketing goes on power consumption too...

But in the end, did it translate to market share? The whole time intel kept pushing the MHz numbers, consumers just kept buying it. A few nerds knew what they were buying and amd's sales went up a little bit, but not everyone reads the reviews, the average consumer just went for the higher numbers (and alleged business practices by intel currently in court, which we won't start on).
By the time the average consumer realised that more MHz didn't mean better computing, intel was ready with their Core-series and they kept on selling...



So will there be a parallel to cameras? is canon like intel and going to keep pushing the MP up, while, say, nikon keep the MP low and push the other side, like ISO and Dynamic Range? Will canon keep their market share because of their marketing and higher numbers, while eventually the consumers drift more to a company that offers lower MP and higher dynamic range? By the time it starts affecting sales figures, will canon have a better dynamic-range/iso option?

and most importantly, will canon make a sensor with so many megapixels that it catches fire?

1354
he did raise another question, which in camera terms translates to "do you have a battery grip, or only use one battery at once?"

I think even with a battery grip, the camera only uses one battery at any given time.  I do know that when I insert a fully charged and a partially discharged battery into the grip, the camera will drain the fully charged battery to the point where the two batteries are approximately equal, then start alternating between them from shot to shot based on the reported shutter count.  I do wonder how it handles operations like Live View or Video, though - does it switch between batteries during the operation, or only at a 'break' (could easily be tested).

That's an interesting behaviour, but certainly understandable (and i should have thought of it already). Keeping the batteries at their highest level (ie, using the higher one before the lower one) is a good move by canon to keep battery life longer.

Electric car batteries connected in series have this thing called 'balancing' they do during charge, they engage resistors to burn off power until they all have the same voltage as the lowest cell. It (apparently) keeps the cells in better condition than if they were all different voltages (it does waste a lot of power though).

in the grip they're definitely not connected in series, that would double the voltage to everything, and i should have realised that they wouldn't be paralleled either without some kind of balancing...
I'd be interested too to see how it works under movie-mode, my guess is that since they say they can measure charge to 1%, as soon as one drops by 1% then it switches to the other (it's not so hard to keep it working during the switch-over)

1355
EOS Bodies / Re: 3D (Again) & 5D Mark III (CR1)
« on: June 21, 2011, 01:30:08 PM »
It would be great if we were able to customize cameras just like we customize PCs, but it's not happening yet.

You mean it's not happening anymore (or less than before).

Medium Format have had interchangeable lenses, focussing screens, viewfinders, film backs, digital backs, full meters, spot meters, you name it, pretty much since they started.
One i know of is Hasselblad ditched the ability to swap film/digital backs when they introduced the H3D (although apparently you can still use the waist-level finder).
Other MF companies still produce digital backs and bodies seperately, but the trend is still more towards integration.

afaik, 35mm has never had the same level of modularity.
ok, so angle finders are available, but they clip onto the back of your viewfinder, they don't replace the entire prism.
has any 35mm ever had a replaceable back? (granted, early DSLR digital backs tacked onto film cameras, and they're not made anymore either).
and replacing your ttl full metering prism with your spot metering prism disappeared with the berlin wall (now i just press a button and scroll a wheel to change, i can tell you what i prefer too)

1356
Nice article there, one bit stuck out for me:
"The display shows each battery’s serial number, displays the last time it was charged, ..."

It depends how the camera works this, if it's "the last time you took it out of the camera before charging" or "the last time you put it back in the camera after charging".
But if it's "we know exactly the last time you charged it because there's a clock in the battery itself" then there's a thing, because that rtc has to be powered from somewhere, ie you leave a nearly-empty battery for a while and the internal clock will drain it until it's past dead (a good battery should turn all its sensors and clocks off before this point, but if it calculates the wrong 'point' then it can still be too far gone).

Does anyone have a battery they charged more than a day ago and not put it in their camera, can they check what date it says 'last charge'?


meanwhile, so far the response from my guys at work are:
"...it seems to me that the #2 battery has been deep discharged. It is illadvised to use this battery again..."
(he doesn't know it's a camera battery, so he probably presumes it's an electric car battery, in which case it can be unsafe to use it again. you're "probably" fine continuing to use it from a safety point of view, but it's definitely not going to perform optimally ever again)

he did raise another question, which in camera terms translates to "do you have a battery grip, or only use one battery at once?"

1357
EOS Bodies / Re: Will Canon Withdraw from the Megapixel War?
« on: June 21, 2011, 12:53:44 PM »
The best photos are not the ones with perfect corner sharpness, they are the ones with perfect composition and lighting.  When everyone forgets about the art of photography and starts to obsess on the science of electronics, visual aesthetics is replaced by minimum chromatic aberrations.

+1 on that.
www.lensbaby.com and skinkpinhole.com are some of my favourite 'artistic' lenses, and you can't get any softer than a pinhole (ok, besides a Zone Sieve, kind of a 'soft-focus' pinhole)

1358
EOS Bodies / Re: Will Canon Withdraw from the Megapixel War?
« on: June 21, 2011, 12:30:46 PM »
Also, don't forget about Diffraction in the megapixel war.

To quote directly from The Digital Picture (he says the same thing for every camera review):
Quote
DLA (Diffraction Limited Aperture) is the result of a mathematical formula that approximates the aperture where diffraction begins to visibly affect image sharpness at the pixel level. Diffraction at the DLA is only barely visible when viewed at full-size (100%, 1 pixel = 1 pixel) on a display or output to a very large print. As sensor pixel density increases, the narrowest aperture we can use to get perfectly pixel sharp images gets wider.
DLA does not mean that narrower apertures should not be used - it is simply the point where image sharpness begins to be compromised for increased DOF and longer exposures. And, higher resolution sensors generally continue to deliver more detail well beyond the DLA than lower resolution sensors - until the "Diffraction Cutoff Frequency" is reached (a much narrower aperture). The progression from sharp the soft is not an abrupt one - and the change from immediately prior models to new models is usually not dramatic.

the 7D (& 60/600/550) has the highest pixel density of any canon so far, and the DLA is f/6.8. I know you can't really tell that from f/11 for most things, but i like to keep my f/ below about f/8 wherever possible, except for really deep DOF landscapes. look at almost any review of any lens with any sensor at www.photozone.de, every MTF chart they produce starts tailing off at f/5.6 - f/11 too, depending on which camera for the exact spot.

edit: example: the TSE-24 ii is arguably one of the sharpest around these days. check out the www.photozone.de MTF Chart. Diffraction is already hitting it between f/5.6 and f/8 in the centre, and between f/8 and f/11 on the edges, and that's tested on a 5d2, with a DLA of f/10.3.


I don't know the exact formula for DLA, nor how badly diffraction affects the picture quality per f/stop past the DLA, but this is another limit we're going to reach sooner or later.
What happens when we reach a DLA of f/2.8? we simply can't pack more pixels in, there'd be no point for anything except wide-open for fast lenses, slow lenses would be pointless. Given that all but the best lenses are sharpest around f/4-5.6 these days, we'll need ever-widening apertures and sharpness wide-open to get anything better than we have now.

just take again the 7D, upscale the sensor with the same density to FF, we get (5184/22.3)*36.0 = 8268 and
(3456/14.9)*24 = 5566, giving a total of 46 megapixels for the same DLA on a Full Frame.
So we've got a bit of a way to go until then, but don't expect wonders once the 40+mp aps-c cameras start rolling in unless you've got fast lenses sharp from wide-open...

1359
ps, i don't have my camera with me so can't check.

What type of battery are they? Lithium Phosphate, lithium, lithium ion, lithium polymer, etc?

1360
My day job (well, not for long, today's my last day), is actually at a firm specialising in fast chargers for Lithium batteries. Blurb from our website:
"After 6 years of 24-7 cycle life testing with different lithium-ion chemistries, cells and packs from multiple suppliers, <company> has built a database containing over one billion records of test results. The Battery Knowledge Centre owns a knowledge base containing evaluations, profiles and in-depth studies on more than 100 battery makers and their products."

So i'll pass the question onto our guys here and ask them. if they don't know then i don't think anyone will...
I do know a bit about batteries, definitely a hot car is the best way to kill them. i've also heard (anecdotal) evidence of situations like yours being fixed by a few hours in the freezer.

I've actually had a problem similar to what you describe, now that i think about it. Customers ran down the battery almost to its failure point, then plugged it in to charge. The battery took on a little bit of charge, decided they were too low to charge, and switched off. However, because the unit in question was still plugged into the mains, our controller was powered on and kept talking to the batteries, depleting them slowly, past their point of no return. Once they hit that 'no return' stage that's it. chemistry changes in the batteries, dendritey things grow inside and can't be gotten rid of, chance of a failure increases a lot. (and failure means failure, explosions and the like, they're truck-sized batteries capable of 3000Amp short circuit current and can fail spectacularly)
end of that story was that we had to redesign our controller, and the customer had to get another few $k worth of batteries (i'm still not sure who paid for it though).

Thankfully, camera batteries won't fail so badly, but it does sound like you've done some permanent damage to it internally. What the inside of the battery looks like i don't know, but more than likely there's some circuitry in there that's powered on all the time, leaving a nearly empty battery alone for a while is a sure-fire way to kill it completely (whether you did or not for this one?).  was it in the camera being nearly discharged for a while before you tried to charge it? even in a damp or humid environment, leakage current does happen through the air (ok, very very very slowly) and will (very very eventually) kill it.

For our design (and maybe for the canon charger too), trying to charge it will inject a little bit of charge every time you attach it, then the charger will ask the battery how it's doing, and that's when the battery says "i'm not good enough to charge". unplugging it for 30s and trying again, you will eventually be able to charge it (which is how we fixed our problem above with a small hack of a timed relay), which may be what you (inadvertantly) did.

also, definitely keeping them fully charged in longer-term storage is a good idea, as is being cool and dry.

1361
EOS Bodies / Re: Will Canon Withdraw from the Megapixel War?
« on: June 21, 2011, 03:45:29 AM »
Up until the 24mp D3X, nikon's best was about 12MP. that was released end of 2008. and after that the best that came along was the 16mp d7000 halfway through last year.

compare canon, the 21mp 1ds3 came a full year before the d3x, the 5d2 even beat the d3x announcement by a few months. at the same time the 50d got 15mp then the 550d a few months later, then the 7d got 18mp (then 550d, 60d, 600d).
even the 1ds2 was 16mp back in mid 2004.


the way i look at it, nikon gave up on the megapixel race years ago. most people argue that their 12mp sensors do better high iso than the canons, but canon certainly beat the crap out of them with regards to megapixels (and i think to sales volumes, can someone verify? i'm late for work)

i don't think the war will be over until 40mp+, medium format is 80mp and still going, they'll get to 200mp at least. not to say that either will stop there, that's just when diminishing returns kicks in and time between major upgrades becomes too long (or are we seeing this already, where are you 1ds4??). and the difference between a 30mp camera and 20mp is the same % as 3mp to 2mp. they sure went from 3-4-5mp fairly fast, we should see leaps to 30/40/50 just as fast. (or are we nearing the tech limit? i don't think so)

1362
EOS Bodies / Re: Eye control
« on: June 20, 2011, 04:42:44 PM »
Did the eye control work with glasses?

i don't think so (although it might work with some types of glass, strengths etc, definitely not all)

1363
EOS Bodies / Re: which one should i choose ? 600D or 60D?
« on: June 20, 2011, 12:42:54 PM »
Regarding 18-55mm lenses, there have been several of them.  Yes, the IS version is optically superior to the older, non-IS versions (both with and without USM).  But, for the original, non-IS versions, only very slight cosmetic changes were made for the MkII designation - the major changes were the shape of the zoom ring rubber grip and the tapered area at the front of the lens.  Similarly, for the 18-55mm IS original vs. MkII, there are no optical changes.  The only changes are cosmetic and firmware (updated IS algorithms).  The MTF curves provided by Canon are identical for the original and MkII versions of the 18-55mm IS.

Likewise, the new 55-250mm MkII is merely a cosmetic update to the original.  Since Canon is selling kits with the 18-55 IS II, they want the 55-250mm in the two-lens kit to match (the lettering/font on the barrel and color of the ring with the focal length markings are different from original to the MkII).

Please check your facts before posting - your misinformation in this and other posts really doesn't help.

and for a bit more info, according to canon camera museum:
18-55 i - sept 2004
18-55 i usm - sept 2004 (from what i read somewhere, the usm was only in japan to start with, made it elsewhere later).
18-55 ii - march 2005
18-55 ii usm - march 2005
18-55 IS i - sept 2007
Also from here (presumably because the canon camera museum takes ages to update, the 70-300L isn't even on there yet)
18-55 iii - feb 2011
15-55 IS ii - feb 2011

read the reviews of the ii version compared to the IS version i. The block diagrams on the canon camera museum are the same, but the resolution figures between the two speak for themselves, really...

between the i-ii-ii and ISi-ISii, nothing more than cheaper manufacturing and a bit of cosmetics, as most have said...


...the 55 - 250 II lens (just introduced) is better than the version I in image quality...
I'd like to see a link to that having been reviewed already...

1364
EOS Bodies / Re: ISO 50
« on: June 20, 2011, 12:17:31 PM »
Actually, 12- vs. 14-bits is not terribly relevant - even Canon's 14-bit cameras deliver only about 9 stops of useable dynamic range.  FWIW, that's based on testing I've done personally with my 5DII and 7D.

DxOMark has some nice nerdly-graphs and such.
ranks the 5d2 at 23.7 usable bits (ie, 7.9 bits per pixel). 7d comes in at 22 (7.33bpp). CF the best full format (according to them), d3x @ 24.7 (8.2bpp) and the best of anything Phase One p65+ @ 26 (8.66bpp).

dynamic range the 5d2 comes in at 11.9evs, 7d at 11.7evs, the pentax k5 tops out 14.1evs, and d3x 13.7evs for comparison.

So changing the ADC from 14 to 15 or 16 bpp is not going to do much, at least how i interpret those results, because the sensor can't even deliver enough range to use the full number of bits as it is (although, speaking from my experience with digital audio processing, more bits will help 'smooth out' the quantization noise, make colour transitions look smoother and such).

1365
EOS Bodies / Re: Eye control
« on: June 19, 2011, 04:17:52 PM »
For that matter, let me ask, how many of you with Canons with the wheel to change AF points actually use that feature?

I've got the 7D, and i'm not sure if it was a custom setting or default, but my joystick sets the AF point, my thumb is practically *always* on it to set where i want it. If it's not there i'm teaching it to press the af-type button to change zone/spot/etc...

if eye control would save me a lot of rsi and physiotherapy, i'd pay an extra $100 for it...

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