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Messages - jrista

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61
Third Party Manufacturers / Re: Nikon's D800E 30% sharper than D800
« on: July 09, 2014, 01:24:58 AM »
Most definitely. I'd love to see a chart of total resolving power versus dollars. Gotta pay to play.

What I know is you need more than a $2,199 Zeiss to resolve 100% of a 36MP 135 format sensor. DXO just did it again, they threw any "scientific" credibility they had out the window, not that they had much left anyway.

A result made all the more comical when you look at the $4,000 Otus results on the D800E, down to 33MP, a drop of over 8% for what is regarded as one of the finest photography camera lenses ever made. I think DXO have two teams of testers and the Canon team, who clearly multiply all their results by 0.9, mistakenly did the Nikon Otus when they did the Canon Otus as well. No that's not true, I believe the Canon testers are OK, it is the Nikon test team that multiply all their results by 1.15.

As for not being able to have 99% of perfection or it being a strange way to look at it, I understand that, I was just trying to illustrate that anybody claiming perfect anything is farcical and it isn't as simple as the lens being capable of resolving more than the sensor. Like the >14 stops of DR in a 14 bit file, extrapolate to ridiculous figures all you want (DXO) but if I can't actually realise that shadow lifting capability it is of no practical use.

Totally agree with everything here. DXO has some really wacko shite goin on with their lens tests. They have the weirdest lens test results I've ever seen...anywhere.

62
EOS Bodies / Re: EOS 7D Mark II Announcement September 5, 2014?
« on: July 08, 2014, 02:14:20 PM »
jrista has an advanced case of the astrophotography bug. That's an expensive bug to catch, at least if you give it full freedom to grow.  ;D   I would be more worried about catching this bug, but unfortunately I live in an area with less frequent clear skies, lots of light pollution, and I don't function too well on little sleep, so my AP window of opportunity is Fridays and Saturdays.

On the other hand, telescopes keep getting better for less money.


Oh, that is SUCH a TRUE statement! :P I do worry about myself now. If I just "let go", and got everything I wanted, this is the bill:

10Micron GM2000HPS UP: ~$24,000 (with all required options)
PlaneWave 17" CDK Telescope: $22,000
SBIG STX-16803 w/ 7-pos Filter Wheel: $11,590
Astrodon LRGB E-series Gen II 50mm Square: $1,225
Astrodon H-alpha 5nm Narrow Band 50mm Square: $875
Astrodon Oxygen-III 3nm Narrow Band 50mm Square: $1,250
Astrodon Sulfur-II 3nm Narrow Band 50mm Square: $1,250

That's a total bill of: $62,190  :o :o :o :o :o :o :o :o

The big benefit of the 10Micron mounts is they use high end absolute encoding on the axes. They can track with <0.1" accuracy without guiding for up to 20 minutes. They also include sky modeling built right into the mount. This stuff is big and heavy as well, so you really set it up in a personal observatory, perfect and tune it's alignment and sky modeling, then just access it all remotely. You log in from your computer, tell the dome to open, point at whatever you want to image, program an imaging sequence, and then just let it run. Go to bed, wake up in the morning, and you have a bunch of image data to work with. ;)

The cool thing about automated observatories these days...you can automate EVERYTHING. You can even pre-program imaging sequences that automatically "wake up" the observatory, open the dome, point it and the scope at the right location, do the imaging, then park the scope and close down the dome and have everything "sleep" when morning arrives. You can even set up weather monitors and cloud detectors, which will again put everything in sleep mode until the clouds pass, then wake the thing up again so it can get back to work when the sky clears. (You can also wire all this into forecasts online.)

Of course, building a nice, fully automated observatory like this, under really dark skies that have a lot of clear time, is like another sixty grand...so...you know....only the independently wealthy really get to play with "toys" like that. :P

63
Third Party Manufacturers / Re: Nikon's D800E 30% sharper than D800
« on: July 08, 2014, 01:37:50 PM »
its' impossible to fully realize the full resolving power of a sensor with a high resolution lens, and to get very close, you rapidly run into diminishing returns. You get to the point where doubling your lens resolution gets you a few line pairs closer.

It's an asymptotic relationship...system resolving power is asymptotically related to the resolving power of the lowest common denominator of the system.

Thus the moral of the story is: if your primary goal is to maximize system resolution (and for the majority of people, that's likely not the case, regardless of what one may read on some fringe forums), always upgrade the weakest component.

Yeah, pretty much. Although that can become prohibitively expensive at some point.

The 7D is a good camera, but it doesn't perform terribly well with the telephoto lens it's most often paired with, the 100-400. However if you move up to one of the Canon great white primes, the 7D becomes a stellar performer at ISO settings 1600 and lower, and becomes viable at ISO settings higher than that in the evenings. It's just that you have to spend a LOT of money on those lenses to maximize the potential of the 7D.

On the flip side, if you upgrade the camera itself, to one with a higher resolution sensor (which the 7D II should have), then instead of spending $6000 to $13,000, you spend maybe $2500-3000. It's still a large chunk of change, but not necessarily prohibitively expensive.

64
Third Party Manufacturers / Re: Nikon's D800E 30% sharper than D800
« on: July 08, 2014, 01:12:25 AM »
The resolving power of an optical system (i.e. a whole camera with lens and sensor) is limited by the resolving power if the least capable component. If that is the sensor, then resolving power of the whole has an asymptotic relationship with the resolution of the sensor.

Thank-you.  I think you've nicely answered my question from the first page of this thread.

Still... there's something about the explanation that seems to be missing for me...  Is there a contrast limit or something in place when making these calculations?
Otherwise it only seems logical that a lens capable of resolving 150 lp/mm (at some contrast ratio) should be able to resolve 100 lp/mm (eg. ~d800e) which is roughly the max resolving power of a sensor, even if it's at some reduced contrast ratio.  :-\

Sorry, I should have stated, those numbers are all for MTF50, or 50% contrast. It is indeed possible to use a lower contrast level, however it's pretty standard to use MTF50 for photography. As we get smaller pixels and AA filters are weakened or dropped, it'll certainly be possible for lenses to meaningfully resolve detail at lower contrast levels, so maybe MTF30 could be used instead. I think by around the Rayleigh limit, contrast is too low for most modern camera sensors to pick up at higher frequencies. The human eye can barely discern contrast at that level, and we have a biological supercomputer processing what our eyes see.

I would actually have to derive all the resolutions for MTF30, I don't have that memorized for key apertures. :P

The D800 has 4.9µm pixels, or 102lp/mm. A 150lp/mm lens, at, what, around f/4.2 or so I guess, has a spot size of 1/(150 * 2), or 2.2µm (To convert from line pairs to spot size, you multiply by two to get lines, and take the reciprocal to get line thickness/spot size). Take the RMS of those two sizes, SQRT(0.0049^2mm + 0.0033^2mm), and you get 0.0059mm (5.9µm). Take the reciprocal of that and divide by two to get line pairs again: (1/0.0059) / 2 = 84.6lp/mm. That's eh, getting there. You can get very close...something like the Otus at a wider aperture probably resolves enough detail to get much closer to the 102lp/mm resolving power of the D800. The point, though, was that getting close-ish isn't too difficult...it's getting very close, i.e. maximizing the potential of a sensor, that actually gets REALLY tough...in fact, its' impossible to fully realize the full resolving power of a sensor with a high resolution lens, and to get very close, you rapidly run into diminishing returns. You get to the point where doubling your lens resolution gets you a few line pairs closer.

It's an asymptotic relationship...system resolving power is asymptotically related to the resolving power of the lowest common denominator of the system. For diffraction limited (or close to it) lenses at fast apertures, that's usually the sensor. For diffraction limited lenses at narrower apertures, that's usually the lens.

65
EOS Bodies / Re: Eos7D mk2, How EXCITED will you be if . . .?
« on: July 07, 2014, 06:12:04 PM »
I bought the 7D when it was first released and I had two impressions....One: I LOVED the ergonomics and control layout over the 5D2.  Two: I was majorly disappointed in the quality of the files out of the camera....just too mushy for my taste.


Agreed. Especially the bold part.  The 7D had the worst IQ of any Canon product I have used.  It was especially weak in crepuscular light, which is where most big-game wildlife shooting occurs.   


Aye, low light is definitely the 7D's weak point. I had a real tough time with the 7D and the 100-400mm lens, things beyond ISO 1600 were unusable, and 1600 itself was borderline. I will say, however, that with the EF 600mm f/4 II lens, the 7D is a remarkable performer, even in lower light. I've taken some amazing shots in extremely low light with the 7D and 600/4, such as this:



7D, 600/4, ISO 3200. Taken well after sunset, as blue hour was starting. With enough light and proper technique, even the "muddy" 7D could be made to perform quite well.


I'll be staying away from anything with the 7D name, no matter the amount of enticing gadgets. I found the 70D to be a far superior camera.


The past IQ of the original 7D doesn't mean the 7D II will have the same problems. For Canon to succeed with the 7D line, the 7D II MUST have better IQ and overall performance than the 70D. It would just be a flop if it did not. If the 7D II does end up being a superior performer to the 70D...would you still adhere to the above statement? (Just curious...personally I find it odd when one single bad experience with one single product permanently taints a person's opinion of something...to me, every product generation is a chance for a new start, a chance for a company to reinvent itself, reinvigorate itself, or if necessary redeem itself (not that Canon needs redeeming, but they do need some reinvigoration in some areas.))

66
EOS Bodies / Re: Eos7D mk2, How EXCITED will you be if . . .?
« on: July 07, 2014, 03:49:58 PM »
  • I'd have mixed feelings, but overall positive if Canon 'bit the bullet' and "swallowed their pride" and used a Sony sensor with 24 mpx with high DR of 14 stops. That might bode well for Canon using a similar sensor to the Nikon 810 / A7r in an upcoming full-frame.

Not gonna happen, as Canon prides themselves too much on their "in house, fully integrated" approach.

  • Native MagicLantern-like Dual-ISO for much greater DR

You want both a Sony Exmor sensor...and ML Dual ISO? How much DR do you want? :P Unless Canon is moving to a 16-bit ADC, which if they used an Exmor is impossible (since Exmor includes the ADC), then having both is moot. You can only get 14 stops of DR out of a camera with a 14-bit ADC.

If Canon natively improves their own sensors DR, which is more than possible, it isn't like Sony has an exclusive right on high dynamic range sensor technology, then having ML Dual ISO is again moot. If Canon tops 13 stops of DR, they would be comparable to the D800/600/810, which all get around 13.2-13.3 stops (as far as editing latitude/shadow lifting goes). Adding ML Dual ISO to that wouldn't really offer any benefit...as to achieve that kind of DR in the first place, ISO 100 would have to have as low read noise as ISO 800 anyway.[/list]

67
Macro / Re: Flower macros
« on: July 07, 2014, 03:41:39 PM »
DPC, you really have an eye for this stuff! Amazing images!

68
EOS Bodies / Re: Eos7D mk2, How EXCITED will you be if . . .?
« on: July 07, 2014, 03:38:55 PM »
I'll get excited if the 7DII has substantially better IQ... AND that sensor gets used in the next EOS M!

Better IQ and much higher performing AF, and used in the next EOS M. I'd be interested in that. I want a more capable ILC for days when I generally can't bring my big DSLR kit...something with high resolution, fast focus, and good IQ (across the board, including better DR) would be nice to have. I could use it for wildlife/birds and landscapes.

69
EOS Bodies / Re: EOS 7D Mark II Announcement September 5, 2014?
« on: July 07, 2014, 03:36:58 PM »
It's funny...I have anticipated this camera for so long, as I've loved my 7D. Now that it's just around the corner...the only cameras I can think about have nothing to do with terrestrial photography! :P

70
Quote
As for Surface...Microsoft's future is dependent upon the entire Microsoft ecosystem being directly competitive with Apple products, specifically. To be quite blunt, Microsoft's hardware partners SUCK ASS. They NEEDED a big, fat, PAINFUL kick in the rear end to knock some sense into them. The mobile windows hardware market has been failing for years...products have gotten cheaper and cheaper, and the quality of those products has tanked right along with price and profit margin.

Well, if that's the way you see it. I see it a bit differently - Microsoft reduced the profitability of these companies up to the point their R&D became mainly small incremental upgrades and now enters the same market, able to out price their hardware due to software licensing costs. Actually, because of this threat, Linux got considerably better video card support from AMD just last year due to Microsoft's actions, and that's just from the top of my head. And what it comes to products getting cheaper, that's probably true. What I don't agree with is quality.

Comparing something to Apple stuff doesn't really impress, it's a company that can't even get their OFFICIAL chargers working (=cutting corners with electrical safety to reduce size of the charger). If we had the same legislation before entering EU, it would not have been even possible to sell the OFFICIAL Apple chargers here due to safety regulation violations.

Generally in Europe, it's considered a bad move to jump to enter the same area as your customers - it is guaranteed to create ill-will, so you really shouldn't be surprised because of this. Funny thing is, this is exactly the recent stuff why Microsoft is not liked, but you're downplaying this example by saying it's a genius move. Well, I don't know, it could be strategical genius at play, but the chances are, you're also taking a risk of alienating your OEMs. It doesn't happen in a second, though, and Microsoft has cash to play. See where I'm getting at?

There is what is "considered", and there is what's actually happening. In terms of what's actually happening, Microsoft's entry into the tablet market has forced their competitors to become competitive. It was a stagnant market. The "cheap" products from Microsoft partners kept getting cheaper and cheaper, shoddier and shoddier, with price points down to a few hundred bucks. There was no quality, because the third-party product manufacturers had built their reputations on cheap and replaceable instead. That wasn't Microsoft's doing.

With Surface now a competitor, and Microsoft primarily competing with the higher end Apple, vs. the ultra low end crap that used to be standard fare for Windows-based products, Microsoft is forcing their PARTNERS to step up their game, enter a higher quality realm that also brings with it the potential for higher profits (as clearly demonstrated by Apple's high profit margins with high quality parts.) Consumers expect, and demand, QUALITY products now...the Windows ecosystem was dying because Microsoft partners designed it to be a CHEAP products venue. Something had to be done about that, otherwise the Windows platform WOULD have died, probably a silent death that no one noticed because there was nothing worth buying.

BTW, Microsoft is NOT price undercutting their other competitors in the windows ecosystem...Microsoft's Surface line is actually fairly expensive, and price cuts have only been because they were NECESSARY in order to increase sales...for comparable hardware, there are many cheaper options than Microsoft's products. There are also even higher quality products from others, like Dell, that rival the value and cost of Apple products.

Is Microsoft's move into the market as a direct hardware player liked by their partners-become-competitors? No, surely not. However that doesn't change the fact that it was necessary. Without Microsoft FORCING their partners-become-competitors to actually BE COMPETITIVE, the entire market would have died. It was RACING towards death already, and racing towards it not really because Microsoft products suck...they don't...it was racing towards death because NONE of the Microsoft/Windows ecosystem products were even remotely competitive with THEIR PRIMARY COMPETITOR: Apple!

I don't deny that Microsoft's move is unpopular and disliked. That doesn't change that it was utterly essential for Microsoft to FORCE their partners to step up their game, and drag themselves out of the muck of the ultra-cheap, ultra-low-quality crapware products they were making, into the higher level game that Apple plays. Apple is the focal point of the mobile computing industry, there is no question about that. Whether they deserve the reputation and respect they have or not, people do adore them and their products. Apple is the baseline...everything else has to be judged by that. A year ago, things still looked pretty bleak for the Windows ecosystem. Today? I just purchased a Dell XPS 15 that tops the specs of a MacBook Pro and Air combined, for less than two grand. It's a SOLIDLY built device that is just as beautiful as any Apple product, well built, blazing fast, fully touch capable. It's a wonderful product. And I HONESTLY do not believe it would have ever come into existence if Microsoft hadn't become a competitor in their own ecosystem.

Sometimes popularity isn't what saves a company...sometimes making the toughest decision possible to spur competition and innovation, even when it's incredibly unpopular, is the right decision. (Just ask Ichan... :P)

Quote
The ribbon was a DIRECT response to years of customer feedback on the Office UI. People hated having to dig multiple levels deep within menu systems to find features in Word and Excel primarily. Microsoft designed the ribbon in an effort to solve that exact problem, based on explicit CUSTOMER feedback about the problems with their old Office design. Ribbon was a success in that it brought everything right to the surface, one level deep in a series of tabs.

I know the background of the Ribbon. I've to F______ use it every F______ day. Including Paint (seriously, what the hell Microsoft?) and ZEMAX, whose latest update incorporated it, despite the CUSTOMER FEEDBACK not to go there. Luckily, with professional software, they have to implement menu structure - and I've seen no-one using the Ribbon in CAD software in our house. What it comes to the Office, I agree that user feedback triggered the change, but the change itself is still botched.

You are saying that Ribbon put everything on the surface, right? Take a look on the attached PNG. What is the circled button that I see there? You know, the one that EXPANDS the options in Ribbon? The thing that should NOT exist based on the design criteria? This is basically a RE-VAMPED menu structure for you, with the exception that this is actually WORSE. The expansion button is so small that it's harder to hit than the older text based menu. I actually couldn't find the button first time I needed it!

Add on top the fact that the Ribbon icon size is sort of fixed (I only need the text part, not the graphic icon to begin with - deciphering icons is harder than text). I would like to place much more buttons there, but can't! Because of that, I still can't orient the Ribbon vertically to take advantage of the nowadays wide display aspect ratios. And I've made my opinion known on the Microsoft side.

The little chevron your talking about only appears when the screen size or window size is too small to display the entire ribbon. It's an adaptive thing. There is a LOT of functionality in Microsoft products. Microsoft's options are either to drop functionality, which is 100% guaranteed to cause an uproar...or...find some way of making all the necessary tools available even on screens that are too small to display it all at once.

Try using office maximized on a larger screen. That little chevron your bitching about? It'll disappear...and the entire contents of the entire ribbon will show up on the screen.

Sorry, but I find your complaints about the ribbon just an angry dude finding a reason to be angry about something...

Quote
Now your just speculating about Microsoft forcing anything on it's customers. You can still, and will always be able to, buy Office stand-alone. I did. I own a couple stand alone copies. I opted for that, instead of the much cheaper $99/yr Office Cloud standard edition. I prefer to store my data locally...but not everyone does. Some people, some corporations and smaller businesses, much prefer to offload the once-necessary costs and complexities of managing their own computer networks and systems onto a larger business entity that has more talented and effective resources for managing such things.

It could be. And I thought I made it clear this is speculation (though based on several snippets of facts). Getting back there, there's no similar legislation in place for data storage as there is for example book-keeping that small enterprises typically favor too, and data storage is actually much more sensitive area. In Europe, I don't think this would fly - you're simply considered stupid if you do this, until the legal standing is clear. Also add on top that Cloud servers that stay on US soil are suspect for US government actions at any second. This is not to say that your average worker cannot upload anything to Cloud, but he's responsible for the brunt if data loss happens.

I'm very glad I don't live in Europe. The EU has demonstrated for decades that it has a fairly anti-business stance, and the penalties they have levied on large corporations are rather extreme at times. It's a punitive system, constantly punishing, punishing, punishing. I'm not really surprised you hold the opinions you do...I guess the actions of the EU make a lot more sense now...

Quote
Cloud is Microsoft's strength. Their biggest competitor there is actually Amazon, and they are making headway, helping spur a competitive market in the cloud services business.

This doesn't make any sense. You're saying Microsoft's cloud is for the enterprise, but as far as I know, Amazon is for consumers. Which is it?

You HAVE heard of the Amazon Cloud Services, right? Amazon is the world's largest online retailer. They couldn't be that if they hadn't developed the technology to support that kind of infrastucture. It was many years ago that Amazon started offering web services to access some of the technological infrastructure they had built, and today, they are the largest provider of core cloud services (i.e. big data, compute cycles, virtualized hosting, etc.) of anyone. Those services are used by enterprise businesses to host...pretty much anything. Even NetFlix is hosted on Amazon's cloud servers.

Microsoft Azure directly competes with Amazon Cloud Services. Microsoft's Cloud Services (i.e. Office in the Cloud) directly competes with Google's web apps. Overall, Microsoft's cloud initiatives are gaining a lot of ground against their competitors.

Quote
The way app stores are run isn't really a Microsoft thing. Apple started that trend, and in many ways, it is essential to the protection of consumers. Just look into how many problems and security issues can and have occurred on the Android platform, with it's open app store, vs. how many of those kinds of issues occur on Apple or Microsoft devices. There needs to be some level of buffer, some small barrier to entry, to help weed out the apps that are designed by data and identity thieves for the purposes of data and identity theft, fraud, etc.

I agree with store safety with Android. But, you're saying app store isn't a Microsoft thing. I think here you'll need to look into the future and not in the past as you so readily advised me. Apple is the most profitable high-tech (HAH!) company on Earth, and it stands for a good reason Microsoft has an incentive to go the same way - and this includes orientation towards the consumer. So, the software companies building on Windows ecosystem can also predict that in the future their profit margin drops due to the Microsoft taking a larger share in the Microsoft Store. Which is fine, Microsoft can do whatever they want with their ecosystem and I suppose you get something back for the price, but I'm saying there will be consequences and market share erosion as not everybody will find the properties worth their money. As you are already seeing with the case of Valve. And I never said this had anything to do with Windows 8, but general Microsoft strategy.

Valve was pissed that Microsoft wanted to take a small cut of all in-app sales. Again, that isn't a strategy that Microsoft pioneered...Apple already does that. Valve would have the same problem if they tried to create an app in the Apple store.

As for cost, Microsoft takes the same amount as Apple. They always have. As a matter of fact, Microsoft often gives discounts for app developers, as an incentive, to get them onto the platform. Fundamentally, though, app developers on both platforms pay $99/yr to develop apps, and get 70% of the revenue from the sales. Both companies take 30%, which is then used to cover credit card transaction fees, infrastructural support fees, and the companies cut (which is less than 20% for both companies).

FYI, I was actually supporting Windows against Linux when 7 was released. It's only now that 8 is released and Microsoft's strategy is clear, and it seems consistent UI changes are the norm, I'm considering switching to Linux in next computer update. Microsoft actually never made the jump easier.

I'm not sure what is "consistent" about UI changes. The only two things that changed between 7 and 8 was the start menu...which became a start screen, and the use of ribbons in the core desktop apps (i.e. Explorer). People on Windows have been using ribbon for years now, so it isn't something new. I haven't heard much about that being a sticking point with potential upgraders, either...the biggest complaints are the start screen. But as you can see from other participants in this thread, the vast majority of the complaints about the start screen are entirely unfounded.

Not to mention, if you really want a start menu...you can have it. There are free and cheap utilities to bring it back if that's something you REALLY REALLY want. It isn't enough to avoid upgrading, because everything else about Windows 8 has been improved over Windows 7.

71
Third Party Manufacturers / Re: Nikon's D800E 30% sharper than D800
« on: July 07, 2014, 10:58:25 AM »
That is laughable for several obvious reasons, first, they are saying the Ziess lens is perfect and causes zero resolution loss, that is impossible, it is either breaking the laws of physics, or their measurements are suspect yet again. And, just read any Nikon forum where people own both, and there are a surprising amount, they will tell you that is simply not true, yes the E does resolve slightly more, but 30% more, no.


Not exactly perfect.  just able to use the full resolution of the sensor.

If they sensor was 8 MP and a lens resolved 8, would you call that perfect?  Just pushes the limit of the sensor.


No that isn't how it works, there is a complex relationship between each individual elements efficiency and a systems efficiency. Pretty much all lenses can actually resolve way more than any sensor, just look at the difference between a lens optical bench tested lens and one that relies on a camera sensor, huge difference.

So if the sensor was a 20MP sensor and the lens and sensor were both perfect then you'd expect to get 20MP of resolution, this is what DXO are claiming for the D800E and Zeiss 135 combo. However if we ignore all other factors and the lens is only 99% perfect it can only possibly resolve 99% of a perfect sensors resolution, and no sensor/camera is perfect. So the perfect sensor and 99% perfect lens could equate to 19.8MP in a simplified form.

For the full equations look here under "System Resolution": http://en.wikipedia.org/wiki/Optical_resolution


(Note, this response is for the benefit of everyone, it is not just a reply to PBD):

I wouldn't necessarily say it's complicated, but total optical system resolving power is non-obvious.

One thing, "perfect" resolution actually means "infinite" resolution. The resolving power of an optical system (i.e. a whole camera with lens and sensor) is limited by the resolving power if the least capable component. If that is the sensor, then resolving power of the whole has an asymptotic relationship with the resolution of the sensor.

I think it's tough to say that a lens resolves 99% of "perfection"...since perfection requires infinite resolving power (at an infinite aperture, to be explicit). What is 99% of infinity? Lens resolving power is also non-linear...it falls off as the aperture is made smaller. Lens bench tests often test at max aperture and at f/8, but that is not guaranteed. So one must be specific when discussing resolving power of a system.

If we have a lens at f/4, and that lens achieves the maximum diffraction-limited resolving power, it resolves 173lp/mm. A theoretical 8mp APS-C sensor would resolve about 80lp/mm. The resolution of the whole camera, lens and sensor combined, can be closely approximated by taking the RMS of the minimum resolvable spot for each, and converting back to lp/mm. The lens resolves a spot of 2.9µm, the sensor a spot of 6.2µm. The two when working together convolve to produce a spot size of 6.85µm, or a system resolution of 73lp/mm. The two together resolve LESS than the resolving power of the least capable...in this case, the sensor.

If we dice all the pixels in our 8mp sensor into quarters (make the pixels half as large), we end up with a 32mp sensor capable of resolving 161.3lp/mm. Combined with the same lens, the system resolution is 117lp/mm. If we make a sensor with the same resolving power as the lens, we have a 39.7mp sensor. The resolving power of the system is 122lp/mm. We are still short of the 173lp/mm of the lens. We haven't actually achieved "perfect" resolving power, despite increasing the resolution of our sensor. You never can...as you increase the performance of one component or the other, the bar just keeps getting higher...the mechanisms that convolve the image signal into the final output are constantly working against you, keeping you from actually achieving the real potential of either component. You would have to RADICALLY increase the performance of one in order to approach the limit of the other. To actually resolve the 173lp/mm spatial resolution possible with an f/4 lens, you would need pixels smaller than 0.25µm, or 250nm in size. That is smaller than the wavelengths of all visible light! It's even smaller than near UV, getting into deep UV. A sensor with pixels that small would be a 5.34 GIGApixel sensor!  And that camera would still resolve 171.7lp/mm...it's still falling short of the 173lp/mm theoretical maximum of an ideal f/4 lens.

The only way to achieve perfect resolution is to have both a lens and a sensor with infinite resolving power. Obviously, such a lens does not exist. The best you can hope for is diffraction limited behavior at a lens' maximum aperture. Few lenses achieve diffraction limited behavior at f/4, most still have a small amount of optical aberrations, especially around the periphery. The Otus is one lens that approaches ideal performance pretty closely, though.

72
EOS-M / Re: Cheap 400mm advice
« on: July 06, 2014, 02:21:01 PM »
Just because a lens is faster for a given focal length doesn't mean it has more resolving power.  It does mean it has more potential resolving power due to larger aperture but aberrations do matter, and small fast mirror lenses are often much poorer optically than larger slower telescopes.

It's not necessarily that it's faster, really. Resolving power is related to the total surface area of the objective (i.e. primary mirror in a relector), which in turn ultimately determines the aperture (physical aperture, not relative aperture), which is ultimately responsible for gathering light. It's a simple test that can be done with stars. Point any two lenses at the same place in the night sky. Ultimately, regardless of which one is actually "faster", the one with the largest physical aperture will resolve more and smaller stars. F-ratio is simply that, a ratio...all it really does is describe in common terms how large the physical aperture of a lens will be for a given focal length. I wasn't trying to say that a "faster" 800mm lens is going to resolve more in my example with 800mm lenses...I was saying that the larger physical aperture is going to be gathering more information per point on any given subject, and thus it will have a higher resolving power.

This is almost exclusively true with telescopes, which are almost always diffraction limited. It is true that cheaper optics in a lens have the potential to introduce aberrations. However in the case of astrophotography, all that really means is instead of resolving a single crisp, bright point of light for a star, you resolve a bright point of light that has some kind of halo around it. Optical aberrations don't necessarily reduce resolution, they just muck with the quality of the image.

73
EOS-M / Re: Cheap 400mm advice
« on: July 06, 2014, 01:29:21 PM »
How about one of these stuck on an EOS M? That should give me 1280mm.

http://www.amazon.co.jp/dp/B00KXMHBXY/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=36YFE91EPADLO&coliid=I3UGJ5SGRPAHD9&psc=1


It ultimately depends on what your goals are. Long focal length is certainly important, and I think around 800mm is a good place to start for shooting the moon with APS-C.

There is another factor, however. Fundamentally, resolving power is linked to the physical size of the aperture. This usually isn't as apparent in normal photography as it is in astrophotography, but when you start resolving the very fine detail that exists in objects in space, this fact begins to become very important.

Assuming you had an 800mm f/4 lens, 800mm f/5.6 lens, and 800mm f/8 lens. Most people's inclination would be to think, they are the same focal length, so they should be the same so long as I expose for longer with the f/5.6 and f/8 lenses. In terms of brightness of the object, that will be true...however the f/5.6 and f/8 lenses won't be resolving as fine a level of detail as the f/4 lens, and the f/8 won't resolve as fine a level as the f/5.6.

It isn't simply a matter of magnifying detail....it's maintaining your resolving power as you magnify it more. With the EF 600mm f/4 L II and a 1.4x TC, I have an f/5.6 lens. The reason my moon photos are so sharp and detailed is due to the fact that my combo maintains a high resolving power, thanks to a large aperture (remember, the entire surface area of the lens is gathering light for every single mathematical point on your subject...the more light gathered for each point, the more complete and refined those points will be when focused on your sensor).

If you just go with a 1250mm f/13.9 lens, the moon will be very large, but you won't actually be resolving more detail than say an 800mm f/8 lens. The 1540mm f/12.1 lens is actually going to be a better option than the 1250mm f/13.9 lens...it has a much larger physical aperture: 127mm vs. 89mm...a 127mm aperture is actually very nice...close to the 600mm f/4, and it would be my top recommendation from the list of telescopes offered by Lee Jay. A 1600mm f/12 optic is going to be a powerhouse for resolving moon detail....not to mention you could do some amazing planetary imaging with that and a barlow lens as well (at 4800mm with a 3x barlow, a simple web cam or something like the QHY5L-II color planetary camera, some video imaging software (I think the QHY5L-II comes with some software) and a tool like RegiStax, you could create AMAZING planetary images, as well as some awesome close-ups of the moon itself.)

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Wordpress should do what you want. It is a multi-user system, so you can set up other users for your wordpress site, and they can upload stuff if they have the right user level (i.e. contributor or editor). WordPress has a LOT of themes, although the best ones are for-pay (usually worth it, one time cost for any given site). WordPress sites hosted at WordPress.com have a decent amount of features, usually enough for the vast majority of people to get by.

If you need ultimate flexibility, you can always find a cheap web host that offers WordPress hosting, and you can install any one of thousands of plugins that pretty much make WordPress one of the most powerful hosting web site and blog platforms on the planet.

If you want to see what WordPress can do, take a look at my personal site: http://jonrista.com. It's built entirely on WordPress, including the blog, photo carousel, gallery, and individual pages.

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EOS-M / Re: Cheap 400mm advice
« on: July 06, 2014, 05:31:28 AM »
Hey guys I was wondering which would be better for achieving ~ 400mm focal length with the M. I would like to take some occasional pics of the moon. I've done it before and found 400mm to be long enough with a bit of cropping.

You want a LOT more focal length than 400mm to image the moon. I used an 840mm lens (EF 600mm f/4 L II w/ 1.4x TC) to produce this image:

Look Jon, stop playing these amateur games and get real. This is what you need.

Haha! Now THAT...is a MOON LENS! :D And apparently, one hell of a giant EOS as well...  :o

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