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Author Topic: The Megapixels are Coming [CR1]  (Read 31831 times)

jrista

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Re: The Megapixels are Coming [CR1]
« Reply #105 on: March 18, 2012, 11:35:12 PM »
Actually Lee Jay is the one who is more correct here.
The system resolution of the object will be the same with an ideal 1.4x as with doubling the number of pixels. If you can gain object resolution with TC you can do the same by increasing the number of pixels.

Assuming a wide enough aperture that does not lose resolution to optical aberrations, and is not yet blurring detail beyond the diffraction limit of the sensor, sure.

Just reminding you that you agreed before - with Tuggem, not myself - that increasing focal length with a TC is equivalent to shrinking the pixels on the sensor.

You also agreed with me on that point:

Quote
The point is, increasing focal length while preserving aperture (and thus increasing f-stop) and decreasing pixel size are equivalent.

To which you replied:

Quote
Not disputing that.

Yes, IN REALITY, not virtually by looking at the sensor through the front of the lens!! I agree that literally using a sensor with more megapixels with the original lens without TCs, and cropping the image produced by a higher density sensor is similar to using a TC with a smaller sensor: both of them magnify the subject relative to spatial resolution. I've never agreed about anything else.

Using a higher density sensor, though, is not exactly the same. A 116lp/mm 18mp APS-C can double-sample an image produced by a lens+TC combo at f/13 (MTF 50, which is about 56lp/mm). That lens+sensor system, despite the fact that the sensor is double-sampling the virtual image, is still only achieving a total resolution of 52.6lp/mm. Lets drop the TC, and double the number of pixels. We are now at 165lp/mm for the sensor and 82lp/mm for the lens. The sensor is oversampling by almost a factor of three, however our system resolution, while its definitely an improvement over the system with a TC and lower resolution sensor, is still only 73.5lp/mm. I believe it was Tuggem who actually said doubling the number of pixels is actually better than using a 1.4x TC and quadrupling pixels is better than using a 2x TC. Crunching the numbers, it appears to really indeed be true (double the pixels is about 40% better than using a 1.4x TC)...assuming its actually a LITERAL INCREASE, as in, you physically use a sensor with double the number of pixels.

For some reason, you dispute the next step, namely that shrinking the pixels results in more pixels in the same area.  Thus, adding a teleconverter is just like increasing pixel count in the same space.  I don't understand what could be more clear about that.

I also want to point out your own statement that started this:

Quote
The 7D is already pretty maxed out when it comes to resolution as well with 18mp in an APS-C format. You might gain a bit more by going to 20 or 22mp, but thats going to make it really hard to get sharp shots right down to the pixel level...and you would only be able to do so at a very narrow range of apertures at the center of the lens before diffraction or optical aberrations kill you.

That statement is in error, and more to the point, it's irrelevant.  Sharp shots down to the pixel level means you are throwing away detail by definition.  If people really want that, then we have an education problem.

I'm not so sure its as much an education problem as it is a mental and perceptual problem. People don't spend money on 18mp, 22.3mp, or even 36.3mp to get what they perceive as soft photos (regardless of how irrational that may be). Thats more than readily apparent in how much flak the 7D gets from people complaining about how soft it is (at apertures much above or below f/4.) Personally, while intellectually I fully understand the value of oversampling optics and downsampling the results to achieve the level of sharpness I want, that whole psychological bent towards wanting sharp results strait out of the camera still exists (and is actually a necessity if you shoot JPEG for immediate review and publish.)

Regardless, even if we use MTF 50, and we agree that many lenses can achieve diffraction-limited performance at f/4 like my now-discontinued 70-200/2.8L IS can, the resolution is:

0.38(0.000550*4) = 172.7lp/mm

Given 3 pixels to resolve 1 line pair, that's 11,554x7,702 = 89 megapixels on APS-c.

Optically, 172.7lp/mm at f/4 is certainly possible, again never disputed that (I believe I've used the number 173lp/mm for f/4 on several occasions in my previous posts.) I've tried to account for low-pass filters (particularly the stronger one on the 7D...although low pass filters are a bit of a wildcard and can never be fully accounted for without a full understanding of their impact on spatial frequencies), and the fact that bayer sensors require interpolation to produce "full color" (or final RGB) pixels once processed, and the fact that the spatial phase of the sensor is not always aligned with the spatial phase of the virtual image, by using 4 pixels / line pair. Perhaps a tad conservative (although it is a general practice to assume 4p/lp when discussing bayer sensors, even by astrophotography enthusiasts), however I think using 3 pixels / line pair is a bit aggressive. Perhaps a happy medium of 3.5 would be more realistic. Either way, sure, at the sharpest aperture after optical aberrations are eliminated and before diffraction sets in and starts diminishing maximum potential resolution, you could keep pushing sensor resolution. Its a very narrow window within which you can achieve more resolution, and there are rather few lenses that are not aberration-bound at wider apertures that can currently support higher resolutions than are attainable at f/4 (the majority of which cost a small to moderate fortune.)

My comment above about 20-22mp is inaccurate on a scientific level, but it wasn't originally intended to be hard core scientific (my desire to be more accurate only came after you decided to conflate the use of TC's with literal increases in sensor spatial resolution.) I think I originally made that comment in the context of the average photographer who usually does suffer from the "psychological impairment" discussed above. I still agree, for most apertures of the lenses the majority of 7D photographers are likely to use, I think the softness of photos caused either by optical aberrations or diffraction around the f/4 "sweet spot" is going to be a turn-off for more photographers than not. I've spent more time arguing the fact that the 7D is not sharpness-impaired, its just that it frequently outresolves the lens at the apertures used, than I have argued my points in this particular thread. ;) In that context, I don't think pushing APS-C resolution much beyond where we have it now is going to buy the average photographer all that much. The window around that sweet spot, wherein you can get very sharp images that keep increasing in detail as you use better and better optics will shrink the closer you get to 70, 80, or 90 megapixels packed into the space of an APS-C sensor. (We haven't even touched on the fact that for all but a few of Canon's L-series lenses, such resolution is also only really possible in the center of the lens, and falloff, sometimes severe, to the corners reduces resolution well below theoretical perfection. There would need to be considerable center-to-corner improvement in lenses to fully support "perfection" across the area of the lens, and in many cases where trade-offs are required...such as wide angle zoom lenses...perfection may be unattainable, at least for the refractive optics of DSLR cameras.)

I think far greater benefits can be gained at the resolution were at now by improving ISO, lowering noise, etc. instead of chasing a difficult to attain perfect resolution at a very narrow aperture range, where all other apertures achieve less and produce softer and softer photos at higher and higher resolutions. Yes, its all psychological, but thats really what matters beyond the rather narrow bounds we've been arguing within lately. Thats all besides the points I've been making thus far, however. And hopefully my comment to the original quote at the beginning of this post clears up my position.

So, two conclusions:

- Teleconverters are just like multipliers on pixel count (1.4x = 2x pixel count), but with reduced field of view which is irrelevant if you're looking at a small portion of the frame anyway.
- We still have plenty of room to grow pixel counts before we are capturing nothing but additional gray sludge.

I'd love the next 7D to be 24MP on APS-C and have f/8 AF sensors.  Such a system would almost achieve MTF50 at f/8 - certainly it would achieve way above the commonly-used extinction points of MTF9, MTF5 or MTF0.  If they can't provide f/8 AF sensors, 32MP or more would be nice.

You are certainly free to conclude all you want, however I still think its factually invalid. The sensor's pixel count DOES NOT ACTUALLY INCREASE, two fold or any other fold. Thats a fixed constant for any given camera, no amount of optics will ever change that. Neither will they improve the spatial resolution of the system at large unless you replace the lens with something that is closer to perfection than its predecessor (and probably replace the teleconverters as well.) Even if you do replace a less than perfect lens with a perfect lens, the final spatial resolution of the system will never surpass that of the sensor itself...you can only approach it.

To turn things around, lets assume the lens is the limiting factor, rather than the sensor. The same rules apply to increasing the physical resolution of a sensor. If you are using a lens that is only capable of resolving 150lp/mm, using a sensor capable of 300lp/mm (2x oversampling) will still result in a system resolution of only 134.3lp/mm. Doubling the sensor resolution again to 600lp/mm still only gets you to 145.7lp/mm, and the returns diminish well beyond the realm of reason to actually approach 149.99lp/mm. The only thing you can do to increase the resolution of the system as a whole at this point is to physically improve the least effective component...a better lens, in this case. With a perfect lens capable of 173lp/mm and your 300lp/mm sensor, your system resolution is now 149.5lp/mm.

There is no one-piece magic bullet that can instantly improve the resolving power of any system by orders of magnitude. If you want to achieve 173lp/mm, you need to improve each and every component of the system to raise the lowest common denominator high enough that it surpasses your target resolution by a sufficient amount. To actually achieve a system resolution of 173lp/mm, you would need both a lens and a sensor capable of 247lp/mm, and that imposes a minimum aperture of f/2.8 in a perfect lens (or less than perfect lens with an even wider aperture.) It would be at this point, with a perfect f/2.8 lens, that we could finally use everything an 80mp APS-C sensor had to offer.



As a note on low-contrast photography and astronomical bodies. The use of extremely low contrast photography, at Rayleigh or even as low as Daws, by astronomers is to determine if two extremely close points of starlight are indeed separate points and thus separate...such as a binary star. Using photography for such purposes is not an average case, it is a rather specialized and more scientific case than anything else. One usually has to explicitly know about contrast, diffraction, MTF, etc., and know exactly what they are looking for, to be able to use MTF 0% photography to identify distant binary stars and the like. Special processing techniques are also usually involved when working at MTF 0%, such as multiple image stacking and superresolution that can use computation and algorithms to produce a final high resolution image that is more likely to show the 5% peak dip between two low-contrast points of light at Daws MTF 0. NorthLight images have this to say about digital photography down to MTF 0 (emphasis added):

Quote
So to resolve all data up to a frequency corresponding to 4000 lines—the Rayleigh criterion-- would require a Nyquist frequency of 8000 vertical lines, corresponding to 100 megapixels.

The Rayleigh criterion was derived based on a simple model that correctly predicted what astronomers could see. More recent astrophotographic techniques allow stars to be distinguished up to the point that MTF drops to zero. This is about 20-25% closer spacing than the Rayleigh criterion, and is referred to as the Dawes limit[14]. If we wished to use this as the criterion for resolution, then the required sensor resolution would be about 150 megapixels. It is also possible for astronomers to detect whether a star image is a single star or a binary star even of there is no separation between the two adjacent maxima: the form of the merged maximum can still be indicative of a binary subject.[15] . But there is a catch to the latter method: you have to know in advance that you are looking for two closely separated points. If you have no a priori information about what the subject is, this method won’t work. So it is pretty much useless for normal photography.

At current digital camera resolutions of 20-35mp, which are well below the 150mp necessary Dawes level photography (0% contrast) and 100mp necessary for Rayleigh level photography (9% contrast), we may be able to achieve useful resolution at less than MTF 50, but outside of specialized cases and potentially specialized processing, we still need considerably more contrast than at either Rayleigh or Dawes for the average type of photography where sharpness strait out of camera is highly desirable.

It should also be noted that much of Rayleigh and Dawes criterion astrophotography for the purposes of identifying binary stars started out with film. Film has better characteristics to gathering detail at low contrast than digital sensors do, so its more capable at resolving fine detail at MTF 9. Conversely, digital sensors are better than film at resolving contrasty detail at closer to MTF 40-50 than film is. For specialized photography, such as astrophotography, where low-contrast detail is supreme, there is probably far more room to grow in terms of digital sensor resolution than there is for general forms of photography, where sharpness and contrast are frequently more important.
« Last Edit: March 19, 2012, 12:53:29 PM by jrista »

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Re: The Megapixels are Coming [CR1]
« Reply #105 on: March 18, 2012, 11:35:12 PM »

SandyP

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Re: The Megapixels are Coming [CR1]
« Reply #106 on: April 03, 2012, 02:53:13 AM »
I hope they are, actually. Here's why...

I shoot weddings, every year, I shoot wedding. I like them, not only because they pay the bills, but because they're fun, and I enjoy that type of shooting. But yes, they're a major money maker for me. I also shoot documentary type stuff a few times a year, which involves shooting thousands and thousands of photos every few days, for upwards of 10+ days at a time. This is taxing. Even with 21MP of my 5D Mark II.

You can see where this is going. File sizes. Blah blah blah, yes, it matters. I was shooting a lot of stuff in SRAW1 on certain parts of the wedding, and during many parts of the documentary shooting in Cuba. Even whilst I knew that a lot of the stuff was going to print when I got back.

Anyways, I do shoot a lot of fashion, and portraits and stuff like that. High resolution is absolutely not needed for me, 21MP has always been amazing, (and a good friend shoots all that stuff with a D3s, at 12MP), but let's face it, 36MP would be nice in SOME situations for editing and potential magazine submissions where they like to crop heavily sometimes.

When I look at the D800, I'm secretly jealous of the resolution. I'm not a megapixel (mega pickles!) junkie, and I don't think the grass is always greener, but I love editing, and when I go to retouch, I'm always at 100% for a lot of the work I do. The D800 is sexy in this regard. DR isn't really my concern, and I see the 5D Mark III isn't quite up to it, but has more then the Mark II.

When I look at the Mark III, I think about all my sexy L glass, and the Canon files that I've always loved from my Mark II. And I see vast improvements where I've always wished they existed (AF being one).

I'm not into video, I'll use it now and then, but it's not my thing.


So, I'd love for Canon to eventually address this market, and I think eventually they will absolutely have to have something to compete with that. And I'll buy that Canon megapixel monster for sure, because I'd like to use specific tools for specific jobs. It wouldn't go to Cuba with me, it wouldn't be at my weddings. But it would be in the studio with me, and it would be at all the on location shoots I do.

Having both would keep me happy forever. Really.


As it is right now, I'm choosing the 5D3, because it's a very well balanced camera. It has good resolution, high ISO and great features such as excellent AF, finally. And in the end, we know that creativity, lighting, and vision have 1000x more to do with good photography than megapixels and the brand of camera you use.

But Canon, wake up a bit more! And surprise us a bit. :)

itsnotmeyouknow

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Re: The Megapixels are Coming [CR1]
« Reply #107 on: April 03, 2012, 06:24:47 AM »
(especially without a low pass filter like the D800).


The D800 does have a low pass filter.  It's the D800e that doesn't.  The medium format Pentax 645D also doesn't have a low pass filter. 

I admire the science in this part of the thread - quite baffles me and I'm no dunce.  The science of pixel peeping is my first impression.  I'll leave viewing photographs to the optimum distance from the appropriate media thank you, that is what art is about.  Do you look at a Turner painting with your head against the painting and criticise the brush strokes?  I thought not.  That's the problem with fora such as these.  I think we run the risk of overexamining things and missing what's actually important

« Last Edit: April 03, 2012, 06:26:45 AM by itsnotmeyouknow »

Panurus

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Re: The Megapixels are Coming [CR1]
« Reply #108 on: April 03, 2012, 07:08:21 AM »
A lot of people knows that Light is a transverse, electromagnetic wave that can be seen by humans. The wave nature of light was first illustrated through experiments on diffraction and interference.
But who have see samples that show this fact.

The post is : The megapixels are coming.

The last time that I had studied this subject, I had found this:




http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_31_en/$File/CLN31_English.pdf

http://www.zeiss.com/C12567A8003B8B6F/EmbedTitelIntern/CLN_31_MTF_en/$File/CLN_MTF_Kurven_2_en.pdf


http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild1/$File/Image_01.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild2/$File/Image_02.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild3/$File/Image_03.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild4/$File/Bild_04.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild5/$File/Bild_05.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild6/$File/Bild_06.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild7/$File/Bild_07.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild8/$File/Bild_08.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild9/$File/Bild_09.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild10/$File/Bild_10.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild11/$File/Bild_11.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild12/$File/Bild_12.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild13/$File/Bild_13.jpg
http://www.zeiss.com/C12567A8003B8B6F/GraphikTitelIntern/CLN31MTF-KurvenBild14/$File/Bild_14.jpg


If you want to go quickly, then you will look at the crop  13.jpg.
left original                   center: 24 Mpix               right:   12 Mpix

If you want to understand more than you have to read the documents.

After you understand why Canon declare:
"The images produced with the EOS-1D X camera’s new sensor are so clean that files can easily be up-sized if necessary for even the most demanding high-resolution commercial applications."

My 2 words:  When white = 100%(RVB 255) and black = 0% (RVB 0)

FTM 50% is  a contrast =  75% - 25 % / ( 75% + 25 % )

If your optics have a contrast of:                                           50    % @  80 lp/mm:
The contrast will be  (87.5 - 12.5) / (87.5 + 12.5) =              75     % @ 40 lp/mm
The contrast will be  (93.75 - 6.25) / (93.75 + 6.25) =         87.5   % @ 20 lp/mm
The contrast will be  (96.875 - 3.125) / (96.875 - 3.125) = 93.75  % @ 10 lp/mm

 Is far from :   100% - 0 % / ( 100% + 0 % ) 

So when the little lines, on my subject, are white and black. on my captor they arrive black washed and white dirty. So the real questions could it be?:

howmunch pixels want I to see the transistion from black washed towards white dirty?

Some days, I say 1DIV is not enough, some days 1DX is enough. Some of my friends think 7D. ;)


Marsu42

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Re: The Megapixels are Coming [CR1]
« Reply #109 on: April 03, 2012, 09:41:38 AM »
but let's face it, 36MP would be nice in SOME situations for editing and potential magazine submissions where they like to crop heavily sometimes.

Isn't there an option on the Nikon to get smaller raw files, too? Esp. since the dr and noise of the 36mp nikon sensor is like the 21mp Canon one...

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Re: The Megapixels are Coming [CR1]
« Reply #109 on: April 03, 2012, 09:41:38 AM »