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Author Topic: Canon EOS Rebel T4i [CR2]  (Read 50368 times)

jrista

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Re: Canon EOS Rebel T4i [CR2]
« Reply #60 on: December 07, 2011, 08:50:26 PM »
According to Canon themselves, their BEST L-series lenses are only capable of resolving about 45mp of detail in a Full-Frame image circle.

If Canon ever said that, whoever said it was about as clueless as clueless can get.  A 1.4x TC is about the same as doubling pixel count.  Do you seriously believe that a 400/2.8 can only support a single 1.4x teleconverter on a 5D II?  If so, look at this:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=37493247

That's 4x worth of TCs on a 400/2.8 on a 7D!  That's the equivalent of 737MP on a full-frame sensor.

I routinely use a 2x on my old 70-200/2.8 on a 20D - the equivalent of 32MP on 1.6-crop or 84MP on full-frame - and get pixel-sharp shots (which shows I'm still undersampling).  The new 70-200 is much better than the old one, and has been shown to support stacked 2x and 1.4x on the 7D (the equivalent of 144MP on 1.6-crop or 369MP on full-frame).  The best primes are better.

I'm not certain what your getting at, however if I understand correctly, I think your conflating two disjoint concepts: magnification and resolution. The magnification of an optical system affects how much a subject is enlarged in the image, and resolution of an optical system is how finely differentiated distinct detail is in the image. The two concepts are distinct, and can vary independently of each other. There is nothing that would prevent an increase to magnification while maintaining resolution...say slapping a teleconverter or four onto a lens. Similarly, there is nothing that would prevent an increase to resolution while maintaining the magnification of a lens.

I don't believe adding on a teleconverter does anything to optical resolution, other than possibly reducing it a bit as your adding more optical elements into the light path, each of which has the potential to diminish resolution with aberrations, flare, etc. (And thats only if you use teleconverters of the same optical quality as your lens...using cheaper teleconverters are most likely going to reduce the maximum optical resolution, not increase it.) I DO believe that adding a teleconverter will affect the magnification of the object your imaging, which is exactly the case with that image of the moon you linked...slapping on four teleconverters magnifies the moon more, however the overall optical resolution of the system should remain about the same.

If you are referring to the resolution an image of the entire moon would be when imaged at that magnification, then yes...you might have to produce an image mosaic 737mp in size at to capture the entire moon at that magnification. But thats NOT the same thing as resolving 737mp worth of detail in the same image circle.

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Re: Canon EOS Rebel T4i [CR2]
« Reply #60 on: December 07, 2011, 08:50:26 PM »

K-amps

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Re: Canon EOS Rebel T4i [CR2]
« Reply #61 on: December 07, 2011, 09:41:47 PM »
i am very happy with my kenko one on all my lenses and testing the 1.4 I found stopping down one more stop from the new wide apperture yields equivelant IQ to the native lens widest apperture ie 70-200 f2.8 put the Tc on at 280mm f5.6 IQ is the same as at 200 f2.8

and it works on all lenses great on the 50 f1.4 to give it a little more reach too

Thanks for your input.

Are they fully automated (AF.metering etc)?  care to post a few pics?
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wickidwombat

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Re: Canon EOS Rebel T4i [CR2]
« Reply #62 on: December 07, 2011, 09:50:46 PM »
i am very happy with my kenko one on all my lenses and testing the 1.4 I found stopping down one more stop from the new wide apperture yields equivelant IQ to the native lens widest apperture ie 70-200 f2.8 put the Tc on at 280mm f5.6 IQ is the same as at 200 f2.8

and it works on all lenses great on the 50 f1.4 to give it a little more reach too

Thanks for your input.

Are they fully automated (AF.metering etc)?  care to post a few pics?
yep I have the DGX version it has full transmission of Af metering and adjusts max aperture you can select by the relevent amount and full exif data (so exif data on a 300mm lens will show shot at 420mm) i'll see if i can dig up some pics
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Lee Jay

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Re: Canon EOS Rebel T4i [CR2]
« Reply #63 on: December 07, 2011, 11:27:21 PM »
According to Canon themselves, their BEST L-series lenses are only capable of resolving about 45mp of detail in a Full-Frame image circle.

If Canon ever said that, whoever said it was about as clueless as clueless can get.  A 1.4x TC is about the same as doubling pixel count.  Do you seriously believe that a 400/2.8 can only support a single 1.4x teleconverter on a 5D II?  If so, look at this:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=37493247

That's 4x worth of TCs on a 400/2.8 on a 7D!  That's the equivalent of 737MP on a full-frame sensor.

I routinely use a 2x on my old 70-200/2.8 on a 20D - the equivalent of 32MP on 1.6-crop or 84MP on full-frame - and get pixel-sharp shots (which shows I'm still undersampling).  The new 70-200 is much better than the old one, and has been shown to support stacked 2x and 1.4x on the 7D (the equivalent of 144MP on 1.6-crop or 369MP on full-frame).  The best primes are better.

I'm not certain what your getting at, however if I understand correctly, I think your conflating two disjoint concepts: magnification and resolution.


No, I'm not.

There are two ways to change the real resolving power of an imaging system of a given aperture - change the focal length or change the pixel size.  They are equivalent, with all else equal (sensor efficiency, read noise, processing, etc.).

Quote
I don't believe adding on a teleconverter does anything to optical resolution, other than possibly reducing it a bit as your adding more optical elements into the light path, each of which has the potential to diminish resolution with aberrations, flare, etc.

We're not talking about optical resolution, we're talking about image resolution.  You can have the sharpest lens in the world and a sensor with 1 pixel won't have any resolution.  The resolution (not pixel count - resolution) of the final image is what matters in a resolving power/aperture/focal length/magnification limited situation.

Quote
If you are referring to the resolution an image of the entire moon would be when imaged at that magnification, then yes...you might have to produce an image mosaic 737mp in size at to capture the entire moon at that magnification. But thats NOT the same thing as resolving 737mp worth of detail in the same image circle.

Yes, it is.  Well, off-axis performance can be an issue, but aside from that, it's the same.

Think of doubing pixel count as a built-in 1.0-1.4x zoom teleconverter with no optical aberrations.
Think of quadrupling pixel count as a built-in 1.0-2.0x zoom teleconverter with no optical aberrations.

More pixels also means better noise performance.  Yes, I know, many here and other places think that's backwards, but they're wrong in nearly every case.  Sure, it means more noise at the 100% crop or 1:1 pixel level, but it also means lower noise in the overall image.  This is for a simple and (should be) obvious reason - modern noise reduction algorithms are spectacularly more efficient at eliminating noise and preserving detail than simple block averaging is.  Larger pixels do nothing but block average.

Think about this - the ideal sensor would capture each photon's location accurately and individually.  This is the most information you can capture and it corresponds to infinite pixel count.  In such a situation, each pixel would be extremely noisy - just on or off.

The main disadvantages to more pixels are, more relative read noise in photon-starved situations (but read noise has improved greatly of late), lower sensor yield, higher demands on the read electronics and processing pipeline, and larger storage and post-processing requirements.  Image degradation isn't a disadvantage of more pixels until your process technology can't produce good fill factors at the smaller sizes.  At the moment, that point is at about 1.5 micron pixels, which are an order of magnitude smaller in area than the ones in the 7D.

I can and have proven the substance of what I just said with real-world photographic testing of real cameras with real optics.

jrista

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Re: Canon EOS Rebel T4i [CR2]
« Reply #64 on: December 08, 2011, 01:33:00 AM »
@Lee Jay: Before we commandeer this thread, we might want to start another one to discuss the topic of resolution. I don't disagree with you on the principal of pixel size and recording image data, but I think your missing the fact that there IS a finite limit on how much optical resolution can be projected (imaged), by an optical system, regardless of what device may be recording that image (digital sensor or film.) We should move this discussion elsewhere and allow the normal topic of this thread to continue, though.

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Re: Canon EOS Rebel T4i [CR2]
« Reply #65 on: December 08, 2011, 03:55:42 AM »
I hope Canon doesn't do a 24MP APS-C sensor.  If you look at the Sony 24MP APS-C sensor it is nowhere as good as the 16MP sensor on the Nikon D7000.

Lee Jay

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Re: Canon EOS Rebel T4i [CR2]
« Reply #66 on: December 08, 2011, 09:14:46 AM »
... I think your missing the fact that there IS a finite limit on how much optical resolution can be projected (imaged), by an optical system, regardless of what device may be recording that image (digital sensor or film.)

Yep....and that limit is reached when pixel density reaches infinity.  What you end up approaching is the limit created by optical aberrations + diffraction.  Many of the best lenses have almost no aberrations and thus you're approaching this limit:

http://en.wikipedia.org/wiki/Spatial_cutoff_frequency

Of course, you don't really need infinity to get "most" of that limit.  But you need a lot more than most people think.  For example, this occurs somewhere in the neighborhood of f/20 on the 7D.  That's higher than you might think or calculate directly due to the combined effects of the AA filter, the Bayer mask and its demosaicing, and the fact that the pixels occupy space instead of being infinitesimally small (which we want so they can actually capture some light).

This is why a lot of astro folks shooting planets with 5.6 micron pixels (roughly 40D size) will shoot at f/28-f/40 (f/30 is common) - that's where they can extract all the detail their aperture can give them.  For example, these were shot by a dedicated amateur with a backyard scope of 14" of aperture at somewhere close to f/30:

http://www.damianpeach.com/barbados10/2010_09_12pic.jpg
http://www.damianpeach.com/barbados10/20100912whole.wmv

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Re: Canon EOS Rebel T4i [CR2]
« Reply #66 on: December 08, 2011, 09:14:46 AM »

jrista

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Re: Canon EOS Rebel T4i [CR2]
« Reply #67 on: December 08, 2011, 10:11:24 PM »

match14

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Re: Canon EOS Rebel T4i [CR2]
« Reply #68 on: December 09, 2011, 03:06:16 AM »
I hope Canon doesn't do a 24MP APS-C sensor.  If you look at the Sony 24MP APS-C sensor it is nowhere as good as the 16MP sensor on the Nikon D7000.

Well it is a good thing that Canon won't be using that 24MP APS-C sensor any  time in the near future then isn't it?

This rumor suggests that they will be making a 24MP sensor soon.  I hope they don't 18MP on APS-C is enough.

moreorless

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Re: Canon EOS Rebel T4i [CR2]
« Reply #69 on: December 09, 2011, 06:24:20 AM »
To be fair the Sony sensor is just one example and represented a larger jump in resolution over a shorter time period than Canon moving to 24 MP would.

thelebaron

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Re: Canon EOS Rebel T4i [CR2]
« Reply #70 on: December 10, 2011, 05:37:26 PM »
Think the T4i will feature iso performance anywhere near what the C300 can do? What that thing can do is incredible, and Id gladly snap up a new rebel just for that kind of high iso performance

tt

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Re: Canon EOS Rebel T4i [CR2]
« Reply #71 on: December 11, 2011, 04:13:33 PM »
Think the T4i will feature iso performance anywhere near what the C300 can do? What that thing can do is incredible, and Id gladly snap up a new rebel just for that kind of high iso performance

It'll be an interesting state of affairs come February/March - either they keep with an old sensor - in which case little change, or upgrade the sensor, but keep same MP - in which case the 650D gets closer to the 7D's performance.
Would cause disruption if the 650D got a sensor better in ISO than the 7D.  But then why not? Do they wait another year till the other lines have updated (5D, 7D)?

whatta

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Re: Canon EOS Rebel T4i [CR2]
« Reply #72 on: December 14, 2011, 03:34:50 AM »
It'll be an interesting state of affairs come February/March - either they keep with an old sensor - in which case little change, or upgrade the sensor, but keep same MP - in which case the 650D gets closer to the 7D's performance.
as far as I know the IQ of 550d/600d is identical to the 7d. same sensor same digic4. So 650d with digic 5 should have better IQ than the 7d.
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Re: Canon EOS Rebel T4i [CR2]
« Reply #72 on: December 14, 2011, 03:34:50 AM »

whatta

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Re: Canon EOS Rebel T4i [CR2]
« Reply #73 on: December 14, 2011, 03:46:02 AM »
Now that dpreview has reviewed the NEX-7 and said "It's no stretch to say that, at its best, the NEX-7 offers the finest still image quality of any APS-C camera, bar none."
http://www.canonpricewatch.com/price-changes/
very interesting aspects, indeed.. I hope the nex7 has not arrived too late for the 650d, and therefore it will have a new sensor as well not only digic5. I am not interested in more MP, but better IQ and iso and DR are always welcome.
« Last Edit: December 14, 2011, 05:47:18 AM by whatta »
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Re: Canon EOS Rebel T4i [CR2]
« Reply #73 on: December 14, 2011, 03:46:02 AM »