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Author Topic: EOS 7D Mark II Information [CR2]  (Read 143919 times)

Pi

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Re: EOS 7D Mark II Information [CR2]
« Reply #240 on: August 06, 2013, 11:43:18 PM »
@ Pi - diagrams are intended to present a simplified view to aid in understanding. The idea is that you then extrapolate to gain a complete understanding.  Are all of your camera lenses a single, biconvex element?  Mine aren't. 

Oh, that is the problem? Here is another image again, a random hit:



Wrong again? source: http://photographylife.com/how-phase-detection-autofocus-works

Quote
News flash - crop sensors don't directly result in deeper DoF any more than wide angle lenses have a deeper DoF.

I did agree on that back in that thread, I see no reason to change the topic.

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Re: EOS 7D Mark II Information [CR2]
« Reply #240 on: August 06, 2013, 11:43:18 PM »

kaihp

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Re: EOS 7D Mark II Information [CR2]
« Reply #241 on: August 06, 2013, 11:44:21 PM »
Keep in mind the timeframe. Five years ago FF was much more expensive to manufacture than it is today. The fact that the 6D, still relatively new, sells for as little as $1700, is quite telling here.

It seems that Canon's fab procedure hasn't changed, at least from what we can tell.  Has the cost of silicon wafers come down that much?  Or could it be that Canon was reaping very high profit margins on the presumed high cost of a FF sensor, and now they've decided to push more units at a lower profit margin, as an alternative strategy to drive the bottom line?

Just sayin'.  Not that I'm cynical, or anything...   ::)

I do believe 300mm wafers have come down in cost. I remember them still having some challenges five to six years ago with defect rates on them (this is pretty agnostic of industry...not specific to sensor fabrication). It is obviously a less serious problem for tiny chips like GPUs and CPUs or other ICs. Growing the wafer crystals has become more refined over the years, in no small part to some of the advancements made while trying to perfect the process for growing 450mm wafer crystals (which, as far as I know, has still not been taken up by any IC manufacturing industry...there is apparently a very high initial cost to jumping that has to be recouped, something no manufacturer seems willing to deal with as of yet).

As far as I know, it's not that actual growing of the Silicon ingots to 300mm (or 450mm for that matter) that is the yield/cost issue. Getting very high quality and uniform ingots has always been extremely important to high-voltage devices (think kilo-Volts), because spikes in dopant concentration can result in avalanche-type catastrophic breakdowns (leading to the magic blue smoke leaving the devices in spectacular ways).

It's the yield of the manufacturing processes for everything you on the base wafer that matter (diffusion, implants, etching, photo lithography, metallization etc).

The problem for the jump to 450mm wafers is that you need the entire infrastructure of a fab to be in place: steppers, aligners, photo lithography, and so on. It's so expensive to develop, that basically the entire IC industry needs to coordinate around it; it's not enough that Intel or TSMC (or both) says "hey, we want to do 450mm now" and presto! they have it.

jrista

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Re: EOS 7D Mark II Information [CR2]
« Reply #242 on: August 06, 2013, 11:53:11 PM »
Keep in mind the timeframe. Five years ago FF was much more expensive to manufacture than it is today. The fact that the 6D, still relatively new, sells for as little as $1700, is quite telling here.

It seems that Canon's fab procedure hasn't changed, at least from what we can tell.  Has the cost of silicon wafers come down that much?  Or could it be that Canon was reaping very high profit margins on the presumed high cost of a FF sensor, and now they've decided to push more units at a lower profit margin, as an alternative strategy to drive the bottom line?

Just sayin'.  Not that I'm cynical, or anything...   ::)

I do believe 300mm wafers have come down in cost. I remember them still having some challenges five to six years ago with defect rates on them (this is pretty agnostic of industry...not specific to sensor fabrication). It is obviously a less serious problem for tiny chips like GPUs and CPUs or other ICs. Growing the wafer crystals has become more refined over the years, in no small part to some of the advancements made while trying to perfect the process for growing 450mm wafer crystals (which, as far as I know, has still not been taken up by any IC manufacturing industry...there is apparently a very high initial cost to jumping that has to be recouped, something no manufacturer seems willing to deal with as of yet).

As far as I know, it's not that actual growing of the Silicon ingots to 300mm (or 450mm for that matter) that is the yield/cost issue. Getting very high quality and uniform ingots has always been extremely important to high-voltage devices (think kilo-Volts), because spikes in dopant concentration can result in avalanche-type catastrophic breakdowns (leading to the magic blue smoke leaving the devices in spectacular ways).

It's the yield of the manufacturing processes for everything you on the base wafer that matter (diffusion, implants, etching, photo lithography, metallization etc).

The problem for the jump to 450mm wafers is that you need the entire infrastructure of a fab to be in place: steppers, aligners, photo lithography, and so on. It's so expensive to develop, that basically the entire IC industry needs to coordinate around it; it's not enough that Intel or TSMC (or both) says "hey, we want to do 450mm now" and presto! they have it.

Agreed on the last part...it is an industry-wide resistance to migrating to larger wafers. New fabs are built at an increasing rate, however, as more IC devices are used in an ever increasing array of applications. I figure someone would have put the money into building a new fab capable of 450mm by now...

I did read an article some time back, maybe seven or eight years ago now, that indicated that growing the crystal did not always produce perfect, uniform growth, and that further refinements of the process could improve quality and render an increase in usable 300mm wafers and fewer defects per wafer. I don't remember if it was online or in a magazine.

Pi

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Re: EOS 7D Mark II Information [CR2]
« Reply #243 on: August 06, 2013, 11:55:37 PM »
Actually, DOF, by definition, is this:

Code: [Select]
DoF = (2 * N * c * f^2 * s^2) / (f^4 - (N^2 * c^2 * s^2))
The factor for CoC, circle of confusion, is c. It is effectively arbitrary. [...]

I suggest you read this first:

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

Do not miss this paragraph:

If the original image is enlarged to make the final image, the circle of confusion in the original image must be smaller than that in the final image by the ratio of enlargement. Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format under the same conditions, so the cropped image has less DOF. (Stroebel 1976, 134, 136–37).

or this:

Note that the acceptable circle of confusion values for these formats are different because of the relative amount of magnification each format will need in order to be projected on a full-sized movie screen.


sagittariansrock

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Re: EOS 7D Mark II Information [CR2]
« Reply #244 on: August 07, 2013, 12:21:35 AM »
By doing so, you've changed the magnification of the image...and thus, you've also changed the DoF.

I am a bit confused. Physically, what exactly is happening to the image when it is magnified digitally? As I understand, DoF is the range within which subjects will be in focus given certain distance, focal length and aperture. This, therefore, makes sense to me:

I guess therefor that one could then state that DoF is, by definition, purely a function of the lens and relative to viewing distance of the final output, at the time the photo is taken. ;)

However, if the magnification alters the DoF (and I am guessing increases it, yes?) then do things that were until now unfocused in the image become sharply focused. Wait, that sounds improbable, no? What is exactly happening here?  ???
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jrista

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Re: EOS 7D Mark II Information [CR2]
« Reply #245 on: August 07, 2013, 12:23:51 AM »
Actually, DOF, by definition, is this:

Code: [Select]
DoF = (2 * N * c * f^2 * s^2) / (f^4 - (N^2 * c^2 * s^2))
The factor for CoC, circle of confusion, is c. It is effectively arbitrary. [...]

I suggest you read this first:

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

Do not miss this paragraph:

If the original image is enlarged to make the final image, the circle of confusion in the original image must be smaller than that in the final image by the ratio of enlargement. Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format under the same conditions, so the cropped image has less DOF. (Stroebel 1976, 134, 136–37).

or this:

Note that the acceptable circle of confusion values for these formats are different because of the relative amount of magnification each format will need in order to be projected on a full-sized movie screen.

"to be projected on a full-sized movie screen"

That would be an enlargement by a factor of 20x, 30x, maybe more? Of course CoC is going to matter with such an enlargement, despite the fact that you sit back by 30 to 50 feet. I don't think most photographers enlarge much more than 2x, and the vast majority of photographers reduce their images (usually quite considerably) for publication online.

As for the quote from Strobel, in the 1970s, film was the primary means by which photography was done. CoC was usually considerably larger back then than it is today with pixels less than 10 microns in size. Particularly in the case of large format cameras. With such large CoC sizes, it was a more important factor, even for something as relatively simple as a 2-3x enlargement. More recent films manufactured with more modern technology have produced silver halide film grains on the order of a few microns in size (one film in particular that was used by Zeiss to test high grade fast optics apparently was capable of resolving 400lp/mm, more than any sensor that I know of as of yet), but generally speaking CoC sizes today are quite small when compared to the film of the 1970s (a CoC that is 2x the pixel pitch of the average pixel size today, which is around 5µm, would be 0.01mm...a CoC for medium and large format film from the '70s would be on the order of 0.2-0.3mm...a difference by a factor of over 20x). It takes a pretty significant enlargement (say projecting on a large movie screen) to make CoC a meaningful aspect of DoF for the majority of photographers today.

I would point out that I speak from experience. I print at 24x36, 30x40, and 32x48 on a fairly frequent basis. For those particular prints hanging on my walls, they are usually viewed standing back ten feet or so...no one has ever complained about my depth of field being too thin or too large, or that the inaccuracies in my 7D AF resulted in a horribly misfocused subject totally unworthy of such a large honor. ;)

Anyway...points have been made. The debate, once again, is going nowhere. I'm going to bed. It's up to you and Neuro now. :P

neuroanatomist

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Re: EOS 7D Mark II Information [CR2]
« Reply #246 on: August 07, 2013, 12:31:37 AM »
then do things that were until now unfocused in the image become sharply focused. Wait, that sounds improbable, no? What is exactly happening here?  ???

That's exactly what happens.  See this example of the converse from privatebydesign.

Anyway...points have been made. The debate, once again, is going nowhere. I'm going to bed. It's up to you and Neuro now. :P

I'm still up, with more work to do.  But I'm done with this debate.  Actually, looking at the thread I dug up above, it seems the circles of confusion were ensnaring people there, too.  Round and round it went/goes...but without me.
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Re: EOS 7D Mark II Information [CR2]
« Reply #246 on: August 07, 2013, 12:31:37 AM »

sagittariansrock

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Re: EOS 7D Mark II Information [CR2]
« Reply #247 on: August 07, 2013, 01:35:32 AM »
then do things that were until now unfocused in the image become sharply focused. Wait, that sounds improbable, no? What is exactly happening here?  ???

That's exactly what happens.  See this example of the converse from privatebydesign.

Ok, so basically the change in resolution alters the perception of what is now "in focus", since being in focus is subjective. Got it.
« Last Edit: August 07, 2013, 03:08:30 PM by sagittariansrock »
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thgmuffin

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Re: EOS 7D Mark II Information [CR2]
« Reply #248 on: August 07, 2013, 04:53:21 AM »

Etienne

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Re: EOS 7D Mark II Information [CR2]
« Reply #249 on: August 07, 2013, 01:24:39 PM »
To summarize:

Full-Frame is better at everything, Crop is cheaper.

While that is a fact, it does not summarize the original thread. In fact, it does not even relate to the original thread!
People (including some of CR's more illustrious contributors) keep posting in this thread how FF is better than Crop. We get it! Why whip this dead horse? If someone disagrees, be magnanimous and quietly laugh at their ignorance or denial.
This thread is about the "hopes and dreams" of people who cannot upgrade to FF or choose not to. Let's discuss this particular thread within that purview, yeah?

This thread was all over the map long before my comment, which was to poke fun at all of that stuff.
I am not anti-crop. Although I the 5DIII is my favorite, I have and use a 60D, and an EOS-M, and I am keenly interested in the upcoming 70D and possible EOS-M successor.

Etienne

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Re: EOS 7D Mark II Information [CR2]
« Reply #250 on: August 07, 2013, 01:33:21 PM »
.
Nothing ignites passionate argument like Religion, Politics, and ... DOF on APS-C

jrista

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Re: EOS 7D Mark II Information [CR2]
« Reply #251 on: August 07, 2013, 01:59:29 PM »
.
Nothing ignites passionate argument like Religion, Politics, and ... DOF on APS-C

And DRoning about DRivel.  :P

ahsanford

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Re: EOS 7D Mark II Information [CR2]
« Reply #252 on: August 07, 2013, 03:14:54 PM »
.
Nothing ignites passionate argument like Religion, Politics, and ... DOF on APS-C

Yep.  It's the inevitable death-spiral of a 7D rumor thread.

- A

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Re: EOS 7D Mark II Information [CR2]
« Reply #252 on: August 07, 2013, 03:14:54 PM »

Pi

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Re: EOS 7D Mark II Information [CR2]
« Reply #253 on: August 07, 2013, 05:14:02 PM »

"to be projected on a full-sized movie screen"

That would be an enlargement by a factor of 20x, 30x, maybe more? Of course CoC is going to matter with such an enlargement, despite the fact that you sit back by 30 to 50 feet. I don't think most photographers enlarge much more than 2x, and the vast majority of photographers reduce their images (usually quite considerably) for publication online.

They post images smaller than 24x36mm? Don't say!

Look, it is really simple. Take any display size you like. Movie screen or a 4"x6" print. Whatever, fix it. Then take any CoC that makes you happy on that display. It can be as big as your head on the movie screen, or as small as a head of pin for a 4x6 print. Fix that, as well. Now, start with a 24x36mm image, and from a 15x22mm one. What blur radius (CoC) on each image, when enlarged, would produce the desired CoC on your favorite display size? You can compute it but without any computation, you can say that the CoC on the 15x22mm image has to be 1.6 times smaller. As simple as that. I do not really know what else to say.


Etienne

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Re: EOS 7D Mark II Information [CR2]
« Reply #254 on: August 07, 2013, 05:23:11 PM »
.
Nothing ignites passionate argument like Religion, Politics, and ... DOF on APS-C

Yep.  It's the inevitable death-spiral of a 7D rumor thread.

- A

+1

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Re: EOS 7D Mark II Information [CR2]
« Reply #254 on: August 07, 2013, 05:23:11 PM »