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Author Topic: EOS 7D Mark II Information [CR2]  (Read 117934 times)

sagittariansrock

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Re: EOS 7D Mark II Information [CR2]
« Reply #210 on: August 06, 2013, 05:40:04 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?
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Re: EOS 7D Mark II Information [CR2]
« Reply #210 on: August 06, 2013, 05:40:04 PM »

unfocused

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Re: EOS 7D Mark II Information [CR2]
« Reply #211 on: August 06, 2013, 05:51:38 PM »

For most uses crop is cheaper overall with equal performance, though there are areas where FF clearly has an IQ advantage.

Let me guess - you have a summer home in northern Alaska and a 'winter' home in Patagonia (where you live like a king), both with glass ceilings.  ;)  Where I live, we have this thing called night...and in winter, night is long.  Indoors often means at least ISO 3200, and I wouldn't say APS-C offers 'equal performance' then.

Jeez, could you distort that quote a little more? What about "most uses" is hard to understand. And, by the way, dumping a little "winky" emoticon doesn't make an insult any less insulting.

It's great that you can afford a 1DX to play with, but for the 99.9% of the population that can't afford a $6,500 camera there are limitations they have to live with.

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?

Yes! This comment came in as I was typing.

The truth is, in 95% of cases, the results from a Rebel T3 and a 1DX will be indistinguishable in the hands of a decent photographer.

Probably 99% of the cases when it comes to the 7D vs. the 5DIII. There are limits to all equipment and the real skill comes in knowing those limits and knowing how to play to the strengths rather than just sitting around gloating about how your big equipment gives you so much more satisfaction. If you know how to use it, you can get and give great satisfaction from little equipment.

Pi

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Re: EOS 7D Mark II Information [CR2]
« Reply #212 on: August 06, 2013, 06:00:19 PM »
Probably 99% of the cases when it comes to the 7D vs. the 5DIII.

I assign very low probability for your "probably" to be close to the truth. I have enough experience with both crop and FF of the same class (excluding the 1D series), and I would say that in 99% of cases (probably   ;)), there is very clear difference when I pp, and in the final result. As I said before, maybe that difference would not matter to most, and that is OK; but it is there, and it matters to me.

JM Photography

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Re: EOS 7D Mark II Information [CR2]
« Reply #213 on: August 06, 2013, 06:09:00 PM »
The truth is, in 95% of cases, the results from a Rebel T3 and a 1DX will be indistinguishable in the hands of a decent photographer.

Probably 99% of the cases when it comes to the 7D vs. the 5DIII.

Indistinguishable in what sense? You certainly can't mean image quality.

neuroanatomist

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Re: EOS 7D Mark II Information [CR2]
« Reply #214 on: August 06, 2013, 06:17:41 PM »
I'm curious about the f/4.5 bit...how exactly does that work? Is that only for the outer points? (I believe the center AF point is still f/2.8 compatible like with most Canon AF systems.)

It works at f/2.8, of course, but that is equivalent to f/4.5, even though some people do not want to hear about that. Assuming that it has the same precision: 1/3 of DOF or so, it is 1/3 (or whatever) of the f/4.5 eq. DOF. It is like shooting with FF at f/4.5, with 1/3 DOF precision. Well, that is 1/3 of the DOF at f/4.5 Even if f/4.5 is all you need as DOF, your precision is lower. Some empirical evidence on that can be found on the FoCal site.

Sorry, but that's incorrect.  The precision of the AF points at a given aperture isn't specified in terms of DoF. Well, ok, maybe it is...but in that case, you keep using the letter F in the abbreviation, and I do not think it means what you think it means. 

The AF sensor precision spec is 'within one depth of focus' for a standard precision point, and 'within 1/3 the depth of focus' for high precision (f/2.8, usually) points.  Depth of focus is in 'image space' and is measured in micrometer distances at the AF (and/or image) sensor. It is related to, but distinct from, depth of field, which is measured in larger distances in 'object space'. 

Depth of field is determined by aperture, subject distance, and focal length (and CoC, but since that is related to sensor size, let's leave that out).  When we discuss 'shallower DoF on FF', that's a function of either subject distance (with APS-C you're further away for the same framing) or focal length (with APS-C, you need a shorter focal length for the same framing). 

However, depth of focus is relatively insensitive to subject distance (once you're out of true macro range) and focal length.  Thus, depth of focus is primarily determined by aperture, and that doesn't change with sensor size.

OTOH, aa stated, from a practical standpoint the APS-C sensor does have a deeper depth of field. So, even though the specified AF sensor precision is the same, the manufacturing tolerances for APS-C could, in theory, be looser.  Users of 1-series bodies have long known their AF is' better' than consumer cameras.  I wonder if part of the recent improvements in measured precision of AF with the 5DIII and 6D derive at least in part from Canon tightening up the manufacturing tolerances.
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neuroanatomist

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Re: EOS 7D Mark II Information [CR2]
« Reply #215 on: August 06, 2013, 06:25:50 PM »
The truth is, in 95% of cases, the results from a Rebel T3 and a 1DX will be indistinguishable in the hands of a decent photographer.

Probably 99% of the cases when it comes to the 7D vs. the 5DIII.

That's just asinine.  (Note the lack of a winky emoticon.)
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schill

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Re: EOS 7D Mark II Information [CR2]
« Reply #216 on: August 06, 2013, 06:31:30 PM »
100% of the pictures I take with my 7D are better than the pictures I take with the 5DIII that I do not own.

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Re: EOS 7D Mark II Information [CR2]
« Reply #216 on: August 06, 2013, 06:31:30 PM »

Pi

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Re: EOS 7D Mark II Information [CR2]
« Reply #217 on: August 06, 2013, 06:54:08 PM »
Sorry, but that's incorrect.  The precision of the AF points at a given aperture isn't specified in terms of DoF. Well, ok, maybe it is...but in that case, you keep using the letter F in the abbreviation, and I do not think it means what you think it means. 

The AF sensor precision spec is 'within one depth of focus' for a standard precision point, and 'within 1/3 the depth of focus' for high precision (f/2.8, usually) points.  Depth of focus is in 'image space' and is measured in micrometer distances at the AF (and/or image) sensor. It is related to, but distinct from, depth of field, which is measured in larger distances in 'object space'. 

I believe I was correct. While DOF and depth of focus are different, 1 D-O-focus is defined as the distance at which you get an image blurred by "1 DOF" (with a fixed COC), so 1/3 D-O-focus corresponds approximately to 1/3 DOF blur.

Another way to look at this: an f/2.8 eq. lens on crop is a f/1.75 one. The crop AF sensor cannot see rays coming from the periphery of such a lens. It has to somehow compensate this by judging the phase difference of f/4.5 (eq.) rays. Of course, those are rays of a shorter FL, so this is not exactly a proof without knowing how the AF system exactly works.


Don Haines

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Re: EOS 7D Mark II Information [CR2]
« Reply #218 on: August 06, 2013, 06:58:59 PM »
We seem to have two groups of people arguing....

One group says that FF has the best image quality.
The other group says that APS-C has the best image quality that they can afford.

Both sides are right.
The best camera is the one in your hands

pj1974

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Re: EOS 7D Mark II Information [CR2]
« Reply #219 on: August 06, 2013, 07:05:59 PM »
We seem to have two groups of people arguing....

One group says that FF has the best image quality.
The other group says that APS-C has the best image quality that they can afford.

Both sides are right.

:D  Great summary.....

... though there is (at least now) a third group of people that say "option C please, both the above are true!"

And you (& I) are in that group, Don!
I appreciate using my Canon DSLRs along with a host of lenses & many accessories to capture quality photos, and share with friends.

pj1974

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Re: EOS 7D Mark II Information [CR2]
« Reply #220 on: August 06, 2013, 07:14:58 PM »
I'm curious about the f/4.5 bit...how exactly does that work? Is that only for the outer points? (I believe the center AF point is still f/2.8 compatible like with most Canon AF systems.)

It works at f/2.8, of course, but that is equivalent to f/4.5, even though some people do not want to hear about that. Assuming that it has the same precision: 1/3 of DOF or so, it is 1/3 (or whatever) of the f/4.5 eq. DOF. It is like shooting with FF at f/4.5, with 1/3 DOF precision. Well, that is 1/3 of the DOF at f/4.5 Even if f/4.5 is all you need as DOF, your precision is lower. Some empirical evidence on that can be found on the FoCal site.

Sorry, but that's incorrect.  The precision of the AF points at a given aperture isn't specified in terms of DoF. Well, ok, maybe it is...but in that case, you keep using the letter F in the abbreviation, and I do not think it means what you think it means. 

The AF sensor precision spec is 'within one depth of focus' for a standard precision point, and 'within 1/3 the depth of focus' for high precision (f/2.8, usually) points.  Depth of focus is in 'image space' and is measured in micrometer distances at the AF (and/or image) sensor. It is related to, but distinct from, depth of field, which is measured in larger distances in 'object space'. 

Depth of field is determined by aperture, subject distance, and focal length (and CoC, but since that is related to sensor size, let's leave that out).  When we discuss 'shallower DoF on FF', that's a function of either subject distance (with APS-C you're further away for the same framing) or focal length (with APS-C, you need a shorter focal length for the same framing). 

However, depth of focus is relatively insensitive to subject distance (once you're out of true macro range) and focal length.  Thus, depth of focus is primarily determined by aperture, and that doesn't change with sensor size.

OTOH, aa stated, from a practical standpoint the APS-C sensor does have a deeper depth of field. So, even though the specified AF sensor precision is the same, the manufacturing tolerances for APS-C could, in theory, be looser.  Users of 1-series bodies have long known their AF is' better' than consumer cameras.  I wonder if part of the recent improvements in measured precision of AF with the 5DIII and 6D derive at least in part from Canon tightening up the manufacturing tolerances.

Thanks Neuro for a well written explanation about DOF, sensor size, focal length, distance to subject & background, AF focussing accuracy. etc, etc.

That's the way I have understood & work with these variables for some time in my photography. It's a shame many people who take photos and own cameras / lenses don't understand or apply these.  People should practice, practice, practice - like I did years ago - taking photos with a FF at f/2.8 or a APS-C at f/1.8 - and determining how to use and control DOF for impact in photos.

That's the reason I'm waiting for a new 50mm f/1.4 - f/2 lens; that's the focal length and DOF that I enjoy taking many photos on my APS-C (Canon 7D).

Quote
I wonder if part of the recent improvements in measured precision of AF with the 5DIII and 6D derive at least in part from Canon tightening up the manufacturing tolerances.

And this, in red font, above is one of the things I'm very keen to see in a 7DmkII.  I have worked very well with my 7D's AF (I have again practiced with many photos and different scenarios). I have been able to achieve photos with with my 7D that I'm very happy - including macro using AF (though I usually use MF for most of my macros), BIF, portrait, event photography, etc.  There are a few scenarios that I would like the 7D's AF to be somewhat more accurate and consistent (like the 5DmkIII) - but the 7D is no slouch WHEN you know how to use it.

Regards all....

Paul
I appreciate using my Canon DSLRs along with a host of lenses & many accessories to capture quality photos, and share with friends.

Don Haines

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Re: EOS 7D Mark II Information [CR2]
« Reply #221 on: August 06, 2013, 07:25:57 PM »
We seem to have two groups of people arguing....

One group says that FF has the best image quality.
The other group says that APS-C has the best image quality that they can afford.

Both sides are right.

:D  Great summary.....

... though there is (at least now) a third group of people that say "option C please, both the above are true!"

And you (& I) are in that group, Don!
I was outside last night doing something stupid..... trying to hand-hold a 60D with a 400F5.6 and a 2x teleconverter and shoot the ISS as it passed overhead. Surprisingly enough, it worked and the resulting image is 22 pixels across. I'd have loved to have a 1DX instead of the 60D and an 800F5.6 instead of the 400F5.6, but with what I can afford to spend, that's just not going to happen. Like so many of us, I have to settle for the best I can afford.
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jrista

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Re: EOS 7D Mark II Information [CR2]
« Reply #222 on: August 06, 2013, 07:29:51 PM »
The only difference then would simply be that the 7D frame is cropped, resolved by a higher density sensor, and thus appears to be zoomed more.

And that decreases the DOF and magnifies the AF errors (just another way to say the same thing).

Cropping does not change the depth of field. Depth of field is a function of the lens...the size of the square inside the imaging circle does not have any impact on the depth of field whatsoever. Circle of Confusion (which CAN be, but is not necessarily, a function of the pixel density, plays a role...but as I stated before, that is for all intents and purposes an arbitrary value. You can pick a number, so long as it is not smaller than the pixel pitch times two at the smallest, and use it for both APS-C and FF):

Code: [Select]
DoF = (2 * N * c * f^2 * s^2) / (f^4 - (N^2 * c^2 * s^2))
Where:

N = F#
f = focal length of LENS (crop factor need not apply)
s = distance to subject
c = circle of confusion

Lets say we are scaling for web. CoC is a non factor...we can pick anything, lets say 30 microns (0.03mm, probably far to small, but it really doesn't matter). If we run that for a 600mm lens at f/4 with a subject at 40 feet, we get a DoF of 4" (four inches), or about a third of a foot. With a CoC of 20 microns, we get a DoF of about 2.6". If we pick a CoC that is some happy medium between three times the pixel pitch of the 5D III and 7D cameras (to allow for AA filters and the nature of a bayer design), we get 16 microns. Our DoF is still about 2". If we are scaling down by 2x or more, these differences are moot...the effective CoC is FAR larger than any of these options.

We could even print somewhere near the native size of a 24mp APS-C or a cropped and scaled 23mp FF, something in the range of 16x24. There is a CoC difference, but from a practical standpoint, it doesn't produce a meaningful visual change in such a print. If we scaled up by 2x or so, then we'll probably start seeing a difference in DoF just by observing the print. Is it a meaningful difference? I guess it depends...if your printing at 150ppi on 30x40, its not really going to be the most significant factor affecting IQ or the sharpness of your subject, and your viewers will usually likely be standing back far enough to compensate for the difference. It may be an issue in this case, but so long as the important parts of your subject are in focus (which in my case is usually a birds head and maybe the side of its body, not even necessarily the whole body...anything on the back side of a bird can be entirely out of focus since it isn't visible...and a bird angled towards the lens can have blurry tail feathers and it doesn't really matter so long as the head and eyes are in clear focus), again CoC isn't really going to be the most important of a factor in determining the depth of field.

The real (actual) focal length of the lens, distance to subject, and selected aperture are the things that truly matter when it comes to DoF. Crop factor should NOT be factored into the focal length to produce an effective focal length first. Pixel pitch differences may need to be factored in if one intends to enlarge and print large, especially if they are printing at a higher resolution than 150ppi on anything other than canvas. Pixel pitch differences are effectively a non-issue if one intends to scale down and publish to the web.

In the event that you get closer with a 5D III+600/4 setup and frame the subject identically, then there would indeed be a fairly significant change in DoF. But that would be because the distance to subject shrunk. All things being equal, I would prefer to have the thinner DoF (and getting closer with a 5D III has the potential to pack even more pixels onto the subject than even a 7D can), even when photographing birds...but it is not always a possibility.

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Re: EOS 7D Mark II Information [CR2]
« Reply #222 on: August 06, 2013, 07:29:51 PM »

skfla

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Re: EOS 7D Mark II Information [CR2]
« Reply #223 on: August 06, 2013, 07:38:54 PM »
Wow this thread has become un-interesting.
still a 5D2 fan

jrista

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Re: EOS 7D Mark II Information [CR2]
« Reply #224 on: August 06, 2013, 07:40:54 PM »
Sorry, but that's incorrect.  The precision of the AF points at a given aperture isn't specified in terms of DoF. Well, ok, maybe it is...but in that case, you keep using the letter F in the abbreviation, and I do not think it means what you think it means. 

The AF sensor precision spec is 'within one depth of focus' for a standard precision point, and 'within 1/3 the depth of focus' for high precision (f/2.8, usually) points.  Depth of focus is in 'image space' and is measured in micrometer distances at the AF (and/or image) sensor. It is related to, but distinct from, depth of field, which is measured in larger distances in 'object space'. 

I believe I was correct. While DOF and depth of focus are different, 1 D-O-focus is defined as the distance at which you get an image blurred by "1 DOF" (with a fixed COC), so 1/3 D-O-focus corresponds approximately to 1/3 DOF blur.

Another way to look at this: an f/2.8 eq. lens on crop is a f/1.75 one. The crop AF sensor cannot see rays coming from the periphery of such a lens. It has to somehow compensate this by judging the phase difference of f/4.5 (eq.) rays. Of course, those are rays of a shorter FL, so this is not exactly a proof without knowing how the AF system exactly works.

Hmm, I know that the image sensor cannot see from the periphery of any EF lens. I was not aware that the AF sensor was also limited in the same way. The point spread is certainly smaller than on a FF sensor (but I always figured that was an advantage as it doesn't have to deal with vignetting). I do not believe that actually limits the sensor's periphery vision. Do you have some kind of reference for this?

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Re: EOS 7D Mark II Information [CR2]
« Reply #224 on: August 06, 2013, 07:40:54 PM »