Canon 6D vs Canon 70D vs Canon 7D

[lalaknight]

Hi,
I'm new to photography and I love it. I'm having a hard time choosing between the 6D, 7D, and 70D. What's the significant differences between these 3? I want to start doing family portraits in natural light, mostly outside in natural surroundings. I also have a 8 month old who's moving all over the place and I want to get LOTS of photo's of her. I'm interested in photo's that have a high depth of field. I work at alot of music festival's (day and night, indoor and outdoor) and I really want to shoot at those. So basically I need a camera for
Natural light
Family Portraits
Baby/Infant
Concerts
Festivals
Action
Outdoor
Headshots

I'm just so confuse as to what to pick. I can't afford a Mark III. These are the only ones in my budget. Thanks so much for all the help and advice in advance.

[pdqgp]

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@RobertTheFat wrote:

Otherwise, buy the 7D (and the 17-55mm f/2.8 lens). It lacks some gaudy modern features of the 70D, but it's a better camera overall. You won't outgrow it anytime soon.

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That's a debatable point.   The 70D lacks really two key features of the 7D but has many more in return that the 7D does not, thus IMO making the 70D by far a better overall camera.

[pdqgp]

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I'd be interested to hear what those "strong indications" are. The 7D2 speculation has been going on for well over a year, with nothing forthcoming.

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I think the strongest indicators are the recent rebates, lower pricing and the fact that many places like Amazon and their sellers have low to no inventory and some even list it as discontinued.

[RobertTheFat]

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@pdqgp wrote:

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@lalaknight wrote:
Hi,
I'm new to photography and I love it. I'm having a hard time choosing between the 6D, 7D, and 70D. What's the significant differences between these 3? I want to start doing family portraits in natural light, mostly outside in natural surroundings. I also have a 8 month old who's moving all over the place and I want to get LOTS of photo's of her. I'm interested in photo's that have a high depth of field. I work at alot of music festival's (day and night, indoor and outdoor) and I really want to shoot at those. So basically I need a camera for
Natural light
Family Portraits
Baby/Infant
Concerts
Festivals
Action
Outdoor
Headshots

I'm just so confuse as to what to pick. I can't afford a Mark III. These are the only ones in my budget. Thanks so much for all the help and advice in advance.

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The differences start with Full Frame vs a Crop Body sensor.   Full frame with grant you better low light image quality, & greater Depth of Field.

Really? I've always understood that depth of field varies inversely with the focal length of the lens. For what's generally accepted as "normal" magnification, a FF camera uses a longer lens (~50 mm) than that of a crop-frame camera (~31 mm). So I guess I'd have expected the crop-frame camera to give you greater depth of field. If that's wrong, I'd be interested to hear why it is.

Those two key areas match several of the types of shooting you list.    That said, crop body cameras will give you more reach and outside the true professonal bodies, more robust autofocus systems and sports capability.   The latter leaves the 7D and 70D a better fit.

The 6D is a great starting point for full frame.   Today, the 70D is the better starting point.   That said, the noise level on a 70D is so very low that it won't really matter for what you've listed.   I have ISO shots in the 12,800 range that are great and unless you're printing posters side by side, you wouldn't notice the difference.

As Canon's motto goes, it starts with the glass, so don't overbuy on the body and not leave yourself room for good glass.  Especially for low light or shooting kids.  You'll need the speed of good glass.

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"Speed" and "good glass" aren't necessarily synonymous, though. There are a lot of cheap f/2.8 lenses around.

[pdqgp]

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@RobertTheFat wrote:

Really? I've always understood that depth of field varies inversely with the focal length of the lens. For what's generally accepted as "normal" magnification, a FF camera uses a longer lens (~50 mm) than that of a crop-frame camera (~31 mm). So I guess I'd have expected the crop-frame camera to give you greater depth of field. If that's wrong, I'd be interested to hear why it is.

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I didn't word my point correctly... I meant more shallow DOF aka better for portraits.

[pdqgp]

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RobertTheFat wrote

"Speed" and "good glass" aren't necessarily synonymous, though. There are a lot of cheap f/2.8 lenses around.

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That's why I said they'll need the speed OF good glass not just speed.

[cale_kat]

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@RobertTheFat wrote:

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@pdqgp wrote:

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@lalaknight wrote:
Hi,
I'm new to photography and I love it. I'm having a hard time choosing between the 6D, 7D, and 70D. What's the significant differences between these 3? I want to start doing family portraits in natural light, mostly outside in natural surroundings. I also have a 8 month old who's moving all over the place and I want to get LOTS of photo's of her. I'm interested in photo's that have a high depth of field. I work at alot of music festival's (day and night, indoor and outdoor) and I really want to shoot at those. So basically I need a camera for
Natural light
Family Portraits
Baby/Infant
Concerts
Festivals
Action
Outdoor
Headshots

I'm just so confuse as to what to pick. I can't afford a Mark III. These are the only ones in my budget. Thanks so much for all the help and advice in advance.

---

The differences start with Full Frame vs a Crop Body sensor.   Full frame with grant you better low light image quality, & greater Depth of Field.

Really? I've always understood that depth of field varies inversely with the focal length of the lens. For what's generally accepted as "normal" magnification, a FF camera uses a longer lens (~50 mm) than that of a crop-frame camera (~31 mm). So I guess I'd have expected the crop-frame camera to give you greater depth of field. If that's wrong, I'd be interested to hear why it is.

Why Full Frame Cameras offer greater control of Depth of Field than Cameras with smaller sensors

If it is a narrow band of DOF, the aperture opening plays a very big role. But the aperture opening is expressed as a relationship between the width of the opening and the length of the lens and in terms (in context) that are derived from 35mm photography. Consequently, a FF camera equipped with a 50mm lens and shooting at f/1.8 has a true aperture opening of f/1.8. In contrast, a Crop body camera equipped with a ~31mm lens will have an "effective" focal length of 50mm in 35mm terms and when used with the same aperture (f/1.8) will have an "effective" aperture of f/2.8. The sensor size matters because specifications expressed in 35mm terms must be converted before a true, or effective, comparison can be made.

The upshot of this is that for any given focal length/aperture combination, a FF camera will have greater control over DOF than a camera with a smaller sensor. (I am certain that there are about a thousand reasons why cameras differ in other ways that can influence their capacity to control DOF but as a generalization, this interpretation holds true.)

Also note, that those in search of narrowed bands of DOF should consider sensor sizes larger than 35mm. The same principle holds true and a Medium format camera (the Hasselblad 2-1/4" square size for this example) equipped with a 80mm lens will have an "effective" focal length of 52mm in 35mm terms. When this lens is used at the same aperture (f/1.8), it will have an "effective" aperture of ~f/1.2. What a win for Medium format photographers!

Those two key areas match several of the types of shooting you list.    That said, crop body cameras will give you more reach and outside the true professonal bodies, more robust autofocus systems and sports capability.   The latter leaves the 7D and 70D a better fit.

The 6D is a great starting point for full frame.   Today, the 70D is the better starting point.   That said, the noise level on a 70D is so very low that it won't really matter for what you've listed.   I have ISO shots in the 12,800 range that are great and unless you're printing posters side by side, you wouldn't notice the difference.

As Canon's motto goes, it starts with the glass, so don't overbuy on the body and not leave yourself room for good glass.  Especially for low light or shooting kids.  You'll need the speed of good glass.

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"Speed" and "good glass" aren't necessarily synonymous, though. There are a lot of cheap f/2.8 lenses around.

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[TCampbell]

Depth of field is controlled by only three factors:

1)  focal length of the lens

2)  distance from the subject

3)  aperture size

This means that "in theory" there is no difference between the depth of field on a full-frame vs. crop-frame camera given the three factors above are the same.  And it turns out... this is actually true.  

But in practice it'll seem like it's not true.  The reason for this is that you probably wont shoot the "same" photo using the same values above.

Suppose for example that you're shooting a simple portrait using a 50mm lens at f/4 with a distance of 10' away using a crop-frame body.

The following would then be true:

At that distance, the dimensions of the frame would be 4.5' x 3'.

The depth of field would be 1.84' (9.16' - 11' would be the focused field.)

Now suppose you switch to a full-frame body but leave eveything else the same.

The angle of view immediately becomes wider (using the same lens) BECAUSE the image circle projected into the camera by the lens was the same... but on the crop-frame camera, the sensor was smaller.  Much of the image "spilled off" the sides of the sensor.  But since the full-frame camera has a bigger sensor... it get's a bigger and wider area of that image being projected into the camera body by the lens.

The new dimensions of the frame will be about 7.25' x 4.75' (I'm rounding a bit here ... this isn't precise).

The depth of field will not change at all... but now we're getting a much wider shot of our subject and what we WANTED was to get approximately the SAME framing around our subject.  This means we'll need to change something.

We can either:

(a) stand closer to our subject, or

(b) use a lens with a narrower angle of view.

If we switch from the 50mm focal length to an 80mm focal length then the dimensional field of view at 10' will be exactly the same (4.5' x 3').

However... since we are no longer using the same focal length lens... the depth of field will become a bit shallower.  It'll be reduced to 1.125' (down from the 1.84' with the 50mm lens).  Also the intensity of the background blur will increase.

The other option we have is to stick with the 50mm lens and move in closer.

If we divide 10' by the 1.6x crop factor, we get 6.25'.  Stand at that distance and you'll get exactly the same dimensional field of view that you were getting with the crop-frame camera (4.5' x 3').  

If we do that, the depth of field changes down to 1.125' (that's the same DoF as it was with the 80mm lens without moving).  

The bottom line (yes I threw around a lot of numbers) is that two things are generaly true:

1)  If you don't change the focal length on the lens, the aperture (f-stop), or the subject distance, THEN the depth of field will remain the same.

but

2)  You PROBABLY will change your behavior when switching cameras because you're usually going after a specific subject-framing.  That means you'll either (a) stand closer, or (b) change the focal length of the lens.  Either of these two will result in a narrower depth of field and stronger background blur.

Most people do #2... and consequently would say that the full-frame cameras have a shallower depth of field and stronger backgroudn blur.  It's not the camera that causes this... it's the shooting behavior of the photographer that causes it.  But the photographer chooses the different lens focal length or subject distance because the sensor size is larger and naturally captures a wider angle of view.

Many people really love that "full frame look".

As for the ISO performance and noise...

 If you think of the sensor as being covered in tiny pixels (technically it's covered in photo-sites which get debayered into pixels but I digres), the larger the pixel, the more light will land on it and the less noise it gets.  Full frame cameras tend to have larger pixels (not always true... but usually true).  Even if they have smaller photosites, they would end up having more of them and, as we typically don't use all the pixels, the image has to be "resampled" down to the size we intend to use for image display.  That resampling results in a side-effect which decreases the noise.

I can show you images I shot with my 5D II at ISO 6400.  They "look" like they're noise-free (even at ISO 6400).  But really that's just because of the web-sized image.  If I take a 100% crop on the image, you do see the noise is there.  But it is generally true that you'll get much better overall noise performance with a full-frame camera.  You'll "feel" like you can shoot about 2 ISO stops higher with a full-frame camera than you would have shot with a crop-frame camera.  

[ebiggs1]

Bob from Boston,

" If that's wrong, I'd be interested to hear why it is."

As a matter of fact like a leopard, a lens can not change it's 'spots'.  So to speak.  A 50mm f1.8 lens remains a 50mm f1.8 lens no matter what body you bolt it on. Doesn't matter if it is a crop, a medium or a FF.  It can not change the way it was born.

A larger sensor will naturally absorb more light because of size, but the lens has no idea what sensor is behind it.

There is a mathematical formula for aperture. If you have a 500mm lens with a 125mm front objective element, the f-stop will be, roughly f/4, for instance.  That can not change.  Changing the size of the sensor, crop to FF, doesn't change that fact.

Assuming the same pixel pitch, each pixel will receive the same amount of light, regardless of the size of the sensor.

A properly exposed photo at f1.8 and 1/1000 at ISO 100 from that 50mm f1.8 lens will remain properly exposed regardless of whether the sensor is a crop, FF or medium format.  It will receive the same amount of light, no matter what size the sensor is.

Now the effective or apparent focal length does appear to change, not the lenses actual  focal length (that can not change) but what is seen by the sensor.

 A  Canon Rebel crop sensor records a smaller portion of the total image that the lens is able to deliver to the sensor, when  viewed at the same print size, the image appears larger. But your lens focal length does not get longer.  It is the field of view or angle of acceptance that makes everything look like the lens has a field of view like one that is 1.6 times as long.

If it was compared to a FF sensor that is.

But in the end all of this is just numbers because you get exactly what you see in the cameras view finder.  It is better to just ignor it and shoot away!

[ebiggs1]

Very well said Tim as always.  You hit the "Post" a second or two before I did.  But a nice explanation.

People, or novice's get way too caught up in numbers than they do in just using the equipment.

[cale_kat]

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@ebiggs1 wrote:

Very well said Tim as always.  You hit the "Post" a second or two before I did.  But a nice explanation.

People, or novice's get way too caught up in numbers than they do in just using the equipment.

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Meh, Tim's post was accurate but wordy. I said the same in a third fewer words. But I don't regard the issue in the context of a test scenario, I just use the analogy of equivalents. Most people get that because it is concise.