Anybody upgrade from a 7D to 6D? What are your thoughts?

[Helevitia]

I am also worried about missing out on the advantage of having a cropped sensor. 

I signed up an account just to comment on this.  There is *no* advantage to a crop sensor.  How would you feel if you had FF camera, but the camera cropped the picture before it saved it to the card?  You would feel cheated!  Same deal, only it's a physical limitation.

Source:  I am a senior optical engineer.

Yes there is an advantage: the resolution of a sensor depends on the size of a pixel, the smallest image that can be resolved into two separated points is one where the distance is circa 2 pixels. The pixel on the 6D is 6.54 micron, that on the 7D is 4.3 micron. So, with the same lens on each body and iso noise not being limiting, the 7D can resolve a separation of 8.6 microns as opposed to the 13.08 microns on the 6D. So, the 7D has 48.8% more reach than the 6D, which is a huge advantage for bird photography and is why the 7D is so popular for nature photographers. I am waiting for the 7D II.

The resolution of a camera system and the subsiquent images depends on a hell of a lot more than pixel density. Stop reading badly written forum posts and test this stuff, it really is very easy.

I posted this a while ago but it is very relevant here, and I didn't explain the test situation very well last time. The attached photo contains three images, the one on the left is from a FF camera, the smaller red rectangle inside that is the full 7D image. Both images were shot from the same place with the same lens using manual focus and 10x Live View, a cable release, remote flash, IS off, very heavy tripod, with a 300mm f2.8 IS @f5.6. This is a typical focal length limited situation and I set this up to see the actual resolution advantage I would get were I to get a 7D, in doing so I have absolutely maximised the advantage of the crop camera, we never shoot in these kinds of ideal conditions other than a studio still life.

In real life testing, when using AF and its associated inaccuracies,  even the small resolution advantage the 7D has in these examples isn't realisable.

So, where is that 7D 48.8% reach advantage?

OK, so I've looked at your pictures and read some more online about FF vs. crop sensors.  Wouldn't it be better to say we are losing picture real estate instead of magnifying the image 1.6x?  If we are, in fact, not actually getting closer to the subject, then why does everyone say it like that?  Why not say the opposite? 

And one other question about this:  If I take a picture with a crop sensor at let's say, 12 ft, I then take the exact same picture with a FF sensor, at around 8ft, I'm going to get the exact same image size.  Now let's assume for a second I cannot move closer to the subject to "equal" the crop sensor size.  Do I miss out on anything? 

Also, what about the resolution within the crop sensor?  If both the crop and FF sensor have the same megapixel, does that mean I have more detail in the picture on the crop sensor vs. the FF sensor or is it really just that it's exactly that, it's cropped out the extra real estate so it's the exact same?  Whew!  Hope I made sense?

[AlanF]

Of course resolution depends on the product of many factors and it depends on lighting as well. But, there are some laws of basic optics and information theory that set upper limits on the resolution of sensors. One of the limiting factors is pixel density. The relative performance of FF and crop depends on lighting, distance and object size amongst other factors. On a bright day where noise is not important, the crop can resolve objects that are too far away to be resolved by FF. As the light gets worse, the sensor and photon noise will lower the resolution of the crop more than FF and the advantage of pixel density will eventually be lost.  I have tested the resolution of a sensor, posted in another forum, and it fits well to the theoretical Nyqvist limit and pixel size. 

[neuroanatomist]

It's called 'crop factor' or a 'crop sensor' for a reason - a smaller sensor crops the FoV, it doesn't magnify the image.

Comparing APS-C vs. FF cropped to the same FoV is going to be influenced by the specific sensors in question. But the IQ likely will not be significantly different (it's a wash between the 7D and 5DII, for example; I haven't done 7D vs. 1D X yet, but will soon).  As for what you're giving up - MP. A 5DII/III image cropped to 7D framing is ~8 MP, not 18 MP. I have some 24x36" prints - 8 MP wouldn't be good for that.

The similar IQ applies in good light.  If light is limiting, FF wins even when focal length limited, in terms of IQ. When not cropping, FF is the clear winner.  For me, when I'm focal length-limited, I'm usually light-limited (need high ISO) as well.  If my 7D vs. 1D X results are similar to privatebydesign's 7D vs. 1DsIII results, my 7D will likely get sold soon.

[vmk]

I'm a 5D III owner and looking for 2nd body. I thought 6D would be a good choice. After 2days using it, I decided NOT to have 6D as a 2nd body.

I'm thinking another 5D III or 1D X

ha ha... getting a 1D X as a "2nd body" makes me smile and makes my wallet hurt

[StepBack]

Helevitia  If u can look at a picture and say it's good that's all that matters.

[bycostello]

curious to know why that is an upgrade?

[AlanF]

Just to be clear, I am not saying the 7D is a bad camera, or that there are not very good reasons to choose one over a FF camera, all I was addressing was the farcical claim of a 48.8% reach advantage.

It is not farcical that the 7D has about 50% more reach than a 6D with the same lens. I have written this before, but it is buried in another thread. Here are some simple calculations and experiments that show the 7D does give extra reach of about 50% over a 6D. Theory tells us that in order to resolve two parallel lines, their images should be at least 2 pixels apart. On a 7D, which has a 4.3 micron pixel, that would be 8.6 micron apart and on a 6D, with a 6.54 micron pixel, that would be 13.08 micron apart. For an object at a distance v, which is much further away than the focal length of the lens, f, the size of the image is given by the size of the object times f/v. For the same lens on a 7D and the 6D with a lens aperture wide enough so it is not diffraction limited (wider than f/6.9 for the 7D, 10.5 for the 6D), the sizes of images on both sensors will be the same for the same distances but the image will span more pixels on the 7D. In order to cover two pixels, the object will be 1.5 times further away for the 7D. I did some experiments to test the resolution of the 7D fitted with an f/2.8 300mm II and 2xteleconverter to give f = 600mm and f/5.6. I photographed a feather whose barbs (middle right, below halfway) in the photo were approximately parallel lines separated by 0.27 mm or 0.31 mm (middle right, above halfway). At 5 m distance, nearly all the barbs, including others that were not parallel to the rows or columns of the sensors were very clearly resolved the calculated distances in the image were 16.1 and 18.7 micron, respectively, for the lower and upper sets. At 9 m separation, the barbs were still clearly resolvable, with calculated image sizes of 8.9 and 10.4 micron, just above the supposed limit for resolution of 8.6 micron. The barbs were just resolved at 12 m, with image sizes of 6.7 and 7.8 micron respectively. The images became unresolvable between 14 and 16 m. My calculations of height of image are reliable within 3 percent since the same calculations gave a pixel size of 4.4 micron for the 4.3 micron pixel. So, despite all its supposed limitations, the 7D resolves images at the closest theoretical limits. In order to have the clean separation seen at 9 m on a 7D, the feather would have to be at 5.9 m from the 6D.  The transition of just being resolvable at 12 m from the 7D would be 7.9 m from the 6D, and the complete loss at 14-15 m from the 7D would be 9.2-10.2 m on the 5D. It doesn’t matter how superior the 6D is than the 7D, the laws of optics and information theory dictate that at 9 m you can resolve the barbs of feathers on a 7D but you see a blur with the 6D using a 600mm lens.
Theory dictates and experiments confirm the extra reach. Of course, if you use a crappy lens, like a Sigma zoom at 500 mm, you won’t get near the theoretical resolution, as you won’t if you are down a coal mine lit by a candle. But, the good Canon lenses at wide aperture are not limiting for resolution in decent light, it is the pixel density that is limiting in resolution.
Why is the extra reach important? You need it to capture high detail at far distances. My bird photography friends with their 1Ds and 5Ds need 50% longer lenses to capture the same detail as can be got on an 18 megapixel crop sensor.  But, in dim light where extreme resolution is not essential, the guys with the 1Ds win.

[Krob78]

I you just take pictures of people and stuff then the 6d would be fine. Anything else then the 7D kills the 6D, also people complain about the noise on the 7D far too much, generally if you take a good picture and no Photoshop then its not a problem.

I think more accurately, if you take good pictures in good light then 7D definitely is better than 6D.  But in low-light, 6D is far superior than 7D.  I've got a 500D and I think this is comparable to 7D ISO performance.  I only raise the ISO to 1600 if it's the last option.  3200, only if I really need to get the shot.  I always envy my friend who's using a 5D2 and doesn't have any trouble going to 6400.  There are also times that you want to raise your ISO for stopping the motion.  Even if you've got a great AF, if you don't stop the motion or at least pan, it's useless.  Just recently, I've shoot my daughter's theatrical concert and almost all of my shots are taken @ 1600 and 3200.  I asked the organizer why the stage is so dimly lit.  The pictures though are still usable in the internet but I hesitate to have it displayed in a 40 inches TV monitor to have my relatives view it.  I had just stored them in my IPAD for their viewing.

I think you nailed it Jason...  I've got lots of great high iso images with my 7D, lots of them, but the key is absolutely lots of light!  Take that same camera and a f/2.8 lens into a room not so well lit and the noise drives you crazy... especially if you're shooting portraits. 

The 7D just isn't made for portrait work in my opinion.  The noise in the shadows is terrible in low light... get them outdoors or get your softboxes set up and it's much better, but inside or portrait work, even with lighting can be difficult when it comes to noise in the shadows and the 7D.  Just makes for much more work in post... yuck...  I've got a multitude of wonderful portraits from my 7D but it's been a lot of work in post...