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5D vs. 7D (is there a difference when acquiring video?)


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#1 Ben Cross

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Posted 07 January 2011 - 12:13 AM

Ok, so this is probably falls into the total newbie side of things as far as technical questions go, but I own a 7D and I keep reading all over the place about the 5D being "superior" for capturing video because of it's full frame sensor. However, isn't 1920 x 1080 the same no matter which sensor you're capturing it on? I am aware of the 1.6 magnification of the APS-C sensor, so admittedly you lose a bit as far as super wide focal lengths, but a little basic math and you can compensate for this discrepancy. So with that said, anyone have an answer on this?

Thanks

BC
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#2 Chris Millar

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Posted 07 January 2011 - 12:29 AM

Sensor size affects DOF - and a lot of people are chasing shallow DOF these days...
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#3 David Mullen ASC

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Posted 07 January 2011 - 12:43 AM

Ok, so this is probably falls into the total newbie side of things as far as technical questions go, but I own a 7D and I keep reading all over the place about the 5D being "superior" for capturing video because of it's full frame sensor. However, isn't 1920 x 1080 the same no matter which sensor you're capturing it on? I am aware of the 1.6 magnification of the APS-C sensor, so admittedly you lose a bit as far as super wide focal lengths, but a little basic math and you can compensate for this discrepancy. So with that said, anyone have an answer on this?

Thanks

BC


In theory, there shouldn't be much difference in quality between the 1080P video from the 7D or the 5D. But since both cameras have to do tricks to get the high megapixel sensor down to HD (line-skipping & pixel-binning) rather than capture and debayer to RGB at full resolution before downsampling, there is a chance that the 21MP sensor in the 5D goes through that decimation down to 2MP a bit smoother than the 18MP sensor in the 7D. The large sensor also means less noise and less depth of field, the lower noise may compress better, and the shallower focus may hide artifacts like moire better. Anyway, I've heard that the HD video from the 5D is marginally better.
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#4 Frank DiBugnara

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Posted 07 January 2011 - 10:49 PM

Very unscientifically, I've noticed from experience that the 5D really does outperform the 7D in video mode. My friend is a professional still photographer who's shot stills with the 5D for quite a while. He just got a 7D as his second camera, and he reports a significant difference in latitude for still images.
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#5 Phil Rhodes

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Posted 08 January 2011 - 12:40 AM

That's my impression, too. A lot of people are buying 7Ds, 550Ds and Panasonic GH1 and GH2 cameras which actually don't have the same hard-to-define pleasantness about the image that the 5D does, at least not quite. I suspect that it may well be to do with dynamic range.
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#6 Hal Smith

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Posted 08 January 2011 - 01:12 PM

In theory, there shouldn't be much difference in quality between the 1080P video from the 7D or the 5D. .......

and the shallower focus may hide artifacts like moire better. Anyway, I've heard that the HD video from the 5D is marginally better.


That is a very astute thought: With the shallower focal distance, moire prone objects in front and back of the focal distance would be less resolved.
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#7 Jacob David

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Posted 12 January 2011 - 07:57 AM

The Canon EOS 7D is Canon's new semi-pro / enthusiast digital SLR and competes primarily with Nikon's recently updated D300s. It's a terrific SLR that shines in photo quality, control placement, speed, and viewfinder size and coverage. Image Quality from this camera is amazing.Detail is very good, and the 28-135 lens accommodates this cameras ability very nicely and Battery Life: still on the first charge off the box, taken about 500 test shots and a few seconds of 720p recording, battery life is about halfway.

Overall this camera is a very impressive and I'd give it a rating of about 90/100. It has alot to offer being a HD video DSLR. It'll provide many rebel users enough room to learn and grow.
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#8 David McDonald

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Posted 12 January 2011 - 05:42 PM

The 5D is probably a superior camera, for reasons stated by everyone above, but I feel like I like the "look" of the 7D more in some cases...even though they're probably almost identical. Anybody notice a difference in the 'look' of the two cameras?
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#9 Adrian Sierkowski

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Posted 12 January 2011 - 05:56 PM

I haven't noticed much of a difference in "look," between the two, however I err towards the 7D in conversations I have about it just because it was nightmarish dealing with the super shallow DoF on the 5D. Regardless of which camera one goes with, I highly recommend cine-style lenses to save some hair follicle.
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#10 John Young

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Posted 12 January 2011 - 07:51 PM

There was a test done some time back between these two and several more HDSLRs. The 5d and 7d DO produce (subtlety) different images. It really came down to what you were shooting.

See:

It's a long test, both actually scientific, and "real world" shooting. Very interesting also regarding the film vs. digital debate. Everyone should see this if they haven't.
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#11 David McDonald

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Posted 12 January 2011 - 11:10 PM

I also agree that the extreme DOF with the 5D is undesirable. When I first started shooting with these cameras (back when 5D was 30p) and not every other kid on youtube had a t2i, the shallow DOF look was more desirable...but it became played out really fast...and now I definitely prefer to have around 6 inches in focus rather than the centimeters you tend to get with the 5D (and even 7D) with an f stop lower than 5.6. I don't really notice much of a difference in 5D and 7D in shallow DOF though...they both have extremely shallow DOF.

The 7D is nice if you want a bit more focal length out of a lens (because of the crop sensor)...but at the same time the 5D can be useful when you need the shot to be a bit wider...I know I've switched from the 7D to 5D a couple of times on-set when the 7D was just a bit too tight and we didn't have a wider lens.
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#12 rob spence

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Posted 13 January 2011 - 03:20 PM

You get exactly the same depth of field on a 5d or a 7d if you use 35 mm stills lenses on both cameras...its the angle of view that changes because of the sensor size differences.
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#13 Adrian Sierkowski

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Posted 13 January 2011 - 03:24 PM

I'm afraid that there is a DoF difference between the vista-vision sized 5d sensor and the Super 35mm sized 7d sensor; it's akin to 35mm and 16mm having differing DoF characteristics based not only on the lenses you'd use to get a "close up" on either system, but also the CoC.
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#14 rob spence

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Posted 13 January 2011 - 03:32 PM

i Adrian,
That's interesting...can you explain how the circle of confusion changes on the same lens when moved from a 5D to a 7D...it's something I haven't come across.
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#15 David Mullen ASC

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Posted 13 January 2011 - 03:39 PM

i Adrian,
That's interesting...can you explain how the circle of confusion changes on the same lens when moved from a 5D to a 7D...it's something I haven't come across.


Well, it's a bit complicated but you can think of the image created by the lens ending up smaller on the smaller sensor, and thus to show it at the same size as the larger image on the larger sensor, it has to be enlarged to match, creating the need for a more critical circle of confusion figure.

What makes it more complicated than that is that the size of the individual photosites on the sensor also factor into circle of confusion figures, but I prefer to ignore that just for sanity's sake, just think of it as an optical enlargement issue.
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#16 Adrian Sierkowski

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Posted 13 January 2011 - 03:42 PM

David said it much better than I did, but here's some more reading.

As for circle of confusion :

http://en.wikipedia....le_of_confusion


You can see that the APS-C is 0.019 mm

and 35mm 0.029 mm

and that small difference can make a larger difference. There are of course more qualified people to explain this a lot better...
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#17 David Mullen ASC

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Posted 13 January 2011 - 03:46 PM

Just thinking strictly in enlargement terms the image on a APS-C sensor is about 1.5X smaller than one on a FF35 sensor, so the circle of confusion figure should be 1.5X more critical for the smaller image -- which is roughly what the 0.019mm versus 0.029mm CoC figures show.

I don't know the exact figures that a calculator would say, but let's say that to match the field of view at the same distance, you'd have a 40mm lens on a 7D and a 60mm lens on a 5D. And let's say you looked on a Depth of Field chart for a 40mm and a 60mm lens and discovered that you'd have to close down the 60mm lens by three stops to match the depth of field of the 40mm lens at the same distance. But once you factor in the 1.5X difference in degree of enlargement / Circle of Confusion figure, meaning that your 40mm lens image on the smaller format would be 1.5-stops more critical in depth of field, that 3-stop difference between the 60mm and 40mm becomes 1.5-stops.

Now those might not be the actual figures, but you get my point. Just looking at the lenses only and not changing the CoC figure gives you much greater depth of field differences than actually occur when the different lenses are used on different sized formats to obtain the same field of view.
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#18 rob spence

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Posted 13 January 2011 - 03:47 PM

Hi david,
thanks for replying.
I was really talking about the given dof characteristics for a given lens. ie if a 50 mm ( 35mm stills format ) is put on a 5D it has a given depth of field, now, ignoring the crop factor on the 7D wouldnt the same lens produce the same dof as on the 5D. Ok so the 50mm lens acts more like a 80mm in real terms because of the crop factor, but surely the dof will be the same in each shot.
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#19 Adrian Sierkowski

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Posted 13 January 2011 - 03:55 PM

It won't, even if the FoV is the same, because the circle of confusion changes, which is what is determining when "in focus" ends. As focus is just 1 point on space, the CoC is what is telling you from x spot to y spot will be in focus. As the cameras themselves have different CoCs, forgetting crop factors and the like, the 50mm lens will behave differently based on the CoC of the format you're recording to.

Check it:

http://www.dofmaster.com/dofjs.html
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#20 David Mullen ASC

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Posted 13 January 2011 - 03:56 PM

Hi david,
thanks for replying.
I was really talking about the given dof characteristics for a given lens. ie if a 50 mm ( 35mm stills format ) is put on a 5D it has a given depth of field, now, ignoring the crop factor on the 7D wouldnt the same lens produce the same dof as on the 5D. Ok so the 50mm lens acts more like a 80mm in real terms because of the crop factor, but surely the dof will be the same in each shot.


No you'd also have to factor in a different CoC figure when the 50mm lens was on the different-sized formats otherwise there would be no circle of confusion figure added to calculations, depth of field would only be determined by focal length, distance, and f-stop no matter what format was used.
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