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Author Topic: 6D & 30D, what do they have in common?  (Read 1267 times)
fike
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« on: March 04, 2013, 02:03:38 PM »
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I have been debating buying the 6D. I like the feature set and am interested in having a full frame camera in the collection.  Today I am using MFT and the Canon APS-C 7D.  the 7D is a remarkably capable camera. I think Canon my have overshot on some of the performance qualities on this camera like frame rate, and buffer size.  It falls down on high ISO noise.  It's performance here is definitely no longer competitive with current offerings.  It's a shame because otherwise the camera is fabulous. 

So why the talk of the 30D?

The 6D and the 30D are very close in pixel pitch.
Canon 6D    = 6.54 um
Canon 30D  = 6.4 um
Canon 7D    = 4.3 um

(One thing I didn't yet say is I use my large DSLR, among other things, for wildlife and bird photography.  THIS is what has kept me on APS-C for so long.) 

So back to this comparison.  In a perfect world where we ignore sensor noise, these pixel pitches would indicate that the same lens (say a 100-400) fitted to each of these cameras at the same focal length will result in the 7D getting the most detail followed by the 30D and the 6D being almost the same. Put another way, viewed at 100% in photoshop, a subject (a bird for example) will be largest on the 7D and nearly the same size on the 30D and 6D. 

Now with that excursion into hypotheticals done I can cut to the meat of the question.  When I upgraded from a 30D to a 50D to a 7D, I never felt like I got some revolutionary increase in resolution.  The increase in resolution (decrease in pixel pitch) never really increased my image quality by the amount you would guess from the increase in megapixels. I would describe it this way: I increased megapixels, but the new megapixels weren't as good as the old ones (because of noise) so I didn't really get in increase in print sizes for my bird photographs. I was improving resolution a little bit, but not linearly.   

The comparison I want to see, and I can't find anyone doing this, is to set a 7D at ISO 800 and a 6D also at ISO 800 and using the same lens and the same subject to evaluate the amount of detail.  At ISO 100, the 7D would probably win, but wildlife photography is rarely done under ideal lighting, so I picked ISO 800.  I could just as easily pick 1600 or 3200 where the 6D might easily run away with the win.

How much better are the 6D pixels than the 7D's?  Does the improvement in per-pixel quality make up for the decrease in resolution between the two and diminish the APS-C advantage for telephoto subjects?
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Fike, Trailpixie, or Marc Shaffer
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I carry an M43 ILC, a couple of good lenses, and a tripod.
Ed B
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« Reply #1 on: March 04, 2013, 05:32:29 PM »
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I really can't comment on the pixel/resolution question but are you sure you want a 6d for birding? It is quite a step down with the auto-focus. While the center point might be very good the others are not for a camera in this price range. There are rumors of a "7D Mk2" coming out this year, might want to see what that brings.
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fike
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« Reply #2 on: March 04, 2013, 06:30:17 PM »
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BIFs (birds in flight) will be a bit harder, but even with the 7D, the most sensitive focus point is the center one.  In challenging conditions, everyone always uses the center point, so if that is the case, the 6D won't be any more inferior.  The bigger tradeoff, in my opinion, is the frame rate.  The 7d gets 8 frames per second and a 25 RAW image buffer.  The 6D is much inferior, though I can't remember what it is.
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Fike, Trailpixie, or Marc Shaffer
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I carry an M43 ILC, a couple of good lenses, and a tripod.
Ray
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« Reply #3 on: March 05, 2013, 07:27:54 PM »
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Hi Fike,
You raise a good question. I think the DXOMark website can partly answer such questions, if you use the 'screen' mode which compares performance at the pixel level.

It looks as thought the smaller 7D pixel is significantly worse than the larger 6D pixel in all major parameters, such as SNR, DR, Tonal Range and Color Sensitivity.

At high ISOs of 1600 and above, the DR of the 6D pixel is very much better. At ISO 800 it's still significantly better, being close to a whole stop better. A 1/2 stop of improved DR is considered to be noticeable in practice.

Even SNR at 18%, for the 6D pixel, is well over one stop better than the 7D pixel at ISO 800, and Color Sensitivity is 2.3 bits better (a 1 bit difference being of noticeable significance).

I remember years ago when I upgraded from the 6mp Canon D60 to the 8mp 20D, the increase in pixel count was irrelevant. What was really noticeable was the lower noise and improved color at high ISOs. However, the 7D has over double the pixel count of the 30D (or the 6D cropped to the 30D format), so I expect that at all ISOs the 7D would provide higher resolution but noisier images.

Whether or not such higher resolution would be significant after noise reduction has been applied to the 7D image, at large print sizes, is another question which can only be answered by someone doing comparison tests. However, the DXOMark comparisons at the link below indicate that the 7D image, when downsampled to the same size as the 30D image, has approximately the same noise, except for DR at low ISOs which is almost a whole stop better at ISO 100, and 1/2 a stop better at ISO 800. But the improvement would be less if one were to downsample the 7D image to a cropped 6D image

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/836%7C0/(brand)/Canon/(appareil2)/619%7C0/(brand2)/Canon/(appareil3)/179%7C0/(brand3)/Canon
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NancyP
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« Reply #4 on: March 05, 2013, 08:19:27 PM »
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The 7D2 should have the necessary 10 fps and adequate buffer, and I imagine that the sensor will have significantly improved high ISO capacity.

Perhaps you want the FF camera for non-bird use? I haven't seen the camera, but the 6D sounds as if it is a decent landscape camera.
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Ray
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« Reply #5 on: March 05, 2013, 10:51:25 PM »
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The 7D2 should have the necessary 10 fps and adequate buffer, and I imagine that the sensor will have significantly improved high ISO capacity.

Perhaps you want the FF camera for non-bird use? I haven't seen the camera, but the 6D sounds as if it is a decent landscape camera.


A faster frame rate is useful, but the DXO tests imply that the 18 million 7D pixels do not have better high ISO performance than 8 million 6D pixels. In fact, the downsampled 7D image is no better than the 30D image, except for deep shadow noise up to ISO 1600. The 6D pixel is marginally better than the 30D pixel and significantly better than the 7D pixel.
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