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Archive 2013 · 70d vs 7d - Resolution

  
 
Scott Stoness
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p.1 #1 · p.1 #1 · 70d vs 7d - Resolution


Here is my question.

IDxomark.com tests indicate that the 70d delivers 20% more resolution than the 7d?
You agree with this conclusion?
Maybe I am misunstanding the Dxo sharpness measure?
Maybe the 7dii will deliver 30mpx and it will be effective at increasing crop sensor resolution?

Background:

I have looked at dxomark and they show 70d achieving more effective mpx than the 7d. Eg. 85/f1.2 v1 on 70d vs 7d achieves 14 vs 11 effective mpx resolution respectively. I have also looked at 35/f2 and 24/70v2 and 70-200v2 and the 70d consistently achieves about 14 vs 11 mpx on 70d and 7d, respectively. Similarly 200-400. This suggests that the combination of extra mpx (20 v 18 70d vs 7d) and new cmos, is delivering a 20% increase in resolution performance (13.5-11.4)/(11.4 assumed because of rounding)

click http://www.dxomark.com/index.php/Lenses/Camera-Lens-Ratings/Optical-Metric-Scores and click canon and aps-c and narrow the search to 85mm and you will see this.

I do not understand the effective mpx measure of Dxomark to know whether this is the case but they Dxomark says that their perceptual megapixel measure - measures what mpx a camera can deliver that you can compare to the actual mpx. It is not clear to me whether this is centre weighted or average or what but I assume that is average. And if this is correct, the 70d is consistently delivering 20% more than the 7d.
this is their description of the perceptual resolution - http://www.dxomark.com/index.php/Reviews/Looking-for-new-photo-gear-DxOMark-s-Perceptual-Megapixel-can-help-you

I have reviewed thedigitalpicture.com for some enlightenment on this issue. They have a sample shot out of both cameras
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=845&Sample=0&FLI=0&API=3&LensComp=458&CameraComp=736&SampleComp=0&FLIComp=0&APIComp=3
Unfortunately, the 70d shot seems to be closer than the 7d so its hard to figure out what it is showing but either 20% is a really small difference or there is not much difference visually, after you account for the 70d being closer.[Closer means that the lines will be more distinct and is an advantage]

Anyway, I reiterate my question - do you think that 70d is delivering 20% more resolution than 7d based on the extra 2mpx and the new design?

I was not trying to compare the cameras in total. There is already lots of discussion such as:
7d and 70d have virtually the same iso perforrmance in raw
7d and 70d have virtually the same performance in dynamic range and color information
7d has different remote shutter release than 70d and it is compatable with 5d's
70d does not have point focus or expansion focus
7d has 8fps vs 6fps for 70d
7d has 23-25 burst with 3s clear vs 70d 15 burst with 10s clear because of cf vs sd implementation
7d has better weather sealing
70d is able to focus continuously on live view vs not on 7d
70d may have better noise than 7d

If 70d is actually delivering more effective mpx with more actual mpx, this bodes well for resolution of the next 7diii for resolution?

Scott



Edited on Sep 12, 2013 at 09:33 PM · View previous versions



Sep 12, 2013 at 06:05 PM
Wahoowa
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p.1 #2 · p.1 #2 · 70d vs 7d - Resolution


Scott Stoness wrote:
I have reviewed thedigitalpicture.com for some enlightenment on this issue. They have a sample shot out of both cameras
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=845&Sample=0&FLI=0&API=3&LensComp=458&CameraComp=736&SampleComp=0&FLIComp=0&APIComp=3
Unfortunately, the 70d shot seems to be closer than the 7d so its hard to figure out what it is showing but either 20% is a really small difference or there is not much difference visually, after you account for the 70d being closer.[Closer means that the lines will be more distinct and is an advantage]


Regarding this point, I believe The-digital-picture.com just uses the same pixel counts vertically and horizontally. For this reason, it makes it appear to be closer for 70D.

To further prove my point, if you compare 7D to 60D (or any other 18MP DSLR) for the same lens you're using, you can see that they have them right at the same spot. And if you compare 7D to 50D, the picture of 7D will appear closer.

Hope this makes sense.

That said, 70D looks really sharp to me. (If you compare 50D to 7D, 7D doesn't appear to be obviously sharper.)



Sep 12, 2013 at 06:57 PM
johnctharp
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p.1 #3 · p.1 #3 · 70d vs 7d - Resolution


The 70D should be noticeably sharper- partly because it has a higher resolution sensor, and partly because the anti-aliasing filter is less aggressive because processing back-end is far more capable. The 7D sensor and processor setup is five years old, after all. Even the 700D manages to outresolve the 7D, and it has the same basic sensor.


Sep 12, 2013 at 07:14 PM
Scott Stoness
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p.1 #4 · p.1 #4 · 70d vs 7d - Resolution


Wahoowa wrote:
Regarding this point, I believe The-digital-picture.com just uses the same pixel counts vertically and horizontally. For this reason, it makes it appear to be closer for 70D.

To further prove my point, if you compare 7D to 60D (or any other 18MP DSLR) for the same lens you're using, you can see that they have them right at the same spot. And if you compare 7D to 50D, the picture of 7D will appear closer.

Hope this makes sense.

That said, 70D looks really sharp to me. (If you compare 50D to 7D, 7D doesn't appear to be obviously sharper.)


Thanks for that explanation. But that implies that the 70d is not necessarly sharper based on thedigitalpicture, Eg if your scrunch the 70d down in size it would not look as much better than the 7d.



Sep 12, 2013 at 09:30 PM
lowa2
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p.1 #5 · p.1 #5 · 70d vs 7d - Resolution


The 70D is very nice resolution wise. Of course you won't see that much of a difference when coming from a 7D, but I find the noise easier to clean up (less chroma) on the 70D.

Can't believe it, but I may be selling my 7D soon



Sep 12, 2013 at 09:39 PM
Wahoowa
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p.1 #6 · p.1 #6 · 70d vs 7d - Resolution


Scott Stoness wrote:
Thanks for that explanation. But that implies that the 70d is not necessarly sharper based on thedigitalpicture, Eg if your scrunch the 70d down in size it would not look as much better than the 7d.


No, I don't think that's the right implication. I think It should imply that 70D is that sharp. How so? Say, from the link you have there, if you want to crop the image you got from 7D to get the same image as you got from 70D, it would not be any sharper. (It's like viewing an image in a small screen always looks sharper than that from a large screen.)



Sep 12, 2013 at 09:54 PM
Pixel Perfect
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p.1 #7 · p.1 #7 · 70d vs 7d - Resolution


Wahoowa wrote:
Regarding this point, I believe The-digital-picture.com just uses the same pixel counts vertically and horizontally. For this reason, it makes it appear to be closer for 70D.

To further prove my point, if you compare 7D to 60D (or any other 18MP DSLR) for the same lens you're using, you can see that they have them right at the same spot. And if you compare 7D to 50D, the picture of 7D will appear closer.


This is the long way of saying tdp uses 100% crops, which is the standard way of presenting the data, same as dpreview does on it's test scene.

The 70D has a 11% more resolution than the 7D based on sensor numbers, but DxO is measuring 20% greater resolution. If that is the case, then I agree with john, that the AA filter on the 7D is much stronger as that's the only real way to account for a near doubling of the base sensor res advantage. 20% is a big bonus if it carries through to real life samples. I'd love to see a comparison between both cameras on say feather and fur detail.

I can pick the 70D up for a crazy low price, but I'm waiting for the birders to get a hold of them and do some comparisons. I'd also love to see some 70D vs 1D IV shots when not FL limited and at high ISO. 70D would have to be more stable in servo work than 7D for me to consider swapping, as 7D is not in the same league as the 1 series in general.



Sep 12, 2013 at 09:55 PM
Wahoowa
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p.1 #8 · p.1 #8 · 70d vs 7d - Resolution


Pixel Perfect wrote:
I can pick the 70D up for a crazy low price, but I'm waiting for the birders to get a hold of them and do some comparisons. I'd also love to see some 70D vs 1D IV shots when not FL limited and at high ISO. 70D would have to be more stable in servo work than 7D for me to consider swapping, as 7D is not in the same league as the 1 series in general.


How crazy low? I'm curios.

I'm planning to replace my 7D with it. Already sold my 7D.



Sep 12, 2013 at 09:58 PM
Pixel Perfect
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p.1 #9 · p.1 #9 · 70d vs 7d - Resolution


Wahoowa wrote:
How crazy low? I'm curios.

I'm planning to replace my 7D with it. Already sold my 7D.


Staff secret, I once slipped up and let it be known a staff price and it was tracked back by a Canon USA employee to me and I got told off big time.



Sep 12, 2013 at 10:05 PM
Policar
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p.1 #10 · p.1 #10 · 70d vs 7d - Resolution


DXO's sharpness measurements are inane and ass-backwards. They're so non-standard and strangely-derived that I'd consider them essentially meaningless.

The 7D does have a REALLY strong AA filter, though. Who knows why? The EOS-M, for instance, is MUCH sharper. I remember the camera came out and everyone ascribed its softness to diffraction limits and lens softness. Barking up the wrong tree.

20% sharper is still only 9.5% sharper in each dimension and that's likely mostly fine detail. Whereas the step up to FF (not fair because of pixel density and corner softness) in theory provides an automatic 60% increase in acutance/micro-contrast/mtf at low frequencies.

But the 7D is quite soft for its stated resolution. I'm sure there's an appreciable difference.



Sep 12, 2013 at 10:07 PM
johnctharp
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p.1 #11 · p.1 #11 · 70d vs 7d - Resolution


DxO's 'ratings' are pretty inane, but if they tested a representative copy of a lens, their 'P-MP' rating seems to be fairly accurate, and the Sharpness Field Maps are quite nice for comparing particular sets of lenses; for those lenses I've used, they're spot on.


Sep 12, 2013 at 10:20 PM
Scott Stoness
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p.1 #12 · p.1 #12 · 70d vs 7d - Resolution


Pixel Perfect wrote:
This is the long way of saying tdp uses 100% crops, which is the standard way of presenting the data, same as dpreview does on it's test scene.

The 70D has a 11% more resolution than the 7D based on sensor numbers, but DxO is measuring 20% greater resolution. If that is the case, then I agree with john, that the AA filter on the 7D is much stronger as that's the only real way to account for a near doubling of the base sensor res advantage. 20% is a big bonus if it carries through to real life samples.
...Show more

The surprise/question for me is - adding pixels does not necessarly create resolution because of defraction/etc between pixels. If 70d created 20%, they got 100% efficiency out of the 11% added pixels and some more (lessor bayer filter?). If just adding pixels worked for resolution, the 70d could have been a 30mpx camera easily. Obviously, there is a trade off that more pixels yields lower iso performance as well, but I am just focussing on resolution.

Anyway, it could be the combination of 11% more pixels and reduction in filters yields 20% more resolution, but that is surprising (maybe Dxomark is wrong or I don't understand their measure) and promising (a no filter 30mpx might provide a large bump in resolution). Adding pixels is easy compared to the diminishing returns on making the pixels better (or Canon would have done it). Thus I would have expected ~5% more resolution rather than ~20%, so maybe they have advanced.


Edited on Sep 13, 2013 at 11:15 AM · View previous versions



Sep 13, 2013 at 08:14 AM
garyvot
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p.1 #13 · p.1 #13 · 70d vs 7d - Resolution


The TDP comparison makes the difference in per-pixel sharpness quite clear to me.

Canon's APS-C DSLR sensors have never been very good in this regard, in my opinion. Hopefully, this sensor and that in the EOS-M are not anomalies but represent genuine new thinking by Canon's engineers.



Sep 13, 2013 at 08:51 AM
jorkata
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p.1 #14 · p.1 #14 · 70d vs 7d - Resolution


The 7D sensor has "unequal green response".
This in turn produces mazing - if not properly handled by the RAW converter.
You can see examples of mazing in this thread here on FM.

Treating the mazing leads to softness.

The 70D sensor doesn't seem to have unequal green response - and hence the better sharpness compared to the 7D.



Sep 13, 2013 at 10:34 AM
garyvot
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p.1 #15 · p.1 #15 · 70d vs 7d - Resolution


jorkata wrote:
The 7D sensor has "unequal green response".
This in turn produces mazing - if not properly handled by the RAW converter.
You can see examples of mazing in this thread here on FM.

Treating the mazing leads to softness.

The 70D sensor doesn't seem to have unequal green response - and hence the better sharpness compared to the 7D.


Forgot about the mazing artifacts. I remember how none of the RAW converters could handle the 7D out of the gate...

This would certainly be a factor. A possibly weaker AA filter could be another one. It's all change for the good though.



Sep 13, 2013 at 11:52 AM
Scott Stoness
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p.1 #16 · p.1 #16 · 70d vs 7d - Resolution


garyvot wrote:
The TDP comparison makes the difference in per-pixel sharpness quite clear to me.

Canon's APS-C DSLR sensors have never been very good in this regard, in my opinion. Hopefully, this sensor and that in the EOS-M are not anomalies but represent genuine new thinking by Canon's engineers.


I am not sure about the last comment - unfortunately DXomark has not tested the best avaible crop from nikon (d7100) but the best that the d7000 could do (11) is 20% less than the 70d (14). Hopefully dxo will provide more data on d7100 soon.



Sep 13, 2013 at 11:54 AM
garyvot
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p.1 #17 · p.1 #17 · 70d vs 7d - Resolution


Scott Stoness wrote:
I am not sure about the last comment - unfortunately DXomark has not tested the best avaible crop from nikon (d7100) but the best that the d7000 could do (11) is 20% less than the 70d (14). Hopefully dxo will provide more data on d7100 soon.


I was not referring to Nikon... The TDP comparison under discussion was with the 7D.



Sep 13, 2013 at 11:57 AM
Scott Stoness
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p.1 #18 · p.1 #18 · 70d vs 7d - Resolution


garyvot wrote:
I was not referring to Nikon... The TDP comparison under discussion was with the 7D.


Okay but the 60d/7d/d7000 (11) was as good as it gets in the industry, and maybe the 70d has improvements. You will still likely be diappointed because the 5diii can achieve 22 on the best lens, which is a large increase in resolution. It may be just a physics limitation on higher density crop that you are disappointed with but the 70d might have solved some of it.



Sep 13, 2013 at 12:26 PM
johnctharp
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p.1 #19 · p.1 #19 · 70d vs 7d - Resolution


If someone is interested in doing the math, you could use DxO's 'P-MP' measure to compute 'effective pixel pitch' using the best lens for each camera/sensor. We might find that, for example, the 70D has very similar effective pixel pitch to the 5D III, and this would be explained by crop cameras needing glass that resolves much more detail in the image center. If glass that can truly resolve the APS-C image circle doesn't exist (and it appears that it doesn't), then we shouldn't see P-MP scores from APS-C cameras that match their sensor resolution like we do on some FF cameras and lenses.

We might find, also, just how much more resolving power Canon's best lenses have, than can be resolved by their best sensors, in the APS-C image circle at least. Would be nice to know just how much more resolution Canon would need on their FF system to actually make use of their (and Sigma's) sharpest lenses .



Sep 13, 2013 at 03:01 PM
Scott Stoness
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p.1 #20 · p.1 #20 · 70d vs 7d - Resolution


johnctharp wrote:
If someone is interested in doing the math, you could use DxO's 'P-MP' measure to compute 'effective pixel pitch' using the best lens for each camera/sensor. We might find that, for example, the 70D has very similar effective pixel pitch to the 5D III, and this would be explained by crop cameras needing glass that resolves much more detail in the image center. If glass that can truly resolve the APS-C image circle doesn't exist (and it appears that it doesn't), then we shouldn't see P-MP scores from APS-C cameras that match their sensor resolution like we do on some
...Show more

The 300 f2.8 v2 yields 22 (dxomark) on a 22mpx camera (5diii). This suggests that the mpx of the camera was the limit as opposed to the lens so there are lens out there that are not llimiting the 22mpx (5diii) camera. In addition, the nikon 400 f4 yields 25 with a 36mpx camera (d800) which suggests that the canon lens would do even better since they are newer and have better florite coatings.

Anyway this does not mean that a crop camera would match the performance of ff but I suspect that many of canon lens are better than nikon (24-70, 600v2, 400v2, 24TS....) and more effective resolution on a crop camera still has room to be useful.

But to your question, I suspect that beyond 30mpx, the lens will be the limiting factor as opposed to mpx of the camera. [guessing a bit better than nikon for the 400 2.8 v2, 300 2.8 v2, and 600 4 v2 for example] But then again it could just be that the d800 cmos is limiting even these lens and it could be 50mpx. Soon we will find out when canon responds to the d800 next year (I am guessing).



Sep 13, 2013 at 04:25 PM
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