Return of Interesting article on DxO about 5D III and D800...

Started Apr 10, 2013 | Discussions thread
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Re: Return of Interesting article on DxO about 5D III and D800...
In reply to Steen Bay, Apr 14, 2013

Steen Bay wrote:

qianp2k wrote:

Steen Bay wrote:

qianp2k wrote:

Steen Bay wrote:

qianp2k wrote:

Steen Bay wrote:/

We can also see that the 7D actually has a higher resolution. The 5D's MTF curve stops at app. 61 lp/mm because it runs out of vertical pixels (app. 61 lp/mm represents the 5D's Nyquist frequency), while the 7D's MTF curve continues to app. 72 lp/mm (on 24 x36mm). The contrast is rather low, but the 7D's resolution is nevertheless higher.

I'd suggest everyone reads these articles to understand these concepts first and understand what that means in real world photos.

From above two DXOMark MTF tests, we can see 7D only extends at MTF 15% or below that virtually invisible by eyes in real world photos even at base ISO when 7D photos buried by higher noises/grains. So that 7D higher resolution (18mp vs 12.8mp from 5D) is only on paper or reflected in larger CR2 file size but unless you have an eagle eye, you just cannot see it

A bit of sharpening makes it easier to see. It's clearly visible if comparing the resolution test chart shots in DPR's 5D and 7D reviews.

a) that depends from shooting distance.  A meaningful test should be done from at least 50x focus-length distance; b) depends on which lens. 7D needs a really good prime such as 100L (85/1.8 is also very nice lens) under perfect neutral gray and grainless/noiseless light condition at base ISO 100; c) doesn't reflect in real-world photos in outdoor harsh light or indoor poor light.

Not 100% sure, but think that DPR uses EF 85/1.8 on Canon FF and EF 50/1.4 on Canon APS-C. Agree that the 5D has better sharpness/contrast/acutance, but the 7D's higher MP count will most often also give it a higher 'resolution' (at least at low ISOs).

As shown in the two snapshots of old MTF charts between 5D and 7D, even with two excellent prime lenses, 100L and 85/1.8, 7D still only outresolves 5D around MTF 15% and below that virtually invisible by normal human eyes, and likely only in center not in edges/corners (on average MTF resolution).  You need to realize DXOMark tested in "perfect" ideal environment at base ISO on neutral gray resolution card virtually noiseless/grainless). I am sure with inferior lenses especially with zoom (such as 14-105L vs EF-S 15-85 or 17-55), then 7D will not be extended much more (that means at even lower MTF such as 5-10%).  Then in real world photos (outside "clean" lab), 7D/60D will be further impacted by higher noises/grains at pixel level (DXOMark SNR test confirms that), so that further will push 7D/60D advantage into lower MTF percentage that will be completely invisible by human eyes as above two articles said.

Therefore DXOMark tests likely use at least 20% MTF as someone suggested to test lenses on respective sensors (systems) to represent what human eyes can resolve (or perceive), and they changed to Perceptual Sharpness for easier understanding.  Ultimately what we can see in eyes only matters.  That should also answer your earlier scenario regarding smaller-sensor sport/wildlife cameras.  That's the reason Olympus FT DSLRs never succeeded in sport venues because Canon and Nikon have 300-600mm super-tele lenses. Then 2.0x crop has no chance, that's the reason why top wildlife photog are willing to lug around big super-tele lenses to achieve the best possible photos not only in IQ but in resolving fine details.  Sure 2.0x crop or even smaller sensor cameras do have "reach" (or pixel density) advantage in small birding that sometime even 600mm is not long enough.  However FF/APS-H owners could add 1.4x, 1.7x and 2.0x TCs, and can bring out 800mm and with 1.4x TC that still can AF at F8.0, that effectively overcome "reach" shortage and will result better IQ photos.

Anyway in theory I don't disagree with you but that has not been reflected in reality, not yet.  The main reason is lens not sensor.  I'm sure smaller sensors can involve better and better, so do larger sensors.  But the point is glass-based lenses.  It's either impossible or actually no longer smaller/lighter for 2.0x crop manufacturers for example to manufacture 300mm/F2.0 prime, or 400mm/F2.8 or 150mm/F1.4 lenses, in order to overcome 2.0x more crop penalties.

As another person said, crop penalty is real and amount of pixels is also real.  But crop format has much larger impact than amount of pixels that vividly confirmed by DXOMark tests.  We all remember in camcorder optical zoom vs digital zoom, that actually is very similar between crop format (digital zoom) vs longer lens (optical zoom).

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From DPR's 5D and 7D reviews - horisontal/vertical resolution (extinction resolution) :

5D - 2300/2000 (2500/2500) LPH

7D - 2500/2450 (3100/3050) LPH

I am not sure how DPR calculated into above data?  From the same AOV?  Using the same lens? Under that MTF percentage? 5D is 8-yr-old and DPR Lab has changed its test environment between when they reviewed 5D and 7D.  I wish DPR can add some old cameras such as 5D into new standard lab samples

That's the problem here.. according to DxO's P-Mpix scxore the 5D beats the 7D, but if looking at DPR's resolution test chart shots, then it's rather clear that the 7D has a higher resolution.

The key is that if those paper resolution actually can be seen by normal human eyes?  In those two DXOMark test charts with very nice prime lenses 100L and 85/1.8 (no mention inferior lenses), we can see 7D is only better at MTR 15% and below (even lower with inferior lenses) that are very low contrast and virtually invisible by human eyes even under grainless/noiseless lab environment (no mention in imperfect real-world environment .  5D is better above 15% MTF that is more meaningful and matter to human eyes.  It's all about perceptual sharpness or perceptual resolution as DXOmark uses two words interchangeably.

5D vs. 7D is just an example. Think that we'll have a similar 'problem' (acutance/sharpness vs. resolution) if comparing for example 5D3 vs. D800, or if looking at the effect of diffraction when stopping down.

I am sure 41mp Nokia 808 is 41mp on paper. In lab test, it may has 1% MTF data higher than 36mp D800 or 2% higher than 22mp 5D3.  The only matter is whether you eyes can actually see that?    If you eyes unable to tell, then those paper resolution is meaningless that you can think but you cannot see, heeh.

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