Canon Lenses not able to handle 50Mpx Resolution?

[jeffa4444]

DXO use their analyzer to check lenses which are shot on a camera body. Lens designers DONT design lenses this way and never have. Lenses are designed using optical formulas based around known values atributable to glass types like say BK16, then coatings, baffles, iris etc all play their part. Lenses are computer modelled these days knowing the details listed above, they maybe optimised for 20 lines per mm, 40 lines per mm etc. based around averaged pixel sizes to attain the best nyquist match (Schneider have a great explaination of this). When lenses are built they are checked on an MTF bench to the specification they were designed for and on an f stop machine and projected to view distortions, chromatic abberations (color fringing) & sharpness at each marked distance. Test lenses usually allow for some adjustment before designs are locked off.
In modern manufacturing glass batches are checked, randon lenses would be taken off production lines and fully tested because scales are normally extrapolated from infinity and say 5 feet otherwise each distance would need to be individually marked & engraved (cinematography lenses are made this way). It all comes down to cost, no lens is perfect hence why even new Canon lenses like the EF 16-35mm f4L still have vignetting wide open and or lenses are soft at the edges into the corners wide open. Lenses are expensive to design, glass particularly rare earth glass is expensive, then laddle in distributor & dealer margins its remarkable we get lenses at the prices we pay.

 

[Mt Spokane Photography]

Canon lenses like the EF 16-35mm f4L still have vignetting wide open and or lenses are soft at the edges into the corners wide open.

Vignetting is as much a property of the sensor as it is a lens. The light striking the sensor at the edges and corners only partially illuminates the photosites due to the angle. Its less of a issue with smaller sensors. The camera processor turns up the pixel gain as you get toward the edges which helps with vignetting, but also hurts IQ at the edges. This makes for a double whammy, the lens properties you mention plus the sensor edge effects make perfection a unreachable goal.

A film camera is much less susceptible to this effect, but its a problem for digital and is not entirely due to the lens.

 

[rfdesigner]

yes canon lenses seriously outperform the current full frame sensors.

if you take a "20Mpix" sensor and use it with a "20Mpix" lens you don't get 20Mpix, you'll probably get about 14MPix, for canon to score nearly as many Mpixies as their sensor ratings on DxO for several lenses then the lenses must be resolving comfortably finer detail than the sensors.

Looking at the 300mm L, I'm making a semi-educated guess of 44MPixels with the 5Ds, and with an infinite Mpix sensor I seem to remember calculating something north of 200MPixels.

 

[StudentOfLight]

yes canon lenses seriously outperform the current full frame sensors.

if you take a "20Mpix" sensor and use it with a "20Mpix" lens you don't get 20Mpix, you'll probably get about 14MPix, for canon to score nearly as many Mpixies as their sensor ratings on DxO for several lenses then the lenses must be resolving comfortably finer detail than the sensors.

Looking at the 300mm L, I'm making a semi-educated guess of 44MPixels with the 5Ds, and with an infinite Mpix sensor I seem to remember calculating something north of 200MPixels.

Based on MTF data from 4.1 micrometer pixels, the 300mm f/4 L will resolve about 39MP of detail on the 5Ds if shooting at close to f/8, it's optimal resolving aperture. If shooting wider open than f/8 the corner performance will not be at its best and if shooting at smaller apertures then the image will start to soften due to diffraction.

On the 5Ds-R you could gain a bit more detail, so I'd say your educated guess reflects more of the capabilities of the lens on the body with OLPF cancellation rather than on the normal 5Ds.

 

[Marsu42]

I don't know if this has been discussed before but rumors are spreading on on the web that the upcoming 50Mpx Sensors are a waste of money since current Gen Canon Lenses are "only" optimized for 35 Megapixel Sensors

I don't know where the 35 metapixie number originates from, but Canon stated that post-2010 (or something about that time) L lenses are optimized for the 5ds sensor.

Afaik they did not say how all other lenses perform though, so that's up to your imagination or testing. My guess is that for example with my 17-40L and 70-300L I'd rather stick to 20mp-ish sensors as the zone of diminishing returns would be reached rather sooner than later.

 

[jeffa4444]

Canon lenses like the EF 16-35mm f4L still have vignetting wide open and or lenses are soft at the edges into the corners wide open.

Vignetting is as much a property of the sensor as it is a lens. The light striking the sensor at the edges and corners only partially illuminates the photosites due to the angle. Its less of a issue with smaller sensors. The camera processor turns up the pixel gain as you get toward the edges which helps with vignetting, but also hurts IQ at the edges. This makes for a double whammy, the lens properties you mention plus the sensor edge effects make perfection a unreachable goal.

A film camera is much less susceptible to this effect, but its a problem for digital and is not entirely due to the lens.

Agreed about sensors but only in as much as the lens design is to a given image circle and the image circle affects No 1 cost of design & manufacture so they are deliberately kept to a minimum and therefor more prone to shading in the corners. Modelling has been done on different micro lens designs the further out from the centre of a sensor a bit like a flower moving to the light in terms of gathering light but manufacturing cost & difficulties have not produced viable products. It all comes down to cost, the bulk of the technicalities can be resolved I would argue modern high contrast lenses are conceivably too sharp in some instances but then that can be mitigated with filters better too much than not enough.