Thanks for the details Simon. I also thought about it a bit and had a reasoning similar to yours, that basically something designed for a specific acquisition chain will probably perform worse on an acquisition chain farther from its spec.
However thinking about it more deeply, 2 things are still boggling my mind. 1 This reasoning is mixing description of digital features with analog ones . A lens quality and specs is not defined by MP resolution (rather by like purity of the glass, glass curvature homogeneity, CoC, TCA, and so on). 2 Some of the lenses we're talking about were developed and (partially) targeted to FF cameras having a sensor with less MP than a current APS-C (for example in Canon, the 6D is a 2012 FF with 20MP). If the reasoning is valid, a lens released at times of FF with 24MP or higher wouldn't be a good match to the previous cameras with less MP. Which doesn't seems to be the case. What I mean by this is that at some point, to ensure a lens will perform well on FF cameras that will be released the following decade, one can assume that the optical manufacturing quality is probably one order of magnitude above the quality required to fit the current camera sensor capabilities. Maybe explaining why you can see problems in older lenses. Please feel free to point any mistake in this reasoning. Maybe are we lucky enough that someone working in the optical lenses or cameras industry is part of this mailing list and provide us some insights about it :) Florian Wernert Software engineer INSA In-training Neuroscience researcher https://www.linkedin.com/in/wernertflorian Le sam. 23 févr. 2019 à 18:12, Sturm Flut <sturmf...@lieberbiber.de> a écrit : > Hi, > > Am 23.02.19 um 16:34 schrieb Florian W: > > Thanks for your answers guys. > > > > Simon, I'm curious to know why to you it's not the best idea ? > > (oversimplifying it a bit) > > Full-frame lenses are designed to deliver their full sharpness across > the whole full-frame image circle. If I put a full-frame lens on my > APS-C D7100, I am basically expecting it to deliver 24 megapixels within > the smaller APS-C image circle the sensor is cropping out. That means I > expect the lens to deliver about 24*2,25 = 54 megapixels over the whole > full-frame image circle. Which not that many standard lenses will do. > > If put my standard 24-70/2.8 on a Nikon D850 and (let's say) it only > delivers 40 megapixels of actual resolution instead of the ~46 the > sensor wants, that's not going to be a catastrophe. If I put it on a > camera with a lower resolution sensor, e.g. the 24 megapixel sensor in > the D750, there is zero problem. But if I put the same lens on the > D7100, the cropped area will only get around 40 / 2,25 = 17 megapixels. > That's suddenly 30% less than what the sensor needs. And not every lens > will even deliver these 40 megapixels. Good APS-C and especially > Micro-Four-Thirds lenses are expensive and hard to make because they > have to be very sharp within the smaller image circle. > > Prime lenses are usually sharper to begin with, so with your 50/1.8 and > 28/2.8 it might not be that much of an issue. But I can clearly see the > problem with my 24-70/2.8, and especially with the good old 70-300/4.5-5.6. > > cheers, > Simon > ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
