Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Started 3 months ago | Discussions thread
Jack Hogan
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Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
In reply to bobn2, 3 months ago

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote: Then you'll find that lenses ranked 1-368 are FF lenses, then we get the Panasonic Leica DG Nocticron 42.5mm F1.2 ASPH at 369. There is some duplication there down to same lens different camera, but there's little point spending a lot of time cleaning up an 'analysis' like that.

What is the relationship between those lens rankings and the factor we are trying to isolate in this discussion: Lens resolution.

Resolution is a factpr in those rankings.

Yes. But not the only and as already indicated, the others introduce systematic bias.

That is why there is absolutely no point wasting time producing 'evidence' for you, Anders. Whatever it is it will not be persuasive enough to budge you from endless argument in support of your own concocted theories.

No there isn't, the (shrinking) target is always moving for some folks

As has been said correctly in this and several other threads mFT lenses typically need to be at least twice as 'sharp' in order to match FF linear spatial resolution in equivalent photographs - precisely for the reason mentioned by the OP: even mFT's admittedly state-of-the-art lens design is typically not enough to compensate for the format's size penalty. There are a few exceptions to this rule, but they are just that, exceptional exceptions.

As has also been said correctly in this thread by noirdesir amongst others, although ideally system tolerances would scale perfectly with size, in practice they typically don't. They don't because the difference in size we are discussing here is not orders of magnitude away: if an improved process becomes available to one size it will soon trickle down/up to the other negating its advantage, as Bob mentioned; and because as the system shrinks at these sizes there are more things that get harder than easier to do as far as 'sharpness' is concerned, making it difficult to scale down perfectly as parts get smaller. This is how The_Suede put it recently:

'And then you have optimization theory and deviation statistics in manufacturing that quite accurately predicts that it's hard to halve tolerances in centering, glass surface imperfections and element-to-element distances in the lens just because you halved the scale. Often you get maybe 2/3 tolerances in a 1/2 scale production scenario'

This doubly applies to tolerances necessary to achieve equivalent focus precision in the real world. So where's the beef?

It's very difficult to compare lens performance on different cameras because there typically are too many variables to keep under control, too few tests from too many sources, each with their own methods. Dxomark.com has put together the best effort to date attempting to control the variables, test multiple cameras and provide meaningful 'sharpness' data as perceived by the average photographer as uniformly as they could - in so doing they created one of the largest and well thought out, if obscure, databases in photography. One may disagree with some of their choices or methods but nobody questions the fact that the folks there are doing scientific work.

Their data confirms* the OP's point. As of today mFT cameras are typically not able to make up for their smaller sensing size with better lenses. The pudding is everywhere, all one has to do is open their eyes to see it.

Jack

*Selecting 'sharpness' under Optical Metric Scores as the ranking criterion in Bob's link to their database (limted to sensors between 12-18MP) shows the first mFT camera/lens combo on page 5 (Zeiss 42.5mm f/1.2 on 16MP EM5), a $1500 lens easily bested by its FF equivalent, a $500 lens on a 16MP body (Df+Nikkor 85mmf/1.8G). The Df on the other hand is well represented on page one with a host of lenses across the range.

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