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

Started Jun 16, 2014 | Discussions thread
knickerhawk Veteran Member • Posts: 5,952
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here.

So you have no data and no data analysis to back up your claim.

If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

You made an assertion. I didn't. So you carry the burden of proof. But here is an example as a starting point:

Well, I considered picking an example like that, but it takes time and doesn't really 'prove' anything at all, does it?

More than the one you refer to below which is systematically biased.

But, if you are interested in bogus 'statistical' analysis, then try looking at DxOmark rankings. So, for instance if we filter the lens test data by MP, as follows:

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.

Bob, that's a little harsh, considering the misleading nature of the DXO lens ratings, which you seem to accept given your willingness to place "evidence" in quotes.  If the evidence is bad or misleading to begin with, then the amount or scaling of it doesn't really matter, does it?  The fact that 368 lenses appear in the dxo lens rating ahead of the first m43 lens tells us nothing if the scaling is distorted in the first place.  The distortion of the "evidence" is further compounded by the fact that there are far more lens+body combinations tested in the larger formats and - even more fundamentally relevant to the discussion here - you've included in your count many lens+body combos for higher resolution sensors than currently available in the m43 format.

If we throw out the higher resolution sensors and adjust for the many more tested combinations, the number is much smaller than 368, but the problem doesn't end there.  The dxo lens score isn't equivalence based.  For instance, the highest score for the Nikkor 24-70mm f/2.8 on a 16mp Nikon body is 25 and the highest score for the Oly 12-40mm f/2.8 on a 16mp m43 body is 20.  Looks like the Oly lens is inferior to the Nikkor by a significant margin, doesn't it? But look what happens when we set the respective dxo score maps at equivalent aperture settings:

That tells a rather different story than the basic score, doesn't it?

At the end of the day, we don't (yet) have much good "evidence" about how the practical limits of lens design and manufacturing will apply to lenses designed for different formats.  At best we maybe have some indications that might show some correlation, but even there it's hard to separate out the inherent optical design/manufacturing issues from the variable market targeting/placement issues (primarily size, weight and cost of the lenses relative to the markets they're targeted at).

Of all postings in this thread, I think your first one, Bob, where you deflate the importance "magnification" and highlight the size issue was probably the most useful.  It's a shame we've gotten so deep into meaningless weeds that we've lost sight of your original insight.

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