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09-25-2014, 12:54 PM   #91
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QuoteOriginally posted by osv Quote
vignetting(and field curvature) is the achilles heel of ff... the fe35 differences on a7r vs. nex7 crop sensor are -1.8 vs. -0.8, per that dxomark link i posted... and that's gotta be after in-camera correction on the a7r :-0

i recently started measuring light falloff with imatest, on the a7r... with legacy primes, going from 24mm to 28mm appears to gain ~2 f-stops in the very furthest corners(wide open, worst case), which is a lot.

yes, legacy lens designs weren't made for short mirrorless registration distances, but there are the rare few lenses that cope pretty well with it, which indicates poor lens design is the biggest factor.

i've shot over a dozen lenses, all of the same scene, at the same aperture... the differences in lens designs are rather surprising.[COLOR="Silver"]
Yeah, but...legacy designs are still shot at their normal registration distances via adapters. But what's changed is that they are now being used on digital sensors vice film. Maybe thats the real difference.

Or perhaps Sony designed "microlenses" into their mirrorless sensors that are more receptive to native e-mount lenses than legacy lenses. Not very sure how those microlenses work.

09-25-2014, 03:50 PM   #92
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QuoteOriginally posted by osv Quote
yes, legacy lens designs weren't made for short mirrorless registration distances, but there are the rare few lenses that cope pretty well with it, which indicates poor lens design is the biggest factor.

i've shot over a dozen lenses, all of the same scene, at the same aperture... the differences in lens designs are rather surprising.
It has become fairly well understood that telecentric wide angle lenses generally perform better on FF than non-telecentric designs. For example, there is this thread on the MFlenses forum: Old wide-angle lenses with dSLR - most telecentric ones?

Also in Wikipedia: Telecentric lens - Wikipedia, the free encyclopedia

As well, it appears that the design of microlenses as well as other factors in the filter packs of cameras such as the A7r has effects on corner performance.

It's not so surprising that the performance of legacy wide angles on FF is hit and miss, as they were designed for film rather than digital sensors. Angle of incidence is much less of an issue on film. More a matter of different parameters than bad design as such.

Over about a 15 year period I accumulated a pretty good selection of wide angle lenses in different mounts, mostly very cheaply, for exploration on film cameras. Since I got my A7r I've been cherry picking them. Yes, there is considerable variation in performance, with a number of lenses that were perfectly good on film not making the cut on the A7r. However, a minority of the old lenses are very good indeed- particularly stopped down, which is what matters to me.

If I was serious about wide open performance, I'd buy modern lenses.

It wouldn't totally surprise me if some of the A7r duds turned out to be quite respectable on a FF with a longer registration distance and different filter pack- for example, a Pentax FF.
09-26-2014, 11:40 AM   #93
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it makes sense that the sony lenses would be designed to work with the sony sensor, and judging by the higher percentage of pixels returned, maybe designed specifically for the 36mp sensor.

the resolution tests for film tend to reflect what i've seen when the lens is mounted on the a7r, at least at stopped-down apertures.

for instance, the smc pentax k24/2.8 has one of the lowest corner rez numbers of any pentax lens that was tested on film:
Measured Resolution Numbers

my testing shows that it has the worst sides of any 24mm lens that i've tested so far:
24mm camera lens test

the pentax-m 28/3.5 showed good on that film rez test, and it looks really good on the a7r in my testing... it beats out six or eight other lenses that i've tested.

that's why i think that things like field curvature play a bigger part in the p.q. equation than people give it credit for.

i'm not sure how any of that fits with the telecentric theory, tho, because i don't know if those lenses are telecentric.

Last edited by osv; 09-26-2014 at 11:56 AM.
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