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03-09-2016, 01:19 PM   #106
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Good article on field curvature. The fact is that most of the world is not flat, and other than copying paintings or walls, there are few subjects where even correction for field curvature will come out solving the problem and rendering perfect focus from one corner to the next.

03-09-2016, 02:16 PM   #107
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For all the fretting by the blogger at the start of that article, we should note what Roger Cicala concludes at the end:

"Now the truth is that the majority of lenses these days exhibit very mild field curvature, if any. But there are certainly a few that do and those few tend to be superb wide-aperture prime lenses."

The more mundane edge softness is something practically every lens has, however.

Last edited by clackers; 03-09-2016 at 02:24 PM.
03-10-2016, 12:22 PM   #108
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QuoteOriginally posted by osv Quote
i needed a fast lens that was sharp across the field wide open for this motorsports situation, and the old vivitar 28/2 in this shot didn't cut the mustard at f/2.8...
Not surprising. Some amount of field curvature was the norm for 28mm back-in-the-day. Most of the Viv 28/2.8 variants were pretty good in that respect, but you pay a price for f/2 on a consumer-grade lens. There are some on this site who might suggest the FA 31/1.8 Limited as a flat-field low-light alternative. BTW, I think you may have missed focus a small bit overall based on the detail in the cage webbing on the first photo. Not a criticism concerning the nature of the shot.


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03-10-2016, 03:17 PM   #109
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fa31 would have rocked! maybe too nice to bring to the track tho, it's a filthy environment.

the focus looks sharper on the back half of the car to me, i think that i did miss it a bit.

03-10-2016, 04:44 PM - 1 Like   #110
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QuoteOriginally posted by slip Quote
a lens that used to be sharp on my K5iis has a slight blur on the K3 due to being able to zoom into the details closer with the higher resolution. I would think that the K1 will be brutal for focusing errors. thoughts?
Randy, I underlined the part ^ that you should think again about. Think about this analogy: a very sharp knife edge that still looks very sharp when viewed with a magnifying glass - but when viewed with a microscope, begins to look like a crumbling, dull wall. Did the knife somehow become less sharp between viewings?

In reality, your lenses will never perform 'worse' with more resolution - they can't. But more resolution allows you to 'magnify' more, which shows you things at 100% you couldn't see before - not because the lens was resolving better at less MP, but because the image just wasn't as magnified. What changed was your absolute value for "100%". This doesn't mean the image looks any better at less resolution, and even if you see flaws more because you're magnifying more, you'll also, sometimes at the same time, see more detail as well.

Every lens, except the truly bad ones, resolve better (MTF) as your MP increases. At some MP point, the curve flattens out and you don't see much of an improvement at typical display sizes, but no lens can ever perform worse with more MP at those display sizes.

In summary: as long as you haven't brushed up against sensor tech limits with read noise and heat, there's almost no IQ-related downside to more MP. The only more-MP downside we really see is with FPS (more data = slower processing,) and file sizes. It's also harder to PP larger files, especially with big batch operations.

Now, sensor manufacturers can reach a current 'sweet spot' where they've maximized DR, or maximized SNR, and that sweet spot may be below the current maximum MP - but it's always a trade off. You sacrifice resolution for perhaps a very small increase in DR on part of ISO the curve, or 1/4 stop less noise on part of the curve, etc... things that may be hard to even notice yet matter to some, but in reality are not keeping the larger-MP bodies from selling the best - for a reason.

.

Last edited by jsherman999; 03-10-2016 at 04:52 PM.
03-10-2016, 05:20 PM - 1 Like   #111
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QuoteOriginally posted by jsherman999 Quote
In reality, your lenses will never perform 'worse' with more resolution - they can't. But more resolution allows you to 'magnify' more, which shows you things at 100% you couldn't see before - not because the lens was resolving better at less MP, but because the image just wasn't as magnified. What changed was your absolute value for "100%". This doesn't mean the image looks any better at less resolution, and even if you see flaws more because you're magnifying more, you'll also, sometimes at the same time, see more detail as well.

Every lens, except the truly bad ones, resolve better (MTF) as your MP increases. At some MP point, the curve flattens out and you don't see much of an improvement at typical display sizes, but no lens can ever perform worse with more MP at those display sizes.
This is a very important point that gets lost in the constant discussion of "sharpness". Rather than "sharpness", the important thing to examine is "resolving power", i.e. the ability to see detail on a given real world subject.

A higher pixel density sensor will never resolve less real object detail than a lower density sensor (unless there is a technical issue with the sensor itself). It will always resolve the same or more, even beyond the so-called "diffraction limit" (which is actually two different but related effects tied to f-ratio and absolute aperture diameter). There will never be an instance where you can point to some particular detail in the lower pixel density photo, and not be able to point out the same, and usually more, detail in the higher pixel density photo taken with the same lens.

Of course the K-1 actually has slightly lower pixel density than the K-5 in the center (and infinitely more pixel density in the FF corners), so I don't even really know what the complaint is.

Last edited by Cannikin; 03-10-2016 at 05:26 PM.
03-12-2016, 09:01 AM   #112
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After 8 pages only one post about printing.

The rubber doesn't meet the road in a darkened basement with a giant screen.

The 4x6's will be fantastic. The 8x10's? Sure you betcha.

How about the 17x22's? If you are using all the megapickles - no doubt.

Cropping for comp? Ya there is a penalty no matter the format.

Sharpness / resolution is secondary to focus, and if what I have read about the K1 AF is half as good as it appears, I might only want to shoot a modern AF lens so that I could benefit from that innovation. For me - $3K (CDN) can buy a lot of Ektar100 for my film bodies if I choose to shoot with K, M, or A legacy glass.
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