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#1
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DSLR lenses not good wide open at wide angle?
The (expensive) Carl Zeiss 16-80 for the Sony Alpha DSLRs is only good
from F5.6 onwards. With wider apertures at wide angle the corners become soft to very soft, depending on aperture and distance from the image centre. According to photozone the same holds for several other DLSR zooms (the Sigma 17-70 being an example). However the lens of the Sony R1 is good wide open at F2.8, even in the corners. Could this be because in the R1 the lens is very close to the sensor (just 2mm distance vs. 2cm in an APS-C DSLR)? Also the Zuiko 14-54 is good wide open, which could be a consequence of the 4/3 design. -- Alfred Molon ------------------------------ Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at http://tech.groups.yahoo.com/group/MyOlympus/ http://myolympus.org/ photo sharing site |
#2
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DSLR lenses not good wide open at wide angle?
"That80sGuy" wrote: In message , Alfred Molon done wrote: However the lens of the Sony R1 is good wide open at F2.8, even in the corners. Could this be because in the R1 the lens is very close to the sensor (just 2mm distance vs. 2cm in an APS-C DSLR)? Yeah, the light gets lost trying to travel 2cm. Finally we've got someone here who understands quantum mechanics! Somewhat seriously, is the above really true? That is, has anyone actually compared the R1 at f/2.8 at 24mm equiv. with the Canon 24-70/2.8 at 24mm (or 24/2.8) on a 5D? (Also note that for the same DOF and the same shot noise, you'd shoot the 5D at f/4.0, not f/2.8 (assuming the same ISO and shutter speed settings), so the comparison with both at f/2.8 is bogus on two counts.) -- David J. Littleboy Tokyo, Japan |
#3
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DSLR lenses not good wide open at wide angle?
Alfred Molon wrote in
: The (expensive) Carl Zeiss 16-80 for the Sony Alpha DSLRs is only good from F5.6 onwards. With wider apertures at wide angle the corners become soft to very soft, depending on aperture and distance from the image centre. According to photozone the same holds for several other DLSR zooms (the Sigma 17-70 being an example). However the lens of the Sony R1 is good wide open at F2.8, even in the corners. Could this be because in the R1 the lens is very close to the sensor (just 2mm distance vs. 2cm in an APS-C DSLR)? Also the Zuiko 14-54 is good wide open, which could be a consequence of the 4/3 design. All the books on photography I have ever read say you should not use any lense at its largest aperature setting or smallest due to light difraction. |
#4
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DSLR lenses not good wide open at wide angle?
In article 8cgfk.74718$kx.60067@pd7urf3no, Dauphin de Viennois says...
All the books on photography I have ever read say you should not use any lense at its largest aperature setting or smallest due to light difraction. Diffraction only occurs at small apertures and there are lenses which perform well even wide open. -- Alfred Molon ------------------------------ Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at http://tech.groups.yahoo.com/group/MyOlympus/ http://myolympus.org/ photo sharing site |
#5
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DSLR lenses not good wide open at wide angle?
"Alfred Molon" wrote: In article 8cgfk.74718$kx.60067@pd7urf3no, Dauphin de Viennois says... All the books on photography I have ever read say you should not use any lense at its largest aperature setting or smallest due to light difraction. Diffraction only occurs at small apertures Right. and there are lenses which perform well even wide open. But they tend to be slow primes, not fast 5x zooms. http://a.img-dpreview.com/gallery/so...s/dsc00563.jpg The lower left corner is mush and has CA (red/magenta on the inner side of edges) to boot. And then there's the upper left... And don't look at the (CA on the) yellow/orange flowers in the mid-left of this one. http://a.img-dpreview.com/gallery/so...s/dsc00575.jpg -- David J. Littleboy Tokyo, Japan |
#6
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DSLR lenses not good wide open at wide angle?
David J. Littleboy wrote:
"Alfred Molon" wrote: In article 8cgfk.74718$kx.60067@pd7urf3no, Dauphin de Viennois says... All the books on photography I have ever read say you should not use any lense at its largest aperature setting or smallest due to light difraction. Diffraction only occurs at small apertures Right. and there are lenses which perform well even wide open. But they tend to be slow primes, not fast 5x zooms. There are two different approaches to designing a zoom. The first approach is to design it to a minimum standard of performance throughout the zoom range. The second approach is to design it to a maximum performance standard at an important part of its range, and simply do the best you can, without disturbing the best performance, at more distant focal lengths than the best one. I get the impression that some of the latest best quality zooms have adopted the latter approach, so that what you get is reasonably good performance for a zoom at the extremes, allied with a part of the zoom range which approaches the quality of a prime. Of course in a lens with more glass elements (as zooms typically have) it will be very hard to avoid a concomitant drop in contrast. -- Chris Malcolm DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/] |
#7
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DSLR lenses not good wide open at wide angle?
In article ,
Chris Malcolm wrote: There are two different approaches to designing a zoom. The first approach is to design it to a minimum standard of performance throughout the zoom range. The second approach is to design it to a maximum performance standard at an important part of its range, and simply do the best you can, without disturbing the best performance, at more distant focal lengths than the best one. This is true of designing anything, not just lenses. A device has some operating envelope. It will perform better in some parts of the envelope than in others. If I limit the allowable range of operation to just the part of the envelope where it works best, I get a device which is limited in functionality, but performs great over that limited range. If I allow it to be used over a larger range, I still have the good performance in the middle, but now you can complain, "But, it sucks near the edge!" So, which is the better design philosophy? Well, neither, really. They're just different. Why do we even have variable aperture, variable focus lenses at all? For any given image, I'm only using one setting. Let's say I take a picture with a fixed focal length lens (f = 85mm), focusing at 15.5 feet, and an aperture of f/8. The fact that the lens is capable of focusing closer or further away, or adjusting the aperture larger or smaller may make the lens useful in other situations, but for that specific image, it's all just a waste. If I told a lens designer to design me a fixed-everything lens for just that exact combination of settings, he or she could probably come up with a lens that produced a better image. The only problem is it would be such a specialized lens, nobody would buy it. Everything is a tradeoff. |
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