Dan De Lion Loc: Montana

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DxO’s test of the superlative Sigma 85mm f1.4 lens on a D810 body graphically shows sharpness trialing off after f5.6 ( https://www.dpreview.com/news/4310712992 ). This isn’t the fault of the lens. Rather it is physics, and applies to all lenses and all focal lengths when shooting with any 36mp body. To get the full sharpness the D810 is capable of, one must shoot at f5.6 or larger, have the camera on a rock steady tripod and use a superlative prime lens. If these conditions are not met, D810 users might as well use a 24mp camera.

Many low-knowledge D810 users claim extraordinary results on flimsy tripods, shot at f11, with zoom lenses (even the HEAVY Trinity.) They are delusional. Delusional in the sense that they would have gotten equally as good results with a 24mp camera or even a 16mp camera. They just don't know any better.

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Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Diffraction. Learn to spell.

Oh, and please share an image with exceptional superlative, better than anything sharpness taken with a high mp camera and a 40 lb tripod - I'd love to see what REAL sharpness looks like. . .

DaveO Loc: Northeast CT

Where can I get one of them there fancy lenses,you know,one of those exceptional superlative types? LOL! All in fun! Maybe??

BebuLamar

So I use a 16MP camera.

LoneRangeFinder Loc: Left field

This implies/ requires a redefinition of diffraction. (!)

Gehenna Loc: The wrong side of the river Styx

How patronizing.

Charles 46277 Loc: Fulton County, KY

It is my understanding that the effect of diffraction increases as the image size decreases--an 8x10 camera shows little diffraction at f32, while a 35mm camera can show quite a bit (so their lenses don't typically stop down to f32 or beyond)--though both may have the same diffraction if magnified enough. (8x10 negatives need little magnification.) The D810 has a 35mm-sized image, so it ought to escape serious trouble at f22 and below. I never heard of any diffraction problem at f8 or f11--on any format. Do you mind enlightening us about what is happening in the D810 as opposed to other cameras? Note--when you say "f5.6 or larger," I assume you mean f4, f2.8, f2, f1.4? Second note--if you mean you must stop down to 5.6 or smaller (f8, etc.), this indeed does depend on the lens design. Some designs are sharp wide open, though they are usually not the fastest lenses. In the past, people were told to stop any lens down a couple of stops before shooting, but this was long ago, when the large aperture was just for focusing on a dim ground glass, and the lens was not corrected at open aperture. The Kodak 203mm f7 lens was a symmetrical dialyte design, sharp wide open. So was the Goerz Artar, the Schneider Repro-Claron, and the Rodenstock Ronar (f8 or f9 lenses). I suspect current lenses are almost all meant to satisfy the demands of every possible use, so there are compromises--they can make them faster, but not quite as sharp without losing sharpness somewhere else. The diameter of the front optic is the primary factor of speed, and this does not have any bearing on diffraction.

RWR Loc: La Mesa, CA

Drat!! And I was hoping to use my 400 and 560 f/6.8 Leitz Telyts with Adox CMS 20 II film. Oh, well, I’ll just take them to Goodwill tomorrow and break out my old 90-230 f/4.5 Soligor & 2X Vivitar teleconverter and use Tri X instead. Bummer!

CO

Diffraction can definitely start to soften fine detail at small apertures. I wonder how much of what is seen on image resolution charts is just due to the characteristics of the lens itself. LensTip.com does extensive tests on lenses. I downloaded their image resolution testing for both of Sigma's 85mm f/1.4 lenses. There's quite a bit of difference in the image resolution. The vertical scale is line pairs per millimeter.

Sigma Art 85mm f/1.4


Sigma 85mm f/1.4

oldtigger Loc: Roanoke Virginia-USA

By your line of reasoning the performance is as poor at f 1.4 as it is at f 11
so i guess the lens should be regarded as a f 1.8 rather than a f 1.4 by those who care about image quality.

Rich1939 Loc: Pike County Penna.

"Diffraction can definitely start to soften fine detail at small apertures"
The question the photographer needs to answer for themselves is, where is the sweet spot for the image size I intend to display the photo at. Diffraction may start at 5.6 but really how evident is that in an 8X10 or a 16X20? On a test bench the diffraction at f/11 can be easily measured with a labs equipment however depending on many factors can the usual viewer notice it? This is part of the photographers decision making process when setting up the shot.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Funny you would make that point. The Sigma has a Tstop of 1.7 - which is a measure of the actual light transmission wide open, rather than a theoretical calculated ratio of aperture to focal length.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

tradio Loc: Oxford, Ohio

I wish you had told me that a long time ago but, it may not have sunk in being all low-knowledge and all.

oldtigger Loc: Roanoke Virginia-USA

For me a lens with super performance at one sweet spot may have its uses but i prefer
one like the art lens which has a several stop wide sweet spot.
Especially when they are the stops i would normally shoot at.