 Harold F. Bonacquist |
Ghosting at F1.4 I have a Nikkor F1.4 prime that I have used very successfully for portraits for some time. I took some stage shots of a local production of Nunsense and the pix seemed ghosted -- with a haze over the image and colored fringes on the edges. I stopped down to F2.8 and the problem disappeared. The shot was all black and white under strong stage lights and I am thinking that the high dynamic range might have something to do with the problem. Is this a problem endemic to fast lenses or just to the Nikkor?
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
Lenses can have an aperture or aperture range where they are at their sharpest. By your situation, your lens is better at 2.8 than 1.4 The high contrast scene made it more evident. The same thing can show up with certain zoom ranges for zoom lenses.
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Lynn R. Powers |
Yep, Gregory pretty much has it summed up. With the powerful lighting and shooting at f1.4 you have a very small DOF. With this combo it accounts for the flare (haze) and the rainbow of colors around the edges. I am surprised that you didn't have to close down to f4. Be happy that you didn't take the photo using a Leica 50mm f0.95 lens wide open. :=)
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Harold F. Bonacquist |
Problem solved: The pix were way overexposed! I normally shoot with a Nikon 7000 and Sigma F2.8 zoom at 1/60 sec and auto ISO. Working under colored stage lights ISO is typically well over 1000. This shoot was under bright white lamps, so I set the speed to 1/125. I went back to look at the pix shot at F1.4: ISO 100. And the pix at F2.8? Also ISO 100! I should be bragging about how well the 7000 did, rather than complaining! Two final questions: (1) Which lens do you think will have more light-gathering power at F2.8: The Nikkor, or the Sigma? (2) Would you expect the Nikkor at F2.8 to be sharper than the Sigma at F2.8, since the Sigma is wide open and the Nikkor is stopped down?
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Lynn R. Powers |
f2.8 is f2.8 regardless of which lens you have. It is the aperture's diameter divided into the focal length of the lens. So if you have a 300mm f2.8 the physical diameter is larger than for a 50mm. But the same amount of light reaches the sensor. The sharpness diference is from lens design, quality of build and the type of glass used.
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Harold F. Bonacquist |
Interesting. As you suspected, I thought that maybe the physical diameter of the lens made a difference. But: The Nikkor 1.4 prime has fewer lens elements than the Sigma 2.8 zoom, doesn't it? Does this have some effect, albeit small, on the amount of light hitting the sensor?
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
Fewer elements means sharper images, less diffraction/chromatic aberration. Unless you want to measure any light that gets reflected of the surface of each element, you're not talking about any effect on the amount of light that reaches the sensor.
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