AcuteShadows
Offline
• • • •
Upload & Sell: On
|
1bwana1 wrote:
If you don't want to get tangled up the formulas, the applications of Snell's law, the effects of RI differences, and dispersion differences, then think of it this way:
Take a look at a full frame image from any of your lenses, at any aperture, and whatever background you are interested in for Bokeh. Then cut the image to approximately the APS-C frame area. You will likely see less vignetting, less aberrations, rounder smoother bokeh, less sharpness fall of toward the edges of that new frame. Just look at the MTF charts for the effect of this on sharpness and aberrations, and the light fall off charts for vignetting. It is easy to see the improvements.
This is the core concept of how the Plena works. The Plena was designed to project a significantly larger image circle than standard full frame lenses do. The sensor of course only shows a crop out of the middle therefore reducing all these aberrations in the FF image.
The above greatly oversimplifies the engineering that Nikon has put into this lens. The large Z mount diameter is an advantage when using this approach to a lens design. Further, Nikon has optimized its elements to take best advantage of this core concept. That includes the use of SR glass elements (I think these are Nikon proprietary and this is only the second lens to have them) that bias the diffraction at the blue end of the spectrum. This reduces aberrations cause by the greater bending of light required to produce the larger image circle.
Other lenses have used the larger image circle concept previously. Still, I think overall the Plena is a innovative lens that delivers some visible differences from standard designs. It will produce a distinct visual esthetic under some circumstances.
Once it is out and available I would be interesting to see how close we could come to creating a similar visual signature with other high quality full frame lenses cropped to a smaller image circle. I am thinking we could get close. This could become another shooting technique in our tool kits. Especially when applied to the very high resolution full frame image sensor cameras.
I find this approach interesting. I have experimented with it briefly on some existing shots, and it does produce round bokeh balls, no vignetting, no CA, and even sharpness across the new frame. This of course is not a meaningful comparison. We will need to shoot the exact same scene framed to the exact same crop, with the exact same f/stop to really see how close we can get. It has potential however....Show more →
I don't know the actual optical design of the Plena, but a lens that merely enlarges the image circle to achieve the desired effect would be probably much larger than the Plena.
Very likely, the optical design combines several concepts, including image-space telecentricity. The Z mount and the small flange distance probably enable the lens to achieve this easier and in a smaller package.
https://en.wikipedia.org/wiki/Telecentric_lens#Image-space_telecentric_lenses
|
