Nano cũng không nét hơn ?

[TiCan_2009]

105mm , f/4

crop

[lil_ryan]

không hiểu gì hết, bác có thể giải thích thêm

[KhongGianPhang]

105mm , f/4
[IMG]http://tican.us/MISC/Samples/Test/P200s.jpg[IMG]
crop
[IMG]http://tican.us/MISC/Samples/Test/P200c.jpg[IMG]

24-105 F4 L IS ???????????

Thân,
KGP

[madi3d8]

Phải hiểu Nano nó có tác dụng gì bác ơi, em research trên trang chủ của Nikon thì thấy ghi như vầy




Improvements with Nanocoating
Nanocoating, unlike multicoating, is not a continued evolution of a previous technology...it is indeed an entirely new approach to solving an old problem. Nanocoating is based on the design of moth eyes, which are known in the scientific community to have one of the lowest reflectance indexes of any material. The general design is based on nano-scale roughly dome/spike-like structures intended to guide as much light as possible into the lens, avoiding reflectance entirely whenever possible.


If and when flare or ghosting does occur, since nanocoating is not designed to work on any given wavelength of light but light in totality, the resulting artifacts or loss of contrast is considerably less than with a multicoated lens. In many cases, careful and close scrutiny is required to find small elements of flare and ghosting in photo taken with a nanocoated lens, and when it does exist, it often does not detrimentally affect IQ.

Transmission levels for nanocoating are at least 99.95% PER COATED ELEMENT/GROUP. At a lost of 0.05% or less, the grand total transmission loss for any lens, even complex lenses with many element groups, will remain very low (i.e. a complex 15 group telephoto lens would end up with a total of 0.75% transmission loss.)

Design of a Lens Nanocoating


The design of the illustration above is taken from a few of the SWC, or Subwavelenth Structure Coating, diagrams I have found on Canon's websites. In comparison to Nikon's Nano Crystal Coating, Canon's SWC is the same thing, although their specific implementation may differ in the details. Canon explicitly calls out the "wedge shape" of the nano-scale structures, and calls out the pseudo-layered nature with wedges of differing size and height. The size and thickness of the structure layer is explicitly designed to be considerably smaller than the wavelengths of visible light used for most photography (around 200nm at the largest, where as the wavelengths of visible light range from 380nm to 790nm or so).

The technological purpose for using such a structure is to eliminate the primary cause of reflection: Large changes in refractive index at material boundaries. Replacing layered multicoating, which creates many interfaces where there could be large changes in refractive index, with a structured coating where there is no single interface thereby creating a "smooth transition" layer. The thickness of the layer is kept small, presumably to minimize the impact to angle of incidence of rays that pass through it (don't actually have any specifically concrete information about why wedges are kept so small.)

Light is effectively "guided in" through the nanostructure layer into the lens element. The ultimate goals is for light to pass through the nano-structure elements and enter the lens element in the spaces between wedges, largely "unscathed". The amount of reflection is minimal, and what reflection does occur usually reflects off of the nano-structure/element interface where one exists. When light reflects off of an internal lens element and back up to a previous element, the same nano-structure coating will have the same effect on that reflected light, helping it pass through the internal elements to either diffuse harmlessly off the low-reflectivity innards of the lens, or right back out the front element...little to no harm done.

Better Sharpness?

Regarding whether nanocoating allows for improved sharpness. I would not be inclined to say that the nanocoating itself can really improve sharpness a whole lot. It certainly improves transmission, such that in lenses with lots of element groups, the total transmission loss is reduced from several percent to usually under, often well under, one percent. In terms of overall IQ improvement, the improved transmission should also improve contrast, even at a microcontrast level. Improved microcontrast will lead to improvements in sharpness, to some degree.

The claim to improved sharpness is more likely due to more freedom in lens design, and the ability to utilize more lens elements a lens designer might otherwise be limited to due to transmission requirements. If you can only use 8 lens elements with multicoating because more would reduce overall light transmission too much, you might be able to use 15 or more with a nanocoating and still have far better transmission characteristics. That offers lens designers the freedom to implement greater control over image reproduction than in the past, which should ultimately lead to improved sharpness.

I believe that is exactly the case with newer Canon lenses, largely "Mark II" generation or "new entrants" such as the EF 8-15mm f/4 L Fisheye lens. It is probably also the case with Nikon lenses with NCC. Canon's newer lenses are significantly outperforming their predecessors in the area of MTF (Modulation Transfer Function, a way of measuring the sharpness and contrast of a lens). Almost all of Canon's L-series lenses introduced since around the middle of 2008 (possible a little earlier than that) that use SWC have theoretical MTF's (most lens manufacturers these days generate MTF charts from computer models of lenses) demonstrating significant jumps on overall resolution, sharpness, and contrast, with some demonstrating nearly "perfect" results according to the criterion of their MTF (which is admittedly lower than most of their lenses should actually be capable of resolving, but consistent in terms of comparison with MTF's of older lenses.)

So, technically, it is not the coating itself that directly improves sharpness (although as it improves contrast it may have a slight direct impact). Improvements to sharpness are more likely due to the ability to make improvements in lens design without as much concern for transmission as in the past. (I guess that could be either corroborated or refuted by comparing the lens designs of new lenses with nanocoatings vs old lenses without.)

Source:
http://photo.stackexchange.com/quest...o-on-this-lens
và trang chủ Nikon

Nói tóm lại là có Nano hay không có Nano, không trực tiếp tác động lên độ sắc nét, mà liên quan đến thiết kế của lens nhiều hơn.

[ktsnag]

Nếu bạn so sánh tâm hình, khó mà phân biệt dc lens nào nét hơn lens nào. Nhưng rìa hình thì khác nhau đấy!
Nhiếp ảnh là một kỹ thuật phức tạp. Nếu chưa rành, rất dễ trở thành thày bói mù xem voi :D

[TiCan_2009]

24-105 F4 L IS ???????????

Thân,
KGP

Nhìn chất lượng hình thấy cũng từ đó trở lên phải không bác ?

[TiCan_2009]

@all: thấy nhiều post cứ sử dụng nano như là thước đo "đẳng cấp" của lens nên tôi mới đùa thế thôi. Quên để nó trong nháy kép

Có một câu hỏi với mọi người: Lens (và cả máy) cỡ giá nào thì có thể chụp ra các tấm hình có chất lượng tương đương ? Các tấm hình trên chỉ crop, re-size chứ không xử lý gì khác.

[Conviction]

Em cũng thấy "có nhiều post" lấy L là "thước đo đẳng cấp" của lens, bác làm thêm cái so sánh đi cho công bằng

[mutsumi]

bác chủ thớt coi bộ khoái gây war =))
tôi tin là con 50 f/1.8D ghẻ khi khép ở khẩu 5.6 thì độ nét cũng đạt được vậy thui :D thậm chí khẩu f/4 cũng nét vậy. Bác có thể đọc so sánh trên photozone.de :D mở cái MTF chart của 2 con này ra mà so =))

[mutsumi]

Người ta mua lens nano để tận dụng những cái khác. Hơn nữa, khái niệm Nano nó chỉ nói về lớp phủ. Khác Canon, L là Luxirous, là đẳng cấp =)) Ống Nikon khi có N chỉ là về lớp phủ Nano coating, và lớp phủ này ko liên quan đến độ nét. nikon có những ống ko có N nhưng độ nét thì kinh hoàng. Ví dụ như cái lens ghẻ 50 f/1.8D tôi mới đề cập đấy =)) Bác chủ mang 1 con L ra so và bảo Nano cũng ko bằng. Thế có khập khiễng ko.
Còn câu hỏi của bác, thì tôi nói thẳng, bên nikon thì tầm giá 2tr5 cho con lens 50 f/1.8D là đủ nét kinh hoàng =))