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new Nikon gear
#31
You can yell. Still does not change things....

 

Two simple questions, with two short answers.

 

1. Why is the 300mm f4E PF so remarkably short and light (same goes for the Canon 400mm f4 DO IS USM II)? 

Answer: Because of the use of the PF (DO) element.

 

2. Does the use of the PF/DO elements mean a whole lot of extra elements are needed to get rid of the aberrations?

Answer: No, one refractive element counters the CA. That is why such lenses have similar number of elements as modern tele lenses without DO/PF elements.

 

Since I am not allowed to use the 400mm f2.8E as measure, because you claim that the bigger aperture would mean more elements, an other 300mm f4 lens with IS group:

Nikkor AF-S 300mm f4E PF VR: 16 elements. Canon EF 300mm f4 L IS USM(pretty old design in its own right): 15 elements.

The increase in elements is pretty normal for modern tele prime design, and is not due to the use of the PF element. By the way. The 500mm f4 and 600mm f4 lenses with IS also have 16 elements. Pretty normal number for modern tele design. Not much to do with the inclusion of DO/PF.

 

Why do both Nikon and Canon use such elements? Only to make such a short and lighter tele possible.

#32
I can't contribute to the technical debate, which I'm reading with a great interest. I have a more practical question about the technologies used by Canon and Nikon to create these new generation "short-long-teles": are they covered by some patent, or can we expect other manufacturers to jump on that wagon?

stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#33
@stoppingdown

 

One cannot patent the use of a fresnel lens, or the use of a fresnel lens with other refractive elements.  A Phase Fresnel lens is also not the same type of fresnel lens as canon is using but rather a different geometry.  That also cannot be patented.

 

@JoJu

 

The length being "exactly" 75mm I would doubt, as all specifications are rounded, but it also doesn't mean anything directly. 

 

@brightcolors

Quote: 

Why is the 300mm f4E PF so remarkably short and light (same goes for the Canon 400mm f4 DO IS USM II)
Yes, but not simply because it exists.  The fresnel surfaces contribute power that would otherwise require shorter radii of curvature.  That reduces aberrations, so more aggressive telephoto ratios may be pursued.  The lightness is partly contributed to (even largely, I would say) by the use of fresnel lenses as they have very little thickness.

 

Quote: 

Does the use of the PF/DO elements mean a whole lot of extra elements are needed to get rid of the aberrations?
Again, not directly.  You requrie one flint to balance the polychromatic aberrations of the fresnel surface.  The structure of the fresnel surface may only be "tuned" to a single wavelength.

 

Looking at  first order, Nikon used a fresnel element to massively increase the power of the P group in the P N configuration.  The direct result of this is that the power of the N group must be massively increased.  This requires stronger curvature, higher refractive index, a GRIN material, or an additional fresnel lens.

 

First order -> http://photonics.intec.ugent.be/educatio...v1ch32.pdf

Smith also wrote Modern Lens Design and Modern Optical Engineering the former of which I am on a team editing the third edition of.  

 

To undo geometrical aberrations, you split and compound elements to distribute the power and "lean on" the refractive index of the material to do some of your work for you if you do not want to use special materials. 

 

This increases the element count

 

Counter-point:

 

Does the use of CAF2, Calcium Fluorite, in and of itself make a lens apochromatic?

 

No, it doesn't.  CAF2's good property is that it has anomalous partial dispersion, which is a big long sciency phrase zeiss likes to use for marketing.  If you look at Nikon's diagrams above you can see dispersion - the spreading out of the different colors.  All materials do this, unfortunately, but they do it to different degrees.  Dispersion stems from the fact that the refractive index is not constant across the spectrum.  If you go here, you can see the graphs of the refractive index of CAF2 and NSK4, a common low dispersion glass:

 

http://refractiveindex.info/?shelf=main&...e=Malitson

http://refractiveindex.info/?shelf=glass...page=N-SK2

 

Visible is approximately .4-1um, or just plug in .38 for the blue of the visible spectrum and .7 for the red side.

 

The big concept to see is that CAF2's refractive index has a point of inflection somewhat close to the visible range.  The refractive index of NSK2 changes .028 across visible while CAF2 changes only .0117 - less than half. 

 

The Abbe number of a material describes its dispersion between green and red - most glasses fall in the range of 65-30 or so.  CAF2's ranges from 95-118 depending on the specific manufacture.  It has phenominal "normal" dispersion but its crystal structure also has a harmonic or some business in the blue range that causes its partial dispersion, the measure of dispersion between green and blue, to be abnormally low. 

 

Does this guarantee apochromatic results?  No, no it doesn't.  It just means that a particular lens may be used to prevent blue CAs, and blue is difficult to deal with, but poor choices may still lead to blue falling to a different focus than green/red elsewhere in the design. 

 

Quote: 

Since I am not allowed to use the 400mm f2.8E
You are not allowed to use any lens - element count has no direct meaning with respect to performance.  Canon's 17mm TS-E has 18 elements - surely that means something here too?  (it doesn't)

 

Quote: 

The increase in elements is pretty normal for modern tele prime design, and is not due to the use of the PF element.
You have no basis for this claim, nor the knowledge to make it accurately.

 

There are generalizations that may be made, such as modern coatings (from the 90s and on) allowing higher element counts without having poor transmission, and CAD becoming better in the past decade or so at guiding the design process that lead to generally higher element counts with newer lenses - but this is independent to the performance of the lens.  Often adding more elements can make your performance worse, as more elements do give degrees of freedom to optimize with but they also impose restrictions. 

 

The use of the PF element in and of itself - i.e inherently did not increase the element count.  What nikon chose to do with it did.

 

Quote: 

By the way. The 500mm f4 and 600mm f4 lenses with IS also have 16 elements.
What do lenses with nearly twice the focal length have to do with this lens?

Canon's 50mm f/.8 has 6 elements.  The 85/1.8 has 9 elements, and the 100/2 has 8 elements.  The focal lengths are spaced the same as 300 -> 500/600, surely there is some correlation between the element counts!!! (there is none)

 

Quote: 

Why do both Nikon and Canon use such elements?
It comes down to weight initially.  If you can cut the thickness of one of your large front elements in half you may reduce the weight by as much as 400-500 grams.

 

Nikon's new 300/4 takes a different approach, using a fresnel surface to drive the telephoto ratio into a very impressive space.

 

The big "takeaway" is this:

 

A fresnel lens does one of two things:

It allows a lens element to become thinner while still having the same power.

OR

It allows an already curved element to contribute more power than it would with the material being used.

 

Neither of these is directly tied to the overall length of the lens.

#34
Quote:@JoJu

 

The length being "exactly" 75mm I would doubt, as all specifications are rounded, but it also doesn't mean anything directly. 
 

I was talking about the length difference. The data I got from the Nikon website:

 

300/4 old: ø 90 × 222.5 mm (app.)

300/4 new: ø 89 × 147.5 mm (app.)

 

And since Japan has also the metric system, I really don't mind about ± 0.1 mm, the difference is 75 mm and I find that pretty impressive. The 70-200/4 has a length of 178.5 mm, so it's longer than the new 300/4.

 

All that fresnel stuff - I admit I gave up trying to understand what the specific differences are.

 

To me the questions are:
  • is the lens sharp enough to burn this amount of money ? After all, it's only f/4 and at least 40% more expensive than the current version.
  • I already read, Nikon wants to reduce the flare via software. So, nothing for me, because I will not change all my workflow and I will especially very NOT fiddle around with Nikon's raw-converter and use another tool to organize my pictures. So, when are flares to be expected? If the answer is "occasionally on pointy highlights, round light sources, sun, waterdrops, reflexes in the eye" they can keep their lightweight shorty.
And while I expect extensive use of lightweight plastic in this lens (which doesn't mean to be a bad thing in my eyes), I can see why the 150-600 Sigma is NO lightweight:

 

[Image: sigma-150-600mm-sports-metal-casing.jpg]

#35
Quote:
  • is the lens sharp enough to burn this amount of money ? After all, it's only f/4 and at least 40% more expensive than the current version.
 

For the IQ, we need to see some real world sample photos. According to the computer-generated graphs, it's not worse, possibly better, than the old one. The 40% goes for weight and stabilisation. If I still bought Nikon stuff, I'd grab it immediately after checking from the first samples that there are no surprises: it would mean not only to save 700gr, but also that I could get rid of the tripod in many cases. Today weigh for me makes the difference between shot or no-shot, or shot-but-what-a-pain-in-the-neck-in-the-evening...
stoppingdown.net

 

Sony a6300, Sony a6000, Sony NEX-6, Sony E 10-18mm F4 OSS, Sony Zeiss Vario-Tessar T* E 16-70mm F4 ZA OSS, Sony FE 70-200mm F4 G OSS, Sigma 150-600mm Æ’/5-6.3 DG OS HSM Contemporary, Samyang 12mm Æ’/2, Sigma 30mm F2.8 DN | A, Meyer Gorlitz Trioplan 100mm Æ’/2.8, Samyang 8mm Æ’/3.5 fish-eye II | Zenit Helios 44-2 58mm Æ’/2 
Plus some legacy Nikkor lenses.
#36
http://www.nikon-asia.com/en_Asia/produc...features/1

 

Saw this recently on the flare and the correction. Looks like the flare might only be a problem on overexposed areas, and the correction isn't that great. On the left light it does seem to recover some of the detail behind it but the flare is still obviously there. If I were to have such a lens I wouldn't worry about the lack of software correction.

 

As for if the lens is worth it, optical quality is only one aspect. As long as that is "good enough" then other factors may be more important.

<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#37
popo, your link does only lead to the lens, not the photo. Bit if you saw it in it's galleries, then it's one of the cropped or downscaled ones. I really want to see a D800E or D810 full res sample.

#38
@joju

Quote: 

And since Japan has also the metric system, I really don't mind about ± 0.1 mm, the difference is 75 mm and I find that pretty impressive. The 70-200/4 has a length of 178.5 mm, so it's longer than the new 300/4.
The short length of this new lens is extremely impressive - I just mean that the fact that the length is 'exactly' 75mm shorter means nothing - i.e there is no significance to the number 75 here.  Bear in mind as well that the length quoted includes some distance in front of the front element for the threads, etc.

 

@stoppingdown

 

Optical CAD is not the enemy.  Unless the lens was poorly designed for manufacturability there will be very close agreement between CAD's MTF results and testing of a real lens sample. 

 

The new lens is exceptionally well corrected for spherical aberration and is limited off-axis by either astigmatism or by coma.  My money would be on astigmatism.  I cannot tell more from the graph.  There may be some unexplained loss of contrast due to the fresnel element that does not appear in spot simulations though.  I would assume the lens will perform very well.

#39
Quote:popo, your link does only lead to the lens, not the photo. Bit if you saw it in it's galleries, then it's one of the cropped or downscaled ones. I really want to see a D800E or D810 full res sample.
The example is at the bottom of that page. It is a crop. It is primarily to illustrate the flare and what the correction does with it.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#40
Quote:@joju

The short length of this new lens is extremely impressive - I just mean that the fact that the length is 'exactly' 75mm shorter means nothing - i.e there is no significance to the number 75 here.  Bear in mind as well that the length quoted includes some distance in front of the front element for the threads, etc.
 

No, I just meant, it's not 75.4 or 74.6 mm diff, that's all.
  
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