Leica announces price and details of its 35mm F1.4 lens for the T system

Marc, I agree with you. It's an electronic lens and will have a limited service life.

How do you think billionaires get to be that way? They watch every penny and don't waste it on bling.

how can u call it wasting ? what is ur benchmark for wasting?

to badi: might the weight difference be the red dot?

Including this lens, there are 5 for the T.

Decent Olympus lenses are not cheap--not priced like Leica either.

The Pen F has shadow compression artifacts even when shooting raw. It's likely a 12 bit camera, while the Leica is 14 bit. And I like the Pen F a lot, and Olympus makes some very good lenses.

OK, then make it a Fuji XE2 and the same four lenses. Now you have spent $2500 rather than $9000 the Leica set will cost.

But we both know if you have to ask about the price, you can't afford to buy a Leica.

For $9000 you could get the E-M1, E-M10 II and all the PRO line lenses and half the great prime lenses including the 12mm, 25mm and 75mm as well as the Panasonic 42.5mm. You would then have two great cameras and a load of great lenses for anything type of shooting you want.

Or else it would cause heavy vignetting when you use aperture at 1.4...

Not the easiest question and concept to understand.

Short version: It is used to correct the aberrations which would otherwise spoil a fast, wide angle biotar(asimetrical planar).

That is the reason why both front and rear group are enhanced.

There are different kind of aberrations. In theory you are correct that some aberrations increase with additional elements even more so large ones in practice this lens can not be made the way it is without the corresponding action of this oversized front element as Leitz engineers know too.
Leica doesn't oversize its expensive optical elements for aesthetics reasons it is too expensive in terms of overhead materials used in vain.

@Yanko All aberrations either increase with ray height in the pupil, or do not vary with ray height in the pupil. Look up the Seidel polynomial and pay attention to the rho or y terms. Or look up the Zernike polynomial and pay attention to the rho terms. Vignetting is simply removing the rays at the edge of the pupil which are more highly aberrated. This improves performance.

While a bigger element may have geometrical reasons for improving correction, a *wider* one never does.

Considering the price of most optical glass is on the order of $10-$30/lb and increasing the diameter by 5mm will only add a few grams, I think Leica is ok spending another dollar or two on a bigger element.

Aesthetics are important. All of the metal micro four thirds lenses are plastic inside, but more expensive metals are used externally because... you guessed it, aesthetics.

@AiryDiscus

Since the nature of the Zernike expansion is different from the Seidel expansion I recommend you to stick to Siedel's polynomials. Also call them polynomials as it is not a single polynomial but there are multiple depending on the order.

Though you can find both on the web to quote here the Siedel's polynomials are used far more often by lens designers and photography professionals.

The two aberrations that are corrected by a larger diameter are quite simple and important:

1. Light falloff. The one you call vignetting.

2. Sharpness falloff - even more important to correct.

Try the lens on a FF to see that it covers a far greater circle that the one needed for an APS-C.

It is engineered on purpose like that and this is a common approach in the industry for a long time. You guessed it - not to for aesthetics reasons ;)

@Yanko

The Zernike polynomial is used to represent the aberrations of the pupil of a lens, so it must be calculated at a number of discrete points across the field of view. The Seidel polynomial, on the other hand, represents the residual aberrations in image space. The Zernike polynomial may be used to yield the W function, while the seidel polynomial yields the epsilon function.

The epsilon function is simply the derivative of the W function for a rotationally symmetric system.

The Seidel polynomial is the colloquial way to analyze aberrations among older and less advanced optical designers. I would argue exactly zero photographers use the Seidel polynomial, as it has no value to them. However, any system without rotational symmetry may not use the Seidel polynomial, and near the diffraction limit the Zernike polynomial is a much better fit. These are the types of systems I work on and design, see http://centerfreeformoptics.org

@Yanko

Vignetting is **__NOT__** an aberration. Aberrations cause a degraded image, or in wave optical terms, a deformed wavefront. Vignetting truncates the wavefront in space which is not an aberration behavior.

"Sharpness" is not an aberration. You cannot correct it by increasing element diameter. Quite the opposite, as (and I have repeated this several times now) you will increase the quantity of each aberration sensitive to the size of the aperture.

I stand by the assessment that the front element of this lens is not sized the way it is for optical correction. Unless it is an extremely high index material, the rays from its edges will simply never reach the second element.

@AirDiscus
Look at the way the elements are mounted in the lens barrel - you clearly see that the front element is oversized so that the rays reaching the second element do not pass through the corners of the element thus the rays thus they pass an area closer to the center that helps them suffer less aberrations. It is so simple and logical.

On vignetting as not being optical:

https://en.wikipedia.org/wiki/Vignetting
"There are several causes of vignetting. Sidney F. Ray distinguishes the following types:
Mechanical vignetting
Optical vignetting
Natural vignetting
Optical vignetting is caused by the physical dimensions of a multiple element lens. Rear elements are shaded by elements in front of them, which reduces the effective lens opening for off-axis incident light. The result is a gradual decrease in light intensity towards the image periphery."

Ken Rockwell classifies optical lightness falloff as lens aberrations too: http://www.kenrockwell.com/tech/lenstech.htm

@AirDiscus

On Zernike vs Seidel:

Bruce Walker and Warren J. Smith write: Notwithstanding their desirable properties, Zernike polynomials must be used with caution in real design situations. http://www.sinopt.com/learning1/desnotes/seizern.htm

Darryl Meister of Carl Zeiss writes: Zernike aberrations are calculated at a specific angle of view, while many Seidel aberration equations include a term that varies with the angle of view, often increasing as the angle of view increases. Consequently, Zernike Astigmatism does not distinguish between on-axis astigmatism produced by surfaced cylinder power and oblique astigmatism produced at off-axis angles of view. Similarly, Zernike Defocus does not distinguish between on-axis defocus produced by surfaced sphere power and curvature of the field produced at off-axis angles of view.
http://www.optiboard.com/forums/showthread.php/42246-Seidel-vs-Zernike

I have to end this - too late here, Cheers!

On the ray paths and the second element,

Changing the /diameter/ of the front element does not alter the path of any existing rays. The radius of curvature and refractive index are fixed. If you reduce the size of the front element, the sum of rays entering the second element is restricted to more central rays which will be better behaved, as you describe. Increasing the size of the front element is counter to this goal.

If you refer to Ken Rockwell as someone qualified to speak on classifying things as aberrations or what-have you, I really have no words. Look merely to the fact that vignetting does not appear in either the Seidel polynomial or Zernike polynomial to see that vignetting is not an aberration.

You will note that the first sentences I wrote (discrete points in field of view...) contains the same information as your Zeiss quote.

The most advanced current design methods are all based on the Zernike polynomial.

The front element size is increased but its borders lay on the lens barrel so a part of it is not used at all, this way you have actually a small element made out of the Better part of the bigger one thus performing better to its edge which is not the edge of the optical element but the age of its used area in this manner.

I'm not sure that is even english.

The fabrication errors on the surface are randomly distributed. There is no concept of a "better" or "worse" portion of the surface aside from the extreme edges (last 5% or less).

Usually about 10-15% to be correct and not 5% but anyway - you seem to be getting it step by step. That is good, it's not the language that doesn't allow you to calmly understand the concept though...;)

Seems I lost a lot of time here.

95% clear aperture is standard for fabricators in the US. 1% is more expensive, and 99.9-100% is also possible.

15% is horribly sloppy, I am not aware of any manufactures who do so poor a job. Perhaps Samyang? The portion of the element outside the clear aperture isn't even included in the light path, so the discussion is moot.

You finally noticed that it is intentionally out of the light path as I pointed earlier repeatedly now we have even more progress, great! All that is left is for you to understand that it is this way not because of aesthetics since Leica optical engineers don't calculate their schemes based on aesthetics and since they always aim to keep very compact and not the contrary. All the best to you I am done with educating ;)

I literally said in my first comment it was either for mechanical mounting reasons, or aesthetics. Both of these imply the extra diameter is outside the path of the light.

But... way to go making yourself feel intelligent. Bravo.

"Good morning,

The diameter of the front-lens is a part of the optical design or calculation. This has nothing to do with aesthetic reasons.
Mit freundlichen Gruessen / kind regards

Leica Camera AG
Am Leitz Park 5 / D-35 578 Wetzlar / Germany"

You were authoritative, sarcastic and negative but wrong....
You are a professional in the field so I suggest that you keep an open mind and learn new facts instead of restraining to fixed mind set that wrongly believes that knows everything.

I will support that with more exact technical data from Leica R&D department soon. The guys are very friendly, professional and open minded - I wish you the same.

@AiryDiscus I find such discussions a waste of energy but people that are reading and considering the product should not be mislead by experts that speak without any prior research with the given new product and negatively mislead the users as you could do here. This is a poor and often met pattern in the comments over new product announcements at DPReview.

If you were not working in the industry I wouldn't bother with your misleading post given your hostile attitude displayed here.