Is there a need for F1.4 lenses....

Started 4 months ago | Discussions thread
juanmaasecas
juanmaasecas Contributing Member • Posts: 867
Re: Is there a need for F1.4 lenses....
1

fferreres wrote:

JimKasson wrote:

fferreres wrote:

Dericali wrote:

fferreres wrote:

DenImage wrote:

fferreres wrote:

DenImage wrote:

I just checked the Sony 85mm GM bokeh test at Lenstip:

https://www.lenstip.com/484.7-Lens_review-Sony_FE_85_mm_f_1.4_GM_Coma__astigmatism_and_bokeh.html

F1.4

F2

F4

As the images indicate, the bokeh ball appears circular in the corner from f4

Den

It's obvious that there is, but it is obvious, any well corrected lens will show this "cat eye" at 85/1.4 or lower. Show me one lens that is largely the same diameter and curvature that doesn't and is high contrast and well corrected.

It's like people complaining about a car leaving marks in the ground after a very close curve at high speed successfully.

I'm not complaining, I don't own or use the 85mm GM.

I actually agree with you, I am stating the 85mm GM has cateye bokeh in the corner like most lenses.

Read my earlier posts, I was responding to Dericali's post where he claimed:

"It’s meant as a demonstration of the shape of bokeh at f1.4 on this lens, if you use the f1.8 version you will get cats eyes"

The only current lens I've seen that doesn't have cateye bokeh balls is the 100mm STF. It's free of any mechanical vignetting, but the 85mm GM isn't.

Den

I just checked Optical limits review of the 85/1.4 GM...

Is this normal for a state of the art oh so this is the culmination of 85/1.4 lenses?

Basically, anything other than the focal plane shows shifts in colors to the strong red or very odd blue/green...the amount of Longitudinal CA is staggering for a lens of this "prestige" ...of course, since this won't show up in MTF scores, why try to minimize it? I am ok with the cat eyes, totally expected, and even Vignetting. But this can't even be fixed in PP.

I was not liking some 1970s 85/1.4 lenses for some of the aberrations, but mainly the unaddressed LoCA in particular. But if this lens rendering is the epitome and very best top of the crop of today's fast 84/1.4 (besides the highly aberrated f1.2s) then, ok...thanks for the extra contrast...but can you make blacks and not red or green?

MTF has been a good counselor, but may need to be completed into scores of the other aberrations.

https://www.opticallimits.com/sonyalphaff/1063-sony85f14?start=1

I'd imagine this effect disappears by f1.8. At f1.4 this lens is not super sharp and is low contrast but it improves dramatically by f1.8.
The GM 85 was one of their first lenses in this series (released early 2016).

The review has samples, and it mostly goes away at f4. F2.8 still has imho significant shift. I am not thinking it is a bad lens, but I had overestimated how corrected these are, and on the other hand can’t stop thinking that if I were a lens designer I’d aim first and foremost to have a high MTF and anything else would be a nice to have.

LoCA in the long wavelengths impacts MTF. Less so in the short ones.

Hi Jim. I eat my words here. Very tasty, and nice to be corrected. I just saw this article and it mentions the work you’ve done around some of these impacts. Not sure how accurate it is but it was very understandable to me:

https://www.strollswithmydog.com/chromatic-aberrations-mtf-mapped/

Found it great to understand a bit more. Can it be the case, it may either be too expensive, or that maybe trying to correct LoCA could result in an even worst trade off, and thus may be preferred for overall sharpness?

I now understand the LoCA (after article) as related to the question, “which color do you want more sharp?” (Usually would be whatever bandwidth are more clustered together for max overall sharpness). In general, best point to focus makes red a little more blurry. Based on what I read LaCA is easier to correct, and LoCA very hard.

Why do we still see this much LoCA in good lenses? To me it’s a mistery.

Because the uncorrected aberrations are what make real pictures beautiful, with a nice rendering and soft bokeh, and not to look clinical, lifeless. Especially for portraits, as the 85 GM, sharpness wide open is not the ultimate goal but a nice rendering, and the designers left the spherical aberration a bit uncorrected in purpose. The Sony 85 1.8 renders with less spherical aberration at 1.8 but the pictures have a super harsh ugly look (to me). the 1.8 still has loca though.

also, at close distances the spherical aberration is more visible (like in your example), but at other distances, not that much.
sony 85 GM and Zeiss 35 1.4 are lenses praised for their rendering and bokeh and aren’t the sharpest wide open. Coincidence? Of course not. There are things beside sharpness and loca or bokeh balls that are difficult to quantify in tests, but using the lenses, you know what lenses deliver beautiful pictures, and other just lack that something.

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