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Will the new fast F2.8 FE mount Zooms be smaller/lighter than the "old" Alpha mount equivalents?


delewin
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I'm just asking the above question because I am thinking that a F2.8 zoom whether it be in FE mount or Alpha mount will need the same amount of glass to collect the light to present it to the image sensor.

 

So, the new FE zooms will be approximately the same weight as the standard pro zooms in the Alpha range:

1.  16-35 F2.8 Z

2.  24-70 F2.8 Z

3.  70-200 F2.8 G

4.  70-400 F2.8 G

 

If that is the case, then using these lenses on the A7R2 size body would feel a "bit" out of balance to say the least.

 

I think I have read somewhere that the shorter gap between the sensor and rear glass element on the FE mount (when compared with the Alpha mount) will actually require a larger diameter glass to obtain the "magic" F2.8 number throughout the zoom range. If this is the case, then the equivalent FE lens could be heavier than the Alpha series lens.

 

 

Can Sony do a magic act and "pull" a lighter lens "out of their hat"?

 

Or, are we going down the path of lower noise / higher usable ISO to off-set the loss of this optical solution?

 

I for one, just love the beautiful Bokeh produced by these F2.8 zoom lenses.

 

What does this community think?

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Most f2.8 zooms are 77mm filter size and some bigger (82mm), so the chances are that optical physics drives the size of glass required as well as the depth of the lens.

 

That said, barrel material can be made much lighter (e.g., composite vs alloy).  The manufacturing composite parts should be cheaper than alloys but its a selling feature too so the chances are that the price will be much higher too.

 

My guess is that Sony knew how unbalanced 2.8 zoom sizes are to a7 series, they focused on f4 as a compromise and improved the ISO sensor performance.

 

 

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I hope someone who knows the math(s) of the situation can reply, but I'll guess based on what is available.

 

At 35-40 there are some reasonable pancake type lenses that work on the A7s, but when you get shorter than that they start expanding forward. I think that is to make sure the light in the corners is not hitting at too great an angle.

 

E.g. The loxia 21 is longer than the 35.

 

Above 50, and the small flange distance doesn't seem to be a problem. eg the batis 85 is about 90mm long, generally shorter than SLR lenses. (Theoretically SLR lenses could be shorter I guess?)

 

The bottom line is that the width at the front needs to be enough to enable F2.8 for the given length, plus the mechanics to do zooming, and I doubt that will be much smaller than the SLR lenses, if at all.

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I've heard the opposite, that the short flange distance allows for smaller lenses, but I'm no expert.  The whole idea of mirrorless vs. DSLR was the size/weight savings, and having giant lenses kind of obviates that.  But Sony has shown a willingness to put quality before weight, as shown with the enormous Sony Zeiss 35mm f/1.4 FE.  So maybe they'll do the same with the 2.8 zooms, in which case the mirrorless system will have to stand on its own in terms of IQ and features versus DSLR and no longer rely on the size/weight savings as a selling point. 

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You pays you sheckels and you make you choice.

 

However, longer, thus heavier, lenses rule for

digital imaging .... until someone can figger out

some way to get rid of all the glass sandwiched

on top of the sensor.

 

As long as we have the thickness of the sensor

filter pack, it will remain beneficial to project the

image from as great a distance as possible, with

no real effect from flange diameter or the flange

to image plane distance.

 

Hopefully, this enormous burden will drive all the

'Imalance Weenies' away from photography. After

they depart, hopefully the Bokeh Cult will be next.

Then we can get back to the fast efficient straight

bladed 5-blade iris.

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