What new LA-EA screw drive adapter should Sony make?

Started 1 month ago | Polls thread
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toughluck Veteran Member • Posts: 3,262
What new LA-EA screw drive adapter should Sony make?

This topic comes up fairly regularly, and I think it would be a good idea to debate it with in a separate thread.

There exists a proper option for SAM/SSM lenses in the shape of LA-EA3. I suppose it could be made a bit more compact, and maybe with external controls, but the option exists and is capable of working well (as demonstrated by A9).

What doesn't exist is a more modern option for screw drive lenses.

The topic of this debate and poll is whether Sony should make a new adapter with the pellicle mirror (possibly removable) or completely mirrorless.
I also want to add an option for an APS-c-only adapter with a focal reducer, making full frame lenses brighter and shorter. E.g., with a 0.7x (square root of 2), a 28-70 lens becomes a 20-50/2; with a 0.65x, the same lens becomes an 18-46/1.8.

Before voting, please read this post. When you do vote, choose an option that you would prefer the most (even if it's much less likely than the next best thing).

Let me list the pros and cons of every available option.

1. Mirrorless
+ Less expensive than SLT+PDAF; you don't pay for the mirror that you don't want to use
+ Tracking performance with OSPDAF is currently better than any SLT
+ No need to calibrate the adapter to account for any differences in plane of focus between the two AF modules
+ No light loss through the pellicle mirror
+ No limitations that currently exist, like that f/3.5 limit in video AF
+ AF will benefit (improve) from firmware upgrades in the future
+ Possibly more compact if the extra bulk of LA-EA4 is due to the mirror and AF module rather than the screw drive motor
– If there is potential for better AF performance with a dedicated module, it won't be realized
– No compatibility with the red AF assist light
– In addition to that, worse performance in low light (by as many as four stops)
– Some lenses (like 500/8 reflex) may be incompatible with OSPDAF and would require the dedicated AF module

The advantages are obvious, I hope. As for disadvantages, no compatibility with AF assist light is a big hindrance, **BUT**, this might only be with the current crop of mirrorless cameras which use blue photosites as focus sensors. Blue AF assist light is unacceptable, white is barely tolerable. But there's nothing that precludes camera manufacturers from devoting some red photosites to allow AF assist light to work. Not even that many are needed: Some in the center, some in 1/3 of the frame to the left and right of center, that's it. The benefit of being able to use AF assist light in low light is huge.

2. Pellicle mirror (SLT)
+ Potential for faster and more accurate focus
+ Works with the red AF assist light
+ Better performance in low light
+ Gives Sony incentive to further improve the dedicated PDAF module to allow better AF also in existing A mount cameras
+ Would work with all legacy A mount lenses
– More expensive than the mirrorless option
– Bulkier
– 1/2 stop light loss
– Hybrid AF functionality might not be available with all lenses, like in A99ii
– Potential for limits to remain (like f/3.5 for video, slower frame rate)

We have no idea if the pellicle mirror option will give us better AF, however. I already pointed out that the AF assist light might work with a redesigned sensor. We also have no idea whether the extra bulk of LA-EA4 is due to the mirror and PDAF module or if it's only due to the screw drive motor, it's probably a bit of both, but we don't know the bit.
As for the mirror, once dedicated PDAF in that revision becomes obsolete (and it eventually will), you have to spend money on a primary feature that you won't use and you still have to live with the extra bulk of this solution. And there are three possibilities:
– If it's not removable and you can't disable it: becomes obsolete, repeat of LA-EA4 situation
– If it's not removable, but you can opt to disable the PDAF module: lose 1/2 stop of light for no gain
– If it's removable: at least you don't have that 1/2 stop light loss.

3. Focal reducer
It's much like the mirrorless option. If it exists, it should be a separate accessory, not either-or.
+ Gives you a full frame equivalent on APS-c
+ Gives you the benefits of the mirrorless option
+ If the focal reducer group is removable, you have a 2-in-1 adapter (make that 3-in-1: native full frame, faster+wider APS-c, more reach with APS-c)
+ You get more resolution, less aberration and less distortion per unit of length compared to the original lens
– Costs more, possibly way more
– The reducer might be aperture-limited
– You get more vignetting and there is opportunity to introduce extra aberrations that did not exist in the original lens
– Will probably make the adapter bulkier, heavier and more delicate
– If the group is removable, realigning it might be problematic

Full disclosure: I am partial to the first option, fully mirrorless. Were option 3 available with removable optics, I'd like that one instead.

But there are some finer points in this debate, too. My most preferred option would be an E mount camera with the screw drive motor in the body itself and a special FE/A mount that would have the screwdriver and be able to use a simple tube to couple to the screw head in the A mount lens (much like A mount teleconverters and extension tubes). Bonus points for an aperture lever.

 toughluck's gear list:toughluck's gear list
Sony a99 II Sony 24-70mm F2.8 ZA SSM Carl Zeiss Vario-Sonnar T* Sony 70-300mm F4.5-5.6 G SSM Sony 35mm F1.4 G Sony 85mm F1.4 ZA Carl Zeiss Planar T* +5 more
50.0% 12  votes
4.2% 1  vote
Focal reducer (removable)
4.2% 1  vote
Mirrorless and focal reducer (not removable)
0.0% 0  votes
Mirrorless and SLT
12.5% 3  votes
SLT and focal reducer (removable)
0.0% 0  votes
All three of the above
4.2% 1  vote
I don't care, I won't get it anyway
12.5% 3  votes
Any of them, I want a better option to carry over my screw drive A mount lenses to E mount eventually
8.3% 2  votes
None, it's a bad idea
4.2% 1  vote
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