The upside to A-mount popularity going down

Started 3 months ago | Discussions thread
SQLGuy Forum Pro • Posts: 10,673
Re: The upside to A-mount popularity going down

ProfHankD wrote:

SQLGuy wrote:

ProfHankD wrote:

SQLGuy wrote:

Although 5-pin lenses don't have distance encoding, the in-body drive in A mount cameras does. No reason Sony couldn't get that same information from the drive motor in the LA-EA4 or LAA-EA5.

Actually, they can't. You might come close using per-lens lookup tables and a focus initialization process that bangs the drive against the infinity stop (if there is one -- not all lenses have one) to set a reference point.

You have screw drive lenses that don't have MFD and infinity stops? Which ones?

I think all have a mechanical stop, but not necessarily calibrated for infinity. For example, my Phoenix 100-400mm can focus notably past the infinity mark... which I've seen on various long lenses, because thermal expansion/contraction can effectively change the infinity position.

They keep track of focus positions, but can't generally tell what the focus distance is... and having that data, which Minolta only added for flash adjustments, actually can significantly help both IBIS and AF. This is just a tiny part of why I'm saying that it's quite difficult for Sony to just make A-mount lenses work with the different infrastructure and protocol of E/FE. Sony never even got native A mount focus performance up to near the levels of native E/FE, and I'm pretty sure it's literally impossible to do it.

That's an interesting statement. Especially since later A mount cameras had hybrid AF as well. What aspect of the A mount design do you think would make it impossible?

Different, fancier, and literally faster, lens protocol for E/FE. Here's a discussion of the E protocol reverse engineering effort. I actually have my NEX-5 sitting next to me right now with a Teensy 3.5 wired into a hacked lens adapter. A-mount uses a very straightforward SPI interface, with the primary purpose being readout of lens ROM data, as describedhere .

This is yet another reason I consider the LA-EA4 more than good enough for me... although I'd rather have an adapter that didn't have a fragile SLT in it and the potential to need micro focus adjustments due to the SLT PD sensor not quite aligning with the main sensor (although all my LA-EA2/4/4 seem surprisingly correct without micro adjustment).

Pretty sure all of mine needed MFA. Some of them quite a lot of it.

I've certainly heard of people having that issue. However, some Sony E bodies didn't provide micro adjustment, so I think Sony might have been a bit more careful about alignment back when they were current. Either that or I just got lucky with the three I have?

E? Or A? I think you meant A.

BTW, the micro adjustment doesn't really fix things -- different lenses might need different micro adjustments if it's off. I suppose I should also note that most of my A mount lenses are slow enough that DoF could hide a small error.

That's why the adjustment is per-lens rather than one setting for the body. It's a problem, though, with some 3rd party lenses that use the same ID for different models.

Ideally, MFA would also allow different adjustments at different focal lengths of a zoom. Sigma allows that, and, I think, also different adjustments at different distances, for some of their EF lenses through their dock.

Among my A mount cameras, the A900 has it, but earlier and/or lower models, like the A390 and KM7D, do not.

Film cameras could have benefitted from MFA, too, but I don't believe it was available in any of them. I guess I could adjust my Sigma lenses with the dock for use on my EOS A2e, but what a pain that would be - shoot some frames, develop them, adjust, shoot some frames, development them...

On the other other hand, this could be handy for my EOS 5D classic or EOS 1D classic, since those also don't have MFA, and, IIUC, the Sigma dock adjustments have no effect when I use those lenses on the MC-11.

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A7R2 with SEL2470Z and a number of adapted lenses (Canon FD, Minolta AF, Canon EF, Leica, Nikon...); A7R converted to IR.

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