A-Mount to E-Mount Adapter with AF but no SLT

Discussion in 'Adapted Lenses' started by mrwinter, May 7, 2013.

  1. mrwinter

    mrwinter TalkEmount Rookie

    11
    May 7, 2013
    I'm thinking about buying a NEX-6 and using my existing A-mount lenses on it. Lenses do not have in built motors.

    I am aware that there is the LA-EA1, which can perform AF, but does not have any form of AF drive. Then there is the LA-EA2 which is nearly as big as the NEX camera body and has a semi-transparent mirror, another sensor AND its own autofocus motor. By the time I screw the LA-EA2 onto the nex, it is nearly the same size and weight as my alpha body.

    Obviously the LA-EA1 has some method of measuring focus and sending signals to a SSM-equiped lens, so why not just sick a motor in the LA-EA1, or mechanically couple to spindle of the E-Mount to an output spindle on the A-Mount?

    Why should having a mechanical focus drive on the output of the A-mount adapter be depenent on completely replacing the focus system of the NEX with SLT?

    Isn't there a third-party product that solves this problem more elegantly, albeit with perhaps a slower AF system?

    Why is non-confusing information on Sony adapters so hard to find? Are they doing this on purpose to cover up some fundamental weakness in the NEX AF system?

    What am I missing?
     
  2. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    You'd have to look long and hard to find an adapter that will AF more slowly than the LA-EA1 I think. It's so slow it's usually faster to manual focus. No matter what you do the NEX won't focus nearly as fast as the dslr will. Ask yourself why you want the NEX and then decide if the tradeoffs are worth it.
     
  3. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Yes, the NEX is awesome and amazing.

    One complaint that comes up often though is the slow focusing. If you did not know the NEX line uses contrast focusing, which is different than most DSLR's. 90% of the time is is more than adequate, but when you start pushing into low light/high speed action you will see some issues arise and miss a few shots.

    Many of our members are still able to get great shots under these conditions, but you need to get creative. 1- Turn off as many focusing aids as possible. Keep it simple. 2- Pre Focusing is the key. Get into focus ahead of the action. 3- The NEX is a great platform to shoot manually, either with the AF lenses, or older manual only focusing lenses.
     
  4. mrwinter

    mrwinter TalkEmount Rookie

    11
    May 7, 2013
    Thanks for the comments.

    Is the autfocus significantly better on the E-Mount lenses (I would at least get the SELP1650 kit lens) than on the LA-EA1 adapter?

    I don't plan to film much, but at least one lens with decent autofocus would be nice.

    I really hate manual focus on my DSLR, because I sometimes where contact lenses and somtimes don't and I think the camera can do a better job of focusing than me. This focus peaking feature looks to be a game changer though.

    Is focus peaking integrated into the viewfinder (as well as the LCD)? and Is this a practical way to use the camera for everyday use?
     
  5. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    :cool:
     
  6. mrwinter

    mrwinter TalkEmount Rookie

    11
    May 7, 2013
    Okay, I think I get it now. PLEASE CORRECT ME IF I AM TOTALLY WRONG :)

    The nex does contrast-AF and phase detection AF

    Phase detection is used in SLT and I assume it is faster and better, but only works under good conditions and with specific NEX lenses.

    There is probably a stack of firmware that needs to be developed for the phase detection AF to work with specific lenses (under a very wide range of conditions!), and this does't exist for alpha lenses on an adapter (whether it 'could' work or not).

    I assume that contrast AF measures sharp edges and is the method used for focus peaking as well. It appears that this method works more of the time than phase detection and with all lenses, but there is no 'directional' information that can be obtained from contrast AF, so it is rubbish to use for controlling the AF drive. The lense would need to go back and forth to obtain directional information for the control algorithm, which makes is slow and awkward and would make any sort of adapter with an AF drive an embarrasment for whoever produces it.

    So, any non E-mount lenses are stuck with a rubbishy contrast AF that works well for focus peaking, but isn't a good control variable for AF algorithms. I don't know about these roumours of a FF nex-9 with native alpha mount either. I assume this camera will still have the same AF issues without adding some sort of new technology. It seems my DSLR uses phase detection (bounced onto an additional sensor like the SLT???) as well - so no technology out there yet that can use the main nex image sensor to do its phase detection AF fast and reliably with all lenses all of the time?

    The answer to my original question appears to be "you can't use an AF drive for alpha lenses with contrast AF because constrast AF sucks for everything except focus peaking. In order to have an AF for adapted lenses you need to replace the entire autofcous system by placing half of an SLT camera on the front of your nex". But I bet Sony don't write that in any of their ads. The just talk about how great the LA-EA2 is, without saying why (at $400 and 200g) it is even needed!

    I think I will get a nex-6 with the SLEP1650 for ist awesome compactness. Focus peaking looks very useable and I'm going to get into it with the LA-EA1. If I ever decide I need AF for my alpha lenses, I can just buy a massive LA-EA2 with additional sensors and mirrors in it and stick it on the front of my camera.

    P.S. Did I see somwhre that the LA-EA1 has a 'lens' in it? Surely its just a $200 spacer with some electrical contacts?
     
  7. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    Nex 6 has got both contrast and phase af. Other Nexes only contrast one. The Nex 6 phase af is implemented differently than in SLR as these use mirror to reflect light to separate phase detection sensor. I think (no knowledge, just assume) that Nex 6 phase detection isn't up to SLR one.

    The advantage with phase detection is that you can measure which of nearby pixels is further away but those points of object must be very close of each other because it is phase angle difference that is measured. So the phase af is in this respect somewhat better than contrast one that only tells if focus is correct or not. On the other hand phase af suffers if phase angles can't be measured.

    Contrast af works but it is somewhat slower. It measures focus by focusing a little bit to the assumed direction. If contrast improves focusing to that direction is continued, otherwise direction is reversed. Faster af needs more computing power (contrasts are measured from images) and better mechanisms. Both cost more and consume more energy.

    The af drive system just focuses lens so it is independent of focusing system.

    I think that LA-EA2 includes semitransparent mirror and phase detector. That way you get a SLR focusing system like in Alphas.

    If we compare nex af performance with older SLRs it isn't as bad anymore.