LA-EA2: what lenses to get?

Started Oct 1, 2012 | Discussions thread
mikew5163
Regular MemberPosts: 335
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Re: LA-EA2 and aperture control
In reply to verybiglebowski, Oct 22, 2012

verybiglebowski wrote:

mikew5163 wrote:

Hi,

Maybe the PD focus can indeed predict where the subject will be after it's waited for the aperture to close, but it shouldn't have to wait in the first place!  And that doesn't help when your subject is moving laterally across the frame.  It simply won't be where it was when you pressed the shutter (unless you shoot wide open of course!).

That is the point actually. With moving subjects, focus will never be in the same position when the shutter is fully pressed and when exposure is made. But, this is the limitation of the focus based on contrast detection. Phase detection based focus should be able to predict where the focus should be in the moment of the exposure.  That means, that even with a time lag that appears after fully pressing shutter button, focus should be more accurate with the LE-EA2 than with a native E-mount lens on NEX 7. Problem is, that this lag might cause a different composition than desired, but we are still talking of a 0.118 s in comparison to the 5DII i.e.

I actually found when I inspected my test shots closely that focus was off on a lot of them, even when the subject wasn't moving.  I was using the centre point to lock focus on the eyes but often finding they weren't sharp, whereas in adjacent frames they were.  It wasn't badly wrong, but more wrong that I've ever seen in a dslr.

There's no need for there to be this lag.  All the adapter / lens have to do is close the aperture down to its preset value; something slrs have been doing for many decades.  I've never come across an slr where this lag was obvious.

We don't know what is the reason for it, it could be that due to smaller amount of light that comes to the PDAF sensors with a translucent mirror, more time is needed to confirm the focus, or the PDAF processor is simply slower. Anyway, it should not affect focus accuracy. It is however a slightly different feeling for photographer.

I notice there is an aperture lever inside the adapter.  I don't know whether the SAM lenses have electronic aperture control or whether they utilise this lever, but if it's the latter then that would explain the delay.  This is 1980s technology!

Maybe I have a faulty adapter / lens, but it sounds from what you and the flikr poster have said that this lag does exist in these adapters.  It's such a shame because for me at least it ruins what would have been a perfect solution allowing me to use the NEX 7 as a compact(ish) system and an slr replacement.  Sadly I'll have to stick with an slr, whereas I'd have liked to release the cash I have tied up in slr lenses.

Well, I have to agree with you here, I prefer to use my DSLR for the fast action too. But, I wouldn't use my 5D MII for that sort of images either, nor will I any present entry level DSLR. If I am serious about fast action, I will grab the body with an adequate focus system, and I will mount an fast focusing lens. As Henry said, that combo costs considerably more.  If I may suggest, try experimenting with a AF-C focus drive and high speed drive mode to see, if that improves your results with SAM 35 and LA-EA2.

You're right - I never got good results with the 5DII with subjects moving towards / away from the camera, but it was fine for small children moving about in the frame.  I've actually sent the LA/EA2 and SAM 35 back now and, for not much more than they cost, picked up a used Nikon D7000 and 35mm 1.8 lens.  I'm hoping they will do the job a bit better than this Sony combo!  As I say, it's a shame the adapter doesn't quite work - it would be so good if it did.

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