a7 + 55 f/1.8 vs 35 f/2.8 point-to-point AF accuracy?

Started Jul 2, 2014 | Discussions thread
Angrymagpie OP Contributing Member • Posts: 642
Re: a7 + 55 f/1.8 vs 35 f/2.8 point-to-point AF accuracy?

viking79 wrote:

If the AF performance is indeed better on the 35mm f/2.8 than with the 55mm f/1.8, then I have one more reason to go for the former instead.

Yes, only because you won't notice focus differences as much (deeper depth of field), but it will probably have a greater tendency to grab the background since the subjects tend to be smaller at wider field of view.

I see. I woke up this morning feeling convinced that I'd get the 35mm f/2.8 over the 55mm f/1.8 for sure. Now I am doubting again! A greater tendency to grab the background? Sounds bad.

I hope this helps, I think it is a misalignment of your expectations of the focus system and how it performs vs an accuracy issue.

I think so. Thanks for clearing this up for me

Unfortunately manually setting the focus point is not something that I envision myself doing too much since I mostly shoot street where I often find myself in situation where I wouldn't have time to do that.

That's why I was hoping that I could count on my camera to distinguish subject(s) & background well. I think the 55mm f/1.8 did fine. I guess I was just not used to the much shallower DOF

If in doubt, focus on the chest/collar, it is usually in line with the eyes. This is what I do at weddings or something if the camera is wanting to grab the background. You should do a visual inspection of the EVF for focus. It is high resolution so you can usually see when it focuses on the background. If you work in moderate to low light, the A7 focus system might become frustrating to you. It may or may not be the camera for you. Remember, a single candle can easily provide enough contrast for the system to focus. You just have to know where to focus and position the light source so it makes contrast. In some situations, like an event, I don't have liberty to easily adjust ambient light on the fly for a candid shot


Thanks Eric, there are truly some wonderful advices. I'd give them a try for sure!

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