LUMIX G Vario 3,5-5,6/12-32mm right side blur issue

Started Jan 9, 2014 | Discussions thread
Anders W
Forum ProPosts: 21,197Gear list
Re: Sorry, shouldn't have said "by design". It may be a fault in a batch though.
In reply to secretworld, 6 months ago

secretworld wrote:

Anders W wrote:

secretworld wrote:

Anders W wrote:

secretworld wrote:

Hey Anders!

I read the post and it sounds logical. But...When I use the manual tick focus method, the centre is sharp from 6-10 ticks (@12mm) and the only difference in the centre visually is when there is moire. When there is no moire causing pattern I can't see any difference, will the focus engine "see" any difference then? I am not convinced yet and practice says that the focus engine indeed focusses through the whole range of 6-10 ticks (where from 9 ticks sides are already soft) It might all depend on the size of the details and with 12mm details can be very very small in landscapes.

In my test scene I can sometimes see the difference in focus point only in a very small part of the image. Like the windows of one distant building. If I point my pinpoint focus there it will work ok, but I have no way of knowing in advance what detail will give the best focus.

Maybe I will use manual "tick"focus for this lens @12-14mm and landscapes. I already know it by heart and because of all the testing I am very fast with it now. With 18mm auto focus is spot on, compared to manual tick, except when it fails completely and at 18mm focus fails the most.

I hope when weather improves I can get some nice shots with this combo, which I want to put in my jacket pocket. All this testing doesn't create a trustful relationship .

Hi Vincent,

What I am saying in my reply to Paul is not that focus precision is unlimited, just that the function is continuous rather than discrete. The lower the resolution of sensor and lens and the slower the lens (more noise, more DoF), the harder it will be to isolate best focus with precision. When you say that the center is sharp in between 6 and 10 ticks, that just means that the differences in that range are so small that you have difficulties distinguishing them, not that there truly is a plateau of perfectly identical focus within that range.

That is what I meant (there is only one point where moire is most), but it has influence on the side sharpness which focus point the camera picks and it seems to be random from the 4 points I see as equal (without moire).

I am not sure the AF even works with demosaiced data (I would guess not) so how much color moiré there is likely uninmportant from an AF point of view. But yes, the camera may well have problem distinguishing reliably between "ticks" close to the peak due to the factor I already mentioned (pretty slow lens so more noise in the AF signal and more DoF, both of which makes it more difficult to set focus precisely) but also things like those you have pointed out like haze and small-scale details at a distance, both of which lowering max contrast and thereby making things more difficult for the AF system.

I must correct myself here. Suddenly weather improved for an hour here and auto focus was more accurate, it picks the same tick I would have chosen. So It is not inaccurate because a range that is equally sharp (except moire) but because of lack of light and or contrast (as you said). In clear but cloudy weather AF performance already decreases a little, which would not be very obvious except for the field curvature showing it.

Glad to hear that it works better in better light. But I think you are well advised to continue not to trust the AF blindly for the kind of shots we are talking about, particularly in so-so light with so-so targets. As I said, I am watching out for this myself since some time back, especially with my very wide and not so fast 7-14/4. While it doesn't have any field curvature based on my testing, it is nevertheless sensitive, particularly at the edges, to slight misfocus.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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