The unsupported statement makes no sense to me either. Perhaps @darix will spare a moment to explain …
Meanwhile, I recommend this extensive paper on where to focus:
http://www.trenholm.org/hmmerk/TIAOOFe.pdf
See chapter 5 et subs.
and this one which is more DOF-related
2 Likes
I think the lens needs calibration, as nothing through phase-detect AF is properly sharp, no matter where I focus (I mean the cityscape scene). Viewfinder always focuses closer, even at close distances (less than 1 m) compared to live view, so I think calibration is the solution.
My best sharpness is through live view (infinity focus in case of the city scape scene).
needs calibration
There’s a problem with that though. The lens doesn’t support docking and my camera doesn’t support calibration. I could theoretically trade it in + about 400€ for a D7500, which is the same DX format, F mount DSLR, about as good as a consumer grade DSLR can be. All my lenses should work with it (even the kit 70-300mm) good idea?
Oh and the field curvature, it’s much less prominent if the lens is properly focused, especially at favourable apertures
Before buying a D7500 which is a nice step up from the D3500 try my suggestion and see how it goes. BTW, inspired by this thread I tested my Canon 10-18mm lens for asymetric field curvature today. Rather than identifying this problem I did identify that at 10mm the sharpest edges only occurred at f5.6 and smaller apertures gave poorer performance probably due to diffraction. It seems lenses can be complicated beasts. Maybe even just closing your lens down a click or two might help. I don’t doubt the suggestion that calibration will reslve your problem but if that is not an option I am just trying to suggest some practical solutions to test out. Good luck and if you get the D7500 you will appreciate the step up.
2 Likes
I tried focusing at hyperfocal (about those 10 m or so) but the problem was the same or worse in case of viewfinder AF (live view hyperfocal is ok).
I need to focus further than that, and ideally the way that live view does it.
I also noticed the following: With AF-C (continuous) the camera keeps readjusting the focus (roughly every second) when aiming at something around those 10-15 meters away. It just doesn’t seem to settle if I hold the focus button down.
It might be just the pattern though, as I’m aiming at grass that might be throwing it off.
*Some edits
1 Like
I tried at F/11, but the picture is still not as sharp as it should be, since the focus still differs by a bit. At that aperture it’s tolerable, but not usable once the light drops, I need at least that F/5.6 for darker scenes.
I would prefer manual focusing in live view and to ignore what any kind of AF gives you. But then, I’m always in manual focus anyway - never shooting stuff in motion …
Does the D3500 have a magnification option in live view? I find it very useful with my G9 especially with the focus peaking.
Yes it does, but then live view AF is pretty reliable anyways. It’s the viewfinder AF that is off with this lens… and MF is too tricky with an optical viewfinder as well.
I forgot that my camera does not have an optical viewfinder, so I can now understand what is meant by “viewfinder AF”.
On my 17-50mm I favor f/4 generally - rarely needing higher or lower f/numbers than that.
If you can afford it the D7500 is a big step up in quality and offers auto exposure bracketing which the D3500 doesn’t.
1 Like