Educate me on AF

413x

413x

413x

Caporegime
Joined
13 Jan 2010
Posts
33,192
Location
Llaneirwg
I am recently struggling with AF

more often than not (far more often) pictures i take are not in focus. the focus indicator says it is in focus but sometimes the shot is completely out of focus.

some of these are hi speed shots and i am probably not very good at it. but others are static and still they are out.

my issue is i dont really know it is me/something im doing etc.

one lens..my 100mm IS 2.8 macro L gets far far more keepers than the rest. it is on the other end of the scale. I get more than i would expect.

all my other lenses are the opposite
this includes
sigma 120-300mm OS f2.8
canon 50mm f1.8
new sigma 35mm f1.4
somewhat canon 10-22mm f3.5-4.5 (although i havent used this in a while)

i just dont know if this is technique (likely), lens, conditions, me being too picky, 60Ds AF
if it wasnt for my 100mm macro L f2.8 iw ould be seriously concerned!

If anyone has any input id be grateful.
i kind of want someone else to use my gear and say its me because of X, Y, Z
i dont actually know anyone who i can physically do this with
 
i have given it a try tonight (not ideally enough light)

however.

so far the macro L is absolutely spot on. its DoF is so narrow the only thing that is in focus is the black line
and it is perfectly in focus
it may have a tiny tiny amount of backfocus. nothing i would worry about.
the line 2mm behind target is ever so slightly more in focus than the one 2mm nearer

the new sigma is definitely back focusing in both live view and viewfinder
 
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i think without a proper measure for 45 degrees you are right. and that lenscal seems to solve that by the looks of it
 
I'll definitely try the cereal box

High speed I accept it is my error. But how to improve I'm not sure. It's like the AF can't focus on the area it is on. I am well aware I am bad at panning but I don't actually know how to improve other than just trying more and more

But even static shots seem to be wildly out too much. This can't be a back/forward issue. There is no focal plane to be seen. The AF just seems to fail. I know the focal point needs contrast. Maybe this is part of the issue.
 
ah definitely a reason for the 7/70d

If anything the sigma 35mm is a small 2mm out using the guide linked
The 100mm macro is near perfection (the dof is so small with that that the black target bar goes out of focus at the top/bottom compared to middle)
I have managed to get a 2mm flower stigma in focus hand held with that lens.

Just tried my long lens.
On the tripod it seems good. At the absolute minimum focus distance and focal length (120mm focal length) it's near spot on too.
It's dof is wider but the target is definitely in the sharp area. (and looks fairly sharp)
The width of the in focus area seems about 4mm (on the chart) and if anything it's slightly forward and definitely correctable in micro

So.. Its me I take it? Somehow I am just not getting the focus to lock to a moving target. Or is it the point I am trying to focus on hasn't sufficient contrast across the focal point? I don't know
 
The new sigma does seem pretty guilty at not focusing on correct spot both by hand and on tripod at different targets.
There are definitely times where the focus point is identified and agrees with what I see when the shutter closed yet the plane of focus is definitely behind this. If the focal plane is about as wide as the focal point the actual plane is about that width behind it.

If this is consistent that's fine as I'm guessing it can easily be corrected. There is after all no range.
 
its definitely noticeable. on mine

100mm L - spot on, at least now i know why i like this lens best)
10-22mm - undetermined
120-300mm - seems ok, more testing required
35mm - seems consistent error (at least consistent!) more testing

the 120-300mm has questions for me, but i think it is not so much back/forward but something with not being able to focus on the point i am trying for. be it lack of contrast, not fast enough, i dont know. To me this now seems as the camera not being fast enough +moving with the target compounded by my poor panning.

the 35mm is def not this, it is absolutely missing the focus point. but sometimes it produces pictures that completely miss. but this never happened in the tests. could it be that my focus point is on target but due to back focus its actually focusing on something 3 feet back?
 
To address the points so far..

The 35mm I can use the dock for but my 120-300mm is not the new dock friendly version

The times when focus is completely missed are the ones I can't understand.
This happens with both the sigma lenses

For the 120-300mm I mainly picked up on it at the airshow. This isn't back focus. The aircraft wouldn't be out of focus for such a minor back focus issue.
So so many shots were completely fuzzy. It's possible it's lack of contrast (the aircraft were often dark) it wasn't my shutter speed (1/800sec)
I think it's something with focusing on a moving target and me here and the added focal length difficulty
It's also a big heavy lens

The 35mm does this complete fuzzy game a bit too but there are less variables. It isn't on moving targets and obviously is an 'easy' focal length.
It's not me on this one (ie unsteady hand) as my 100mm l never does this with a shallower DoF
2 shots on high speed seem to come out one ok, one fuzzy. I am thinking is me again, but I can't think how it can happen.
 
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if its me thats fine, i did wonder. As long as its not defective kit that is the main thing. It could quite possibly be the 60Ds AF holding it back as well as me. again, if this is the case that is also fine.

there are a fair few like the second one with lower ISO.
 
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