Faulty focus?

Tight Fart

Tight Fart

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Name
Richard
Edit My Images
Yes
Canon 300mm F4 L IS on a 7D.
I'm not confident that the auto focus is working reliably, it seems to focus in front of where it should, I took some test pics on the way home from work today and this one sums up what I think the camera (lens) is doing wrong.
2101932180049001931S600x600Q85.jpg


The rest of the pics are similar, the focus point is on the leg and hip of the chick last on the right and the shoulder of the one next to him 3rd from left?
I think it's a lens problem as the camera is fine on my other lenses.
 
Its doing nothng wrong, auto focus (with all AF points on) will focus on the closest object, that being the other ducks arse on the right.

If you wanted the ducklings in focus manually change the AF point to the one that would be over them. Either that or go for a smaller apperture to increase the depth of field, at f4 its going to be pretty shallow. You can see hoow shallow it is just by looking at the grass.
 
The first question is what aperture were you using?
What focusing method did you employ was it centre spot or another part of the screen?
Mick
 
Guys, read the post - it wasn't even long!

"The rest of the pics are similar, the focus point is on the leg and hip of the chick last on the right and the shoulder of the one next to him 3rd from left?"

I suspect the focus point might have caught that big mutha at the right that is in focus. If not this is quite a severe focussing error, and as it is happening on a lot of photos then calibration is in order.
 
trencheel303 said:
Guys, read the post - it wasn't even long!

"The rest of the pics are similar, the focus point is on the leg and hip of the chick last on the right and the shoulder of the one next to him 3rd from left?"

I suspect the focus point might have caught that big mutha at the right that is in focus. If not this is quite a severe focussing error, and as it is happening on a lot of photos then calibration is in order.
Click to expand...

He edited the post from what t was. :gag:
 
It was set centre waited to pick up on the 9 in the centre, it picked 3 out on the ducklings, yet it's focus is in front of them.
I am viewing them showing the focus points, I not sure that I can save them with that showing.
I could understand it if it had a red focus point on the Mother Duck!
 
They're Goslings, not ducklings. Canada Geese Goslings. Not that this changes your issue.....


Tight Fart said:
It was set centre waited to pick up on the 9 in the centre, it picked 3 out on the ducklings, yet it's focus is in front of them.
I am viewing them showing the focus points, I not sure that I can save them with that showing.
I could understand it if it had a red focus point on the Mother Duck!
Click to expand...
 
What type of focus are you using on the 7D? I can't think what they are all called!

If you are using the one focus point then you need to invesigate more. If you are using zone focus (Or whatever it's called - where you have a number of focus points in use) this could explain what's happening.

Also, did the big goosey thing walk infront while you were focussing?

Does that make sense?
 
I've tried the one shot, al servo etc they're all the same.
It makes sense and no the big Goosey thing hadn't moved :help:

Can any one tell me of a way of posting the pics showing the focus points?
 
Tight Fart said:
I've tried the one shot, al servo etc they're all the same.
Click to expand...

I'm not meaning 1 shot, AI servo. I am asking about the type of focus you are using. You can select the 1 focus point or you may have the multi point selected (zone I think it's called) which selects the focus within 9 or so points I think.

When you focus on something, what focus point do you get in the viewfinder? A square within a rectangle, a number of squares with brackets?

I'm not being very technical here, sorry!! But I can not get to my 7D manual at the moment to explain better.

Ahh, have a look here, and that explains the spot and zone focus. Could be you're using the wrong one.

Sorry if you know all of this already.
 
The focus points are larger than the little red boxes you see in the viewfinder. I suspect it's included the big duck's arse.

But the only way to tell for sure is for you to take a photo where it's obvious where the focus should be. Try shooting an advertising poster or similar - ensuring that the poster fills the frame and is parallel to the focal plane.
 
swag72 said:
I'm not meaning 1 shot, AI servo. I am asking about the type of focus you are using. You can select the 1 focus point or you may have the multi point selected (zone I think it's called) which selects the focus within 9 or so points I think.
Click to expand...

Tight Fart said:
It was set centre waited to pick up on the 9 in the centre
Click to expand...

From this I guess that he's using zone
 
Do these 2 show it better?

Here the water in front is in focus yet the focus point is on the duck.

2775282250049001931S600x600Q85.jpg


and here the duck int the centre shows as the focus point yet the duck at the front is sharpest

2351707220049001931S600x600Q85.jpg
 
Looks likr you need to do some controlled testing and use the micro adjustment as required.
I have micro adjusted all of my lens where fitted to my 50D.

Just bought an ef-s 60 macro, think that needs testing/adjusting too.

Good job the cameras have that functionality, my 1D (mk2) doesnt.

Matt
 
You really need to do some controlled tests. Although those pics don't look promising, the subjects are obviously mobile. Focus-recompose technique is a common problem when depth of field is very shallow. Also the 7D is well known for having a complex AF system which takes some getting used to.

In you tests, don't be tempted to use one of those A4 printouts that you download from the web and shoot at very close distance, it will probably lead you astray.

Also, the focus point indicator only tells you which point/s was used, which is not necessarily the area of the subject actually focused on, if it moves between focusing and shooting.
 
HoppyUK said:
You really need to do some controlled tests. Although those pics don't look promising, the subjects are obviously mobile. Focus-recompose technique is a common problem when depth of field is very shallow.
Click to expand...

Yep. Even at f/2.8 on a 50mm lens I often fudge everything up using focus and recompose. Now I just select what AF point I want. No more focus and recompose for me = more kept images.
 
Taken it out again today, I can't see that it's nailed the focus at all so I'll take it in to a Canon service centre and see what they say.
I have tried the macro adjustment and it does seem to improve things a bit (+10)
 
the ghost said:
http://focustestchart.com/focus21.pdf
pdf for you to read if you want
it for nikon users but print out page 18 for you test the set lens in camera front - rear focus adjjustment
Click to expand...

That's exactly the kind of focus test that will lead you astray.

There are several reasons why, but the main one (that the author fails to address) it that it is shot at an artificially close distance, for reasons of convenience and because it exagerates shallow depth of field in order to better see the variance.

What it fails to take into account is that all AF systems work within a tolerance and that is pushed to the max at extremes. The result is that if you correct for absolute accuracy at very close range, you might end up throwing it out for normal distance shooting. And bear in mind that zooms quite often focus slightly differently at different focal lengths.

Any focus calibration ends up as a compromise (albeit a very fine one) but it should be a compromise based on relevant data.

The Matt said:
Try it on a tripod on non-moving subjects, just to rule out movement on your part or the subjects.
Click to expand...

That sounds more like it. The sort of focus error indicated in the OP's pics is way beyond the range of normal user microfocus adjustment.
 
The Matt said:
Try it on a tripod on non-moving subjects, just to rule out movement on your part or the subjects.
Click to expand...

And make sure there's only one thing the camera can focus on - an advertising poster or a sheet of newspaper attached to a wall. Make sure your target is flat (no stupid 45º stuff to confuse things) and parallel to the camera's sensor. Use a tripod and a fast shutter speed. Take one image using AF (Single point, centre, One-Shot Focus) then take another using Liveview manual focus. Compare the two. If there are gross differences the lens needs to go back to Canon. If there are minor differences then Micro Focus Adjustment may help.

But you really need to do a proper test where there is only one possible variable (AF vs MF).
 
The lens went back to Canon today and they say that the IS has failed and thats also throwing out the focus, £160 labour £65 parts +vat, ouch!
The tripod method didn't help either but then again you turn the Is off on a tripod so it wouldn't have.

The seller has been very good and already given a full refund before getting the lens back!! top man.
 
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