Canon 85mm f1.8 auto focus problems

nessiemac

nessiemac

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Dave
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Hi all,

Just bought a new lens as above to try and get some great shots of the kids and for some low light stuff.

Lens arrived yesterday and straight away the autofocus seems very hit and miss. I know that depth of field at f1.8 is very shallow but it seems to be getting 1 sharp photo for very 20 or so!! Had a play with micro adjusting the lens following the Dot Tune method but still no joy.

Wether outside in the sun or inside with flash i can't get it to be consistent at all. I used to have a 50mm f1.8 and never had any issues with that in the past.

I have some photos to show what i mean. All taken indoors with flash and all exact the same settings.

1.


Test 1 by nessiemac1, on Flickr

2. 100% crop of above


Test 1 A by nessiemac1, on Flickr

3. Exact same as above i second later...


Test 2 by nessiemac1, on Flickr

4. And 100% crop of above.


Test 2 A by nessiemac1, on Flickr


So is it me and what am i doing wrong or is it an issue with the lens?

Cheers

Dave.
 
If you have any more lego guys can you put them in a little V shape ? Might let you better see where the camera is focusing when it's missing the focal point you want, as in that photo above it looks like a couple of 'cm' behind the target. If it's consistently focusing on the same (but not correct) area then that might make diagnosing / understanding the issue easier.
 
More lego figures? I have a house full!!!!

Anyway. Set them up with the focus on the cop in the middle. They are all 2 cm further back from each other with closest on the left

5 shots one after the other with 4 like this.......

Nice sharp cop.


IMG_9370 by nessiemac1, on Flickr

and then no 4 of 5 missed focus.


IMG_9369 by nessiemac1, on Flickr

All taken one after the other with same settings and focused on the same point.
 
Anyone any ideas to try and eliminate me or the lens from the problem?
 
Shutter speed? Tripod or handheld? Centre spot AF? Single shot or AI AF? What mode? P, Av etc?
Matt
 
MatBin said:
Shutter speed? Tripod or handheld? Centre spot AF? Single shot or AI AF? What mode? P, Av etc?
Matt
Click to expand...

Shutter speed on above examples was 1/500 at f1.8. Handheld with centre AF point and one shot. Shot in manual.
 
nessiemac said:
Shutter speed on above examples was 1/500 at f1.8. Handheld with centre AF point and one shot. Shot in manual.
Click to expand...
Put it on a tripod or other solid support and try again. Handheld there are two ways to create user error: (1) AF point not always in exactly the same place on the target; (2) camera moving backwards or forwards after AF lock is achieved. Using a tripod will definitely rule out any technique issues.
 
StewartR said:
Put it on a tripod or other solid support and try again. Handheld there are two ways to create user error: (1) AF point not always in exactly the same place on the target; (2) camera moving backwards or forwards after AF lock is achieved. Using a tripod will definitely rule out any technique issues.
Click to expand...

^^^ This. And you're too close. That can introduce errors that are not present in normal distance shooting.

Try a target like this: camera square to the box, distance 2m or so, tripod, centre AF point on the front of the box near the ruler, then see where the sharpest point falls on the ruler and micro-adjust to that. Mark the ruler so you know exactly where the front of the box is.

 
Last edited:
I'd be willing to wager a sizeable sum that the problem is that you are moving very slightly after focus is locked.
 
Just want to say thanks to everyone who has replied with all your ideas, much appreciated.

So i had a play and set the tripod up last night and took 10 shots, all with the same setting and 2 sec delay so i wasn't touching the camera, centre point focus and one shot and got these results

1. Perfect focus and sharpness virtually exactly the same 10 times....



IMG_9436 by nessiemac1, on Flickr

and earlier with some good light, 1/1000th with tripod and same settings

2. 10 of these perfect again....


IMG_9463 by nessiemac1, on Flickr

Went through each lego figure in turn and got the same consistent results each time.

So......it's me then!!:roll eyes:

I had a go handheld and using AI servo and actually was a lot better so thanks to who said to try that.

Look like lots of practice

Thanks again guys.

Dave
 
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