Lens blur question

gsxr1

Sigma 70-200mm F2.8 EX DG Macro HSM II at 200mm f2.8 (1/400)
Beginners question

I was taking some photos from the kicthen at the birds this morn.

I am using a canon 1000d

I focus locked the bird in the center with a beep and the red light.

But the focus line of the lens seems to focus below center. This is a brand new lens . I took loads of shots and the head of the bird seems to thrown out of focus in most.
Is this a fault with me , the new lens or the camera. Can this be adjusted in the camera setting??

PopeBuckfastXVI

Might be something like this, with the narrow depth of field involved

pete4130

I had the mk1 version of that lens a few years ago. I found its focus to be poor/innaccurate and its colour reproduction to be bad. It wasn't long before I sold it and upgraded to the Nikon 80-200 2.8.

Shooting at 200mm (on a crop sensor) means its 300mm+ and I presume handheld means you'll need at least 1/300th second and a steady hand to get a sharp shot but ideally you'd need 1/600th minimum (double the effective focal length).

Again at full reach at 2.8 your depth of field is going to be very small especially given how close to the subject you seem to be. If it was brighter you could have stopped down to f/4 or 5.6 to get the whole bird in focus. You can print some charts off online to check your lens focusing points to see how accurate it is.

Some Sigma lenses can have some front or rear focusing issues so its worth checking.

DutchGuy

As illustrated in the diagram above - a camera's focus plane is parallel to the camera so by pointing the camera down at the bird the focus plane does not run all the way through the bird unless the aperture is smaller thus increasing the depth of field. If you focus on the head of the bird (using servo focus if possible) is the head in focus?

At 300mm f2.8, the depth of field will be approx 3cm for a subject 5m away (according to http://www.dofmaster.com/dofjs.html) so the margin for error is pretty small.

gsxr1

I was about 3meters aways.

So . I should back off , drop down to f4 and increase shutter speed then??

I need to try this in the daylight tomorrow.

I think the early versions of this lens did have focus problems, but this is the latest. I believe this problem was ironed out. At least I hope so. I intend to use this for motor sport.

Paddy@CIRL

If you're still having focus problems with it (Sigma are notorious for QC on their lenses) Give Hahnel in Bandon, Co.Cork a ring. They should be able to calibrate the lens for you FOC (Although you may have to pay postage)

pete4130

It's hard to get really good vibrant shots in poor light. Any lens at near closest focusing distance and wide open will be at its weakest optically.
Try upping your ISO if you can so you can stop down to f/4 or 5.6 without sacrificing your shutter speed.

Like dutchguy said you were shooting from an angle so the focal plane is going to be paralel to that angle.

Borderfox

Looks like a bit of back focus, you can send the lens back for calibration but I would double the iso and up the shutter speed

gsxr1

The ebay seller is Kingtradecameras London. I am now waiting on word back.

I was hoping I could keep the warranty work in Ireland.

Who would be the closest to Kildare/Dublin?

Borderfox

Cork for Sigma

Borderfox

I would check it on a tripod or resting on a table and focus it on a certain point and check it at 100% before I send it in. Out of all the Sigma lenses I have had none needing calibration

gsxr1

Borderfox wrote: »

I would check it on a tripod or resting on a table and focus it on a certain point and check it at 100% before I send it in. Out of all the Sigma lenses I have had none needing calibration

Thanks I will google the checking method. I hope its ok.
Why would they send it from a factory without checking it?

Is this the people who fix sigma stuff
hähnel industries ltd
Parnell Street, Bandon
Co. Cork

Borderfox

Yeah thats the ones, might be just a small difference between bodies

chisel

I have the mark 2 of this lens and it is a fair step up to use the 2.8 compared to say the 70-200 F4 (i.e. you need to step up your camera craft). Its a much heavier lens, harder to hold and short DOF at near distances. Like Pete4130 says, its hard to get vibrant images in poorish light. Try adjusting your settings to slightly overexpose - say 1/2 a stop and see do things get better.

And do indeed try using a tripod with a static object - I had similar results to you when I got my copy, which led to slight heart attacks, but turned out to be me:(

magicbastarder

Borderfox wrote: »

Cork for Sigma

i had great fun with them. they didn't want to import a lens i wanted. i mailed the head office in japan about it and copied them on it and their tone changed instantly.

gsxr1

I did a seris of tests.

70mm f2.8 to f 8
200mm f2.8 to f 8

2 different distances from camera

4 pics at 2 meters
4 pics at 6 meters camera to subject


all on a tripod on AV mode

Have a look.
http://www.flickr.com/photos/kennys-canon-photos/sets/



Sigma want a set of test shots to see a possible issue with back focus problems

TBH I cant see any problem with these.

Can you?

Borderfox

need to see 100% crops of the shots to decide

gsxr1

Borderfox wrote: »

need to see 100% crops of the shots to decide

here ya go.
100% via cs5
http://www.flickr.com/photos/organize/?start_tab=sets

eeyore2502

I have this lens and it has been fixed twice in cork. Firstly when I upgraded to my 7D the auto focus on the lens didn't work so it was sent to cork to be fixed. Then shortly after that I noticed the lens was not focusing where I had set it to and had to be fixed again in Cork.

Hope you get it sorted.

Borderfox

1a is soft
2a is sharp
3a looks good
4a looks ok
5a is soft
6a is sharp
7a is sharp
8a is soft

Any that are soft are not really that bad and I would presume wide open, even the Canon 70-200 f2.8 IS L is not sharp wide open (its good but not as sharp as slightly stopped down)

Heres a shot from the Sigma 120-300 f2.8 wide open http://pix.ie/keithjack/2078727 you can click on the sizes to see th original size.