Inconsistent focusing with prime lenses

Mister Vain

I recently got a Sigma 50mm 1.4 art lens after using zooms for years. While I love the big aperture and bokeh, the focusing is very inconsistent. It's ok when using flash but if I'm working with natural light, nearly half the photos do be out of focus.

I tried the Canon 50mm 1.8 before and had similar problems. Has anyone experienced this or have any advice on how to improve focus? I know a tripod would held with camera shake but its not very practical when shooting portraits on location.

CabanSail

Can you share some examples?

When shooting at f1.4 your DoF will be very narrow.

Splinters

I have 3 of the Sigma Art primes (24, 35 and 50) and as much as I love the image quality all 3 of them needed to be calibrated as soon as I got them. I picked up the Sigma USB dock on ebay for next to nothing and used it to calibrate them all. Its worth doing as now I find the focus extremely reliable in any circumstances.

Mister Vain

Splinters wrote: »

I have 3 of the Sigma Art primes (24, 35 and 50) and as much as I love the image quality all 3 of them needed to be calibrated as soon as I got them. I picked up the Sigma USB dock on ebay for next to nothing and used it to calibrate them all. Its worth doing as now I find the focus extremely reliable in any circumstances.

I just did a bit of research on that and it can actually be done with a ruler and a few adjustments in camera. Only problem is my camera doesn't seem to have the AF micro adjustment option. I have a Canon 550D. Does the USB dock come with software?

Splinters

You're right that some some calibration can be done in camera but not to the extent of the Sigma dock. The dock allows you to calibrate it over multiple distances which your camera will not.

You may find the focusing is off by a certain amount close up, but further away distances could be out by a different value, or even may not be out at all. The dock lets you calibrate different values for different distances. Your camera will allow you to make one overall adjustment which will apply to focusing over all distances. Honestly for the minor cost of the dock its worth getting for this feature alone.

Also I'd rather the lens was perfectly calibrated within the lens itself. I use both a D750 and D810 and now I dont need to change anything in the calbration of either camera, and as its done on the lens itself.

The dock doesn't come with any software. That can just be downloaded for free from the Sigma website. You could download it now and have a look but its useless to you without the dock itself.

DaireQuinlan

I like that Sigma has persuaded people to pay to do what they should have done originally before shipping their product :-/

Splinters

Thats very true, as much as I do love the image quality its not ideal buying 3 lenses from the same series and all 3 quite noticeably needed calibration. To be fair I haven't had any issues since doing the calibration but in an ideal world Sigma would have done that themselves.

Fat_Fingers

Apart from lense calibration you also need to watch you technique. At certain distance shooting wide open f1.4 will have such a narrow DOF that you can't afford any movement. Certainly not recompose technique.