A Comparison Canon 100-400 f4.5-5.6L 11 v Sigma 150-600 f5-6.3

[Skyelines]

I bought the Sigma 150-600 some while ago for wildlife for which it performs reasonably well at close range but I have recently been frustrated by it's unreliability in getting a sharp focus. It usually takes a number of attempts to get a picture in sharp focus. The greater the distance that the point of focus is the more unreliable the AF becomes.
I bought the Canon 100-400 for landscape and closer wildlife and found the the focus was more reliable and the resolution noticeably better.
I tried a comparison today as the air is cold and clear and the sun is out. I took two images with each lens of the same scene and cropped both images to show the same area (more or less) and treated to the same adjustments in Lightroom. To upload to Flickr I did reduced the pixel count of the Sigma image to match the canon one so both show at the same size (965 wide).
Here are the best results of each lens. The walkers in the picture are 6 1/2 miles away.

I'm thinking that getting a 1.4 extender will give me a better combo with the Canon lens than the Sigma on its own for wildlife.

Sigma gave two very poor pictures

Walkers on the Storr-5447

Canon gave a slightly out of focus one and this one

Walkers on the Storr-5449

[Trev B]

I got both Canon 100/400 II plus 1.4 extender and Sigma 150/600 S. Can't say I find any difference between the two with regards to focusing. Use the 100/400 as a carry about lens, more inclined to use the Sigma as a static lens - laying up waiting or watching something, ie. deer fox etc. However my targets are not six and half miles away.

[Skyelines]

I got both Canon 100/400 II plus 1.4 extender and Sigma 150/600 S. Can't say I find any difference between the two with regards to focusing. Use the 100/400 as a carry about lens, more inclined to use the Sigma as a static lens - laying up waiting or watching something, ie. deer fox etc. However my targets are not six and half miles away.

At close range (20-30 metres) I also can't find much difference between the two except slightly better resolution on the Canon but the Sigma needs about twice as many attempts to get a sharp image as with the canon especially in lower light and less contrast.

[Trev B]

At close range (20-30 metres) I also can't find much difference between the two except slightly better resolution on the Canon but the Sigma needs about twice as many attempts to get a sharp image as with the canon especially in lower light and less contrast.

I try to work within the 50 yds max range, depending on the target, small birds obviously closer.

[ST-EOS]

I seem to remember reading about a Sigma Dock that was used to calibrate their lenses, I wonder if that may be allow you to fine tune the lens auto focus.

[Trev B]

I seem to remember reading about a Sigma Dock that was used to calibrate their lenses, I wonder if that may be allow you to fine tune the lens auto focus.

I got a Sigma Dock, but have not calibrated the lens now for two years. - not needed too! But it did improve it when I first calibrated it, Black Fox who was a form member at the time gave me a lot of advice regarding calibrating it.

[Skyelines]

I have the Sigma dock and have done some calibration but only for close targets.

Even at close range the AF is unreliable, which is my greatest frustration with the lens. I've tested this on a tripod - I can press the button and the lens settles on a focus, take the picture and the result is out of focus, press the button again and it might be in focus. Do it three or four times and maybe just one is in focus. The further away the target the worse the unreliability of AF becomes.

I'm not sure I understand how calibrating the lens would make the reliability of AF greater if the focus never reliably hits the same spot.
Any explanations?

[Trev B]

I have the Sigma dock and have done some calibration but only for close targets.

Even at close range the AF is unreliable, which is my greatest frustration with the lens. I've tested this on a tripod - I can press the button and the lens settles on a focus, take the picture and the result is out of focus, press the button again and it might be in focus. Do it three or four times and maybe just one is in focus. The further away the target the worse the unreliability of AF becomes.

I'm not sure I understand how calibrating the lens would make the reliability of AF greater if the focus never reliably hits the same spot.
Any explanations?

I would say there is a fault with the lens and it needs a visit back to Sigma. I have no problem with mine with close focusing

[Bill53]

You don't mention which version of the Sigma you have (sport or contemporary), I have the contemporary model and have not had any problems with focusing. As Trev suggests may need sending to Sigma for testing/calibration.

[antoeknee]

Contemporary here too. No focusing issues either. Photographed red necked phalarope very close, only issue was when they came too close. Not much more than arms length.
Can only recall taking handful of landscapes and no issue with those either.
Tend to agree with others and suspect possible issue with your lens.

[Skyelines]

Thanks for all your thoughts, looks like I should get the lens looked at.