350D + Sigma 70-300 APO DG Macro problem

the Sigma 70 - 300 has, lets say variable, quality, i have a very good example, but i know of people who have ones that are so soft you can see it through the viewfinder. Contact Sigma in your country and ask if they will calibrate the lens, they should do it under warrenty as a blurred lens is no good to anyone

It's looking very much like you have a complete dud of a lens.This model lens is usually very good but occasionally they make a poop example.

The focus distances you are talking about can't possibly won't make such a difference.

I had a dud of this model lens which gave appalling results as it got closer to 300mm.
Your images seem to look the same as what i was getting -I'm currently downloading your images but it will take awhile so i'll come back later and leave a more valid opinion .

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Ok there's no doubt about it- you have a dud lens!
In fact it is giving allmost identical flaws to the bad one i had. Mine was really quite good at shorter focal lengths but pretty much useless towards 300mm.Even stopping it down didn't do much .


Why i say it's the lens,not the technique-
Firstly the persimon (?) tree images obviously aren't back focussed
They are also not front focussed-in both the 200mm and 300mm shots i can see that some of the closer branches are fading out of the focus zone. The focus is about where you wanted it -right in the middle of the tree.
The car is easy too.There the focus point is on the left edge of the top spoiler/wing or just abit further forward.

Also ,it is NOT camera shake blur- or to be more exact,there's no way it could consistantly cause that much blur!


That eagle shot from your friends lens is awsome isn't it! As others have allready said though,don't expect that kind of sharpness from a normal example of this model lens.
In fact i would guess that your friend rarely get's pics that good from his lens.That one would be a rare exeption ?

Here are a couple of shots i have from my dud lens (all 100% crops,no proccessing).
The first is a center crop at 200mm f5 ,the second at 300mm f5.6
The camera was moved closer for the 300mm shot to give an absolute sharpness comparison.Notice how badly the image quality degrades!

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Here's a center crop at 300/5.6

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I must appologise for the above pic-it's abit front focussed which could confuse the issue if anybody notices that fact.
Unfortunately i don't have alot of example shots at 300mm from this lens because they were mostly so bad i threw them.
This pic does show the kind of effect quite well ,in spite of it's other issues

I'm affraid that is what you get with this lens. Try stopping down a bit or only going to 200mm. It is still the best lens for the money IMO though.

Thaks all for the tips, now im getting with my lens, some results:

A car +- 250meters away at 300mm (panning)

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Glad you are now satisfied with it. the panning shot is excellent, i must try some panning shots with my Sigma too

Panning shot is great but the birds look a little over sharpened...

The panning shot is great! So cool
There is something odd going on if the lens only occasionally gives such results. But i think that image is deceiving and may be giving the wrong impression (slightly anyway).
Cars allways tend to look sharp no matter what the lens being used-it's all those straight lines,contrasting edges and sheets of gradual tones.The high contrast and black and white subject helps it look good too.

The bird shots are much improved but now look obviously oversharpened.And look at the aperture used! You shouldn't have to stop down that far and STILL get average results

No i'm sorry to say you definitely have a very poor example of this lens.
I'm experienced at this- being a buyer & seller of used lenses i've had the opportunity to use a whole bunch of consumer telezooms ,about 30+ so far(obviously several of the same model in some types)
Trust me,your lens shouldnt be this bad !