Sigma 100-300 EX F/4 replacement for Canon FF

Davenor wrote:

I bought the Sigma, the non DG version, back in 2004 for my 300D. It has since then survived a 400D and a 7D. Although the 7D still gets some some usage, the majority of the shots is done with the 6D I bought a couple of years ago. I'm very unhappy with the shots from the 6D/Sigma combination and for that reason I've found myself using the 135 F2 instead, even if the situation craves a longer lens.

The biggest problem with the Sigma on the 6D is uneven image quality across the frame using focal lengths from 150-300 and apertures from F4 to F8. I would say that roughly 40-50% (depending on the FL and aperture) central pixels are sufficiently sharp while the other areas are suffering from some kine of blur that looks like motion blur. I guess the lens has always suffered from this phenomenon, but with the crop cameras the "sharp" part covered much more of the frame. Can anyone comment on this behaviour? At 300mm, the lens needs to be stopped down to F/16 for completely alleviating the issue. Please zoom into the attached image and look at the sharpness of the "unmown part" of the grass.

I've been looking at two lenses that could replace the Sigma, the Canon 70-300L and the Canon 100-400 II. My understanding is that the original 100-400 is rather poor IQ-wise and I don't think I would like the pump zoom. The 70-300L is almost half the price compared to the 100-400 but what about its performance? I want good performance across the frame at all FLs and apertures. Can the 70-300 give me that or is the 100-400 what I need? I could surely use the reach of the longer lens but at the same time I would also appreciate the 70-100 FLs when I'm out walking.

thanks
David

I also had the 100-300 Sigma (the DG version) for many years and replaced it with the 70-300L.  I did love the 100-300 f4 but found the following gains with 70-300L:

- General image quality is superior (don't even feel the need to stop down most the time)

- Keeper rate is superior (better AF precision/speed, plus the benefits of IS which really is good for at least 3 stops)

- A significant amount lighter (around 400g) and more compact in your bag

The only downside really is the 70-300L is it isn't really made for use with a TC (yes, I know it works with some Kenko models but i'd classify that as for emergency use only rather than a regular partner for the lens).

That all said, the 100-400L II wasn't even on the horizon when I bought my 70-300L and I would well have considered that if it'd been an option.  Undoubted quality, extra reach and the weight is broadly similar to the 100-300 Sigma.