Coming from the 70-200mm f4 I was expecting this Prime 300mm lens to offer a major step-up in term of sharpness and resolving power. It is slightly better sometimes, but sometimes worse, and leaves you feeling underwhelmed.
Comparing these two, the 70-200mm f4 to the 300mm f4 in real world situations, I used:
- a new 70D body
- Handheld, at the same distance to the subject, around 25 meters
- Both lens at f5.6 (which is the sweet spot for the 300m)
- Shutter 1/500th or faster
- Both lenes mirco adjusted, giving no difference on Live View vs Viewfinder focussing
- Both cropped in software to give the same image and sufficiently zoomed in to reveal sharpness.
The 70-200 yields sharp results every time, and I mean when expanded up so the subject fills the same frame as the 300. Many shots on the 300 come out softer, some are about the same, and about a ⅓ of them are slightly better on the 300m. (after correcting the 300mm's CA in Lightroom). The results vary greatly, some good and some bad, so maybe a the IS not locking on reliably? You'd think a noisey IS also means vibration, which can't be good. I swapped the lens for another copy guess I just had a bad one, but the second was the same. It's also sensitive to UV filters, and I had to take the UV filter off the 300mm to get comparible performance to the 70-200.
So surely it must be easier to make a prime lens sharper than a zoom lens? And also easier to make an a smaller aperture sharp, compared to the enormous technical challenge of the huge f2.8 - which Canon managed to make incredibly sharp. So what's up Canon? Can we get an update to this lens please? You shouldn't need to heft around the 2.4kg of f2.8 glass just to get sharp images at f5.6. I get the feeling that today's 20mp crop sensors are very revealing of any softness, which you can now see in this lens design from 1997. On the early full frames cannons from 10 year ago (11mp) it was probably fine, but times have moved on. We now have around 9 pixels were there was only one.
Don't get me wrong this is a very good lens, but needs an update to bring into line with the 70-200 below, and the 300mm f2.8 above.