I saw the christopher frost review and it indicated perfect sharpness in the corners of the image at all focal lengths wide open. However my new 28-70 is soft in the corners (purchased from B&H). Luckily this one gets sharp by f/4, my other does not get sharp till probably f/8. I know I'm being silly cause it doesn't really matter most of the time but I am just wondering if my lens is not as good as typical for this and maybe I should try to return it... I paid $2,699, is that why it isn't "perfect"?
I think there is certainly some level of subjectivity in the claim of perfect corner sharpness, but this lens is definitely well known for performing very well compared to other lenses in the same focal range and aperture even in the far margins of the frame in most cases. Great sharpness (as judged by most users) at f/4 sounds typical, but your second copy not showing adequate sharpness until f/8 seems a little outside of expectations. That one may be worth talking to B&H about, or you can choose to send it in to the factory service center for examination under warranty.
Whether it is Rockwell or Frost reviews are just what some guys opinions are. They are worth exactly what you paid for them. Nothing! Some guys are nuts over reviews and spend lots of time watching and reading them. I don't.
No lens is perfectly sharp all the way to the corners. Do I need to repeat that? If the lens does what you want that's all that matters. You can rest assured that the Canon RF 28-70mm f/2 L USM Lens it is the best lens in that category you can buy. If you are not happy with how it performs you don't have any better option.
Forget the reviews and go out and make some beautiful pictures.
I'd contact B&H as Mark35mmF2 suggests. I've made 2 exchanges with them the last 5-6 years and both were to my satisfaction. Today however, they are closing for Succos. They won't reopen until 10/9.
I was on their site last night looking to spend a gift card 🤣
The $2699 price you paid was an excellent deal on a normally $3100 lens. The B&H BUILD Expo pricing ended 9/14. I'd work with B&H as you won't see this lens at that low price again for a while. Black Friday or Christmas (maybe)
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