lens quality issue - is this acceptable?

doug56hl

I've got a Sony 28-70mm lens along with an A7. The lens quality seems poor to my eyes with everything outside a narrow zone in the center of frame being very soft.

Now that the better weather is here I've been doing some comparison photos between this lens and some others I've got. Examples below for the Sony and a Canon 40mm pancake mounted on the A7. Photos were focused in the same place, processed from the raw file, are at F8 and have equal sharpening of 60 applied in Lightroom. While both the Canon and the Sony 28-70mm produce similar sharpness at the center of the frame, they are very different at center edge and the corners.

Reviews of this lens vary with some saying OK/good and others poor. From the attached photos is the results all that can be expected for this lens or should it have better image quality? It's RRP is almost twice that of the Canon (albeit that is a prime). I've also done photos at 28mm, 35m, 50mm and 70mm and in all cases anything but the center 10-15% of the frame is very soft.
Also tried F11 but results aren't any better.

Anyone had any sucess in getting Sony to do a warranty repair to fix lens quality? It's outside the retailer return window but still within the 6 month period where the manufacturer has to show it wasn't a pre-existing fault. I suppose the question is whether this lens is of merchantable quality?

John7

According to DXO tests, sharpness should be pretty good across the frame at F8.0, except 70mm which is a bit weaker at the 2/3 area to the edges

Sony FE 28-70mm F3.5-5.6 OSS mounted on Sony A7R II : Measurements | DxOMark

doug56hl

Exactly.
DXO also shows a sharpness field map at 50mm F8 very similar to the the almost twice as expensive Sony 24-70 F4 Zeiss. And a better field map than the 24-70 at 35mm. But other reviews say poor. So obviously a lot of copy variation which is what user reviews/comments also note.

My question is whether the apparently poor copy I've got would be repaired/replaced by Sony with a good one. And, of course, whether from the photos this is a poor copy. To my eyes it is...

12harry

Sorry to read yr problem...
Have you just bought this? - go back to the supplier and ask for a refund. . . . it's possible the OSS (if present) has been jammed in a wrong-position. . . . but either way, if it doesn't look good, then it probably isn't.
Modern digital cameras and their lenses are significantly better ( within the Mpx ) than older lenses, simply because the calculations and manufacture are so much better.
ALT - You could try a local Camera Club, in case someone has the same camera/lens and compare. ( They can offer Opinions, etc.).
Do you get this same fault with another lens? Is it possible the sensor has been jarred - so it is not quite "normal" to the lens centre-line?

Difficult to help more, sorry.

doug56hl

Thanks
No it's past its return window now, hence why thinking of asking Sony to fix/replace it.
This is my local camera club...
I had thought of a misaligned sensor as softness seems far worse on the left side using the 28-70mm but other lenses are acceptably sharp in the corners/edges as my photos using the 40mm Canon lens mounted on the A7 show.

I'm getting good results from APS-C Sony E mount lenses although they don't cover the entire FF sensor so sensor could still be out at the extremes. But I also tested my Canon 16-35mm F4 L lens at various focal lengths on the A7 and my Canon 6D to specifically rule out a sensor issue and the results are identical sharpness wise on both bodies, and that is sharp!

snerkler

I’m only on the phone at the mo so can’t analyse the pics but if it’s softer on one side than the other then this suggests lens decentering or misalignment. Have you dropped the lens or knocked it heavily?

doug56hl

No, it was like it out of the box.
While I say softer on the left it's also very soft on the right, just not as soft.

snerkler

Back on the computer, that lens is shocking tbh. How come you didn't return it straight away? I'd contact Sony and take it from there, if it's within the warranty period then they can't really argue imo. However, I would still see if you can get it replaced.

doug56hl

Thanks for looking.
A combination of bad weather to get out and take photos plus low expectations as I saw many reviews/comments as to poor image quality of this lens. Plus it was part of A7 body/ kit lens bundle and amazon went out of stock for quite a period while I had thoughts of returning it.

Also a factor was that amazon seems to only allow one return swap for higher value items after which it just refunds and as I got the bundle for the best price it's ever been (£270 less than current price) I didn't want a refund. Odds were I could just have got another poor lens and/or a body with its own issues in a swap.

Add to that a lot of should I/shouldn't I prevarication until the return period had passed. If the photos are down-resed to 4K size for viewing on a TV the results aren't as bad (for one thing the 16:9 crop cuts out the corners). I thought I could live with that especially as the lens itself was basically 'free', the cost for the A7 body on it's own now (£190 more) is higher than the price I got the bundle at.

However I've now seen some much more favourable reviews/comments on the lens which means there are good  copies of it out there, so thinking Sony should do something about it under warranty. The odds then of getting a better lens as a result seem higher. Luck of the draw isn't mentioned in the CRA...

I'll raise a return with Sony and send it back to them next week and see what they say.