RF 28-70mm soft left edge or normal performance?

In my opinion, this is not acceptable however it may still be within Canon specifications. If you have the option to exchange or return... this is probably the best path forward.

Try focusing on the left/right edges vs. using the center and then compare. From what you show it does look like the lens is a bit de-centered, but most lenses suffer from this to some degree. Also, do other Focal lengths show similar results? Does the difference disappear or minimize stopping down a bit? If it persists even on stopping down then it is a more serious problem as you have no means to correct it in use.

You have a very expensive lens so you have a right to be a bit more picky than someone buying a kit lens. I'd mostly worry if you aren't able to get the difference to minimize when stopped down. If it is only noticeable wide open then at least you have a means to counteract it. Getting another lens or repairing/adjusting it might just result in some other problem.

I'd think Canon would be amenable to checking it and correcting if necessary. I've only ever sent in one new lens to them that had a rather bad problem and they replaced part of the optical assembly and all was fine.  Yours may be a bit of a borderline case, but again it is a very expensive lens so I'd hope they would at least check and adjust it if possible.

Claude Ganter wrote:

In my opinion, this is not acceptable however it may still be within Canon specifications. If you have the option to exchange or return... this is probably the best path forward.

Thank you for your opinion. I'm still on the fence if to keep or return this. Took some more pictures today and some it's bit better on some but problem can been seen on most.

It is still possible to return this, so I should probably do that and get a new copy.

jwilliams wrote:

Try focusing on the left/right edges vs. using the center and then compare. From what you show it does look like the lens is a bit de-centered, but most lenses suffer from this to some degree.

I have tried this and corners get much better, but center will go way off. One test image of this performance is here:

28mm, f2, focus in lower right corner.

Also, do other Focal lengths show similar results? Does the difference disappear or minimize stopping down a bit? If it persists even on stopping down then it is a more serious problem as you have no means to correct it in use.

At 35mm it can be seen. From 40mm to 70mm I can't see this problem.

Stopping down helps only a bit. It can still be seen on f11 at 28mm.

You have a very expensive lens so you have a right to be a bit more picky than someone buying a kit lens. I'd mostly worry if you aren't able to get the difference to minimize when stopped down. If it is only noticeable wide open then at least you have a means to counteract it. Getting another lens or repairing/adjusting it might just result in some other problem.

I'd think Canon would be amenable to checking it and correcting if necessary. I've only ever sent in one new lens to them that had a rather bad problem and they replaced part of the optical assembly and all was fine. Yours may be a bit of a borderline case, but again it is a very expensive lens so I'd hope they would at least check and adjust it if possible.

I'm still on return window for this lens. This was manufactured about a month ago according to label on the package. More I think this, returning seems to be best solution at the moment. Thank you very much on your comment, it helps me a lot.

Maybe send it back to the store for another one.

shawnphoto wrote:

I have two of them and one of them was like this also. I sent it in to Canon, long story short, they adjusted it a little and it is somewhat better.

Based on what I have seen I think it is pretty apparent that this is probably within Canon's specifications for the lens although they may replace it if you complain to them.

Thanks, it must be difficult to make this kind of lens perfect for all focal lengths.

Here is the thing, as tempting as it is to use this for landscapes, they must see it as a portrait lens first and foremost otherwise they wouldn't be putting so many out with these problems.

Portratis will be my main use case for this lens. Was hoping it would also work for landscape. Focus stacked landscapes are good enough for me with this lens on wide end, because corners and left edge is ok when focused on those part of the image.

And I should mention I had two other 28-70's that were similar. They just would not get sharp at at the edges, but one of them was particularly bad at infinity. No matter what f-stop the left 1/3rd of the frame at 28mm looked wrong. It also didn't focus properly and would hunt a lot, which I only realized once I had received a replacement. The lens should be very reliable with focusing even when using eye detect AF.

Fortunately focus has been great on this lens, it is fast and accurate.

I wish my current lens was also perfect, sadly it is not. And the annoying thing is it was only at 28mm, every other focal length was near perfect. But, because I shoot groups of people frequently I decided to send it in. The fixes they applied were OK. It was odd because it was razor sharp on most of the frame, but then the right edge just degraded to pure mush. Somehow they were able to even it out a bit. Sometimes I think about sending it in again but having gone through 4 of the lenses in total and currently having 2, I think I have realized the futility of pursuing it further.

This was also information I was looking for. I was suspecting that this kind of performance might be quite a normal for this kind of lens. I was debating myself wether to buy this one or couple of fast primes and 24-70mm f2.8. Because I don’t like to change lenses too much, got this one. Now it seems, I might need to get something wider than 35mm for landscapes. Yay! One more lens to get (maybe next year, this years hobby budget was reserved for this one).

I’m just a hobbyist who likes to take photos and I’m willing to accept some compromises. I dont make money from my photos, I just like to take them. I’m fortunate enough that I can get this kind of lens just for a hobby.

I only say this to help save you the headache, it might be best to just try another lens unless you just really love the 28-70. It took over 3 months of back and forth emails and mailing lenses before I got where I am at and it still isn't *perfect*.

And I thank you this information, even though I was already pretty sure I would send this back. I don’t like sending stuff back and now I have one more lens for my wish list. Maybe Canon will make something like 16-28mm f2 one day and if that is going to be good enough for landscapes, I will probably get that one.

For portraits it is still amazing though...

I agree.

I also messed around with it using an extension tube:

Great images!

Thanks all for comments. I will send this back and get a new one.

Followup to this old thread. After some months, I received a new copy of the RF 28-70mm f/2 L. This copy is much better and I absolutely love what this lens does to images

Here is one full resolution test shot taken from the same place than earlier. 28mm, f2, iso 100, 1/1600s, hand hold.

Second copy of the lens is much much better.

SteveinLouisville wrote:

A little dark in the corners, but nothing that DPP4's peripheral lighting adjustment tool won't fix in 5 seconds.

Yes, this was just a quick test photo taken at the same place to check lens. I don’t usually take this kind of photos at f/2.

edit: here is one more landscape photo which is edited little bit more. Main use for this lens is family photos:

Dan W wrote:

Did also some close distance testing inside. Left is also here pretty bad compared to right side. Siemens stars are crops from the extreme corners. Focused camera center of the lens and took picture (ibis off) and set lens to manual focus. Moved camera on tripod head (without moving tripod) so that I could set Siemens star in the each corner and took picture and combined all in this image.

Test setup 5 images from tripod, focus center.

Some more picture can be seen on: https://mve.kuvat.fi/kuvat/Testikuvia/

Site might be slow outside Finland.

OK, maybe I'm confused but each of these clearly shows the target taken at an angle??? DOF plays a definite roll in IQ

You are right, the corners are taken at an angle. I tried to explain test procedure in the text before image.

"Did also some close distance testing inside. Left is also here pretty bad compared to right side. Siemens stars are crops from the extreme corners. Focused camera center of the lens and took picture (ibis off) and set lens to manual focus. Moved camera on tripod head (without moving tripod) so that I could set Siemens star in the each corner and took picture and combined all in this image."

This Siemens star was just next to that test target in the center. I didn't have big enough space to make test setup where I could just take one picture from 5m and have center and all corners at the same plane of focus. Recomposing made that test possible and it showed me, that left side of the image was really much worse than right side.

I send that lens back to dealer and got a new one after few months. Second copy of the lens was much better. Extreme corners and edges aren't perfect on the second copy either when shot at f/2, but they get better on smaller aperture. This didn't happen on the first copy of the lens and left edge of the whole image was soft even on f/11.