topic Re: Sharpness issues with 16-35mm lens in EF & RF Lenses

Sharpness issues with 16-35mm lens

Richard3 — Wed, 09 Dec 2015 02:40:52 GMT

I am using 16-35mm 1:2.8 Canon EF lens. Being wide angle I have noticed the far left and right sides of the images are not sharp. Using auto focus around F11. Does anyone have an explanation.

Re: Sharpness issues with 16-35mm lens

ebiggs1 — Wed, 09 Dec 2015 08:16:35 GMT

It would be helpful to know what camera you are using but in a nut shell here is a reason. Lens diffraction. This is caused by the aperture blades when you stop down a lens. Any lens not just the 16-35mm. A perfect lens has no diffraction but we know that is not possible as nothing is perfect. It is a myth that diffraction only occurs at small f-stops. It happens at the very first f-stop even if it is f2. It is just not as noticeable. Most lenses have a sweet spot where all is in harmony. This is usually f8 or f5.6. All the bads are corrected and the diffraction is limited. All is well with the world.

Another complication is the Bayer array. Green gets more attention than red or blue light. The interpolation of these colors produces the final full image. What happens when the diffraction limit is reached is, there will be the loss of green pixel luminosity. And the resulting loss of sharpness. ( overly simplified )

If your lens is pretty sharp at wide open f-stop, you could be seeing lens diffraction. It is also possible you have a decentered lens group. That will require Canon Service. I have not got to try that lens yet so I can't say first hand how sharp they are but

I would bet it is darn good.

Re: Sharpness issues with 16-35mm lens

Richard3 — Thu, 10 Dec 2015 00:46:04 GMT

Thank you for your thoughts. I will try setting the lens at f8 or f5.6 and compare the results. The Camera I use is 5D Mark 11. Thanks again, Richard

Re: Sharpness issues with 16-35mm lens

Waddizzle — Thu, 10 Dec 2015 01:07:44 GMT

There could be another, simpler explanation...depth of field. You are using a wider lens. Are the objects at the edges of your frame the same distance from the lens as the objects in the center of your frame?

Testing the lens at f/8 would reduce potential issues associated with depth of field.

Re: Sharpness issues with 16-35mm lens

ebiggs1 — Thu, 10 Dec 2015 17:06:19 GMT

"Are the objects at the edges of your frame the same distance from the lens as the objects in the center of your frame?"

This would depend on focus point. Assuming he focused on an object more close to the camera and not a distant mountain, I doubt seriously that is the issue. Most likely it is diffraction or decentering. Diffraction he can correct, Decentering he can not.

Then again it may be all the better the lens is. Is it version 1 or version 2 ?

Re: Sharpness issues with 16-35mm lens

Waddizzle — Thu, 10 Dec 2015 19:29:32 GMT

@ebiggs1 wrote:
"Are the objects at the edges of your frame the same distance from the lens as the objects in the center of your frame?"

This would depend on focus point. Assuming he focused on an object more close to the camera and not a distant mountain, I doubt seriously that is the issue. Most likely it is diffraction or decentering. Diffraction he can correct, Decentering he can not.

Then again it may be all the better the lens is. Is it version 1 or version 2 ?

Yes, that's exactly what I meant by "center of frame", the focus point. I just assumed that the center was the focus point.

Re: Sharpness issues with 16-35mm lens

Richard3 — Sat, 12 Dec 2015 00:38:00 GMT

Thanks for advise guys. The lens is series 11. The subjects are generally flat mostly interiors of properties for sale. Focal point generally towards the centre of the image. I think from advise given the issue may have to be resolved by taking to Canon for checking.

Re: Sharpness issues with 16-35mm lens

TCampbell — Sat, 12 Dec 2015 14:26:45 GMT

It's hard to guess without sample images.

Actually ... even better would be to go outside, find a nice large flat brick wall, and take a photo of it so that the brick wall is literally filling the frame corner to corner... shoot at a low f-stop (so we have a very shallow depth of field) and (the important part) make SURE the camera is "parallel" to the plane of the wall (if the camera is angled then the distance to one corner of the frame will not be the same as the distance to the opposite corner of the frame and that would cause uneven focus even if the lens and camera are working perfectly.)

If you do that and then post the images we can evaluate if it looks like your lens is normal.

Re: Sharpness issues with 16-35mm lens

Waddizzle — Sat, 12 Dec 2015 15:59:43 GMT

@TCampbell wrote:
It's hard to guess without sample images.

Actually ... even better would be to go outside, find a nice large flat brick wall, and take a photo of it so that the brick wall is literally filling the frame corner to corner... shoot at a low f-stop (so we have a very shallow depth of field) and (the important part) make SURE the camera is "parallel" to the plane of the wall (if the camera is angled then the distance to one corner of the frame will not be the same as the distance to the opposite corner of the frame and that would cause uneven focus even if the lens and camera are working perfectly.)

If you do that and then post the images we can evaluate if it looks like your lens is normal.

Yes, do that. Use a tripod, and take note of the distance to the wall in the center of the frame and the edges of it.

Re: Sharpness issues with 16-35mm lens

ebiggs1 — Sat, 12 Dec 2015 16:22:44 GMT

:... find a nice large flat brick wall, and take a photo of it so that the brick wall ..."

I strongly advise against doing this. It is almost useless on a ultra wide angle lens. It won't tell you or indicate much to you.

You have one of two problems. Diffraction or de-centered. One you can fix the other you can't. My .02 cents and worth every penny.

Re: Sharpness issues with 16-35mm lens

RobertTheFat — Sat, 12 Dec 2015 16:42:41 GMT

@ebiggs1 wrote:
:... find a nice large flat brick wall, and take a photo of it so that the brick wall ..."

I strongly advise against doing this. It is almost useless on a ultra wide angle lens. It won't tell you or indicate much to you.
You have one of two problems. Diffraction or de-centered. One you can fix the other you can't. My .02 cents and worth every penny.

The problem is that it doesn't really sound like diffraction, and an "L" lens is almost never decentered unless it's been dropped. Since the issue occurs only at the extremeties of the image, where depth of field is probably least helpful, I'd be more inclined to suspect front- or back-focusing. I'd at least run an AFMA check before sending it in.

Re: Sharpness issues with 16-35mm lens

TCampbell — Sat, 12 Dec 2015 21:43:12 GMT

@ebiggs1 wrote:
:... find a nice large flat brick wall, and take a photo of it so that the brick wall ..."

I strongly advise against doing this. It is almost useless on a ultra wide angle lens. It won't tell you or indicate much to you.
You have one of two problems. Diffraction or de-centered. One you can fix the other you can't. My .02 cents and worth every penny.

There will be a moderately spherical plane of focus. I wouldn't expect it to be as sharp in the corners as compared to the center. I'm more interested in seeing how much difference we're talking about and is it at least centered (symmetric).

So far we don't have any sample images to look at so we can't tell if it's normal or in need of service.

No lens will be as crisp at the edges as it is in the center... but some lenses are better than others.

Re: Sharpness issues with 16-35mm lens

ebiggs1 — Sun, 13 Dec 2015 14:30:02 GMT

"No lens will be as crisp at the edges as it is in the center ..."

Yes, this is the third most likely possibility. It may be all the better the lens actually is. I have never shot one so I can not say from personal hands on experience. I did use the first version but did not own one. It isn't all that sharp to begin with. I would expect Canon improved the new version II.

Re: Sharpness issues with 16-35mm lens

RobertTheFat — Sun, 13 Dec 2015 14:38:49 GMT

@ebiggs1 wrote:
"No lens will be as crisp at the edges as it is in the center ..."

Yes, this is the third most likely possibility. It may be all the better the lens actually is. I have never shot one so I can not say from personal hands on experience. I did use the first version but did not own one. It isn't all that sharp to begin with. I would expect Canon improved the new version II.

The word from those who have tried them all seems to be that the new version of the 16-35 f/2.8 is sharper than the old one, but not quite as sharp as the slightly newer 16-35 f/4. I can't say, as I've used only the f/4. It's certainly plenty sharp.

Re: Sharpness issues with 16-35mm lens

Mitsubishiman — Sat, 26 Dec 2015 01:40:42 GMT

I can only give you my two cents worth, I have the lens, Version 1, I have utilized it on both of my cameras, Canon EOS 40D, Canon EOS 7D

I do not have the identical Version 2, however

I have never experienced the problem you have encounterd and I have utilized the lens on a wide variety of camera settings, my advice hopefully that if it was a recent purchase, warranty should cover it.