EF24-70 F2.8L MKII soft edges?

[LesC]

I've had my EF24-70 F2.8L MKII lens for about 2 1/2 years now and I've never been convinced it's a stunning as reviews suggest it is. It's permanently fitted to my EOS 6D and having been into photography for 25years + I like to think I know the technique side of thing at least (but happy to stand corrected)

I've had some very sharp images from it but now and again I'll get some such as the example below that just look soft at the edges. Performance seems to be inconsistent but I can't nail it down to any particular settings ie certain focal lengths, F stop etc.

I'll admit that at fullscreen on my 24" monitor photos such as the example below look fine; it's only at say over 50% and particularly at 100% that the softness really shows. I'd just like to gauge if there is something wrong with the lens, my technique or if I'm just expecting too much? I've had some shots taken with the humble EOS100D (SL1) + 18-135 lens that have seemed sharper although admittedly although I've not done any scientific tests on identical scenes and the sensor has a smaller pixel count so at 100% appears smaller on screen that shots from the 6D.

I should add that I've sent sample shots to both my (well respected) camera dealer & to Canon who both felt it was OK and last year the lens was checked by Canon for sharpness/alignment when it went in to have filter thread replaced after a knock. It was passed as OK and indeed I've had some lovely sharp images from it since.

So on to the sample images & selected crops. It was taken in woods around midday on a cloudy day at focal length of 55mm @ F16, shutter speed of 2 secs, ISO 100. Lee landscape polariser fitter & camera was tripod mounted with cable release used. There was a light breeze hence movement in the foliage but no where near enough to move the trees. I focused on the left of the two nearest trees which was about 3m + way. Possible a little near than needed (hyperfocal distance should be 6.36m) but at F16, the area of softness (shaded red) was nowhere near infinity and appears softer than other areas even further away?

Picture was shot in RAW & converted to JPG to post here but no other processing carried out.

Original image is the untouched image straight from the camera but had to convert to jpg & reduce quality to 8 (High) in Photoshop to reduce filesize in order to post here. If anyone wants to see the original RAW file I can post it on Flickr/Dropbox etc for download.

Photo 1 full image shows the whole photo with sections shown in crops highlighted to show positioning.

Red section 100% shows a 100% crop that I feel is too soft.

Blue section 100% shows a 100% crop of an area at around the same distance that appears sharp(er) to me.

At the end of the day I have little choice in what to do - either sell it or keep it; it's no longer under warranty and Canon say it's fine. I'm tempted to go for the new 24-105 F4l MKII to see what the difference if any is although I know in theory at least that my lens should be superior.

I suppose it does what I want it to do for most of the time, just that for the cost I expected outstanding results at all times. So thoughts greatly appreciated please - does it seem ok/within parameters (as Canon would say) or am I just expecting too much? Or is it my technique?

 

[Larsskv]

I believe the main problem with your sample image is softness due to diffraction.

I am on my fourth copy of the 24-70 f2.8 LII. The first copy was damaged when my tripod fell over. My first copy and the one I have now is fairly good even in the corners, but are not perfect. My second copy was a little bit worse, and left something to be desired. My third copy was very bad in the upper right part from 24mm to maybe 50mm.

I got the 16-35 LIII on a rebate a few weeks ago. It far outperforms the 24-70 f2.8LII in corner sharpness at 24, 28 and 35mm, and becomes even better when both lenses are stopped down. It is as sharp as my 35LII when both are stopped down to f5.6.

 

[Pookie]

I believe the main problem with your sample image is softness due to diffraction.

def... shooting for 25+ years and not aware of this?

cloudy day at focal length of 55mm @ F16, shutter speed of 2 secs

 

[LesC]

Thanks guys - was aware of diffraction but didn't expect the effect to be that noticeable

So what should I have done - F11 & focus further into the scene?

As to the 2 sec shutter speed - is that relevant as camera was tripod mounted??

 

[Pookie]

Thanks guys - was aware of diffraction but didn't expect the effect to be that noticeable

So what should I have done - F11 & focus further into the scene?

As to the 2 sec shutter speed - is that relevant as camera was tripod mounted??

Your best return by graph is not F11 across the entire field...

 

[Sporgon]

Irrespective of defraction it looks like a centering issue to me.

 

[LesC]

Thanks guys - was aware of diffraction but didn't expect the effect to be that noticeable

So what should I have done - F11 & focus further into the scene?

As to the 2 sec shutter speed - is that relevant as camera was tripod mounted??

Your best return by graph is not F11 across the entire field...

True, but F5.6 or F8 won't necessarily give enough DOF?

 

[Deleted member 91053]

I would agree with Sporgon. Mine is sharp all over the image!

 

[Mt Spokane Photography]

One of the things I like is the edge to edge sharpness. While not perfect at the edges, they are very good, far better than your photo.

Check for decentering, you can print out a star chart, shoot it, and decentering will be obvious.

http://www.bealecorner.org/red/test-patterns/

 

[LesC]

One of the things I like is the edge to edge sharpness. While not perfect at the edges, they are very good, far better than your photo.

Check for decentering, you can print out a star chart, shoot it, and decentering will be obvious.

http://www.bealecorner.org/red/test-patterns/

Thanks for this. I only have an A4 printer but presume I just need to focus close enough to fill the frame. Any particular settings ie F stop to use or will decentering be obvious at any aperture if present? I guess I need to use one of the two Star 'Bars' charts?

 

[pwp]

Thanks OP for bring attention to this. My 24-70 f/2.8II has very good edge to edge sharpness. Like many photographers my primes in this focal range became obsolete overnight and were quickly sold.

My shooting style tends to use a range from f/2.8-5.6 and rarely beyond. The results are plain stellar. But when I go past f/5.6, the results can disappoint. Shots at f/8 are nowhere near as crisp as f/5.6, f/11 cannot be relied on for commercial quality output and I'd never consider shooting at f/16 as your example image was.

Is this simply a characteristic of this lens to optimise performance in the wider apertures at the expense of the narrower apertures or should I be taking my lens down to CPS for a health check?

-pw

 

[Pookie]

I should add that I've sent sample shots to both my (well respected) camera dealer & to Canon who both felt it was OK and last year the lens was checked by Canon for sharpness/alignment when it went in to have filter thread replaced after a knock. It was passed as OK and indeed I've had some lovely sharp images from it since.

Does sound like technique and diffraction would be the problem... then again, I've got 3 copies of this lens and none look like this, only take mine out to f/8 and on rare occasions f/11. It's never seen f/16.

Hyperfocal should be around 60ft @ f/5.6, 40ft @ f/8, 30ft @f/11, and 20ft @ f/16.... I bet you could have backed up a bit, chose better and went for hyperfocal for a crispier image.

 

[JPAZ]

Mine spends most of its time at f /7.1 or faster and I've not noticed this. When I get issues with sharpness, it is usually my fault cause I am using a low shutter speed hand-held. I'd re-do some test shots at a larger aperture and see if that solves the issue. If not, agree it could be a de-centering issue. One final thought, I've gotten some poor results with stellar lenses shot through a lousy UV filter. Did you have anything mounted on the front?

 

[LesC]

Had both a Hoya Pro 1d skylight filter and a Lee landscape polariser fitted neither of which have given any problems on any lenses before. I'll try some test shots to see what I get under test conditions.

Am I right in assuming that if decentering is a problem it would be more apparent at smaller apertures, say F8 rather than F16?

Should it be apparent at all focal length too?

 

[JPAZ]

A couple of things to look at.......

https://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover/

http://blog.kasson.com/the-last-word/simple-decentering-test/

 

[LesC]

Thanks for that; I'd printed out a star chart but didn't realise that was what I'm supposed to do - I just tokk a series of properly focused shots at various apertures!

I'll try again tomorrow

 

[Mikehit]

I find it hard to believe that f16 on a FF camera will give diffraction that bad. The two extracts are about the same distance apart from the camera but the one at the edge is far, far worse.

This article illustrates effects of diffraction all the way to f32 and IMO this is nowhere near what LesC has seen.


https://photographylife.com/what-is-diffraction-in-photography/

 

[bholliman]

I find it hard to believe that f16 on a FF camera will give diffraction that bad. The two extracts are about the same distance apart from the camera but the one at the edge is far, far worse.

This article illustrates effects of diffraction all the way to f32 and IMO this is nowhere near what LesC has seen.


https://photographylife.com/what-is-diffraction-in-photography/

Agreed! I've owned a 24-70 f/2.8L II for 4 years and have occasionally shot at f/16. Diffraction softens the results a little (similar to what the TDP lens IQ tool shows below), but nothing like the OP's examples. There is something else going on to cause that level of softness.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=787&Camera=979&Sample=0&FLI=2&API=6&LensComp=787&CameraComp=979&SampleComp=0&FLIComp=2&APIComp=3

 

[LesC]

First thing; many thanks to all who've added to this thread, your contributions are much appreciated & helped greatly.

OK, so I've done the decentering tests at various focal lengths and apertures with camera mounted on substantial tripod, liveview so mirror locked up and as level/perpendicular to chart as possible. As you can see from the images below, it seems decentering is not an issue.

However, I still think something is not quite right - the 3rd image , "Full frame 55mm F8" still appears to show the right hand side of the frame to be less sharp that the other side. An identical image at F16 shows much less difference between the left & right sides of the frame.

These shots were obviously taken at the minimum focus distance of the lens - about a foot away - so I'm assuming the effect is less obvious at greater distances so perhaps why for the majority of times I've not noticed a problem. And of course I'll admit some times 'operator error' may be a factor as more often than not I shoot without a tripod.

I also checked back to see what Canon had said when the lens was checked last year and they only said "lens checked for focus and sharpness" so not sure how much testing was actually done. I had also earlier (when I first had the lens) sent some images to Canon which ironically seemed to show some softness on the left side of the frame which they suggested was lens aberration which could be corrected in DPP.

So I'm left in a bit of a quandary - the lens appears at least at times somewhat less sharp on the right edge, however I have little confidence that Canon would even acknowledge there is an issue or even if they do, there's a risk they'll only make it worse. I may in the first instance email them some shots to see what they say.

In the long term, I may try either the Canon EF24-105L F4 IS MKII or wait for reviews of the soon to be release Sigma Art 24-70 F2.8 which also has IS. I feel a decent copy of either may give better results than my current 24-70.

Seems to me that Canon's QC leaves something to be desired - I naively expected that by paying for the best I could safely assume the lens would be nigh-on perfect or at least very good. Seemingly not the case

 

[Sporgon]

I guess you've got some elements out of alignment - "de-centered". Complicated lenses like the 24-70 don't take knocks well, and if you've given it a bang that's probably the cause of the problem, despite what Canon service have said.

I had a 5D that got dropped. Everything was OK except the camera started back focusing, which it hadn't done before. Canon service checked it and said it wasn't out of alignment. I find these problems happen when you have an issue which is great enough to be irritating, but only slight in technical terms.