Canon 300mm f/4L IS chromatic aberration

Hi all,

I've only had this lens for about 2 months and noticed that in almost all shots there is quite a noticeable magenta/green fringe. Is this to be expected with this lens? The on-line reviews seem to suggest that this is not normal.

Any help would be appreciated.

Thanks,

Paul.

Hi Paul, sounds like you have a problem there. I have the same lens and have used it with the 40D and now the 7D and have never had that happen with any images.

Andy Gregory

Thanks Andy,

I think there is something wrong with the lens. I've done a comparison with my 70-200 f4 and the 300 f4 appears to be worse! Both taken at f/11.

Fringing increases with increased aperture, and in any event at F11 the lens is becoming defraction limited with modern DSLR bodies, ie lens image quality deteriorates significantly. - repeat your test wide open, and take any lens protective filters off

What are we looking at in your tests as these look like highly magnified test chart scales - ie are we looking at 100% crops?... if so then these don't look that bad to me (both sets show fringing)- high contrast boundaries exagerate the fringing effect and modern sensor photosite pitch/spacing out resolve all but the very best of lenses so a 100% crop will always show up "defects".

If these are 100% crop then a more realistic test of lens output would be a 25% crop ie a 800 x 800 pixel patch downsized to 400 x 400 pixels - this is much closer to print output reality

Hi Mike,

Thanks for your informative reply. I've taken test chart shots wide open and the issue is still present. They were 100% crops, so I've done as you suggested. I'll attached them to this thread, I've also attached an example real world picture at f4, again a 800x800 reduced to 400x400 pixels.

Thanks,

Paul.

The 300f/4L at f/4. The fringing is more pronounced on the right hand side. The photo is sharp at the centre and is taken with a tripod with a gimbal head, this is a right hand crop.

My 70-200 f/4L at f/4. Taken with a tripod and a gimbal head, this is a right hand crop.

Paul

I can't see any obvious problems with the Dunnock image other than the colour balance being slightly off.

Have a look at the DPReview website, they have a series of lenses comprehensively tested including the Canon 70-200 F2.8L lens, you can pay with different aperture and zoom settings and see the effect on fringing and sharpness across centre/edge of image. Even the 70-200 F2.8L exhibits the symptoms you are seeing - fringing increases with increased aperture and fringing is worse at the edge of the lens.

I would be more concerned by the focus on your lens, it looks to be front/back focussing by the fuzziness of the test chart images. Have you tried the slanting ruler test to judge if you have a focus issue?

Hi Mike,

The dunnock image was cropped from the centre of the image and the fringing that I can see is on the tail. The image is an unprocessed RAW so the levels will be off, I didn't want to skew the effect I was seeing.

I previously checked the comparisons on the-digital-picture.com and thats why I questioned my copy of the lens.

I'll check the focus micro adjustment settings again and re-post an example. If this is normal, I will be getting a refund. I've shot many Canon primes, none have shown this level of CA.

Thanks,

Paul.

Um, I don't think you've a lot to worry about Paul - to be honest, the fringing doesn't look to be very noticeable at all - and in areas of high contrast, you'll see some hints of it anyway. I'm no too sure you need to worry about the focus either as the photos you've shown that you've shot with it (Red Kite etc) seem pretty sharp - the 300/4+1.4 doesn't always give the best results and you've got better shots than I've managed with the same combination!

Thanks Nick,

I'd expect some hints of CA as you say, but its more than that on this lens, you can clearly see the fringing at 25% zoom on some pictures. I removed the CA from the red kite shot in processing, it was quite pronounced along the wing edges, but it was against the sky. So at the time I thought it may have been just harsh lighting. Now looking back at my images, I can see that the fringing is there on every shot I have taken.

I've arranged to have the lens looked at by Canon. I can then hopefully see if its me or if the lens is really out of spec!

Thanks,

Paul

For anyone that is interested: I had the lens looked at by Canon and they repaired the lens. Its much improved now.

Thanks.