Canon 85/1.8 CA?

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vaizki

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Jukka
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Ok so picked up a second hand Canon 85/1.8 today, and when I got home, I noticed some pretty extreme CA / purple fringing (I think) in the shots. Now I expected this to happen wide open or nearly at f/1.8 but for example this shot (100% crop) was at f/2.8:

998761663_9ibrk-O.jpg


The shot is of a wooden lantern, and the white-gray behind it is a house wall some 7-8m away. It was not very bright at all outside either, overcast. Shots at f/1.8 are even worse. f/4 is better but not much.

I know this is pixel peeping but I've looked at a lot of photos at 100% and never seen CA this strong in my shots. If it is even CA.

Duff lens or just a "feature" with the 85/1.8?
 
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Oh and another one, this one is not cropped but a full 18Mpx pic scaled down to 800 wide for the forum. Here the green and purple are very visible in the chrome. However this IS at f/1.8 ... but in a pretty dim garage.

998776955_5CwFw-L.jpg
 
This lens has a bit of a reputation for a variety of CA effects - which this certainly is. It is prone to bright lights also, or can be.

I particularly recall a highly respected member here had similar problems and sent it back. I think he got a good copy in the end, not sure if it was fixed or replaced.

I hate 'bad copy' rumours but this lens has had too many of them for it to have no basis of truth.

Edit: having said that, I can't really tell how bad that is without seeing the full frame, and running the file through DPP might fix it completely. Other first impressions are that it maybe looks sharp enough and there's not much flare?? Very hard to say too much from the images you've shown.
 
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There is some purple and cyan fringing around extreme highlights, that's about it. Unfortunately your shots have lots of those highlights.

Other expensive lenses have very similar issues. The list includes 200mm f/2.8L, 24-70mm f/2.8L, Tokina 12-24mm f/4 (CA), and 85mm f/1.2L is far from perfect (vignette and fringe).
 
I have to admit I've seen nothing like that from mine..it must be a bad batch job..
 
That is awful, noisy at ISO 200 too.

I've been waiting for the Sigma 85mm f1.4 but I'm beginning to think that I deamed it and was therefore thinking of getting this lens.
 
Ok guys I'm going to give the seller a heads up that I think there might be something wrong with the lens.. Any CA test scenario that you can recommend? Don't know how I'd compare it to another 85/1.8 without actually getting hold of one.

woof, well the noise is from my crappy 7D so can't blame the lens for that.. :|
 
My two pennarth' for what it's worth.....

I think you've just discovered that your 7D's high pixel density is excellent at resolving CA and why shouldn't it be? Stick the lens on a 10-12 Mp sensored body and view uncropped to see whether you've been sold a lemon....I suspect you'll find your lens is performing as it was designed to do although I stand to be corrected.

Bob
 
This is an abberation known as spherochromatism (purple fringing in front of the focussed area, green fringing behind), and is a type of CA that is quite prominent on lenses like this, which contain no exotic glass elements to try and combat such. This lens was made in the early 1990s for film - with no such considerations for high resolution digital, no Ultra low dispersion or aspherical elements either.

i would expect the abberations to be manageable at f/2.8-4, and gone by f/4-8. As Bob has said, the camera body is probably not helping the matter, and the first image certainly doesn't help as the contrasting edges help exacerbate the problem.
 
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Thanks again guys, I will shoot some 400D and 1D test shots. I'm going to TORTURE this lens and post some pics.. might not have the time in next few days though :(

Am I right in guessing that the 135/2 should perform much better wide open in these situations? That's what I'm really after but a good deal on the 85/1.8 and grabbed it as an interim solution and I really like the size & weight too. But if I can't shoot wide open then well what's the point really.. I have the 100/2.8 macro as well and could use that instead.
 
Mine shows some purple fringing at f1.8 but at f2.0 its gone. It does look like your lens is showing more than average for this lens.
 
vaizki said:
Thanks again guys, I will shoot some 400D and 1D test shots. I'm going to TORTURE this lens and post some pics.. might not have the time in next few days though :(

Am I right in guessing that the 135/2 should perform much better wide open in these situations? That's what I'm really after but a good deal on the 85/1.8 and grabbed it as an interim solution and I really like the size & weight too. But if I can't shoot wide open then well what's the point really.. I have the 100/2.8 macro as well and could use that instead.
Click to expand...

If you end up selling it I'll bite your hand off for it.
 
"woof, well the noise is from my crappy 7D so can't blame the lens for that.. "

Jukka, I've just read back what I wrote and I think it reads harsher than I meant it too. I actually think that most people are a little too bothered by things like CA and noise as they're mostly only visible if pixel peeping or maybe if cropping and printing very large. One thing that I do know is that many little faults visible on the screen are invisible in a final print.
 
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Sure the 7D is very revealing, but it's also only got a pokey little sensor that misses out the worst bits.

Good thread here on the 85 1.8. Note the comments from tdodd though I don't think the links are still working http://www.talkphotography.co.uk/forums/showthread.php?t=125490 He seems to have got a good one in the end :)
 
this is quite normal for a fast prime wide open and given the 85 1.8 is quite an old design very normal.

i have the 135 f2 and at f2 on some surfaces it's possible to see the bokeh fringing. 99% of the time you don't notice it, but some high contrast textures and patterns make it show more.

i really don't think your lens is faulty and is operating well within it's limits - i'd like to see a crop from a portrait or similar though.
 
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"this is quite normal for a fast prime wide open and given the 85 1.8 is quite an old design very normal."

I've never seen anything like this with any of my fast primes, or zooms, even after zooming to past 200%. I think that the oldest design I have is the Canon 50mm f2.5 but it doesn't do this but I can accept that it very well may be an older design issue but if you want this sort of length on a Canon body at the moment the choice is a bit limited. You can get a macro at about this length but you'll be limited to f2.8.
 
woof woof said:
...I've never seen anything like this with any of my fast primes, or zooms, even after zooming to past 200%.
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Two points.....
There are no fast zooms when we're talking of f/1.2 to f/1.8 primes....all zooms are slow (relatively speaking).
"Zooming" past 200% on a 20D image is only just approaching 100% on a 7D image

Taking a 100% crop from a 7D and showing it 800 pixels wide is taking a 3mm wide sensor sample and then displaying it on a screen at 150mm minimum (more on a larger monitor). Either way, it's magnified 50+ x....quite a test of a lens designed nearly 20 years ago.

Bob
 
I'm perfectly aware that zooms are slower than "fast" primes. I added the additional zoom lens comment for extra info. as in my innocence I expect a prime, fast or not, to perform well compared to a zoom.

I'm in two minds as to if this should matter (to me) as these faults may never show up in a print or even when viewing a full image or a reasonable crop on screen but there's also the view that if we're going to stop being picky to this sort of level there's probably little point buying ever more complex and hopefully ever more capable kit.

On balance I'll probably end up crossing this lens off the list of possible purchases until Canon get around to updating it as lens design has clearly moved on in the last 20 years.
 
woof woof said:
"this is quite normal for a fast prime wide open and given the 85 1.8 is quite an old design very normal."

I've never seen anything like this with any of my fast primes, or zooms, even after zooming to past 200%. I think that the oldest design I have is the Canon 50mm f2.5 but it doesn't do this but I can accept that it very well may be an older design issue but if you want this sort of length on a Canon body at the moment the choice is a bit limited. You can get a macro at about this length but you'll be limited to f2.8.
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take a look at the comparison between the canon 85 1.8 and the 85 1.2 here:

http://www.the-digital-picture.com/...&Camera=453&Sample=0&FLI=0&API=0&LensComp=120

and the zeiss 85 1.4 and nikon 85 1.4 af if:

http://www.the-digital-picture.com/...&Camera=453&Sample=0&FLI=0&API=0&LensComp=641

purple fringing is very apparent on the high contrast edges of the test chart with both sets of lenses. looking through the test charts on the digital picture it's certainly a problem which seems to affect some focal lengths more than others.


but like i said before, depending on what you photograph, you may never actually notice it in your photographs, with my own lenses it certainly only showed up at certain times, and in the case of the 100mm macro (which i used to own) and 135 you can really only see it against certain textures... 95-99% of the time you don't ever see it at all, even at 100% magnification.

from what i've read, even coatings on the sensor can have an impact on some of these aberration making them more or less apparent too. not sure about the science of that one, but i've seen it mentioned many times.
 
woof, I wasn't really LOOKING for the CA, they just jumped at me right away from the images I took on my way back from the face-to-face deal. I shot maybe 12 frames and just looked at them for fun when I noticed this.

A quick torture test.. shot with 4Mpx Canon 1D, these are uncropped but resized to 800 wide (they come out as 2464 x 1648 from the camera so about 1/3 of original dimensions):

f/1.8:
999686481_UJa7Z-O.jpg



f/2.8:
999686502_pTeJv-O.jpg



f/4:
999686533_3iX4Y-O.jpg


Yes, they're blinders.. ok a bit too much maybe for any lens?
 
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vaizki said:
woof, I wasn't really LOOKING for the CA, they just jumped at me right away from the images I took on my way back from the face-to-face deal. I shot maybe 12 frames and just looked at them for fun when I noticed this.

A quick torture test.. shot with 4Mpx Canon 1D, these are uncropped but resized to 800 wide (they come out as 2464 x 1648 from the camera so about 1/3 of original dimensions):

<snip>

Yes, they're blinders.. ok a bit too much maybe for any lens?
Click to expand...

That's bad :thumbsdown:
 
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