lots of CA... is my lens bad ?

[cmM]

I just got an 85mm f/1.8, because I need it to shoot a few fashion shows, so my 100-400 will have to wait for a couple more weeks.
Anyway, I've read lots of complaints about chromatic aberration at large apertures, and min has lots of that. I've also read about people getting a second copy which performed better.

My question to you is.... is this acceptable, or should i exchange it ?

F/2.0
http://www.cmuntean.net/images/ca.jpg
100% crop
http://www.cmuntean.net/images/ca_crop.jpg

F/2.8
http://www.cmuntean.net/images/ca2.jpg
100% crop
http://www.cmuntean.net/images/ca2_crop.jpg

Should I worry about it, or they're all like that ?

[Scottes]

Well the f/2.8 is much better, but why have an f/1.8 lens if you need to use it at f/2.8? Bummer.

[cmM]

Well the f/2.8 is much better, but why have an f/1.8 lens if you need to use it at f/2.8? Bummer.
Exactly.

Now usually I'd use less than f/2.8 in low light situations, indoors. CA (I think) only occurs in high contrast areas... right? WOuld that happen in an indoor shot ? I wonder...

[Jon]

Is that CA or purple fringe? Looks like purple fringe to me. The two have different causes; chromatic aberration's a problem with the lens focussing the different wavelengths (colours) of light at the same point (think a spectrum from a prism) and happens everywhere (less at the center, more at the edges), while purple fringe seems to be a reaction of the sensor to overload in high-contrast situations. You might try shooting a subject that's less contrasty, but with some specular reflections and see what things look like. The f/ 1.8 photo looks a bit overexposed, too.

[Belmondo]

Is that CA or purple fringe? Looks like purple fringe to me. The two have different causes; chromatic aberration's a problem with the lens focussing the different wavelengths (colours) of light at the same point (think a spectrum from a prism), while purple fringe seems to be a reaction of the sensor to overload in high-contrast situations. You might try shooting a subject that's less contrasty, but with some specular reflections and see what things look like. The f/ 1.8 photo looks a bit overexposed, too.

That was my thought, too. Maybe try the same shot somewhat underexposed and see if it's still there. This example doesn't look like 'textbook' CA to me.

[timmyquest]

Is that CA or purple fringe? Looks like purple fringe to me. The two have different causes; chromatic aberration's a problem with the lens focussing the different wavelengths (colours) of light at the same point (think a spectrum from a prism) and happens everywhere (less at the center, more at the edges), while purple fringe seems to be a reaction of the sensor to overload in high-contrast situations. You might try shooting a subject that's less contrasty, but with some specular reflections and see what things look like. The f/ 1.8 photo looks a bit overexposed, too.

I dont care what the cause is, something is wrong his camera and his lens should be able to handle this shot :cry:

[Jon]

I dont care what the cause is, something is wrong his camera and his lens should be able to handle this shot :cry:

Yes, but you have to identify the cause to be able to identify the solution (assuming you aren't just looking for a kludge!).

[cmM]

Is that CA or purple fringe?

That is purple fringe. Color fringes are caused by transverse chromatic aberrations.

But anyway.... is it too much ?

I'll try a less exposed shot later today (i'm at work now).

[drisley]

Actually....

As soon as I read the title, I new you had an 85F1.8 8)

Purple fringing like shot #1 is quite normal for the 85F1.8, and most non-L primes.
When I first bought my 85F1.8, I noticed the same problem, and posted a similar question here. Most 85F1.8 users replied they too get the same. It's really the only weakness of that awesome lens.

However, usually the fringing disappears about F2.8. So, your copy may be slightly bad. Somebody here had an 85F1.8 that fringed all the way up to F4, so he exchanged it and got a better sample. For that lens, fringing is acceptable up to about F2.5, and might still show a little at F2.8 under extreme circumstances.

If I had a camera, I would go outside and test mine for you. But alas... got no imaging device except my scanner *l*

[CyberDyneSystems]

Sorry I just feel I need to throw in my two cents on this..

If you take a lens and take a shot that is designed to show you pruple fringing... then you very well might get purple fringing.

Pointing a camera at back lit tree branches while wide open at f/1.8 is not ever likely to offer a great photo..

If you use test lens how you intend to use it however.. the results may be a lot different.

I guess I'm saying I just don't see the point of this test?

[cmM]

Sorry I just feel I need to throw in my two cents on this..

If you take a lens and take a shot that is designed to show you pruple fringing... then you very well might get purple fringing.

Pointing a camera at back lit tree branches while wide open at f/1.8 is not ever likely to offer a great photo..

If you use test lens how you intend to use it however.. the results may be a lot different.

I guess I'm saying I just don't see the point of this test?
You are deffinitely right CDS. The point of this test is nothing but the result of me reading a bunch of articles and threads about this lens showing purple fringes at large apertures, and a few examples where it's just might be a bad copy.

It's paranoya... I'll shoot something more relevant... tonight: I'm shooting a fashion show tonight for one of the designers.... I guess I can go post in the "pro" forum now :mrgreen: . I better get it right cause otherwise she'll kick my ass :P

[roanjohn]

Its normal :D :D :D

http://photography-on-the.net/forum/showthread.php?t=30172&highlight=85+f1+8

Ro1

[cmM]

Its normal :D :D :D

http://photography-on-the.net/forum/showthread.php?t=30172&highlight=85+f1+8

Ro1
Okay.... I'll leave it alone.


If it really pisses me off in the next couple weeks I'll just exchange it. Thankfully I bought it locally from Calumet.

[CyberDyneSystems]

Hmm,.. yes..

....if you HAVE to exchange it.. then clearly there will be no other option but to exchange for a 135mm f/2... :roll:

... you know.. if fate forces your hand... :wink: :lol:

[cmM]

Hmm,.. yes..

....if you HAVE to exchange it.. then clearly there will be no other option but to exchange for a 135mm f/2... :roll:

... you know.. if fate forces your hand... :wink: :lol:

....it's passed through my mind :P . I must resist however. There are many things I need before that lens...

[drisley]

This Pbase user (http://www.pbase.com/jxsq/mpsf_championship_2004)has both the 85F1.8 and 135F2L, and here is what he said:

"Quality-wise, I'd say they are very very close. For my copy, both 85/1.8 and 135/2 is very sharp even at wide-open. I do found my 85/1.8 have some CA sometimes, 135/2 is much better in this regard."

As an owner of both lenses I totally agree. As mentioned before, the 85F1.8 is prone to CA/fringing up to about F2.8. I've even seen small amounts of CA/fringing on L lenses under extreme circumstances.
If it bothers you, and you can easily exhchange, you might want to do it just for peace of mind. Chances are good that you will get the same results.

[drisley]

I just found a free piece of software that corrects purple and blue fringing. Seems to work well
It's called PFree (http://www.sd3.info/pf828/PFree/PFree0-1.html).

[cmM]

I just found a free piece of software that corrects purple and blue fringing. Seems to work well
It's called PFree (http://www.sd3.info/pf828/PFree/PFree0-1.html).
Cool
Thanks Drisley, I downloaded it. I'll give it a try see how well it works.

Thanks again :wink:

[drisley]

NP, that is an awesome lens, and that purple fringing is it's only drawback.
It's nice to find a solution!