CVickery wrote:
That's not really CA, but it's 'purple fringing' (sorry I don't recall the technical name). LCA gives you the red/cyan or blue/yellow effect and the sliders will fix it. Purple fringe is another issue and AFAIK the way to fix it is to select the purple and desaturate the color until the effect isn't objectionable. I owned the EF100/2 and it has the same problem with high contrast areas.
it's most likely longitudinal chromatic aberration (front/back as opposed to side to side type) where it tosses magenta/purple in front and green behind
lenses that are not fully APO often get it near wide open
that's why I said it depended on the edge that it is occuring on. *if* it is something prominent and should be rendered very sharp just desaturating the fringe does nothing to bring back the actual edge. Yeah, in distant leaves and stuff it just gracefully vanishes...
>>Funny you would write that - in a few cases I have decided to convert an image with significant fringing to BW precisely _because_ doing so made the fringing a non-issue. :-)
winzphoto wrote:
I'm getting some really bad Chromatic aberration with a fairly new 85mm 1.8.
1) Are you (owners of this lens) seeing similar problems (high contrast areas) with the lens - purple fringing, etc.
2) How can I correct this photo without desaturating the edges that are bad? Editing in LR2, but the Chromatic Aberration (Red/Cyan & blue/yellow) sliders make hardy any improvement to the photo. (I have several other photos from the shoot with the same problem)
Shot on 5D Mark II at f1.8 (RAW)
I'm aware this lens has problems with CA at times, but this seems extreme. Is there something else going on here?
No really, the 1.2 shows just as much or more purple fringes. To some extend the issue can be interconnected to exposure.
I own both and I do not see a big difference between the two
I never noticed much in the way of purple with mine but I do see green fringing wide open on OOF points. The lens is superb stopped down where i generally use it but I wouldn`t choose it for shallow DOF shots.
Just looking at the more recent post of this image... the problem here is produced by the overexposure of the sunlit areas, for example along the top edge of the gentleman's shoulders. I'll bet that the blown highlight indicator was flashing on this one. (I have a bag full of good lenses, and I'm certain that this issue would have cropped up with this exposure using any of them.)
Probably the best time-of-exposure solution here would have been to watch the histogram and reduce the exposure a bit to avoid the blown highlights. Yes, you'd have to do a bit of work in post to bring back some of the shadow detail, but if you shoot RAW that should be do-able.
Still, given what you have here - and the pleasant expressions on the two subjects - it is possible to salvage the shot using some of the techniques described in this thread.
Am I the only one that thinks the image is slightly backfocused?
Perhaps check foliage and chain behind the couple and see
if they are sharper than the couple themselves.
Being slightly out of focus will have a large effect upon the purple fringing.
It's very difficult to total nail the focus on an image like this at
wide aperture. But even if you do nail the focus, there will still be
purple fringing when the image has strongly overexposed areas.
You can try fill flash, or some of the post processing techniquies described,
but this kind of natural lighting will always take some work to get right.
I found the EF 85 f/1.8 to be excellent at suppressing CA fringing.
Couldn't put my hands readily on a wide open shot to demonstrate that, so this f/2 one will have to do, 50% enlargement crop.
Now, if you wanna see some real "purple rain" (drops) try this kind of a shot with the 85L at f/2.
PetKal wrote:
I found the EF 85 f/1.8 to be excellent at suppressing CA fringing.
Couldn't put my hands readily on a wide open shot to demonstrate that, so this f/2 one will have to do, 50% enlargement crop.
Now, if you wanna see some real "purple rain" (drops) try this kind of a shot with the 85L at f/2.
actually you can see some greenish and magentaish on the oof drops and hazing on the branches, that low light shot doesn't reveal it as much as some shots do though
I bough a 85 1.8 last week and it has the same purple and green fringing issues. I was doing foucs testing...pointing camera at 45 degrees. I noticed purple fringing at f/1.8 on all the out of focus foreground edges...and green fringing on all out of focus background edges. but nothing on the line that was in sharp focus (its a different isssue that that was not the line I wanted it to focus on :-) In fact, the fringing made the back-focussing issue very obvious :-)
trumpet_guy wrote:
Am I the only one that thinks the image is slightly backfocused?
Perhaps check foliage and chain behind the couple and see
if they are sharper than the couple themselves.
Being slightly out of focus will have a large effect upon the purple fringing.
It's very difficult to total nail the focus on an image like this at
wide aperture. But even if you do nail the focus, there will still be
purple fringing when the image has strongly overexposed areas.
Bingo. Getting focus spot-on will help to some extent. Stopping down a bit will help as well as the fringing happens more in OOF areas.
And just to reinforce what has already been said, this is normal with the 85 f/1.8. I get this on mine too.
A reason why I sold mine and got the 85mm f/1.2L II.
You need to step down (e.g. f/2 or f/2.8) with this 85mm f/1.8 lens in situations like this.
The f/1.2L doesn't have this much CA even at f/1.2.
+1
Actually, I regard this as the only weakness with the f/1.8 compared to the f/1.2, its susceptibility to purple fringing at even moderately contrasting lighting conditions and wide open(-ish) apertures. May step on a few toes though
OTOH, lets not turn this into another battle of 85s thread!
A reason why I sold mine and got the 85mm f/1.2L II.
You need to step down (e.g. f/2 or f/2.8) with this 85mm f/1.8 lens in situations like this.
The f/1.2L doesn't have this much CA even at f/1.2.
I think that's an unfair generalization of the f/1.8's capabilities, particularly given the example.
To my eye, the depth of field is correct for the subjects, since the bench, chain, and flowers surrounding them all appear sharp. But the couple look soft, so I'd have to assume the shutter speed was too slow to freeze their movement. Any lens is going to have a problem with that in a strongly backlit scenario, but, yes, the less expensive lens with the sub-L optics and coatings is going to make it more evident. To correct it completely, you need to better control the light. Ideally, you'd put some fill light on your subjects so you can up the shutter speed enough to freeze them and get a more natural graduation of tone between the shadow side and the back light. You could also place a diffuser above them out of frame to soften the light falling on their shoulders, allowing you to safely use a higher ISO and, again, up the shutter speed.
