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PostPosted: Sat Apr 28, 2007 3:26 pm    Post subject: Reply with quote

lulalake wrote:

HI Orio,
Ca and bloom(fringing) are two different issues. CA happens when a lens can't focus red and blue light at the same point, which must be corrected in all lenses as red and blue don't focus at the same point.
CA looks like there is a small halo of red on one side of any and all objects in the picture and a halo of green or blue on the other side
Fringing/blooming is specific to digital cameras. It occurs in high contrast-opposite color areas such as tree branches against sky, the rail against the sky etc etc.
All digital cameras experience this, it's just the degree of it that is what is in question. CMOS sensors tend to have less than CCDs, large individual sensors tend to have less than small ones.
There are PS actions that get rid of it pretty well if it is bothersome.
Jules


hi Jules
I was suspecting something like this, that is why I mentioned pixel bleeding in the sensor, although it may not be precisely what you say. But it was just too strange for an optical problem like CA to stop suddenly just because there is less contrast. Also the thing that the red bleeding on the fence happens on both sides.
What does not fit in the picture for me is that I have not noticed such bad problem with other lenses, just with this one. So if it is a sensor problem, why does not show up with other lenses too?
I can not figure out this.

So symptoms do not match the CA, but at the same time, a sensor problem would be noticed with other lenses not just this one.
What is the answer that can make all pieces of the puzzle fit?


PostPosted: Sat Apr 28, 2007 4:11 pm    Post subject: Reply with quote

[quote="Orio"] So symptoms do not match the CA, but at the same time, a sensor problem would be noticed with other lenses not just this one.
What is the answer that can make all pieces of the puzzle fit? [/quote]

I think higher contrast lenses exascerbate the issue. Try a high contrast lens on branches against a blue sky then a low contrast lens on the same scene.

You might see more fringing with the high contrast lens.

Cheers

Jules


PostPosted: Sat Apr 28, 2007 7:22 pm    Post subject: Reply with quote

CA and "bleeding" cause similar optical errors but in different colours, as far as I know.
CA is red/cyan and "bleeding" is blue/yellow, or the other way around. I keep confusing that. Wink

As to the pictures:
- You shot this photos with a high f-number, since the dust spots on the sensor are clearly visible and the DoF is wide.
- The 2nd picture shows an even more closed aperture.
- Sharpness is excellent - in both cases.
- Colurs are are vivid but still seem to be genuine.
- CA (or bleeding) is visible but only very slightly - no problem at all.

So either this is quite an approved lens and these pictures proof its quality or it is a lens of which nobody of us would have expected such a performance.
And you wanted to "flabbergast" us... (I have a certain feeling that the latter is true!) Wink

Carsten


PostPosted: Sat Apr 28, 2007 7:57 pm    Post subject: Reply with quote

LucisPictor wrote:

So either this is quite an approved lens and these pictures proof its quality or it is a lens of which nobody of us would have expected such a performance.
And you wanted to "flabbergast" us... (I have a certain feeling that the latter is true!) Wink
Carsten


What is flabbergast? Smile

Anyway, no, I just wanted to surprise you, because I imagined you would have mentioned 135mm format lenses, and I wanted to just say "No! This is not a normal lens, it's a Flek wideangle - but shooting as a normal lens on the 5D"

Just that, a very silly entertainment number
Razz


PostPosted: Sat Apr 28, 2007 8:08 pm    Post subject: Reply with quote

Orio wrote:
What is flabbergast? Smile


This is English slang that Carsten must have picked up when he was visiting the not-so-touristy places in Kent Smile

"I'm flabbergasted" = "I'm amazed" or "I'm really surprised"
An even less-refined way of saying it is "I'm gobsmacked!"

You're learning some strange English words today Orio Smile


PostPosted: Sat Apr 28, 2007 8:20 pm    Post subject: Reply with quote

Ok then I wanted to flabbergast you Razz


PostPosted: Sun Apr 29, 2007 9:54 am    Post subject: Reply with quote

Laughing Laughing Laughing


PostPosted: Sun Apr 29, 2007 1:42 pm    Post subject: Reply with quote

Our gast has been duly flabbered..... Laughing