Just a couple of gulls from today

[tommy6206]

Been playing around with the Bigma today..

http://img.photobucket.com/albums/0803/tommy6206/Sigma%20lens/CRW_4950copy.jpg

http://img.photobucket.com/albums/0803/tommy6206/Sigma%20lens/CRW_4949copy.jpg

http://img.photobucket.com/albums/0803/tommy6206/Sigma%20lens/CRW_4278.jpg

Thanks for looking..

[myth337]

what is the cropping on #1??
i'm interested in the dark line on the left edge of the white...

[tommy6206]

It was cropped but not much the dark area is the sea .see the other pic and you will see what i mean.Its 2 different shots by the way and not a crop of the other..

[myth337]

no no no.. not the bottom dark blue sea... I meant the blue line along the edge of the gull's breast and on top of the head!! looks like a bit of chromatic abberation or something.

[tommy6206]

well apart from the resize and jpeg effects it looks ok here

[luisv]

what is the cropping on #1??
i'm interested in the dark line on the left edge of the white...

Maybe a little too much use of the PS sharping tool?

[myth337]

oh.. My profound apologies!! I completely forgot to mention that the shots are great!!
The coloring on #1 is really great.. the white contrast to the deep blue sky (and water)... and the warm glow of the sun in #2 makes a great mood!

BUT..... I have been seriously dissatisfied with several digital cameras, and a few lenses that I have plugged onto my 300D. You can tell from my Wish List Signature that I am shopping. ;)

The Bigma (if we are referring to the 50-500) is one of the lenses that many people have referred to me, and I am strongly interested in seeing if this little dark blue line on the breast of the kind gull (he was nice enough to pose for you..) is a result of Chromatic Abberation!! (which is very prominant when you have a bright (white) area with a sharp edge alongside a very dark (in this case blue) area...)

Purely a Technical Research question, in the neverending quest for knowledge and evaluation of other peoples experiences.

.. Lee

[tommy6206]

Here is the original and a 100% crop both untouched apart from resize for web.No processing at all apart from save as jpeg and resized for web

http://img.photobucket.com/albums/0803/tommy6206/Sigma%20lens/full-image.jpg

http://img.photobucket.com/albums/0803/tommy6206/Sigma%20lens/100crop.jpg

[myth337]

This 100% crop shows exactly what I was talking about...

The dark line on the edge of the white breast is caused by Chromatic Aberation (http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/aber2.html) ... light from different wavelengths going thru the lens at different angles.

Normally, you see this very pronounced on P&S cameras, because of their inherent small lens, especially when you are shooting high contrast subjects with sharp edges.

If you look at your second shot.. with the gull standing on the rock, the breast is not so white.. and the sky is not so blue.. so the effect is not there.

I've noticed this effect on some of my shots with different lenses on my 300D as well...
.. and like my sig says.. I'm shopping for lenses, and analyzing stuff to death to find out what other people experience with their stuff... so I can figure out what to buy. ;)

Please don't take my interest in this as a negative opinion of you, your photo, or your equipment!!! :D

Thank you for your time and patience. Carry on photographing!!! ;)

.. Lee

[Dragonslayer]

This 100% crop shows exactly what I was talking about...

The dark line on the edge of the white breast is caused by Chromatic Aberation (http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/aber2.html) ... light from different wavelengths going thru the lens at different angles.

Normally, you see this very pronounced on P&S cameras, because of their inherent small lens, especially when you are shooting high contrast subjects with sharp edges.

If you look at your second shot.. with the gull standing on the rock, the breast is not so white.. and the sky is not so blue.. so the effect is not there.

I've noticed this effect on some of my shots with different lenses on my 300D as well...
.. and like my sig says.. I'm shopping for lenses, and analyzing stuff to death to find out what other people experience with their stuff... so I can figure out what to buy. ;)

Please don't take my interest in this as a negative opinion of you, your photo, or your equipment!!! :D

Thank you for your time and patience. Carry on photographing!!! ;)

.. Lee

Actually it is most likely a halo that occurs when applying USM to any image that has whites or bright colors against a blue background, if it was chromatic abberation it would be blue or red. I have the bigma also and it's been a great lens for macro with Ext tubes to birds.

[myth337]

USM sounds like a possibility.. but like the man says.. untouched.

It is actually not normal to see this with long lenses, hence.. my questions.

I've seen the color of the edge range sometimes from dark blue, which this appears to be on my semi-calibrated monitor, to a purple(ish) range which looks kind of funky.

[Dragonslayer]

USM sounds like a possibility.. but like the man says.. untouched.

It is actually not normal to see this with long lenses, hence.. my questions.

I've seen the color of the edge range sometimes from dark blue, which this appears to be on my semi-calibrated monitor, to a purple(ish) range which looks kind of funky.

Well if he would list his workflow here it would help. Are these from raw? Was there any sharpening on the file when brought in from raw, as some raw image editors apply normal levels of sharpening. If they were shot Jpg then what level was the sharpening set to? If no sharpening was applied anywhere then there might be an issue with the lens, I will see if I have any images with white against blue and see if this shows on any of mine... I have seen chromatic abberations on many images with many lenses even Canon l series and Nikkor lens so Picking a lens that has might be tough. Also what aperture was this shot at, the bigma performs better closed down a little.

The image look pretty good also, I forgot to mention that, the whites though looks a little warm to hot in areas, might have benefited from some minus EV exposure compensation.

[PhotosGuy]

:D:D Dragonslayer beat me to it!
SO much to learn, isn't there? ;)

[tommy6206]

It seems that there was some sharpness added in the raw converter in PScs2. It remebers last setting used on the raw file.so when I reset it to camera default settings the blue fringe went.so yes it was down to sharpness setting.I think that clears that up and the lens is fine lol.


PS the 100% crop pic above has now been changed .No sharpening done in the raw file

[myth337]

Much much much better!!!

I never do any sharpening... (well.. haven't figured out which settings to use yet...) so the only thing I could think of was the Chromatic Aberration stuff.

It looks as if this forum has it's uses after all!!

Thanks guys... ;)