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 Post subject: C.A. issue
PostPosted: Wed Aug 20, 2008 2:08 pm 
I know how cromatic aberations are formed & what kind of light boosts the chance of getting them. Is underexposing a photo stoping a certain amount of CA to appear? Of course,in a RAW software you can increase the exposure to normal,but it could affect the general quality of the photo. How much underexposing I could apply without harming the image quality?


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 Post subject:
PostPosted: Wed Aug 20, 2008 4:48 pm 
Razvan,

I do not believe that underexposing will eliminate CA. CA happens before the light even strikes the camera sensor, so exposure value should not have an effect on it. If you underexpose and image and then brighten it in post-processing, you'll probably see the same CA, but with overall lower image quiality due to the brightening. How much you can brighten before having a noticeable loss of quality will vary from image to image.

Your camera manufacturer may provide software for removing CA. In the case of Canon, Digital Photo Pro can apply CA removal that is tailored to the particular lens used ot take a given photo, and it does a pretty good job. Not sure if Panasonic offers something similar, but it might be worth checking.


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 Post subject:
PostPosted: Wed Aug 20, 2008 7:43 pm 
I wasn't thinking of a brand in particular,just as a theory...
Then, I guess it's up to the polarizing filter & additional CA remover tools to get things done.
Thank you for the reply!


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 Post subject:
PostPosted: Sat Aug 23, 2008 12:07 am 
Vertigo wrote:
CA happens before the light even strikes the camera sensor


I have one more question...then why some lenses are more sensitive then others to CA ?


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 Post subject:
PostPosted: Sat Aug 23, 2008 9:04 am 
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Posts: 9835
Location: UK
Razvan wrote:
I...I guess it's up to the polarizing filter & additional CA remover tools to get things done...

I sincerely doubt that a polarising filter will make any difference to C.A.
Quote:
...then why some lenses are more sensitive then others to CA ?

It's down to design and cost. The perfect lens doesn't exist so all camera lens designs are a compromise. The number of lens elements, which types of glass to use and manufacturing tolerances are all relevant. The videos available via Canon's Virtual Lens Plant might be of interest if you have a little time to spare.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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