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Another whats going on here thread ?

  • 19-02-2007 7:55pm
    #1
    Muineach
    Closed Accounts Posts: 575 ✭✭✭


    hya's,
    So I was out taking a few photo's and when I got home I came across this, now I'm not sure if its the lens, the lighting etc, I had noticed it before but this time it was fairly serious. I know the pic isnt great but its one of these odd photos that make me ask "what the f**k going on".
    Now I took the photo in JPEG format which probably didnt helped.

    The "zoom_image" is an unaltered close up of the rocks, what I wanted to do was a slight change on the levels, one for the rocks and one for the sky, but what ended up happening was the "color" on the rocks got emphasied.

    The "zoom_cloud" and "zoom_rock" are one where levels were applied to cloud/rock. I tried selecting each rock/rock then modifying the selection (Selection->Modify-> Grow/Expand etc.) but the main problem is with the color rather than the selection.

    So is the color in the zoom image due to the lens or is it due to a jpeg compression thing ? I know theres a technical term for this but I can't remember.

    So any ideas ?

    BTW I did find a "workaround" which involves the cloning the line around the rocks, which I might say it a right pain in the arse :)

    The camera was a Canon Digital Rebel and the lenes was the standard Canon 18-55mm one, if thats any use.

    Thanks,
    Muineach


Comments

  • #2
    magicbastarder
    Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 50,891 CMod ✭✭✭✭magicbastarder


    looks like chromatic aberration at first glance - the strength of 'focussing' glass has depends on the wavelength of the light, and this is one reason why multiple element lenses are needed; to engineer the effect out.

    http://en.wikipedia.org/wiki/Chromatic_aberration


  • #3
    Fajitas!
    Registered Users, Registered Users 2 Posts: 16,624 ✭✭✭✭Fajitas!


    Aye looks like fringing alright - What was your white balance set to though? On the off chance.

    It could be compression too though...


  • #4
    TJM
    Registered Users, Registered Users 2 Posts: 548 ✭✭✭TJM


    Desaturating that photo should be a relatively easy fix. Photoshop and Paint Shop Pro both have chromatic aberration tools which might help, though I've never got the hang of them myself.


  • #5
    Muineach
    Closed Accounts Posts: 575 ✭✭✭Muineach


    Well just checked the photos and they all taken as "Auto" mode (I know, the shame) with ISO 100, and I have a range of them taken each between 1/ 100-150 with a f value of 5.3-8.0.
    I realise now that if I had taken them as RAW files I could have dealt with it in the RAW converter within Photoshop to some degree anyway.
    Guess I'll chalk this one up to another learning experience, just like the time I left AV +2 on the setting and never realised because the sun was glaring on the screen grrr :)

    So as for a new lens would a
    Canon EF-S 17-85mm f4-5.6 IS USM lens
     be a good choice ? or anyone know an equivalent cheaper model ?

    I also have a medical complaint that can give me the shakes now and again, so I'm thinking an IS would be handy :P

    Thanks
    Muineach


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