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Thread: focus comparision

  1. #1

    Default focus comparision

    C&C away however I'd appreciate some pointers I have about focus too.

    I'd like to know why I'm not able to get pictures in focus specially objects like the cat in the first picture but the car seems to be in focus. The distance from my camera to the objects are quite the same and I'm using AF.

    I'm using a Canon D350 and 75-300mm f4-5.6 lens.

    please advice.

    Cat


    Car
    Last edited by funkydonkey; 28th June 2006 at 10:40 AM.

  2. #2
    Moderator ortega's Avatar
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    Default Re: focus comparision

    i think the problem is with focal lenght

    the car should have been shot at the wider end of your lens and the cat at the tele end
    am i right?

    DOF is reduced as

    1. the focal gets longer
    2. focal distance gets shorter

    higher chance of camera shake is greater when

    1. focal lenght gets longer
    2. magnification gets higher

    so keep this in mind and read up on camera holding techniques
    when using longer focal lenghts or close up shots.

    BTW your car shot is a little under on my screen.

  3. #3

    Default Re: focus comparision

    Quote Originally Posted by ortega
    i think the problem is with focal lenght

    the car should have been shot at the wider end of your lens and the cat at the tele end
    am i right?

    DOF is reduced as

    1. the focal gets longer
    2. focal distance gets shorter

    higher chance of camera shake is greater when

    1. focal lenght gets longer
    2. magnification gets higher

    so keep this in mind and read up on camera holding techniques
    when using longer focal lenghts or close up shots.

    BTW your car shot is a little under on my screen.
    Thanks of ryour inputs. much appreciated.

    From the image's DOF, yep the car has been shot at the wider end of the lens and the cat at the tele.

    Do you reckon this is a problem with camera shake or something wrong with my lens?
    If you notice the cats picture the whiskers look blur due to shake, the eyebrows(whiskers like) look well in focus.
    I normall follow the standard techniques of hold and shooting however. Any links or tips to hold specially for long focal length shots?? I guess a trippod could have solved the issue but, Could not afford to set up my tripod while the subject was moving thru one of the back alleys.

  4. #4
    Moderator ortega's Avatar
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    Default Re: focus comparision

    Quote Originally Posted by funkydonkey
    Thanks of ryour inputs. much appreciated.

    From the image's DOF, yep the car has been shot at the wider end of the lens and the cat at the tele.

    Do you reckon this is a problem with camera shake or something wrong with my lens?
    If you notice the cats picture the whiskers look blur due to shake, the eyebrows(whiskers like) look well in focus.
    I normall follow the standard techniques of hold and shooting however. Any links or tips to hold specially for long focal length shots?? I guess a trippod could have solved the issue but, Could not afford to set up my tripod while the subject was moving thru one of the back alleys.
    i do not think that your lens is at fault

    it looks like a case of shallow DOF plue camera shake
    the whole image looks a bit soft -> slight camera shake -> increase shutter speed
    the wiskers are actually also OOF so it looks more blur than the eyebrows

    the only way is to mount your camera on a tripod and repeat the same settings (focal lenght/camera to subject distance) and shoot again to see if it is due to camera shake
    shoot on a bright sunny day to get a smaller aperture and maximum DOF

    http://www.nikonians.org/html/resour...dholding1.html

  5. #5

    Default Re: focus comparision

    from the two exif. Its clear why the cat is blur and the car is sharp.

    Cat shot, 300mm 1/200 shutter speed f5.6
    You are shooting below the 1/focal length speed and unless you can handhold it, it will be soft or OOF due to handshake

    Car shot, 105mm 1/1600! shutter speed f4.5
    This one definitely can handhold. With that kind of shutterspeed.

    The 2 is not equal comparison. Nothing wrong with the lens as for certain lens, the tele side tends to be soft and also, its difficult to do handhold at 300 unless you own those big mamas! =)

    I like the car shot. =)

  6. #6

    Default Re: focus comparision

    Quote Originally Posted by tltan
    from the two exif. Its clear why the cat is blur and the car is sharp.

    Cat shot, 300mm 1/200 shutter speed f5.6
    You are shooting below the 1/focal length speed and unless you can handhold it, it will be soft or OOF due to handshake

    Car shot, 105mm 1/1600! shutter speed f4.5
    This one definitely can handhold. With that kind of shutterspeed.

    The 2 is not equal comparison. Nothing wrong with the lens as for certain lens, the tele side tends to be soft and also, its difficult to do handhold at 300 unless you own those big mamas! =)

    I like the car shot. =)


    Thanks Tltan and Ortega for the pointers, I'm glad u even went all the way to check the details of my file. I'll surely keep them in mind and not bitch about the "cheap" lens i own

  7. #7

    Default Re: focus comparision

    I had the same 75-300 lens and it's a bit soft... Would suggest you get the 75-300 IS USM lens if possible. At least it's reasonably sharp...

    (By the way, it's 350D, not D350 )
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  8. #8

    Default Re: focus comparision

    Quote Originally Posted by philliptan
    I had the same 75-300 lens and it's a bit soft... Would suggest you get the 75-300 IS USM lens if possible. At least it's reasonably sharp...


    (By the way, it's 350D, not D350 )

    hehe thanks for the feedback at least I know from someone what my lens is capable of. How much is the USM IS of the same lens? is it f4-5.6 as well?

  9. #9
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    Default Re: focus comparision

    I don't know about the rest. but the cat seems to be popping out of my screen. like some 3d effect.

  10. #10

    Default Re: focus comparision

    Camera shake may be most likely reason for blurr cat shot. The rule of thumb for shutter speed is 1/(2xfocal length) so for the 300mm shot, your shutter speed should have been 1/600. You were shooting at 1/200.

    But that is still doable with very steady hands.

    The other thing is what I called focus acquisition. This concerns the auto focus algorithm which in passive auto focus depends critically on the contrast of the focusing point. The better the contrast the more accurate the focus.

    The car has better contrast. I do not know where you select as you focus point. The cat in contrast is very flat in its contrast.

    This is another possible reason for the softer focus in the cat. One way to experiment maybe is to shoot a low contrast subject at various shutter speed and see if the softness remains. And then repeat but with a better contrast subject.

  11. #11

    Default Re: focus comparision

    Actually.. I find the cat with a slight blurr quite nice leh

    Quote Originally Posted by funkydonkey
    C&C away however I'd appreciate some pointers I have about focus too.

    I'd like to know why I'm not able to get pictures in focus specially objects like the cat in the first picture but the car seems to be in focus. The distance from my camera to the objects are quite the same and I'm using AF.

    I'm using a Canon D350 and 75-300mm f4-5.6 lens.

    please advice.

    Cat


    Car

  12. #12

    Default Re: focus comparision

    Quote Originally Posted by espion
    Camera shake may be most likely reason for blurr cat shot. The rule of thumb for shutter speed is 1/(2xfocal length) so for the 300mm shot, your shutter speed should have been 1/600. You were shooting at 1/200.

    But that is still doable with very steady hands.

    The other thing is what I called focus acquisition. This concerns the auto focus algorithm which in passive auto focus depends critically on the contrast of the focusing point. The better the contrast the more accurate the focus.

    The car has better contrast. I do not know where you select as you focus point. The cat in contrast is very flat in its contrast.

    This is another possible reason for the softer focus in the cat. One way to experiment maybe is to shoot a low contrast subject at various shutter speed and see if the softness remains. And then repeat but with a better contrast subject.
    Thanks for the tips again. Very insightful and logical. Its great to be learning from you guys.

    Just wondering do most pro photographers actually have the time to think of these settings when they have an object like the cat which was waking along the street or sitting for a short while?

    As for the car the focus point was towards my left middle somewhere on the bonnet. Yes as for the cat it was hard to get enough contrast because I shot it against the road which was pretty much flat as compared to the cat.

  13. #13

    Default Re: focus comparision

    Quote Originally Posted by jeryltan
    Actually.. I find the cat with a slight blurr quite nice leh
    Thanks buddy...guess its an artistic way of looking at things but not so very acceptable with the community. I would have preferred it sharp as well

  14. #14

    Default Re: focus comparision

    something no one has said.. but i like the car pic..
    nicely taken.

  15. #15

    Default Re: focus comparision


    GREAT CHOICE for choosing Audi

  16. #16

    Default Re: focus comparision

    Quote Originally Posted by jdredd
    something no one has said.. but i like the car pic..
    nicely taken.
    Thank you

  17. #17

    Default Re: focus comparision

    i agree with them. the car pic is is nicely composed.
    the raindrops add to the effect
    if only the Audi Logo wasn't cut off..
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  18. #18

    Default Re: focus comparision

    Thank you for the comments . I wished the logo wasnt cut off too. Didnt really pay attention to the logo was more focused on the rear lights. Btw I used to own an A95 too...cool camera. Any portfolio taken with that camera to share?

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