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Thread: How to focus but blur the background?

  1. #21
    Senior Member +evenstar's Avatar
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    Default Re: How to focus but blur the background?

    Quote Originally Posted by Zaknafein
    hmmm, its this true? can someone verify this pls?
    i always thought its the that the general rule of 1/focal length refers to 35mm equivalent?
    yes, you have to factor in the sensor size...
    eat. drink. shoot

  2. #22
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    Default Re: How to focus but blur the background?

    Quote Originally Posted by Clockunder
    I do not disagree that it's not sharp and may even be said to be blur.

    That's why I said it's near the threshold level of 1/71. In fact, it's below the guideline.

    I was just trying to show that if the actual requirement is 1/280, the a picture taken at 1/60 would have lots of handshake blur liao as I was aiming and shooting without making any conscious effort to steady my shots at that time.

    To reinforce my point that the guideline should be based on actual focal length rather than the 35mm equivalent, here are some handheld taken pictures (with the 35mm equivalent focal length in brackets) many of which I've posted in this forum before. They may not be very sharp (partly due to the wide-opened aperture at long focal length), they provide evidence to support my argument about using actual focal length as a guide for handheld shots :

    71.2mm (280mm) @1/60


    56.7mm (223mm) @1/60



    71.2mm (280mm) @1/74


    71.2mm (280mm) @1/125
    all i can say is only the botanic garden is valid... the rest of the picture were taken with flash on...

  3. #23

    Default Re: How to focus but blur the background?

    Quote Originally Posted by ExplorerZ
    all i can say is only the botanic garden is valid... the rest of the picture were taken with flash on...
    Opps! When I was going through the pictures I had posted in this forum before, I didn't take note whether flash was used in those pictures and picked some "not so good" examples. Paiseh. Thanks for pointing it out.

    Here are another 2 examples where no flash was used. They were previously posted in this forum too.

    71.2mm (280mm) @1/93 (not exactly very sharp but acceptable)


    71.2mm (280mm) @1/62

  4. #24

    Default Re: How to focus but blur the background?

    Quote Originally Posted by Zaknafein
    does that means there is also an advantage in smaller sensor size compared to bigger sensor size in this sense? excluding other factors like ISO, picture quality.

    for a PnS shooting at 300mm, one would need only about 1/100 shutter speed to get a relatively sharp shot. but for DSLR, if 1 is using a 188mm focal length with 1.6x crop factor, bringing it to shooting at ~300mm, would need about 1/200 shutter speed to get a relatively sharp shot?
    A general answer is yes. Those very slim compact cameras have CCD sensors so small that one can just snap around at 1/15 easily if it is not zoomed at all (actual focal length 5-8mm). That is why some DSLR newbies are puzzled as to why they get blurred images at 1/15 when he could easily shoot at 1/15 previously with their PnS's.

    However, for a PnS at 300mm (35mm equivalent), the actual focal length is somewhere between 50-70mm only and therefore you don't get as much details in PnS as a DSLR shooting at an actual focal length of 188mm.

    Moreover, DSLRs have much better noise handling than PnS and hence, one can push up the ISO much more easily to get a faster shutter speed without worrying as much about noise levels. If the PnS can shoot at 1/100, a DSLR can shoot the same composition @1/200 with the ISO one stop higher and still get more details than the PnS.

    More details and less noise are the 2 main reaons why I'm considering upgrading to a DSLR. Much faster focusing is also another major reason (for action photography such as Wakeboarding, Powerboat, Street/Beach soccer, etc.).
    Last edited by Clockunder; 14th July 2006 at 05:09 PM.

  5. #25
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    Default Re: How to focus but blur the background?

    yes, WA lenses have great DOF, while tele lenses have less DOF

  6. #26
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    Default Re: How to focus but blur the background?

    It sounds reasonable. Like Canon S3, the lens ratio is 1:6, so 70+mm equals to 400mm+ is normal.

    Quote Originally Posted by Zaknafein
    hmmm, its this true? can someone verify this pls?
    i always thought its the that the general rule of 1/focal length refers to 35mm equivalent?

  7. #27
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    Default Re: How to focus but blur the background?

    Hi ortega,

    Can u please advise if WA lenses will give more perspective? Like building "tapering" steeper from near end to far end, as compares to the non-WA lenses?

    Thanx.

    Quote Originally Posted by ortega
    yes, WA lenses have great DOF, while tele lenses have less DOF

  8. #28
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    Default Re: How to focus but blur the background?

    Quote Originally Posted by lastboltnut
    Hi ortega,

    Can u please advise if WA lenses will give more perspective? Like building "tapering" steeper from near end to far end, as compares to the non-WA lenses?

    Thanx.
    yes it will, this is because the angle of view is wider

    take for example a head shot, if the size of the head is the same in the frame
    the shot taken with a WA lens will look rounder then the shot taken with a tele lens

  9. #29
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    Default Re: How to focus but blur the background?

    So can I say that WC for P&S works the same rite?

    Thanks again.

    Quote Originally Posted by ortega
    yes it will, this is because the angle of view is wider

    take for example a head shot, if the size of the head is the same in the frame
    the shot taken with a WA lens will look rounder then the shot taken with a tele lens

  10. #30
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    Default Re: How to focus but blur the background?

    Quote Originally Posted by lastboltnut
    So can I say that WC for P&S works the same rite?

    Thanks again.
    yes it should

    try it out, shoot digital does not cost money

  11. #31
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    Default Re: How to focus but blur the background?

    Yah, shoot digital is doesn't cost $, but buying the WC cost $.....I haven't buy yet lah.

    Thanks for your advise.

    Quote Originally Posted by ortega
    yes it should

    try it out, shoot digital does not cost money

  12. #32
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    Default Re: How to focus but blur the background?

    oh you mean the WA conversion lens....

    i was talking about the built in lens

  13. #33

    Default Re: How to focus but blur the background?

    Quote Originally Posted by Clockunder
    Opps! When I was going through the pictures I had posted in this forum before, I didn't take note whether flash was used in those pictures and picked some "not so good" examples. Paiseh. Thanks for pointing it out.

    Here are another 2 examples where no flash was used.....
    im confused, again.
    the flash by ITSELF does not affects handshake right? even is flash was used, the point here is that, it is still taken at about 1/70 shutter speed and the pics still turns out relatively sharp.
    if u were to use flash and push shutter speed to say, 1/150, then the comparison wont be a fair test.... or did i have a misconception some where?
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  14. #34

    Default Re: How to focus but blur the background?

    Quote Originally Posted by Clockunder
    A general answer is yes. Those very slim compact cameras have CCD sensors so small that one can just snap around at 1/15 easily if it is not zoomed at all (actual focal length 5-8mm). That is why some DSLR newbies are puzzled as to why they get blurred images at 1/15 when he could easily shoot at 1/15 previously with their PnS's.

    However, for a PnS at 300mm (35mm equivalent), the actual focal length is somewhere between 50-70mm only and therefore you don't get as much details in PnS as a DSLR shooting at an actual focal length of 188mm.

    Moreover, DSLRs have much better noise handling than PnS and hence, one can push up the ISO much more easily to get a faster shutter speed without worrying as much about noise levels. If the PnS can shoot at 1/100, a DSLR can shoot the same composition @1/200 with the ISO one stop higher and still get more details than the PnS.

    More details and less noise are the 2 main reaons why I'm considering upgrading to a DSLR. Much faster focusing is also another major reason (for action photography such as Wakeboarding, Powerboat, Street/Beach soccer, etc.).
    thx a lot for the reply. understand a lot more now. so ur considering DSLR? im trying very hard to resist that virus.
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  15. #35

    Default Re: How to focus but blur the background?

    Quote Originally Posted by ortega
    yes, WA lenses have great DOF, while tele lenses have less DOF
    does this applies all the time? and is this why most ppl use focal length about 75mm for portrait shots, to have a shallow DOF using a bit of tele without having to stand too far away from subject?
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  16. #36
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    Default Re: How to focus but blur the background?

    Quote Originally Posted by Zaknafein
    does this applies all the time? and is this why most ppl use focal length about 75mm for portrait shots, to have a shallow DOF using a bit of tele without having to stand too far away from subject?
    most of the time ppl use a short tele for portraits is because the short tele slightly flattens the features, so that the person does not look too fat. a long tele will sometimes flatten the features too much in even light and make the image look 2d.

    they choose a bigger aperture to get a shallow dof.

  17. #37

    Default Re: How to focus but blur the background?

    ic. thx. maybe ill do some testing using diff focal length to see how it flattens or enhance a person's features
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  18. #38
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    Default Re: How to focus but blur the background?

    Yah, I was talkin bout Wide Converter....I am using Canon S3 IS, not a DSLR user...

    Quote Originally Posted by ortega
    oh you mean the WA conversion lens....

    i was talking about the built in lens

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