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Thread: auto focus points + image stabilizer inquiries

  1. #1

    Default auto focus points + image stabilizer inquiries

    Hi everybody.

    i have some qns in mind regarding DSLR.

    1) i saw on the viewfinder of a canon 550D that there are a total of 9 AF POINTS. under auto mode, when i aim at direction and hold the shutter down halfway, i saw 5 POINTS lighted up in red. and when i adjusted to manual focus, there is only 1 point (which is at the center) lighting up in red when i hold the shutter halfway down.

    so what does it meant when the 5 points light up? can anyone explain to me simply?

    the next thing i knew when i shot using manual focus was that, the item which i placed the 1 and only AF point at, was the sharpest,while the rest of the part of the image was pretty blur.

    so does it meant that those areas which are targeted by the lighted AF points would result in being coming out as the sharpest part in the image formed?

    2)is it very very important to have image stabilizer i knew canon and nikon built their IS on the lens. so i was thinking if i were on budget, and bought a non-is lens, will my photos taken be ultra lousy? does the IS really play a big part?

  2. #2
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    Hi everybody.

    i have some qns in mind regarding DSLR.

    1) i saw on the viewfinder of a canon 550D that there are a total of 9 AF POINTS. under auto mode, when i aim at direction and hold the shutter down halfway, i saw 5 POINTS lighted up in red. and when i adjusted to manual focus, there is only 1 point (which is at the center) lighting up in red when i hold the shutter halfway down.

    so what does it meant when the 5 points light up? can anyone explain to me simply?

    the next thing i knew when i shot using manual focus was that, the item which i placed the 1 and only AF point at, was the sharpest,while the rest of the part of the image was pretty blur.

    so does it meant that those areas which are targeted by the lighted AF points would result in being coming out as the sharpest part in the image formed?

    2)is it very very important to have image stabilizer i knew canon and nikon built their IS on the lens. so i was thinking if i were on budget, and bought a non-is lens, will my photos taken be ultra lousy? does the IS really play a big part?
    1) When you choose AUTO AF points, the sensor will detect whatever it can focus. it does its own algorithms to give you the "best" results. If you picked single, you can choose the point where you want the sensor to focus, this gives the most accurate focus point since you make the decision for it, especially you want the subject focus and background blurred.

    2) Depends. If you get a good exposure, you are likely to nail that shot. IS may not be a big deal but having it can save your photo moments to be sharp at least for higher chances of getting it right. All film era shoot without IS. Only recent years, it comes in our lens. I would opt for IS for the lens I want to get.

  3. #3

    Default Re: auto focus points + image stabilizer inquiries

    thanks alot for that reply. haha.
    i think i sounded very noobish isnt it?

    well actually while i was trying out a DSLR on auto AF mode,i realized that there are 5AF points lighted up. then i got puzzled. i was wondering if there are only 5AF points lighting up,does that means the rest of the portion that are not targetted by the AF points would be blur, and only those areas targetted by the 5AF points would be produced clearer and sharper?

    then what's the point of buying it, since my objective is to take a clear and crisp photo of the entire area i point my camera too

  4. #4

    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    thanks alot for that reply. haha.
    i think i sounded very noobish isnt it?

    well actually while i was trying out a DSLR on auto AF mode,i realized that there are 5AF points lighted up. then i got puzzled. i was wondering if there are only 5AF points lighting up,does that means the rest of the portion that are not targetted by the AF points would be blur, and only those areas targetted by the 5AF points would be produced clearer and sharper?

    then what's the point of buying it, since my objective is to take a clear and crisp photo of the entire area i point my camera too
    close down your aperture size to get sharper image throughout.

  5. #5

    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    thanks alot for that reply. haha.
    i think i sounded very noobish isnt it?

    well actually while i was trying out a DSLR on auto AF mode,i realized that there are 5AF points lighted up. then i got puzzled. i was wondering if there are only 5AF points lighting up,does that means the rest of the portion that are not targetted by the AF points would be blur, and only those areas targetted by the 5AF points would be produced clearer and sharper?

    then what's the point of buying it, since my objective is to take a clear and crisp photo of the entire area i point my camera too
    I suggest reading up a bit on the basics of photography, specifically depth-of-focus. As for the AF points, if you read the manual (you can see it online) you'll have all your answers.
    Alpha

  6. #6
    Moderator Octarine's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    then what's the point of buying it, since my objective is to take a clear and crisp photo of the entire area i point my camera too
    Basics of Physics tell you that a lens has one focus point (I don't refer to these red markings in viewfinder!). Objects placed there will create a sharp image. Secondly, aperture affects how much in front and behind this focus point is also sharp (perceived as sharp).
    Our eyes do a constant focusing, wherever we look at. That's why to us the world looks sharp, nearly always. Our brain does all the adjustments in the background. The camera can only make guesses based on algorithms. The highlighted AF points in viewfinder are suggestions based on what the camera recognizes. You can either accept those settings or correct them. Most cameras allow you to manually select one or more AF points to be used.
    If you don't want to go into these details and just have everything sharp everywhere - stop looking at DSLR, get a Point n Shoot cam.
    EOS

  7. #7
    Member Senifer's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    go f16 and shoot slowly and you get a clear crisp sharp photo overall. lol
    Nikon D90 | N18-105mm | T90mm | SB-600
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  8. #8
    Moderator Octarine's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    2)is it very very important to have image stabilizer i knew canon and nikon built their IS on the lens. so i was thinking if i were on budget, and bought a non-is lens, will my photos taken be ultra lousy? does the IS really play a big part?
    Image stabilization is in market only since a couple of years. How do you think all those people in the last 50 years took their pictures? Seems there is another way, independent from an IS, to get good pictures.
    There is a rule of thumb that links focal length to shutter speed: shutter speed (in seconds) should be faster or equal to 1 / focal length (in mm). For everything else there are tripods.
    EOS

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    Member dingaroo's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    If you had read your manual from front to back diligently, you'd have known that if you camera is in Auto mode, the camera overrides the photographer's choice of settings. In particular, the Auto Focus points will be chosen by the camera.

    That's why we never encourage photographers to shoot in Auto mode. In any of the manual modes, you can specify the point of focus as you compose your picture. Please read the manual again, to find out how that is done.

    You've bought a very good camera, but using a dSLR is not like using a P&S camera. It requires a bit more of knowledge on the photographer's part.

    Cheers!
    A picture a day keeps the blues away!

  10. #10

    Default Re: auto focus points + image stabilizer inquiries

    Thank you sooooo much. i really appreciate the advises that you all have shared.

    i came from a PNS background, and have not ever touched a DSLR before until recently when i read about it, and got interested in photography because of fellow classmates and friends.

    i am using a olympus fe-20 PNS at the moment, as i have not decided on which DSLR to buy. i read online on quite a few photgraphy forums and started to understand the jargons and basics. however when i went to try the EOS 550D the other day, i was wondering to myself, among the 9AF points, how come only 5AF points light up? does it mean that only those areas targetted by the 5AF will be sharp, and the remaining parts bur?

    because coming from a PNS, i did not know about about those bokeh effects and all. then i was always thinking to get the sharpest and crispiest image for the entire pic. and that's why the 5/9AF points lighting up question came into my mind.

  11. #11
    Moderator Octarine's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    however when i went to try the EOS 550D the other day, i was wondering to myself, among the 9AF points, how come only 5AF points light up? does it mean that only those areas targetted by the 5AF will be sharp, and the remaining parts bur?
    Yesno.
    Those 5 AF points show you areas where the camera has picked up a clear focus. The AF system as some algorithms helping to recognize e.g. a single person in front of others. Then the AF points over the person would be sharp, the rest not. How much blur? That depends on the sensor size, your lens (especially the focal length, the aperture) and the distance between your main object and the background / other details in the picture. Read up about Depth of Field, subject isolation, aperture: Understanding Depth of Field

    because coming from a PNS, i did not know about about those bokeh effects and all. then i was always thinking to get the sharpest and crispiest image for the entire pic. and that's why the 5/9AF points lighting up question came into my mind.
    For PnS cameras these effects of bokeh, subject isolation, Depth of Field don't really matter. Due to the small sensor and the lenses with very short focal length there isn't any of these effects. Everything is always sharp. That's why handphone cameras don't have movable lenses, it's all fixed.
    Depth of Field and subject isolation are parts of the composition in photography. Especially in portraits (but also other styles) it is recommended to isolate the person from background.
    EOS

  12. #12

    Default Re: auto focus points + image stabilizer inquiries

    for Octarine. Very informative and direct explations
    D7000. AF-S 18-105

  13. #13

    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by Octarine View Post
    Yesno.
    Those 5 AF points show you areas where the camera has picked up a clear focus. The AF system as some algorithms helping to recognize e.g. a single person in front of others. Then the AF points over the person would be sharp, the rest not. How much blur? That depends on the sensor size, your lens (especially the focal length, the aperture) and the distance between your main object and the background / other details in the picture. Read up about Depth of Field, subject isolation, aperture: Understanding Depth of Field


    For PnS cameras these effects of bokeh, subject isolation, Depth of Field don't really matter. Due to the small sensor and the lenses with very short focal length there isn't any of these effects. Everything is always sharp. That's why handphone cameras don't have movable lenses, it's all fixed.
    Depth of Field and subject isolation are parts of the composition in photography. Especially in portraits (but also other styles) it is recommended to isolate the person from background.
    thanks alot mate. really appreciate it

  14. #14

    Default Re: auto focus points + image stabilizer inquiries

    right now, i am weighing and doing a comparison between a canon 550D and a pentax KX.
    so far, i have demoed the canon 550D at courts and really liked the way it feels on my hand. and i also quite liked the controls and menus. the only thing is that for the $1000+ im paying, i only get a 18-55mm kit lens and in future, must buy lenses with IS (which i suppose will cost more)

    as for the pentax kx, at funan slr revo, they do not have any demo set. and i didnt really have the chance to tryout. so it's hard to know if i really like it or not. but i really am attracted to the price . it's good pricing ,esp for newbie liked myself who doesnt really know much about dslr, and wouldnt feel comfortable in spending too much,right at the beginning. just liked for those who dont know anything about cars,they wouldnt buy a bmw 5-series outright unless they are super rich , etc.

    as for my budget (factoring the dry box and filter), i am setting it at $1500. if there is any recommendation on how i should go around to get my dslr and the accessories within budget, please share it with me. i would greatly appreciate it

    PS: i am new in photography and have been reading up alot recently on DSLR.

  15. #15

    Default Re: auto focus points + image stabilizer inquiries

    Try Manly at Chinatown for K-x.
    Normally Mr Quek let you tryout the camera unless no stock.

  16. #16
    Moderator Octarine's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by rockdhop View Post
    the only thing is that for the $1000+ im paying, i only get a 18-55mm kit lens and in future, must buy lenses with IS (which i suppose will cost more)
    Why do you think you need lenses with IS? There are many good lenses available without any IS, be it Canon or 3rd party lenses for Canon mount. Even Canon L lenses (professional grade lenses) of shorter focal length don't have IS. Reason: for shorter focal length (up to 50..70mm) there is no real need, it's easy to handhold. General rule of thumb: shutter speed should be faster or equal to "1 / focal length". For the kit lens it means: faster or equal 1/50s at its longest end. Pretty easy to achieve in daylight, also considering the low weight of the lens.
    For longer lenses there are also affordable models with IS in Canon line-up, e.g. EF-S 55-250mm f4-5.6 IS.
    EOS

  17. #17

    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by Octarine View Post
    Why do you think you need lenses with IS? There are many good lenses available without any IS, be it Canon or 3rd party lenses for Canon mount. Even Canon L lenses (professional grade lenses) of shorter focal length don't have IS. Reason: for shorter focal length (up to 50..70mm) there is no real need, it's easy to handhold. General rule of thumb: shutter speed should be faster or equal to "1 / focal length". For the kit lens it means: faster or equal 1/50s at its longest end. Pretty easy to achieve in daylight, also considering the low weight of the lens.
    For longer lenses there are also affordable models with IS in Canon line-up, e.g. EF-S 55-250mm f4-5.6 IS.
    imo it's better to factor in crop factor also, so 55*1.6 = 88, so ard 1/80 or 1/100 (if IS is off)

    For me, I combine handholding technique with IS/VR, works better than thinking IS is magic.

  18. #18

    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by brapodam View Post
    For me, I combine handholding technique with IS/VR, works better than thinking IS is magic.
    True, handholding technique is important. In the past, people took excellent photos without IS.

  19. #19
    Member dingaroo's Avatar
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    Default Re: auto focus points + image stabilizer inquiries

    Quote Originally Posted by natio View Post
    True, handholding technique is important. In the past, people took excellent photos without IS.
    Talking about handholding technique, do you find it irritating when people are using the dSLR and hold it like a P&S?

    Sorry for OT to TS.

    Cheers!
    A picture a day keeps the blues away!

  20. #20

    Default Re: auto focus points + image stabilizer inquiries

    70-200 f2.8 IS good lens

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