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Thread: A Question on Macro Photography..

  1. #1
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    Default A Question on Macro Photography..

    Hello all!

    I just acquired a dedicated macro lens for my dslr, the Tokina 100mm f2.8.

    I've been playing with it for awhile now but still kinda confused. haha.

    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?

    3. How would you use a macro lens? any specific steps?


    Thanks all!

  2. #2
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    Default Re: A Question on Macro Photography..

    Quote Originally Posted by mynameisjizeng View Post
    Hello all!

    I just acquired a dedicated macro lens for my dslr, the Tokina 100mm f2.8.

    I've been playing with it for awhile now but still kinda confused. haha.

    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?

    3. How would you use a macro lens? any specific steps?


    Thanks all!
    yes it is perfectly normal. read the manual provided in the box. it will have more info.

  3. #3
    Senior Member giantcanopy's Avatar
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    Default Re: A Question on Macro Photography..

    yes

    The lens entrance pupil remain the same,

    When you focus to 1:1, the distance from the lens to the sensor plane
    increases. Aperture = diameter of the lens entrance pupil ( stays the same ) divided by distance. Hence u find the aperture smaller as u approach 1:1.

    I do not really get the last question on how to use the macro lens but i think you would use ur macro lens like other lenses ? I go manual when i shoot little critters. You might wanna play ard and develop your preference

    Ryan

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    Default Re: A Question on Macro Photography..

    Sorry out of topic here. How much you pay for your tokina?
    thanks.
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  5. #5
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    Default Re: A Question on Macro Photography..

    heh i got it 2nd hand for around $450.

    i prefer it over the tamron cuz of the built and the extra tele. it's a little heavier tho..


    anyway thanks for all the comment. yeah i meant for macro, is manual focusing better?

    it seems like when i vary the mag ratio, it's like i can "zoom in and out" of the photo even tho it's a fixed 100mm. hmmm..

  6. #6

    Default Re: A Question on Macro Photography..

    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?
    Not sure. Read the lens manual.

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?
    In Aperture priortiy and manual mode (camera), you should able to set the desire aperture values like f8 in any magnification.

    3. How would you use a macro lens? any specific steps?
    Do you mean how to achieve 1:1 magnification ? Recommend to set to manual focus, turn the focusing ring to the minimun focusing distance. Move your camera setup to focus the object. Recommend to use a tripod with focusing rail.
    See my Photo Gallery at the Clubsnap

  7. #7
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    Default Re: A Question on Macro Photography..

    What mode are you using on your camera? Shutter or aperture priority or full manual?

    Quote Originally Posted by mynameisjizeng View Post
    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?
    Switch to manual focus at the shortest distance possible and move your body to get into focus, set the aperture to about F/11 to F/16 for good DOF, set the shutter to about 1/200 and use a flash.

    Quote Originally Posted by mynameisjizeng View Post
    3. How would you use a macro lens? any specific steps?

  8. #8

    Default Re: A Question on Macro Photography..

    Quote Originally Posted by mynameisjizeng View Post
    Hello all!

    I just acquired a dedicated macro lens for my dslr, the Tokina 100mm f2.8.

    I've been playing with it for awhile now but still kinda confused. haha.

    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?

    3. How would you use a macro lens? any specific steps?


    Thanks all!
    yup. thats perfectly normal and happens in all macro lenses. the aperture will be a little smaller once you go to a closer focusing distance
    it doesnt really affect the pics, as if u shot at f/2.8 at 1:1 using 100mm, the DOF will be really shallow

    basically, its easier to manual focus with a macro lens, choose the DOF urself
    like ykia said, do stop down to smaller apertures, you'll be surprised at how small the DOF can get
    also, use a flash (pop-up should be good) and use a fairly fast shutter speed (1/[more than focal length])
    there is a lot of camera shake when doing macro shots so be sure to use a tripod as well

    good luck and have fun

  9. #9

    Default Re: A Question on Macro Photography..

    Quote Originally Posted by giantcanopy View Post
    yes

    The lens entrance pupil remain the same,

    When you focus to 1:1, the distance from the lens to the sensor plane
    increases. Aperture = diameter of the lens entrance pupil ( stays the same ) divided by distance. Hence u find the aperture smaller as u approach 1:1.

    I do not really get the last question on how to use the macro lens but i think you would use ur macro lens like other lenses ? I go manual when i shoot little critters. You might wanna play ard and develop your preference

    Ryan
    Are you confusing shooting distance with focal length (i.e. opitcal centre of lens to sensor)?

    Aperture F number is the ratio between focal length and aperture physical size (diaphragm) and has nothing to do with shooting distance.

  10. #10

    Default Re: A Question on Macro Photography..

    Quote Originally Posted by mynameisjizeng View Post
    Hello all!

    I just acquired a dedicated macro lens for my dslr, the Tokina 100mm f2.8.

    I've been playing with it for awhile now but still kinda confused. haha.

    1. Why does the max aperture change when i focus the camera? isnt it supposed to be a constant f2.8?

    2. At mag ratio 1:1, why is the max aperture f5.6? is this normal?

    3. How would you use a macro lens? any specific steps?


    Thanks all!
    What exposure mode [manual or shutter priority or aperture priority or auto (aka normal)] did you shoot in?

  11. #11
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    Default Re: A Question on Macro Photography..

    hi all,

    thanks for all your help! seems like the best way to shoot is using MF. hmmmm.
    still stuck in camp (NS) so havent been able to try out all as advised so far.

    is it true to say that macro lenses operate in (quite) a different way than normal lenses? it seems quite confusing to me! haha.


    btw i was using aperture-priority for all my trial shots.

  12. #12
    Moderator catchlights's Avatar
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    Default Re: A Question on Macro Photography..

    yes, you will lost two stop when shooting 1:1, be it Tokina lens, Tamron lens, Nikon lens, Canon lens, Marco lens or with extension tube, all are the same,

    so the maximum aperture of your Tokina lens at 1:1 become f5.6, nothing wrong with your lens.
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  13. #13

    Default Re: A Question on Macro Photography..

    why does it become f5.6?
    when focusing to 1:1 the front lens needs to move far away from the sensor, side effect of this is that the picture circle which the lens is throwing onto the sensor is increasing. You still capture the same amount of light but it is dispersed over a larger area. same amount of light over bigger area means less light onto the sensor, this appears to the camera as if you have closed the aperture and therefor longer shutter speed is required. Some macro lenses have extra lens elements that will bundle the light back into the original circle and the light drop off is less.

    when you change the mag ratio then you move closer to (1:1) or further away (1:3) from the object so it is really a zooming in and out....

    if you want to shoot at max magnification then its best to focus by moving the camera instead of turning the focus ring, cause focusing will reduce the mag ratio.
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  14. #14
    Senior Member zac08's Avatar
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    Default Re: A Question on Macro Photography..

    Anyone with the 105 VR? Since it's IF, does it still get the varying aperture issue?
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    Default Re: A Question on Macro Photography..

    Quote Originally Posted by zac08 View Post
    Anyone with the 105 VR? Since it's IF, does it still get the varying aperture issue?
    Yes it does.
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  16. #16
    Senior Member zac08's Avatar
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    Default Re: A Question on Macro Photography..

    Quote Originally Posted by majere2sg View Post
    Yes it does.
    Thanks for enlightening me...
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  17. #17

    Default Re: A Question on Macro Photography..

    canon cameras do not seem to reflect the true aperture for macro lenses. i.e. @ 1:1 for the tokina 100f2.8 macro, a 400D would still display aperture as f2.8 (which is incorrect)

    Nikon however displays the actual aperture. f5.6 in this case for the tokina lens.

    So, yes, it's perfectly normal, just that canon bodies do not accurately indicate this.

  18. #18
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    Default Re: A Question on Macro Photography..

    In case you miss it, there is another thread on the subject. Interesting read..

    http://forums.clubsnap.org/showthread.php?t=315215
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  19. #19
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    Default Re: A Question on Macro Photography..

    hmmm thanks guys.

    think the usage of macro lenses depends quite alot on the laws of physics. time to dig out a textbook. haha..

    Thanks michael for putting things into bite sized info. think i more or less get it, but still gotta try it out myself.. hmm..

    is this why macro lenses can only be prime, and not zoom?

  20. #20
    Senior Member zac08's Avatar
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    Default Re: A Question on Macro Photography..

    Quote Originally Posted by mynameisjizeng View Post
    hmmm thanks guys.

    think the usage of macro lenses depends quite alot on the laws of physics. time to dig out a textbook. haha..

    Thanks michael for putting things into bite sized info. think i more or less get it, but still gotta try it out myself.. hmm..

    is this why macro lenses can only be prime, and not zoom?
    Not true, Nikon does have the first macro zoom lens :

    AF Micro 70-180mm f/4.5-5.6D ED
    Michael Lim
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