A Question on Macro Photography..


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Aug 10, 2006
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Upper Bukit Timah
#1
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!
 

advrider

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Sep 3, 2007
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#2
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.
 

giantcanopy

Senior Member
Feb 11, 2007
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#3
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
 

F2point8

Senior Member
Sep 25, 2007
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#4
Sorry out of topic here. How much you pay for your tokina?
thanks.
 

Aug 10, 2006
552
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Upper Bukit Timah
#5
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..
 

megaweb

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Jan 17, 2002
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#6
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.
 

ykia

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Apr 23, 2005
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#7
What mode are you using on your camera? Shutter or aperture priority or full manual?

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.

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

Jul 19, 2007
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#8
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 ;p
 

Clockunder

New Member
Apr 12, 2005
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#9
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.
 

Clockunder

New Member
Apr 12, 2005
1,767
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#10
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?
 

Aug 10, 2006
552
0
0
Upper Bukit Timah
#11
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.
 

catchlights

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Sep 27, 2004
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#12
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.
 

Michael

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Apr 5, 2005
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www.pbase.com
#13
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.
 

zac08

Senior Member
Feb 21, 2005
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#14
Anyone with the 105 VR? Since it's IF, does it still get the varying aperture issue?
 

scenar

New Member
Aug 23, 2005
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#17
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.
 

Aug 10, 2006
552
0
0
Upper Bukit Timah
#19
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?
 

zac08

Senior Member
Feb 21, 2005
11,755
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#20
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
 

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