Macro Autofocusing - aperture change with focus distance?

[bambang indrayoto]

I just purchased a new Tamron macro 90mm f2.8 SP Di (the newest

model type 272E). I just realized that I cannot always maintain f2.8

at all focus distance. The maximum aperture varies : 2.8 at infinity

and 5.6 at the closest distance. Is this normal? Is this behaviour

normal to all macro lens including nikkor 105 f2.8 and other brands?

 

I did not realised it since in macro shot I always using manual

exposure mode setting the aperture at above 11.

 

I wonder whether this contributes autofocus hunting when trying to

focus very near distance (almost at magnification 1:1).

 

I put this to Nikon forum since I use D2X.

 

Thanks

[bjørn rørslett]

Virtuall all "macro", i. designated for close-up, lenses, change their effective aperture when they focus closer. Your Tamron is no expection. The amount of this change varies between optical constructions and is often less than the +2 stops expected by the standard equation assuming no change in focal length and unity pupil factor.

 

The only lens known to me without any alteration of effective aperture along its focusing range is the 70-180 mm Zoom-Micro-Nikkor.

[alan_olander1664878205]

Autofocus doesn't work very well when shooting macro subjects. It's often best to focus manually.

[joseph_smith3]

The reason why it hunts in AF is that the lens has many choices of what to focus on because of the collapsed effective focus range. I do not use the AF feature on my macro AF lenses, but focus manually or preset the focus and move the camera/lens in and out to achieve focus. Joe Smith

[anupam]

<a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00Bzl1">This question that I asked</a> might help.

 

<p>-A

[david_h._hartman]

If you want to use AF with macro set the camera so AF is only

activated by the AF-ON button and not the shutter release.

Compose, select your subject (the exact area where you wish to

have sharpest) and focus via the AF-ON button then move the

camera in and out for precise focus. I use AF-C (continuous servo).

This can be useful if shooting hand held using electronic flash.

You might use this to photograph a subject that doesnt say

put long enough to setup a tripod such as a butterfly. Otherwise

AF is pretty useless for close-up and macro photography.<br>

<br>

See Custom Setting a5: AF Activation in your manual.<br>

<br>

Regards,<br>

<br>

Dave Hartman

[bambang indrayoto]

Thanks a lot for all the answers. regards,