In article <4h986d$t32@ustsu10.ust.hk>, lsavio@cs.ust.hk says...

>I am interested in taking some close-up/macro shots. I current have
>the Nikkor AF50/f1.8 and the 105/f2.5 AIS. What I am considering is
>to add one of those Nikon close-up filters (0, 1, 2, 3T, 4T ...) to
>my lenses. I've a few questions:
>1) The manual of both lenses has listed infomation for only the
>closeup lenses No. 0-2 only. Does it mean that I can't use the 3T and >4T even though they are also 52mm in diameter? What will happen if I >use the 3T and 4T?

The manual on the 105mm may be too old to mention the T's (and they
are 2-element achromats designed to be used with longer lenses).
Even the stronger 4T may not get you much closer with the 50mm, but
should be worthwhile on the 105mm. (They will be sharper than the
single-element 0-2 close-up lenses, though.)

>2) What does the 'T' stand for in close-up lenses 3T, 4T, 5T and 6T?

Probably "Telephoto".

>3) What kind of reproduction ratio should I need for the following
>objects (or similarly sized ones): flower, tomato, inserts like >grasshopper or butterflies?

It varies, depending on how much of the image area you want those
items to occupy - you can figure it out by measuring the short side of the image area in mm's, and relating that number to the short side of
the 35mm frame, which is 24mm (as in: subject rectangle short side = 50mm; 24/50 is approximately 1/2 life size, or 1:2). For these
subjects, I am often working from 1:3 - 3:1, though 1/4 - 1/2 life size
will do for many macro subjects (I have fun entering the bug's world at 1.4x-3x magnifications....)

>4) I know I am not going to get image quality as good as macro lenses. >But how acceptable will the image quality be using the closeup lenses >from Nikon? Or will the use of an extension tube instead enable me to >get better image quality?

Do not use an extension tube with the 105mm f2.5, since its performance
is already compromised at minimum-focus, and will get worse on a tube
(unless the lens is well stopped-down). The Nikkor 4T (or Sigma 52mm
achromat made for the Sigma 90mm macro) should work fine on the 105mm
by f8-11. At f11-16, sharpness can be close to a good macro lens.
The 50mm AF is too short to use easily with either a tube or strong close-up lens, since you will be too close to the subject. Sharpness
can be good by mid apertures, though.

>5) I have an F70 without mirror lockup, but I do have a resonably good >tripod (Manfrotto 190/Bogen 3001). Will the absence of mirror lockup >affect sharpness much?

It should be fine (your subject will be moving more than the camera
much of the time), though exceedingly awkward to use. Easier is
mounting a TTL flash up at the end of the lens, pointed directly at the subject (use whatever simple odds-and-ends parts which will allow you
to get the flash where you want it, and use an SC-17 TTL remote cord). At f16 and with the (relatively large) flash-head near the subject, the light is soft and natural-looking, the DOF will be reasonable, the shutter speed will not be an issue, and the rig makes for far easier hand-held camera positioning than trying to use a tripod for macro.

>Thanks a lot for any information!
>Savio

You're welcome!
Hope This Helps