Macro Lens Question

[frjeff]

In my ongoing debate on which macro lens to buy, the following question:
I know that the Canon 100mm does not extend (which seems to my feeble mind to be an advantage).
Do the Tamron 90mm and the Sigma 105mm both extend then?

The advantage to non-extending is????

[Lester Wareham]

In my ongoing debate on which macro lens to buy, the following question:
I know that the Canon 100mm does not extend (which seems to my feeble mind to be an advantage).
Do the Tamron 90mm and the Sigma 105mm both extend then?

The advantage to non-extending is????

You might find this of interest http://translate.google.com/translate?u=http%3A%2F%2Fwww.nnplus.de%2Fmacro%2FM acro100.html&langpair=de%7Cen&hl=en&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools and this http://www.zen20934.zen.co.uk/photography/Macro_Equipment.htm#Lens%20Table

So to answer your question, yes and yes. The first link tells you by how much.

The advantage is in handling (macro lenses with OLE get a lot longer) and less likely to scare bugs. You can manage however ie the MP-E 65mm which extends by a factor of 3.

[gasrocks]

If your lens is IF (internal focus) and does not change in length as you focus, then the f/stops are true at any distance. Many macros do extend and the marked aperture is wrong at close distances. Comes into play if you ever were going to shoot in full manual, perhaps. My Sigma 150/2.8 Macro lens comes with hood and collar, front does not rotate, lens does not change in length - the way all lenses should be.

[Lester Wareham]

If your lens is IF (internal focus) and does not change in length as you focus, then the f/stops are true at any distance. Many macros do extend and the marked aperture is wrong at close distances. Comes into play if you ever were going to shoot in full manual, perhaps. My Sigma 150/2.8 Macro lens comes with hood and collar, front does not rotate, lens does not change in length - the way all lenses should be.

This not true, you will still meter a light loss with the Canon 100mm.

[gasrocks]

Another reason to get the Sigma.

[Lester Wareham]

Another reason to get the Sigma.

Hmmm 895g vs 600g, quite a big deal for handholding and only a small gain in WD, each to their own. :p